The FOA Reference For Fiber Optics – Fiber Optic Network Design

Fiber Optic Network Design

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Learn more about Fiber Optic Network Design from the FOA 

Fiber optic network design refers to the specialized
processes leading to a successful installation and operation
of a fiber optic network. It includes first determining the
type of communication system(s) which will be carried over
the network, the geographic layout (premises, campus,
outside plant (OSP, etc.), the transmission equipment
required and the fiber network over which it will operate.
Designing a fiber optic network usually also requires
interfacing to other networks which may be connected over
copper cabling and wireless.

Next to consider are requirements for permits, easements,
permissions and inspections. Once we get to that stage, we
can consider actual component selection, placement,
installation practices, testing, troubleshooting and network
equipment installation and startup. Finally, we have to
consider documentation, maintenance and planning for
restoration in event of a future outage.

The design of the network must precede not only the
installation itself, but it must be completed to estimate
the cost of the project and, for the contractor, bid on the
job. Design not only affects the technical aspects of the
installation, but the business aspects also.

Finally, a fiber optic network designer needs to understand
the processes of installation. We recommend you review the
FOA Guide sections on fiber optic installation covering

Finally, a fiber optic network designer needs to understand the processes of installation. We recommend you review the FOA Guide sections on fiber optic installation covering basic
fiber installation and OSP
fiber installation

Campus network design

Campus network design

Working With Others

Designing a network requires working with other personnel
involved in the project, even beyond the customer. These may
include network engineers usually from IT (information
technology) departments, architects and engineers overseeing
a major project and contractors involved with building the
projects. Other groups like engineers or designers involved
in aspects of project design such as security, CATV or
industrial system designers  or specialized designers
for premises cabling may also be overseeing various parts of
a project that involves the design and installation of fiber
optic cable plants and systems. Even company non-technical
management may become involved when parts of the system are
desired to be on exhibit to visitors.

Qualifications For Fiber
Optic Network Designers

It’s the job of the designer to understand not only the
technology of communications cabling, but also the
technology of communications, and to keep abreast of the
latest developments in not only the technology but the
applications of both.

Designers should have an in-depth knowledge of fiber optic
components and systems and installation processes as well as
all applicable standards, codes and any other local
regulations. They must also be familiar with most telecom
technology (cabled or wireless), site surveys, local
politics, codes and standards, and where to find experts in
those fields when help is needed. Obviously, the fiber optic
network designer must be familiar with electrical power
systems, since the electronic hardware must be provided with
high quality uninterruptible power at every location. And if
they work for a contractor, estimating will be a very
important issue, as that is where a profit or loss can be
determined!

Those involved in fiber optic project design should already
have a background in fiber optics, such as having completed
a FOA CFOT certification course, and may have other training
in the specialties of cable plant design and/or electrical
contracting. It’s also very important to know how to find
in-depth information, mostly on the web, about products,
standards, codes and, for the OSP networks, how to use
online mapping services like Google Maps. Experience with
CAD systems is a definite plus.

The Communications System

Before one can begin to design a fiber optic cable plant,
one needs to establish with the end user or network owner
where the network will be built and what communications
signals it will carry. The contractor should be familiar
with premises networks, where computer networks (LANs or
local area networks) and security systems use structured
cabling systems built around well-defined industry
standards. Once the cabling exits a building, even for short
links for example in a campus or metropolitan network,
requirements for fiber and cable types change. Long distance
links for telecommunications, CATV or utility networks have
other, more stringent requirements, necessary to support
longer high speed links, that must be considered.

Before one can begin to design a fiber optic cable plant, one needs to establish with the end user or network owner where the network will be built and what communications signals it will carry. The contractor should be familiar with premises networks, where computer networks (LANs or local area networks) and security systems use structured cabling systems built around well-defined industry standards. Once the cabling exits a building, even for short links for example in a campus or metropolitan network, requirements for fiber and cable types change. Long distance links for telecommunications, CATV or utility networks have other, more stringent requirements, necessary to support longer high speed links, that must be considered.

But while the contractor generally considers the cabling
requirements first, the real design starts with the
communications system requirements established by the end
user. One must first look at the types of equipment required
for the communications systems, the  speed of the
network and the distances to be covered before considering
anything related to the cable plant. The communications
equipment will determine if fiber is necessary or preferable
and what type of fiber is required.

Premises Networks

Premises
cable systems are designed to carry computer networks ( LANs, local
area networks ) based on Ethernet which currently may operate at speeds from 10 megabits per second to 10 gigabits per second. The typical LAN has copper and fiber sections and links to connect to wireless access points for universal WiFi connectivity. Data
centers are unique applications that house multiple Internet servers and storage networks operating at very high speeds using combinations of short copper and fiber links. Other systems may carry security systems with digital or analog video, perimeter alarms or entry systems, which are usually low speeds, at least as far as fiber is concerned. Premises telephone systems can be carried on traditional twisted pair cables or, as is becoming more common, utilize LAN cabling with voice over IP (VoIP) technology.

Premises networks are usually short, often less than the 100
meters (about 330 feet) used as the limit for standardized
structured cabling systems that allow twisted pair copper or
fiber optic cabling, with backbones on campus networks used
in industrial complexes or institutions as long as 500 m or
more, requiring optical fiber.

Premises networks generally operate over multimode fiber.
Multimode systems are less expensive than singlemode
systems, not because the fiber is cheaper (it isn’t) nor
because cable is cheaper (the same), but because the large
core of multimode fiber allows the use of cheaper LED or
VCSEL sources in transmitters, making the electronics much
cheaper. Astute designers and end users often include both
multimode and singlemode fibers in their backbone cables
(called hybrid cables)  since singlemode fibers are
very inexpensive and it provides a virtually unlimited
ability to expand the systems. LANs and data centers
operating at speeds over 10Gb/s are migrating to singlemode
fiber so more premises cabling systems include singlemode.

Premises networks will include a entrance facility where
outside plant and premises communications systems meet. This
facility must include not only cabling connections but
compatible communications equipment. Since it is indoors, it
must consider issues for building and electrical codes, such
as the common requirement that bare OSP cables can only come
50 feet (about 15 meters) before being terminated in
fire-rated cables unless it is in conduit.

Outside Plant Networks

Outside
plant networks refers to all systems that are outdoors, not inside buildings or campuses. They are typically longer networks uses for telecom, CATV, utilities, security, metropolitan networks, etc.

Telephone networks are mainly outside plant (OSP) systems,
connecting buildings over distances as short as a few
hundred meters to hundreds or thousands of kilometers. Data
rates for telecom are typically 2.5 to 10 gigabits per
second using very high power lasers that operate exclusively
over singlemode fibers. The big push for telecom is now
taking fiber directly to a commercial building or the home,
since the signals are now too fast for traditional twisted
copper pairs.

CATV also uses singlemode fibers with systems that are
either hybrid fiber-coax (HFC) or digital where the backbone
is fiber and the connection to the home is on coax. Coax
still works for CATV since it has very high bandwidth
itself. Some CATV providers have discussed or even tried
some fiber to the home, but have not seen the economics
become attractive yet.

Besides telecom and CATV, there are many other OSP
applications of fiber. Intelligent highways are dotted with
security cameras and signs and/or signals connected on
fiber. Security monitoring systems in large buildings like
airports, government and commercial buildings, casinos, etc.
are generally connected on fiber due to the long distances
involved. Like other networks, premises applications are
usually multimode while OSP is singlemode to support longer
links.

Metropolitan networks owned and operated by cities can carry
a variety of traffic, including surveillance cameras,
emergency services, educational systems, telephone, LAN,
security, traffic monitoring and control and sometimes even
traffic for commercial interests using leased bandwidth on
dark fibers or city-owned fibers. However, since most are
designed to support longer links than premises or campus
applications, singlemode is the fiber of choice.

For all except premises applications, fiber is the
communications medium of choice, since its greater distance
and bandwidth capabilities make it either the only choice or
considerably less expensive than copper or wireless. Only
inside buildings is there a choice to be made, and that
choice is affected by economics, network architecture and
the tradition of using copper inside buildings. Next, we’ll
look at the fiber/copper/wireless choices in more detail.

Cabling Design

Copper, Fiber or Wireless?

While discussions of which is better – copper, fiber or
wireless – has enlivened cabling discussions for decades,
it’s becoming moot. Communications technology and the end
user market, it seems, have already made decisions that
generally dictate the media and many networks combine all
three. The designer of cabling networks, especially fiber
optic networks, and their customers today generally have a
pretty easy task deciding which media to use once the
communications systems are chosen.

