- Fiber Optic Installation
- All fiber optic applications are not the same. At the FOA, we're mainly concerned with communications
fiber optics - telco, CATV, LAN, industrial, etc., but fiber optics are also used in medical or nondestructive testing
inspection and lighting.
- Even
within communications applications, we have applications that differ widely in usage and in methods of installation. We
have "outside plant" fiber optics as used in
telephone networks, CATV, metropolitan networks, utilities, etc. or
"premises" fiber optics as found in buildings and campuses. We have
fiber on "platforms" like cars, planes and ships (and the space
station.) Just like "wire" which can mean lots of different
things - power, security, HVAC, CCTV, LAN or telephone - fiber optics
is not all the same.
- Since all these applications require different installation procedures, let's look at them in more detail.
- Outside Plant (OSP)
Direct Burying Cable By Plowing It In
Telephone companies and the Internet (which started on the telco
backbone) all use lots of fiber optics, all of which is singlemode and
most of which is outside buildings. It hangs from poles (aerial), is
buried underground directly or pulled through conduit or is sometimes
even submerged underwater. Most of it goes relatively long distances,
from a few thousand feet to hundreds or thousands of miles (or
kilometers) mainly in point-to-point links connecting phone switches.
FTTH Optical Network Unit Electronics
- One
telco application is different, FTTH (fiber to the home.) Here the
connection is from a phone switch in a central office or pedestal to
the home. Most systems use passive optical network (PON) architectures
with signals going through splitters that allow up to 32 users to share
one link and carry bidirectional signals. These bidirectional signals,
some carrying CATV too, require APC (angled PC) connectors.
FTTH in new home construction is virtually all run underground in
conduit while rebuilds in older neighborhoods may use aerial or
underground construction. One new development is the usage of prefab
cabling already terminated with weather-sealed connectors.
CATV Amps and Splices On Aerial Cable
- CATV
systems also use lots of singlemode fiber in the backbone, using an
overbuild architecture, bypassing coax already installed to connect
local nodes that serve fewer subscribers with higher quality signals.
The big advantage for CATV is reliability, as fiber is much more
reliable than copper systems. Most CATV is aerial except in newer
residential developments. Most CATV systems are analog optical
conversions of coax signals, so reflectance of connectors is a
big problem, requiring APC (angled PC) connectors.
Coils of OPGW On A High Voltage Tower Spliced To Underground Fiber Optic Cable
- Utilities
also use lots of fiber. Many new high voltage distribution lines have
optical fibers in the center of the ground wire (OPGW - optical power
ground wire) that are used for grid management and communications,
sometimes even leasing lines to telcos for long distance signals.
Utilities also use fiber in substations for control signals, since
fiber is not affected by high voltages or electrical noise. Unlike the
long distance links, these fiber links generally use multimode fiber,
sometimes even step-index PCS fibers for their low speed signals.
Traffic Control Cable Spliced In Pedestal- Municipalities
are becoming big users of optical fiber too. Rather than use lots of
telco phone lines for data, it's usually cheaper to install their own
town-wide network. Adding traffic controls and CCTV surveillance
cameras is also common. Some cities have gone ahead and offered
connections on their own data network to businesses and homes when
telcos or CATV companies are not offering broadband services at
adequate speeds. Again, most of these networks are singlemode fiber,
often underground in existing conduits but sometimes on utility poles.
Outside Plant Installation
- Most
outside plant installations are singlemode fiber, and telco cables
often have very high fiber
counts, up to 288 fibers or more, with a growing percentage being
ribbon cables. CATV or utilities use more loose tube cables with lower
fiber counts. Cable designs are optimized for the
application: cables in conduit for pulling tension and resisting
moisture, buried cables for resisting moisture and rodent damage,
aerial for continuous tension and extreme weather and undersea for
resisting moisture penetration. Installation may require special equipment
like pullers or plows, and even trailers to carry giant spools of
cable. Undersea applications require special cable-laying ships.