Long Distance and Outside
Plant Cabling

Other than telco systems that still use copper for the final
connection to the home, practically every cable in the
telephone system is fiber optic. CATV companies use a high
performance coax into the home, but it connects to a fiber
optic backbone. The Internet backbone is all fiber. Most
commercial buildings in populous areas have direct fiber
connections from communications suppliers. Cities use SM
fiber to connect municipal buildings, surveillance cameras,
traffic signals and sometimes offer commercial and
residential connections, all over singlemode fiber. Even
cellular antenna towers along highways and on tall buildings
usually have fiber connections. Remote areas such as central
Africa depend on satellite communications since cables are
too expensive to run long distances for the small amounts of
traffic involved.

Designing long distance or outside plant applications
generally means choosing cabling containing singlemode (SM)
fiber over all other media. Most of these systems are
designed to be used over distances and speeds that preclude
anything but SM fiber. Occasionally other options may be
more cost effective, for example if a company has two
buildings on opposite sides of a highway, a line-of-sight or
radio optical wireless network may be easier to use since
they have lower cost of installation and are easier to
obtain relevant permits.

The choice of the actual singlemode fiber, however, can
depend on the application. Depending on the length of the
link, the wavelength of the transmitters, data rate of the
transmission and if CWDM or DWDM are planned, different
types of fiber may be optimal. Refer to

The choice of the actual singlemode fiber, however, can depend on the application. Depending on the length of the link, the wavelength of the transmitters, data rate of the transmission and if CWDM or DWDM are planned, different types of fiber may be optimal. Refer to the
section on on fiber for more details.

Premises Cabling

The desire for mobility, along with the expansion of
connected services, appears to lead to a new type of
corporate network. Fiber optic backbone with copper to the
desktop where people want direct connections and multiple
wireless access points, more than is common in the past, for
full coverage and maintaining a reasonable number of users
per access point  is the new norm for corporate
networks.
Most building management systems use proprietary copper
cabling, for example thermostat wiring and paging/audio
speaker systems. Security monitoring and entry systems,
certainly the lower cost ones, still depend on  coax
copper cable, although high security  facilities like
government and military installations often pay the
additional cost for fiber’s more secure nature.

Surveillance systems are becoming more prevalent in
buildings, especially governmental, banking, or other
buildings that are considered possible security risks. While
coax connections are common in short links and structured
cabling advocates say you can run cameras limited distances
on Cat 5E or Cat 6 UPT like computer networks, fiber has
become a much more common choice. Besides offering greater
flexibility in camera placement because of its distance
capability, fiber optic cabling is much smaller and
lightweight, allowing easier installation, especially in
older facilities like airports or large buildings that may
have available spaces already filled with many generations
of copper cabling.

When these premises communications systems connect to the
outside world, it is generally to singlemode optical fiber.
The entrance facility and equipment room must accommodate
the equipment needed to make those connections.

Use of Cabling Standards

Many documents relating to cable plant design focus on
industry standards for both communications systems and cable
plants. US standards come from the TIA or Telcordia while
worldwide standards may come from ISO/IEC or ITU.

It is important to realize why and by whom these standards
are written. These standards are written by manufacturers of
products to ensure that various manufacturers’ products work
together properly. Whenever users specify standards for any
project, it is important that the contractor/installer
understand what standards are being referenced and ensure
that such standards are relevant to the job being done.

To better understand installation and testing requirements,
FOA recommends designers and installers refer to the

To better understand installation and testing requirements, FOA recommends designers and installers refer to the NECA/FOA-301
standard on installing fiber optic networks and the FOA
standards since they are written by contractors, designers, installers and users for their needs.

Choosing Transmission Equipment And Links

Choosing Transmission Equipment And Links

Choosing transmission equipment is the next step in
designing a fiber optic network. This step will usually be a
cooperative venture involving the customer, who knows what
kinds of data they need to communicate, the designer and
installer, and the manufacturers of transmission equipment.
Transmission equipment and the cable plant are tightly
interrelated. The distance and bandwidth will help determine
the fiber type necessary and that will dictate the optical
interfaces on the cable plant. The ease of choosing
equipment may depend on the type of communications equipment
needed.

Telecom has been standardized on fiber optics for 30 years
now, so they have plenty of experience building and
installing equipment. Since most telecom equipment uses
industry conventions, you can usually find equipment for
telecom transmission that will be available for short links
(usually metropolitan networks, maybe up to 20-30 km), long
distance and then really long distance like undersea runs.
All run on singlemode fiber, but may specify different types
of singlemode.

Shorter telecom links will use 1310 nm lasers on regular
singlemode fiber, often referred to as G.652 fiber, it’s
international standard. Longer links will use a
dispersion-shifted fiber optimized for operation with 1550
nm lasers (G.653 or G.655 fiber). For most applications, one
of these will be used. Most telco equipment companies offer
both options.

Most CATV links are AM (analog) systems based on special
highly linear lasers called distributed feedback (DFB)
lasers using either 1310 nm or 1550 nm operating on regular
singlemode fibers. As CATV moves to digital transmission, it
will use technology more like telecom, which is already all
digital.
The choices become more complex when it comes to data and
CCTV because the applications are so varied and standards
may not exist. In addition, equipment may not be available
with fiber optic transmission options, requiring conversion
from copper ports to fiber using devices called media
converters.

In computer networks, the Ethernet standards, created by the
IEEE 802.3 committee, are fully standardized. You can read
the standards and see how far each equipment option can
transmit over different types of fiber, choosing the one
that meets your needs. Most network hardware like switches
or routers are available with optional fiber optic
interfaces, but PCs generally only come with UTP copper
interfaces that require media converters. An Internet search
for “fiber optic media converters” will provide you with
dozens of sources of these inexpensive devices. Media
converters will also allow the choice of media appropriate
for the customer application, allowing use with multimode or
singlemode fiber and may even offer transceiver options for
the distance that must be covered by the link.

CCTV is a similar application. More cameras now come with
fiber interfaces since so many CCTV systems are in locations
like big buildings, airports, or areas where the distances
exceed the capability of coax transmission. If not, video
media converters, usually available from the same vendors as
the Ethernet media converters, are readily available and
also inexpensive. Again, choose converters that meet the
link requirements set by the customer application, which in
the case of video, not only includes distance but also
functions, as some video links carry control signals to the
camera for camera pan, zoom and tilt in addition to video
back to a central location.

What about industrial data links? Many factories use fiber
optics for its immunity to electromagnetic
interference.  But industrial links may use proprietary
means to send data converted from old copper standards like
RS-232, the ancient serial interface once available on every
PC, SCADA popular in the utility industry, or even simple
relay closures. Many companies that build these control
links offer fiber optic interfaces themselves in response to
customer requests. Some of these links have been available
for decades, as industrial applications were some of the
first premises uses of fiber optics, dating back to before
1980. Most operate over regular graded-index multimode fiber
although some have been designed around large core PCS
(plastic-clad silica) fibers.

Whatever the application, it’s important for the end user
and the cabling contractor to discuss the actual application
with the manufacturer of the transmission hardware to ensure
getting the proper equipment. While the telecom and CATV
applications are cut and dried and the data (Ethernet)
applications covered by standards, it is our experience that
not all manufacturers specify their products in exactly the
same way.

One company in the industrial marketplace offered about
fifteen different fiber optic products, mainly media
converters for their control equipment. However, those
fifteen products had been designed by at least a dozen
different engineers, not all of whom were familiar with
fiber optics and especially fiber jargon and specifications.
As a result, one could not compare the products to make a
choice or design them into a network based on
specifications. Until their design, sales and applications
engineers were trained in fiber optics and created
guidelines for product applications, they suffered from
continual problems in customer application.

The only way to make sure you are choosing the proper
transmission equipment is to make absolutely certain the
customer and equipment vendor – and you – are communicating
clearly what you are planning to do.

Planning The Route

Having decided to use fiber optics and chosen equipment
appropriate for the application, it’s time to determine
exactly where the cable plant and hardware will be located.
One thing to remember – every installation will be unique.
The actual placement of the cable plant will be determined
by the physical locations along the route, local building
codes or laws and other individuals involved in the designs.
As usual, premises and outside plant installations are
different so we will consider them separately.
Premises and campus installations can be simpler since the
physical area involved is smaller and the options fewer.
Start with a good set of architectural drawings and, if
possible, contact the architect, contractor and/or building
manager. Having access to them means you have someone to ask
for information and advice. Hopefully the drawings are
available as CAD files so you can have a copy to do the
network cabling design in your computer, which makes
tweaking and documenting the design so much easier.

Having decided to use fiber optics and chosen equipment appropriate for the application, it’s time to determine exactly where the cable plant and hardware will be located. One thing to remember – every installation will be unique. The actual placement of the cable plant will be determined by the physical locations along the route, local building codes or laws and other individuals involved in the designs. As usual, premises and outside plant installations are different so we will consider them separately.Premises and campus installations can be simpler since the physical area involved is smaller and the options fewer. Start with a good set of architectural drawings and, if possible, contact the architect, contractor and/or building manager. Having access to them means you have someone to ask for information and advice. Hopefully the drawings are available as CAD files so you can have a copy to do the network cabling design in your computer, which makes tweaking and documenting the design so much easier.

If the building is still in the design stage, you may have
the opportunity to provide inputs on the needs of the cable
plant. Ideally, that means you can influence the location of
equipment rooms, routing of cable trays and conduits,
availability of adequate conditioned power and separate data
grounds, sufficient air-conditioning and other needs of the
network. For pre-existing  buildings, detailed
architectural drawings will provide you with the ability to
route cabling and network equipment around the obstacles
invariably in your way.

Outside plant (OSP) cabling installations have enormous
variety depending on the route the cable must take. The
route may cross long lengths of open fields, run along paved
rural or urban roads, cross roads, ravines, rivers or lakes,
or, more likely, some combination of all of these.  It
could require buried cables, aerial cables or underwater
cables. Cable may be in conduit, innerduct or direct buried,
aerial cables may be self-supporting or lashed to a
messenger. Longer runs often include crossing water, so the
cable may be underwater or be lashed across a bridge with
other cables.

GIS
(Geographic Information Systems)

Outside
plant installations depend heavily on maps and data about
the cable plant route. This can include basic data on the
local geology, locations of road, buildings, underground
and aerial utilities, and much more. 
GIS (Geographic Information Systems) are
generally used to create very detailed maps of the routes
of OSP cable plants during the design phase. It is beyond
the scope of this book to examine GISs in detail but the
designer should learn how to utilize a GIS to create the
design to facilitate not only the design of the cable
plant but also create documentation for the network.

It
is important to understand the limitation of GIS. For
example the type of ground along the route can determine
the methods of underground installation, with deep soil
permitting direct burial, other soils requiring trenching
and conduit and rocky areas precluding underground
installation of any type. Aerial installations must be
based on knowledge of the owners of the poles and the
processes necessary to gain permission to use the poles
and make ready for new cable installations.

Do
not use GIS alone. It is just one tool that can assist the
designer but is not a replacement for traditional
processes including site visits to evaluate the route.

Site Visits

And as soon as possible, you must visit the site or route
where the network will be installed. Outside plant routes
need to be driven or walked every foot of the way to
determine the best options for cable placement, obstacles to
be avoided or overcome, and to determine what local entities
may have input into the routing. Often cities or other
governments will know of available conduits or rules on
using utility poles that can save design time and effort.

For installations inside current buildings, you should
inspect every area to be absolutely certain you know what
the building really looks like and then mark up drawings to
reflect reality, especially all obstacles to running cabling
and hardware and walls requiring firestopping that are not
on the current drawings. Take pictures if you can. For
buildings under construction, a site visit is still a good
idea, just to get a feeling of what the final structure will
be like and to get to know the construction managers you
will be working with. They may be the best source of
information on who the local authorities are who will be
inspecting your work and what they expect.

OSP network route on satellite map

OSP network route on satellite map

With all those options on OSP installations, where do you
start? With a good map. Not just a road map or a
topographical map, but satellite images overlaid on roads is
much better, like “Google Maps” can provide. Creating a
route map is the first step, noting other utilities along
the route on that map, and checking with groups that
document the current utilities to prevent contractors from
damaging currently installed pipes and cables.

Once you have marked up maps, the real “fun” begins: finding
out whose permission you need to run your cabling. OSP
installs are subject to approval by local, state and federal
authorities who will influence heavily how your project is
designed. Some cities, for example, ban aerial cables. Some
have already buried conduit which you can use for specific
routes. Since many municipalities have installed city-owned
fiber networks, they may have fiber you can rent, rather
than go through the hassle of installing your own.

Unless you are doing work for a utility that has someone who
already has the contacts and hopefully easements needed, you
may get to know a whole new set of people who have control
over your activities. And you have to plan for adequate time
to get approval from everyone who is involved.

Dig
Once

Governments
and other organizations that control rights-of-way face a
difficult problem in the Internet age – the continual
digging up of their properties for cable plant
installation. It’s not uncommon for roads to be dug up
multiple times for different cable plant owners and
operators. This is expensive and disruptive. A simple
solution is what is generally referred to as “Dig Once,” a
process where the cable plant installer who digs up
rights-of-way installs excess conduits or ducts for future
cable plant installation.

When
installing one cable with its associated ducts or
conduits, the installer adds in several extra ducts for
future use on the route. The number and type of ducts is
based on projected future uses but is probably a minimum
of 2 to 5. The requirement for additional ducts is
specified in the contract with the cable plant owner
and/or installer and the local authority generally owns
the installed ducts. Future users lease duct space from
the local authority and pull in their own cables.

This
“dig once” policy is especially useful in metropolitan
areas where digging is most disruptive and cities looking
at becoming “smart cities” find themselves in need of
large fiber optic backbones to support desired services.

Call Before You Dig!

Digging safely is vitally important. The risk is not just
interrupting communications, but the life-threatening risk
of digging up high voltage or gas lines. Some obstacles may
be found during site visits, where signs like these are
visible. There are several services that maintain databases
of the location of underground services that must be
contacted before any digging occurs, but mapping these
should be done during the design phase and double-checked
before digging to ensure having the latest data.

If all this sounds vague, it is. Every project is different
and requires some careful analysis of the conditions before
even beginning to choose fiber optic components and plan the
actual installation. Experience is the best teacher.

Choosing Components

Choosing Components For Outside Plant Installations
The choice of outside plant fiber optic (OSP) components
begins with developing the route the cable plant will
follow. Once the route is set, one knows where cables will
be run, where splices are located and where the cables will
be terminated. All that determines what choices must be made
on cable type, hardware and sometimes installation
methodology.

Cables

When choosing components, most projects start with the
choice of a cable. Cable designs are optimized for the
application type. In OSP installations, cables may be
underground, direct buried, aerial or submarine (or simply
underwater.)

When choosing components, most projects start with the choice of a cable. Cable designs are optimized for the application type. In OSP installations, cables may be underground, direct buried, aerial or submarine (or simply underwater.) More
on OSP cable types

Underground cables are generally installed in conduit which
is usually a 4 inch (10 cm) conduit with several innerducts
for pulling cables. Here cables are designed for high
pulling tension and lubricants are used to reduce friction
on longer pulls. Automated pulling equipment that limits
pulling tension protects the cables. Very long runs or those
with more bends in the conduit may need intermediate pulls
where cable is pulled, figure-8ed and then pulled to the
next stage or intermediate pulling equipment is used.
Splices on underground cables are generally stored above
ground in a pedestal or in a vault underground. Sufficient
excess cable is needed to allow splicing in a controlled
environment, usually a splicing trailer, and the storage of
excess cable must be considered in the planning stage.

Direct buried cable is placed underground without conduit.
Here the cable must be designed to withstand the rigors of
being buried in dirt, so it is generally a more rugged
cable, armored to prevent harm from rodent chewing or the
pressures of dirt and rocks in which it is buried. Direct
burial is generally limited to areas where the ground is
mostly soil with few rocks down to the depth required so
trenching or plowing in cable is easily accomplished.
Splices on direct buried cables can be stored above ground
in a pedestal or buried underground. Sufficient excess cable
is needed to allow splicing in a controlled environment,
usually a splicing trailer, and the storage of excess cable
must be considered.

Microtrenching
is another method used for underground installation,
generally on roadways or in private yards for fiber to the
home connections. Microtrenching involves digging a narrow
and shallow trench about 25mm (1 inch) wide and 200-250mm
(8-10 inches) deep using a special tool. Tools are
available that can cut through asphalt or concrete
roadways or sidewalks or for cutting in bare ground. After
cutting the trench, one can install a special cable or
microducts in which cables can be installed by blowing. A
typical trench can accommodate a microduct with up to six
ducts providing for future expansion.

Aerial
installations go from pole to pole, but the method of
securing cables can vary depending on the situation. Some
cables are lashed to messengers or other cables, such as
CATV where light fiber cables are often lashed to the heavy
coax already in place. Cables are available in a “8”
configuration with an attached steel messenger that provides
the strength to withstand tension on the cable. Some cables
are made to directly be supported without a messenger,
called all-dielectric sefl-supporting cables that use
special hardware on poles to hold the cables.

Optical ground wire is used by utilities for high voltage
distribution lines. This cable is an electrical cable with
fibers in the middle in a hermetically-sealed metal tube. It
is installed just like standard electrical conductors.
Splices on aerial cables can be supported on the cables or
placed on poles or towers, Most splices are done on the
ground, although it is sometimes done in a bucket or even on
a tent supported on the pole or tower. Hardware is available
for coiling and storing excess cable.

Sometime OSP installations involve running cables across
rivers or lakes where other routes are not possible. Special
cables are available for this that are more rugged and
sealed. Even underwater splice hardware is available.
Landings on the shore need to be planned to prevent damage,
generally by burying the cable close to shore and marking
the landing. Transoceanic links are similar but much more
complex, requiring special ships designed for cable laying.

Since OSP applications often use significant lengths of
cables, the cables can be made to order, allowing
optimization for that particular installation. This usually
allows saving costs but requires more knowledge on the part
of the user and more time to negotiate with several cable
manufacturers.
To begin specifying the cable, one must know how many fibers
of what type will be included in each cable. It’s important
to realize that fiber, especially singlemode fiber used in
virtually all OSP installations, is cheap and installation
is expensive. Installation of an OSP cable may cost a
hundred times the cost of the cable itself.

Choosing a singlemode fiber is easy, with basic 1300 nm
singlemode (called G.652 fiber) adequate for all but the
longest links or those using wavelength-division
multiplexing. Those may need special fiber optimized at
1500-1600 nm (G.653 or G.654). For premises and campus cable
plants, OM3 type laser-optimized 50/125 multimode fiber is
probably the best choice for any multimode OSP runs, as its
lower attenuation and higher bandwidth will make most
networks work better.

Including more fibers in a cable will not increase the cable
cost proportionally; the basic cost of making a cable is
fixed but adding fibers will not increase the cost much at
all. Choosing a standard design will help reduce costs too,
as manufacturers may have the cable in stock or be able to
make your cable at the same time as others of similar
design. The only real cost for adding more fibers is
additional splicing and termination costs, still small with
respect to total installed cost. And remember that having
additional fibers for future expansion, backup systems or in
case of breaks involving individual fibers can save many
future headaches.  

Common traits of all outside plant cables include strength
and water or moisture protection. The necessary strength of
the cable will depend on the installation method (see
below.) All cables installed outdoors must be rated for
moisture and water resistance. Until recently, most people
chose a gel-filled cable, but now dry-water blocked cables
are widely available and preferred by many users. These
cables use water-absorbing tape and power that expands and
seals the cable if any water enters the cable. Installers
especially prefer the dry cables as it does not require the
messy, tedious removal of the gel used in many cables,
greatly reducing cable preparation for splicing or
termination.

OSP cable construction types are specifically designed for
strength depending on where they are to be direct buried,
buried in conduit, placed underwater or run aerially on
poles. The proper type must be chosen for the cable runs.
Some applications may even use several types of cable.
Having good construction plans will help in working with
cable manufacturers to find the appropriate cable types and
ordering sufficient quantities. One must always order more
cable than route lengths, to allow for service loops,
preparation for termination and excess to save for possible
restoration needs in the future.

Like cable types, cable plant hardware types are quite
diverse and should be chosen to match the application type
and cable types being used. With so many choices in
hardware, working with cable manufacturers is the most
expeditious way to chose hardware and ensure compatibility.
Besides cable compatibility, the hardware must be
appropriate for the location, which can be outdoors, hung on
poles, buried, underwater, inside pedestals, vaults or
buildings, etc. Sometimes the hardware will need to be
compatible with local zoning, for example in subdivisions or
business parks. The time consumed in choosing this hardware
can be lengthy, but is very important for the long term
reliability of the cable plant.

Splicing And Termination
Hardware

Splicing and termination are the final category of
components to be chosen. Most OSP singlemode fiber is fusion
spliced for low loss, low reflectance and reliability.
Multimode fiber, especially OM2, 3 and 4, is also easily
fusion spliced, but if only a few splices are necessary,
mechanical splicing may provide adequate performance and
reliability.

Finished splices are placed in a splice tray and placed in a
splice closure outdoors or optionally in trays on patch
panels indoors. They are sealed to prevent moisture reaching
the splices and are designed to be re-entered for repair or
re-routing fibers. Splice closures are available in hundreds
of designs, depending on the placement of the closure, for
example underground in a manhole or vault, above ground in a
pedestal, buried underground or mounted on a pole. Closures
must also be chosen by the number and types of cables being
spliced and whether they enter at both ends or only one. The
numbers of cables and splices that a closure can accommodate
will determine the size of the closure, and those for high
fiber count cables can get quite large.

Splice trays generally hold twelve single fiber fusion
splices but may hold fewer ribbon or mechanical splices.
Each splice tray should securely hold the splice and have a
cover to protect the fibers when stacked in the closure.

Singlemode fibers are best terminated by fusion spicing
factory-made pigtails onto fibers in the cable and
protecting the splices in a closure or patch panel tray. If
termination is done directly on multimode OSP cables,
breakout kits will be necessary to sleeve fibers for
reliability when connectors are directly attached. This
takes more installation time than splicing pre-terminated
pigtails on the cables, as is common with singlemode fiber
cables, and may not save any costs. Even complete
preterminated outside cable plant systems are becoming
available, reducing the time necessary for termination and
splicing. Talk to the cable manufacturers to determine
feasibility of this option.

Outdoor terminations are sometimes housed in pedestals or
equipment housings such as those used for local phone
switches or traffic control systems. Some of these closures
may not be fully sealed from dust and moisture, in which
case it is recommended that the fiber connections be inside
a more protective housing to prevent future unreliability.

Choosing the proper components for OSP installations can
take time, but is important for system operation. Once
components are chosen, the materials lists are added to the
documentation for purchase, installation and future
reference.

Choosing Components For
Premises Installations

Premises cabling and outside plant cabling will coexist in
the entrance facility or the equipment room where the two
are connected. The choice of premises fiber optic components
are affected by several factors, including the choice of
communications equipment, physical routing of the cable
plant and building codes and regulations. If the design is a
corporate network (LAN), the design will probably include a
fiber optic backbone connecting computer rooms to wiring
closets. The wiring closets house switches that convert the
fiber backbone to UTP copper for cable connected desktops
and either copper or fiber to wireless access points. Some
desktops, especially in engineering or design departments,
may require fiber to the desktop for it’s greater bandwidth.
Extra cables or fibers may be needed for security systems
(alarms, access systems or CCTV cameras) and building
management systems also.

Design of the fiber optic cable plant requires coordinating
with everyone who is involved in the network in any way,
including IT personnel, company management,  architects
and engineers, etc. to ensure all cabling requirements are
considered at one time, to allow sharing resources.

As in OSP design, consider the fiber choice first. Most
premises networks use multimode fiber, but many users now
install hybrid cables with singlemode fibers for future
expansion. The 62.5/125 micron fiber (OM1 fiber) that has
been used for almost two decades has mostly been superceded
by the new 50/125 laser-optimized fiber (OM3 or OM4), as it
offers substantial bandwidth/distance advantages.

Virtually all equipment will operate over 50/125 OM3 or OM4
fiber just as well as it did on 62.5/125 OM1 fiber, but it’s
always a good idea to check with the equipment manufacturers
to be sure.  Remember in the design documentation to
include directions to mark all cables and patchpanels with
aqua-colored tags, indicative of OM3 or OM4 fiber.

Cable in premises applications is generally either
distribution or breakout cable. Distribution cables have
more fibers in a smaller diameter cable, but require
termination inside patch panels or wall mounted boxes.
Breakout cables are bulky, but they allow direct connection
without hardware, making them convenient for industrial use.
Fiber count can be an issue, as backbone cables now have
many fibers for current use, future expansion and spares,
making distribution cables the more popular choice.

On all indoor cables, the cable must be rated as
fire-retardant per the NEC, CEC or other building codes. In
the NEC terminology, indoor cables are generally OFNR-rated
(Riser) unless the cable in air-handling areas above
ceilings, where OFNP (plenum) is needed. Cable jacket color
for OM3 cables can be ordered in aqua for identification as
both fiber optics and OM3 or OM4 50/125 fibers.

If the cable is going to be run between buildings,
indoor/outdoor designs are now available that have dry
water-blocking and a double jacket. The outer jacket is
moisture-resistant for outdoor use but can be easily
stripped, leaving the fire-rated inner jacket for indoor
runs.

Fiber optic connector choices are also changing. STs and
even SCs are succumbing to the success of the smaller LC
connector. Since most fast (gigabit and above) equipment
uses LC connectors, using them in the cable plant means only
one connector needs to be supported. The LC offers another
big advantage for those users who are upgrading to  OM3
fiber. The LC connector is incompatible with SC and ST
connectors, so using it on 50/125 fiber cable plants
prevents mixing 50 and 62.5 fibers with high fiber mismatch
losses.

Premises fiber optic cables need to be run separately from
copper cables to prevent crushing. Sometimes they are hung
carefully below copper cable trays or pulled in innerduct.
Using innerduct can save installation time, since the duct
(which can be purchased with pull tapes already inside) can
be installed quickly without fear of damage and then the
fiber optic cable pulled quickly and easily. Some
applications may require installing fiber optic cables
inside conduit, which requires care to minimize bends,
provide intermediate pulls to limit pulling force or use
fiber optic cable lubricants.

The hardware necessary for the installation will need to be
chosen based on where the cables are terminated. Premises
runs are generally point-to-point and are not spliced.
Wherever possible, allow room for large radii in the patch
panels or wall-mounted boxes to minimize stress on the
fibers. Choose hardware that is easy to enter for moves,
adds and changes but lockable to prevent intrusion.

In premises applications, it’s worth considering a
preterminated system. These use backbone cables terminated
in multifiber connectors and preterminated patch panel
modules. If the facility layout is properly designed, the
cable manufacturer can work with you to create a “plug and
play” system that needs no on-site termination and the cost
may be very competitive to a field-terminated system.

Creating A Materials List

For every installation, a complete materials list must be
created listing each component needed and quantities
required. This list will be used by the installation crew,
but first it will be used to estimate the cost of the
project.

It is very important to list every component. Some
components can be estimated based on other quantities. Ducts
for example will be ordered in lengths similar to the cable
pulled into them. Each fiber needs termination on both ends
of the cable plant. Splice trays and closures must be
ordered according to the numbers of fibers in the cables.

You should include extra quantities for installation. Every
splice point, for example, needs 10-20 meters extra cable
for splicing in a splice trailer, stripping for the splice
and service loops. Extra cable should also be ordered to be
kept for possible future restoration. Extra connectors or
pigtails are needed to replace those improperly installed
during installation. Some contractors routinely order 2-5%
more than they estimate is necessary for the job.

While ordering more components than necessary can be costly,
it’s less expensive than being short during the actual
installation, especially for special order items like cables
or patchcords. Excess components should be packed and stored
as part of a restoration kit.

Cable Plant Link Loss
Budget Analysis

Loss budget analysis is the calculation and verification of
a fiber optic system’s operating characteristics. It is used
to estimate the loss of a cable plant being installed,
determine if the cable plant will work with any given
transmission system and provide an estimate for comparison
to actual test results. A link loss budget encompasses items
such as the length of the link, fiber type, wavelengths,
connectors and splices, and any other sources of loss in the
link. Attenuation and bandwidth are the key parameters for
budget loss analysis, but since we cannot test attenuation,
we generally use limits for loss set by the standards for
the systems or networks we are going to use on the link. (

Loss budget analysis is the calculation and verification of a fiber optic system’s operating characteristics. It is used to estimate the loss of a cable plant being installed, determine if the cable plant will work with any given transmission system and provide an estimate for comparison to actual test results. A link loss budget encompasses items such as the length of the link, fiber type, wavelengths, connectors and splices, and any other sources of loss in the link. Attenuation and bandwidth are the key parameters for budget loss analysis, but since we cannot test attenuation, we generally use limits for loss set by the standards for the systems or networks we are going to use on the link. ( Here
is a table of link losses from industry standards for many
links .) The designer should analyze link loss early in the design stage prior to installing a fiber optic system to make certain the system will work over the proposed cable plant.

From the system standpoint, we have a limit to the loss it
can tolerate on the cable plant, called a power budget,
determined from the output of the transmitter and the
required input of the receiver. We define these errors for
the system as “bit-error rate” and they may be caused by too
little power or too much power at the receiver. It is
important to note that most calculations focus on the cable
plant loss being low enough for the system power budget.
However, on some systems, especially laser-based singlemode
systems, the receiver may not tolerate too low a loss which
causes high power at the receiver and may overload it,
causing transmission errors. Under such conditions,

From the system standpoint, we have a limit to the loss it can tolerate on the cable plant, called a power budget, determined from the output of the transmitter and the required input of the receiver. We define these errors for the system as “bit-error rate” and they may be caused by too little power or too much power at the receiver. It is important to note that most calculations focus on the cable plant loss being low enough for the system power budget. However, on some systems, especially laser-based singlemode systems, the receiver may not tolerate too low a loss which causes high power at the receiver and may overload it, causing transmission errors. Under such conditions, an
attenuator is added at the receiver end of the link to
lower the power to an acceptable level

Both the passive and active components of the circuit can be
included in the budget loss calculation. Passive loss is
made up of fiber loss, connector loss, and splice loss.
Don’t forget any couplers or splitters in the link. If the
specifications for a type of system or network are not
known, industry generic or standard loss values for the
fiber optic components can be used for calculating the loss
budget for the cable plant. Prior to system turn up, test
the insertion loss of the cable plant with a source and
power meter to ensure that it is within the loss budget.

The idea of a loss budget is to ensure the network equipment
will work over the installed fiber optic link. One issue is
what values should one should use for component losses when
making the calculations. One can use the values in some
industry standards like TIA-568 which are considered very
high, one can use typical values, one can use values from
component manufacturers which may be nearer typical or the
user may have values that they require, not unusual for
sophisticated users like telcos. It is normal to be
conservative over the specifications. Don’t use the best
possible specs for fiber attenuation or connector loss to
allow some margin for installation and component degradation
over time.

The best way to illustrate calculating a loss budget is to
show how it’s done for a typical cable plant, here a 2 km
hybrid multimode/singlemode link with 5 connections (2
connectors at each end and 3 connections at patch panels in
the link) and one splice in the middle. See the drawings
below of the link layout and the instantaneous power in the
link at any point along it’s length, scaled exactly to the
link drawing above it.

Cable Plant Passive Component Loss

Step 1. Calculate fiber loss at the operating wavelengths
(length times standard estimates of loss at each wavelength)

Cable
Length (km)

2.0

2.0

2.0

2.0

Fiber
Type

Multimode

Singlemode

Wavelength
(nm)

850

1300

1300

1550

Fiber
Atten. (dB/km)

3
[3.5]

1
[1.5]

0.4
[1/0.5]

0.3
[1/0.5]

Total
Fiber Loss (dB)

6.0
[7.0]

2.0
[3.0]

0.8
[2/1

0.6
[2/1]

(All specifications in brackets are maximum values per
EIA/TIA 568 standard. For singlemode fiber, a higher loss is
allowed for premises applications, 1 dB/km for premises, 0.5
dB/km for outside plant. )

Step 2. Connector Loss
Multimode connectors will have losses of 0.2-0.5 dB
typically. Singlemode connectors, which are factory made and
fusion spliced on will have losses of 0.1-0.2 dB. Field
terminated singlemode connectors may have losses as high as
0.5-1.0 dB. Let’s calculate it at both typical and worst
case values.

Connector
Loss

0.3
dB
(typical adhesive/polish connector)

0.75
dB
(prepolished/splice connector and TIA-568 max
acceptable)

Total
# of Connectors

5

5

Total
Connector Loss

1.5
dB

3.75
dB

(All connectors are allowed 0.75 max per EIA/TIA 568
standard)
Many designers and technicians forget when doing a loss
budget that the connectors on the end of the cable plant
must be included in the loss budget. When the cable plant is
tested, the reference cables will mate with those connectors
and their loss will be included in the measurements.

Step 3. Splice Loss
Multimode splices are usually made with mechanical splices,
although some fusion splicing is used. The larger core and
multiple layers make fusion splicing abut the same loss as
mechanical splicing, but fusion is more reliable in adverse
environments. Figure 0.1-0.5 dB for multimode splices, 0.3
being a good average for an experienced installer. Fusion
splicing of singlemode fiber will typically have less than
0.05 dB (that’s right, less than a tenth of a dB!)

Splice
Loss

0.3
dB

Total
# splices

1

Total
Splice Loss

0.3
dB

(For this loss budget calculation, all splices are allowed
0.3 max per EIA/TIA 568 standard)

Step 4. Total Cable Plant Loss
Add together the fiber, connector and splice losses to get
the total link loss of the cable plant.

Best Case [TIA 568 Max]

Best Case [TIA 568 Max]

Wavelength
(nm)

850

1300

1300

1550

Total
Fiber Loss (dB)

6.0
[7.0]

2.0
[3.0]

0.8
[2/1]

0.6
[2/1]

Total
Connector Loss (dB)

1.5
[3.75]

1.5
[3.75]

1.5
[3.75]

1.5
[3.75]

Total
Splice Loss (dB)

0.3
[0.3]

0.3
[0.3]

0.3
[0.3]

0.3
[0.3]

Other
(dB)

0

0

0

0

Total
Link Loss (dB)

7.8
[11.05]

3.8
[7.05]

2.6
[6.05/5.05]

2.4
[6.05/5.05]

These values of cable plant loss should be the criteria for
testing. Allow +/- 0.2 -0.5 dB for measurement uncertainty
and that becomes your pass/fail criterion.

 
Equipment Link Loss Budget Calculation
Link loss budget for network hardware depends on the dynamic
range, the difference between the sensitivity of the
receiver and the output of the source into the fiber. You
need some margin for system degradation over time or
environment, so subtract that margin (as much as 3dB) to get
the loss budget for the link.

Step 5. Data From Manufacturer’s Specification for Active
Components (Typical 100 Mb/s multimode digital link using a
1300 nm LED source.)

Operating
Wavelength (nm)

1300

Fiber
Type

MM

Receiver
Sensitivity (dBm@ required BER)

-31

Average
Transmitter Output (dBm)

-16

Dynamic
Range (dB)

15

Recommended
Excess Margin (dB)

3

Step 6. Loss Margin Calculation

Dynamic
Range (dB) (above)

15

15

Cable
Plant Link Loss (dB @ 1300 nm)

3.8
(Typical)

7.05
(TIA)

Link
Loss Margin (dB)

11.2

7.95

In the past, as a general rule, the Link Loss Margin was
expected be greater than approximately 3 dB to allow for
link degradation over time or splicing for restoration. LEDs
or lasers in the transmitter may age and lose power,
connectors or splices may degrade or connectors may get
dirty if opened for rerouting or testing. If cables are
accidentally cut, excess margin will be needed to
accommodate splices for restoration. Today some systems,
particularly high bit rate multimode LANs, have little
margin due to the high bandwidth required. Some of these
links require assuming fiber and connector loss to be
extremely low to even accommodate the small power budget
available. Under such conditions, one has to assume lower
values, especially for connector loss, and, of course,
require installers to be extremely careful in installation
to meet these needs.

FOA offers a free App for smartphones and tablets to
calculate loss budgets. Check the App Store for “FOA
LossCalc.”

Project Documentation

Documentation of the cable plant is a necessary part of the
design and installation process for a fiber optic network
that is often overlooked. Documenting the installation
properly during the planning process will save time and
material in the installation. It will speed the cable
installation and testing since the routing and terminations
are already known. After component installation, the
documentation should be completed with loss test data for
acceptance by the end user. During troubleshooting,
documentation eases tracing links and finding faults. Proper
documentation is usually required for customer acceptance of
the installation. All this documentation gets included in
the project paperwork that includes a Scope of Work (SOW),
Request For Proposal or Quotation (RFP or RFQ) and the
project Contract between the contractor and the customer.

Documentation of the cable plant is a necessary part of the design and installation process for a fiber optic network that is often overlooked. Documenting the installation properly during the planning process will save time and material in the installation. It will speed the cable installation and testing since the routing and terminations are already known. After component installation, the documentation should be completed with loss test data for acceptance by the end user. During troubleshooting, documentation eases tracing links and finding faults. Proper documentation is usually required for customer acceptance of the installation. All this documentation gets included in the project paperwork that includes a Scope of Work (SOW), Request For Proposal or Quotation (RFP or RFQ) and the project Contract between the contractor and the customer. More
on the project paperwork is here

The documentation process begins at the initiation of the
project and continues through to the finish. It must begin
with the actual cable plant path or location. OSP cables
require documentation as to the overall route, but also
details on exact locations, e.g. on which side of streets,
which cable on poles, where and how deep buried cables and
splice closures lay  and if markers or tracing tape is
buried with the cable. Premises cables require similar
details inside a building in order for the cable to be
located anywhere in the path.

Most of this data can be kept in CAD drawings and a database
or commercial software that stores component, connection and
test data. Long outside plant links that include splices may
also have OTDR traces which should be stored as printouts
and possibly in computer files archived on disks for later
viewing in case of problems. A computer with proper software
for viewing traces must be available, so a copy of the
viewing program should be on the disks with the files. If
the OTDR data is stored digitally, a listing of data files
should be kept with the documentation to allow finding
specific OTDR traces more  easily.

The Documentation Process

Documentation begins with a basic layout for the network. A
sketch on building blueprints may work for a small building
but a large campus, metropolitan or long distance network
will probably need a complete CAD layout.  The best way
to set up the data is to use a facility drawing and add the
locations of all cables and connection points. Identify all
the cables and racks or panels in closets and then you are
ready to transfer this data to a database.

Fiber optic cables, especially backbone cables, may contain
many fibers that connect a number of different links which
may not all be going to the same place. The fiber optic
cable plant, therefore, must be documented for cable
location, the path of each fiber, interconnections and test
results.  You should record the specifications on every
cable and fiber: the manufacturer, the type of  cable
and fiber, how many fibers, cable construction type,
estimated length, and installation technique (buried,
aerial, plenum, riser, etc.)

It will help to know what types of panels and hardware are
being used, and what end equipment is to be connected. If
you are installing a big cable plant with many dark (unused)
fibers, some will probably be left open or unterminated at
the panels, and that must be documented also. Whenever
designing a network, it’s a very good idea to have spare
fibers and interconnection points in panels for future
expansion, rerouting for repair or moving network equipment.

Documentation is more than records. All components should be
labeled with color-coded permanent labels in accessible
locations. Once a scheme of labeling fibers has been
determined, each cable, accessible fiber and termination
point requires some labeling for identification. A simple
scheme is preferred and if possible, explanations provided
on patch panels or inside the cover of termination boxes.

Protecting  Records

Cable plant documentation records are very important
documents. Keep several backup copies of each document,
whether it is stored in a computer or on paper, in different
locations for safekeeping. If a copy is presented to the
customer, the installer should maintain their own records
for future work on the project. One complete set on paper
should be kept with a “restoration kit” of appropriate
components, tools directions in case of outages or cable
damage. Documentation should be kept up to date to be useful
so that task should be assigned to one on-site person with
instructions to inform all parties keeping copies of the
records of updates needed. Access to modify records should
be restricted to stop unauthorized changes to the
documentation.

Planning for the
Installation

Once the design of a fiber optic project is complete and
documented, one might think the bulk of the design work is
done. But in fact, it’s just beginning. The next step is to
plan for the actual installation. Planning for the
installation is a critical phase of any project as it
involves coordinating activities of many people and
companies. The best way to keep everything straight is
probably to develop a checklist based on the design during
the early stages of the project.

The Project Manager

Perhaps the most important issue is to have a person who is
the main point of contact for the project. The project
manager needs to be involved from the beginning, understands
the aims of the project, the technical aspects, the physical
layout, and is familiar with all the personnel and companies
who will be involved. Likewise all the parties need to know
this person, how to contact them (even 24/7 during the
actual install) and who is the backup if one is needed.

The backup person should also be involved to such a degree
that they can answer most questions, may even be more
technically savvy on the project, but may not have full
decision-making authority. The backup on big jobs may well
be the person maintaining the documentation and schedules,
keeping track of purchases and deliveries, permits,
subcontractors, etc. while the  project manager is more
of a hands-on manager.

Design Checklist

Planning for a project is critical to the success of the
project. The best way is to develop a checklist before
beginning the design process. The checklist below is
comprehensive but each project will have some of its own
unique requirements that need to be added. Not all steps
need be done serially, as some can be done in parallel to
reduce time required for designing the project. The designer
must interface with many other people and organizations in
designing a project so contacts for outside sources should
be maintained with the design documentation.

Design Process

Link communications requirements

• Link route chosen, inspected, special requirements noted
  including inspections and permits

• Specify communications equipment and component
  requirements

• Specify cable plant components

• Determine coordination with facilities, electrical and
  other personnel

• Documentation completed and ready for installation

• Write test plan

• Write restoration plans

Contractor package for the install

• Documentation, drawings, bills of materials,
  instructions

• Permits available for inspection

• Guidelines to inspect workmanship at every step, test
  plan

• Daily review of progress, test data

• Safety rules to be posted on the job site(s) and
  reviewed with all supervisors and installation personnel

Requirements for completion of cable plant installation

• Final inspection

• Review test data on cable plant

• Instructions to set up and test communications system

• Final update of documentation

• Update and complete restoration plan, store components
  and documentation

Developing A Project
Checklist

The final project checklist will have many items, all of
great importance. Each item needs a full description, where
and when it will be needed and who is responsible for it.
See Chapter 10 for a recommended project installation
checklist. Components like cables and cable plant hardware
should indicate vendors, delivery times  and where,
when and sometimes how it needs to be delivered. Special
installation equipment needs to be scheduled also, with
notes of what is needed to be purchased and what will be
rented. If the jobsite is not secure and the install will
take more than a day, security guards at the jobsite(s) may
need to be arranged.

A work plan should be developed that indicates what
specialties are going to be needed, where and when. Outside
plant installations (OSP) often have one crew pulling cable,
especially specialty installs like direct burial, aerial or
underwater, another crew splicing and perhaps even another
testing. OSP installers often do just part of the job since
they need skills and training on specialized equipment like
fusion splicers or OTDRs and installation practices like
climbing poles or plowing-in cables. Inputs from the
installation crews can help determine the approximate time
needed for each stage of the installation and what might go
wrong that can affect the schedule.

And things will go wrong. All personnel working on the
project should be briefed on the safety rules and preferably
be given a written copy. Supervisors and workers should have
contact numbers for the project manager, backup and all
other personnel they may need to contact. Since some
projects require working outside normal work hours, for
example airports or busy government buildings where cabling
is often done overnight, having a project manager available
– preferably onsite – while the work is being done is very
important.

During the installation itself, a knowledgeable person
should be onsite to monitor the progress of installation,
inspect workmanship, review test data, create daily progress
reports and immediately notify the proper management if
something looks awry. If the project manager is not
technically qualified, having someone available who is
technical is important. That person should have the
authority to stop work or require fixes if major problems
are found.

Licenses, Certifications,
Facilities and Power/Ground Issues

This chapter primarily focuses on the unique aspects of
fiber optic cable plant design and installation, but this
process cannot be done in a vacuum. Projects may require the
sign-offs of architects or PEs (Professional Engineers) who
are licensed in the area and involved in the project. Cable
plants may require working with cities or counties for
permits or easements, cooperation from other organizations
to allow access through their property and construction
disruptions. Any communications system requires not only the
cable plant but facilities for termination at each end,
placing communications equipment, providing power (usually
uninterruptible data quality power) and a separate data
ground which may require the services of an electrical
contractor. Inside the facility, connections must be made to
the end users of the link. The installation may require
inspections by building and/or electrical inspectors and
contractors may require electrical and/or low voltage or
fiber optic licenses from local authorities. Customers often
require certifications such as the FOA CFOT for contractors
and installers to work on a project.

The large number of options involved in almost every project
make it impossible to summarize the issues in a few
sentences, so let’s just say you must consider the final,
complete design to gain cooperation and coordinate the final
installation. One of the most valuable assets you can have
when designing and installing a fiber optic project is an
experienced contractor.

Developing A Test Plan

Every installation requires confirmation that components are
installed properly. The installer or contractor wants to
ensure the work is done properly so the customer is
satisfied and callbacks for repair will not be necessary.
Customers generally require test results as well as a final
visual inspection as part of the documentation of a proper
installation before approving payment.

In our experience, however, there is often confusion about
exactly what should be tested and how documentation of test
results is to be done on fiber optic projects. These issues
should be agreed upon during the design phase of the
project. Project paperwork should include specifications for
testing, references to industry standards and acceptable
test results based on a loss budget analysis done during the
design phase of the project.

In our experience, however, there is often confusion about exactly what should be tested and how documentation of test results is to be done on fiber optic projects. These issues should be agreed upon during the design phase of the project. Project paperwork should include specifications for testing, references to industry standards and acceptable test results based on a loss budget analysis done during the design phase of the project. FOA
standards are an easy way to have test methods agreed among all parties.

The process of testing any fiber optic cable plant may
require testing three times, testing cable on the reel
before installation, testing the

The process of testing any fiber optic cable plant may require testing three times, testing cable on the reel before installation, testing the insertion
loss of each segment as it is installed with an optical loss test set (OLTS, another name for a light source and power meter), perhaps verifying every splice as it is made using an OTDR and finally testing complete end to end loss of every fiber in the cable plant. Practical testing usually means testing only a few fibers on each cable reel for continuity before installation to ensure there has been no damage to the cable during shipment. Then each segment is tested as it is spliced and/or terminated by the installers. Finally the entire cable run is plugged together and tested for end-to-end loss for final documentation.

One should require visual inspection of cable reels upon
acceptance and, if visible damage is detected, testing the
cable on the reel for continuity before installing it, to
ensure no damage was done in shipment from the manufacturer
to the job site. Since the cost of installation usually is
high, often much higher than the cost of materials, it only
makes sense to ensure that one does not install bad cable,
which would then have to be removed and replaced. It is
generally sufficient to just test continuity with a fiber
tracer or visual fault locator. However, long spools of
cable may be tested with an OTDR if damage is suspected and
one wants to document the damage or determine if some of the
cable needs to be cut off and discarded (or retained to get
credit for the damaged materials.)

After cable installation, splicing and termination, each
segment of the cable plant should be tested individually as
it is installed, to ensure each splice, connector and cable
is good. One should never complete splicing cables without
verifying the splices are properly done with an OTDR before
sealing the splice closure. Finally  each end to end
run (from equipment to equipment connected on the cable
plant) should be tested for loss as required by all
standards. Remember that each fiber in each cable will need
to be tested, so the total number of tests to be performed
is calculated from the number of cable segments times the
number of fibers in each cable. This can be a time-consuming
process.

Before finishing, it is important to ensure the fibers are
documented and arranged properly. When equipment is
installed, another parameter becomes important,

Before finishing, it is important to ensure the fibers are documented and arranged properly. When equipment is installed, another parameter becomes important, polarity . Most fiber links use two fibers transmitting in opposite directions, so it’s important to check that the transmitters are connected to the receivers which often requires a crossover somewhere in the cable plant. Documentation should show how the fibers are to be connected to equipment. If the contractor installs the communications equipment, it may be necessary to test
each data link also.

Required vs. Optional
Testing

Testing the complete cable plant requires insertion loss
testing with a source and power meter or optical loss test
set (OLTS) per  standard test procedure. The test plan
should specify the “0 dB”  reference method option
(one, two or three reference cables) as this will affect the
value of the loss. Some standards call for a one cable
reference, but this may not be possible with all
combinations of test sets and cable plant connectors. The
required test methods need to be agreed upon by the
contractor and user beforehand.

Testing the complete cable plant requires insertion loss testing with a source and power meter or optical loss test set (OLTS) per standard test procedure. The test plan should specify the “0 dB” reference method option (one, two or three reference cables) as this will affect the value of the loss. Some standards call for a one cable reference, but this may not be possible with all combinations of test sets and cable plant connectors. The required test methods need to be agreed upon by the contractor and user beforehand. FOA
standards provide a simple solution to this problem.

OTDR testing is generally done on outside plant cables, but
OTDR testing alone is often not acceptable for cable plant
certification. Long lengths of outside plant cabling which
include splices should be tested with an OTDR to verify
splice performance and look for problems caused by stress on
the cable during installation.

While there are advocates of using OTDRs to test any cable
plant installation, including short premises cables, it is
generally not required by industry standards nor is it
appropriate for short links common to premises cabling. The
shorter lengths of premises cabling runs and frequent
connections with high reflectance often create confusing
OTDR traces that cause problems for the OTDR autotest
function and are sometimes difficult for even experienced
OTDR users to interpret properly.

Long OSP cables may require special testing for

Long OSP cables may require special testing for spectral
attenuation (S), chromatic dispersion (CD) and
polarization mode dispersion (PMD) . These are specialized tests required to ensure DWDM and high bit rate systems operate properly.

Coordinating Testing and
Documentation

The Test Plan should be coordinated with the cable plant
documentation. The documentation must show what links need
testing and what test results are expected based on loss
budget calculations. The Test Plan should also specify how
the test data are incorporated into the documentation for
acceptance of the installation and for reference in case of
future cabling problems that require emergency restoration.

Planning for Restoration

About once a day in the USA, a fiber optic cable is broken
by a contractor digging around the cable, as this photo
shows. Premises cables are not as vulnerable, except for
damage caused by clumsy personnel or during the removal of
abandoned cables. Any network is susceptible to damage so
every installation needs a restoration plan.

Efficient fiber optic restoration depends on rapidly finding
the problem, knowing how to fix it, having the right parts
and getting the job done quickly and efficiently. Like any
type of emergency,  planning ahead will minimize the
problems encountered.

Documentation for
Restoration

Documentation is the most helpful thing you can have when
trying to troubleshoot a fiber network, especially during
restoration. Start with the manufacturer’s datasheets on
every component you use: electronics, cables, connectors,
hardware like patch panels, splice closures and even
mounting hardware. Along with the data, one should have
manufacturer’s “help line” contact information, which will
be of immense value during restoration.

During installation, mark every fiber in every cable at
every connection and keep records using cable plant
documentation software or a simple spreadsheet of where
every fiber goes. When tested, add loss data taken with an
optical loss test set (OLTS) and optical time domain
reflectometer (OTDR) data when available. Someone must be in
charge of this data, including keeping it up to date if
anything changes.

Equipment For Restoration

Testing and Troubleshooting

You must have available proper test equipment to
troubleshoot and restore a cable plant. An OLTS should also
have a power meter to test the power of the signals to
determine if the problem is in the electronics or cable
plant. Total failure of all fibers in the cable plant means
a break or cut in the cable. For premises cables, finding
the location is  often simple if you have a visual
fault locator or VFL, which is a bright red laser coupled
into the optical fiber that allows testing continuity,
tracing fibers or finding bad connectors at patch panels.

For longer cables, an OTDR will be useful.  Outside
plant networks should use the OTDR to document the cable
plant during installation, so during restoration a simple
comparison of installation data with current traces will
usually find problems. OTDRs can also find non-catastrophic
problems, for example when a cable is kinked or stressed, so
it only has higher loss, which can also cause network
problems.

Tools and Components

Once you find the problem, you have to repair it. Repair
requires having the right tools, supplies and trained
personnel available. Besides the test equipment needed for
troubleshooting, you need tools for splicing and
termination, which may include a fusion splicer for outside
plant cables. You also need components necessary for
restoring the cable plant.

For every installation, a reasonable amount of excess cable
and installation hardware should be set aside in storage for
restoration. Some users store the restoration supplies along
with documentation in a sealed container ready for use.
Remember that the fiber optic patchcords that connect the
electronics to the cable plant can be damaged also, but are
not considered repairable. Just keep replacements available.

One big problem in restoring damaged cables is pulling the
two cable ends close enough to allow splicing them together.
You need several meters of cable on each end to strip the
cable, splice the fibers and place them in a splice closure.
Designing the cable plant with local service loops is
recommended. If the cable ends are too short , or the
damaged cable is underground or buried, you will have to
splice in a new section of cable. Since the restoration
cable must match the damaged cable or at least have a
greater nuber of fibers, the best source of cable for
restoration is cable leftover from the original
installation. Manufacturers also can supply cable
restoration kits that include cable and splice closures.

What else besides cables and cable plant hardware should be
in a restoration kit? You should have a termination or
mechanical splice kit and proper supplies. For splices, you
need splice closures with adequate space for a number of
splices equal to the fiber count in the cable.  All
these should be placed in a clearly marked box with a copy
of the cable plant documentation and stored in a safe place
where those who will eventually need it can find it fast.

Preparing nd Training
Personnel

Personnel must be properly trained to use this equipment and
do the troubleshooting and restoration. And, of course, they
must be available on a moments notice. The biggest delay in
restoring a fiber optic communications link is often the
chaos that ensues while personnel figure out what to do.
Having a plan that is known to the responsible personnel is
the most important issue.

Major users of fiber optics have restoration plans in place,
personnel trained and kits of supplies ready for use. It’s
doubtful that most premises users are ready for such
contingencies. Users may find that the cost of owning all
this expensive equipment is not economic. It may be
preferable to keep an inexpensive test set consisting of a
VFL and OLTS at each end of the link and having an
experienced contractor on call for restoration.

Managing A Fiber Optic
Project

Managing a fiber optic project can be easiest part of the
installation if the design and planning have been done
thoroughly and completely, or, if not, the hardest. But even
assuming everything has been done right, things will still
probably go wrong, so planning for the unexpected is also
very important. Here are some guidelines for managing the
project that can minimize the problems and help in their
speedy solution.

Managing a fiber optic project can be easiest part of the installation if the design and planning have been done thoroughly and completely, or, if not, the hardest. But even assuming everything has been done right, things will still probably go wrong, so planning for the unexpected is also very important. Here are some guidelines for managing the project that can minimize the problems and help in their speedy solution. See
the FOA YouTube Video on Project Management 

On Site Management and
Supervision

First, someone has to be in charge, and everyone involved
must know they are the boss, including them. During the
project, they must be readily available for consultation and
updates. While this may sound obvious, sometimes the network
user’s representative has other responsibilities (like
managing an IT department) and may not be able or willing to
direct full attention to the project. Whoever is assigned
the task of managing the project must be involved and
available, preferably on the job site, full time. If
necessary, delegate responsibility to the contracting
construction supervisor with requirements for daily reports
and personal updates.

Make certain that everyone responsible for parts of the
project have appropriate documentation and have reviewed the
installation plan. Everyone should have toured the relevant
job sites and be familiar with locations. They must also
know who to contact about questions on the sites, within the
network user, the contractor and any outside organizations
such as local governments or utilities. Everyone needs to
have contact information for each other (cell phones
usually, since email may be too slow and instant messaging
will probably not be available to field workers.) The onsite
supervisor should have a digital camera and take plenty of
photos of the installation to be filed with the
documentation for future reference and restoration.

Locations of components, tools and supplies should be known
to all personnel. On larger jobs, managing equipment and
materials may be a full time job. Special equipment, like
splicing trailers or bucket trucks, should be scheduled as
needed. Rental equipment should be double checked with the
suppliers to ensure delivery to the job site on time.
Contacts for vendor technical support should be noted on
documentation for the inevitable questions arising during
installation.

Contacts with Local
Authorities

Outside plant installs may require local authorities to
provide personnel for supervision or police for protection
or traffic management on public job sites, so they must also
become involved in the scheduling. If job inspections are
required, arrangements should be made so that the job
interruptions for inspections are minimized. Supervisory
personnel must be responsible for job site safety and have
appropriate contact information, including for public
services like police, fire and ambulance.

If the project is large enough to last several days or more,
daily meetings to review the day’s progress are advisable.
At a minimum, it should involve the onsite construction
supervisor and the network user’s person in charge of the
project. As long as things are going well, such a meeting
should be short. On longer projects, overnight security
personnel at job sites should have contact information for
the job manager who must be available 24/7 as well as public
service contacts.

Continuous Inspection,
Testing and Corrections

Inspection and testing of the installed cable plant should
not be left until after the job is completed. Testing
continually during installation can find and fix problems
such as cable stresses or high termination losses before
those problems become widespread.  Each installer doing
testing should have documentation with loss budget
calculations and acceptable losses to use for evaluating the
test results. Installers should be double-checking each
other’s work to ensure quality.

What do you do when (not if) things go wrong? Here judgment
calls are important. When something happens, obviously it is
the responsibility of the onsite supervisor to decide
quickly if they can take care of it. If not, they must know
who needs to be brought in and who needs to be notified. By
reviewing progress regularly, disruptions can be minimized.
Equipment failures, e.g. a fusion splicer, can slow
progress, but other parts of the project like cable laying
can continue, with splicing resumed as soon as replacement
equipment is available. Problems with termination should be
reviewed by an installer with lots of experience and the
cure may require new supplies or turning termination over to
more experienced personnel. Never hesitate to call vendor
support when these kinds of questions or problems arise.

Following the completion of the install, all relevant
personnel should meet, review the project results, update
the documentation and decide if anything else needs to be
done before closing the project.

Planning
For
A Safe Installation

Safety
is an important part of the planning process for any fiber
optic installation. Later in this chapter, we have a
section called ” Safety In Working With Optical Fiber”
that covers the issues specific to dealing with optical
fiber when preparing cables and splicing, terminating and
testing them. But with any installation there are many
other aspects of safety that the installer must consider.

Work
areas for OSP installation are often near roads, railways,
utilities or other areas with potential hazards. Digging
trenches or directional boring requires knowing where
underground utilities are located and confirming their
locations before final digging. Premises installations
often require working near power cables and other indoor
utilities, as well as workers who may be in a building
during the installation.

The
installer is expected to know and follow all laws, codes
and local requirements for safe installations such as
those by agencies like OSHA in the USA. Workers should be
trained in these practices also. Work sites should have
safety regulations posted including required safety gear
to be worn by workers and supervisors should monitor the
site to ensure these rules are followed.

Getting trained specifically in fiber optic network design
is available through some

Getting trained specifically in fiber optic network design is available through some FOA-Approved
schools . The material is covered in part in some advanced fiber optic courses offered by the FOA-approved schools and by large manufacturers who help you understand how to build networks using their products. The FOA has a fiber optic design certification ( CFOS/D .)