- OSP
cables are generally loose tube, ribbon or slotted core design. Jackets
are chosen to withstand an outdoor environment appropriate for the
application, usually black polyethelyne (PE.). Strength members
must be strong enough to absorb all the tension loads in the
installation process or long term loads from aerial installation.
Cables usually include fiberglass rod
stiffeners in the center to prevent kinking. Jackets may be
doubled with armor between them to prevent rodent penetration or
crushing or strength member to allow pulling by the jacket. More on
cables: 1, 2.
Cables
should be pulled with swivel pulling eyes to prevent causing a twist in
the cable. OSP installations in conduit may require lubrication to
reduce frictional loads and/or intermediate pulls. Intermediate pulls
require pulling the cable to a point, laying onthe ground in a "figure 8"
pattern to prevent putting a twist in the cable, then pulling the next
section. Care should be taken to not pull cable around courners too
tightly, with a minimum bend radius of 20 times the cable diameter
under tension, although cable can have a bend radius of 10 times the
cabel diameter under no tension.-
Long distances mean cables are spliced together for higher reliability
and lower loss, since cables are not manufactured longer than about
4-12 km (2.5-7 miles) depending on cable type, and most splices are by
fusion splicing. Splices are placed in sealed splice closures designed
for the particular application (buried, pedestal, aerial, etc.)
Singlemode cable is generally not field terminated, since polishing for
low loss and reflectance requires much care and is hard to do by hand.
Connectors (generally SC or LC styles) on factory made pigtails are
usually fusion spliced onto the end of the cable.
- After installation,
every fiber and every splice are generally tested with an OTDR and data
stored for future reference in case of damage requiring restoration.
- For
outside plant networks, the installer usually has a temperature
controlled van or trailer for splicing and/or a bucket truck for aerial work.
Installation equipment may include fusion splicers, OLTSs, OTDRs and
other special cable handling equipment which can be quite expensive.
- Many outside plant telephone installs for the big telcos are done by the
telco themselves, while a small number of large, specialized installers
do installs for independent telcos, CATV companies, utilities and
municipalities.
- Premises Cabling
By contrast, premises cabling- cabling installed in a building or on a
campus - involves shorter lengths, rarely longer than a few hundred
feet, with fewer fibers per cable typically. The fiber is mostly
multimode, except for the forward-thinking user who installs hybrid
cable with both multimode and singlemode fibers for future high
bandwidth applications. Premises cabling standards, also called
structured cabling standards, are covered in the TIA-568 standard for
commercial building cabling, installed in a "star architecture" Fiber
has become so popular for premises applications that the appropriate
industry standard, TIA-568, allows fiber in the backbone, to the
desktop, in zone cabling and centralized fiber cabling. Centralized fiber cabling
uses no copper cables at all and allows siting all the electronics in
the main computer room and at the user, not requiring hubs or switches
in telecom closets. Centralized fiber cabling therefore needs no power,
grounding or AC in telecom rooms, nor in fact, even a telecom room
itself, and thereby offers considerable potential for cost savings if
properly designed.
 Typical LAN Fiber Equipment
- LANs
- local area computer networks - are one of the most common premises
applications for fiber. Since fiber was first used for LANs, speeds
have increased from 10 Mb/s (millions of bits per second) to
10 Gb/s (billions of bits per second) with 40 or even 100 Gb/s on the
horizon. During that time, most fiber installations used 62.5/125 (OM1)
or FDDI-grade fiber (FDDI was the first 100 Mb/s network based solely on
fiber) while copper went through 2 grades of coax cable, shielded
twisted pair and Categories 3, 4, 5, 5E, 6 and 6A unshielded twisted
pair copper (UTP.)
LANs
today combine fiber backbones, Cat 5e or Cat 6 to desktop computer
users and fiber or copper to wireless access points, generally
following the TIA-568 standard's guidelines. With more users
choosing wireless for mobility, not only for laptops but for mobile
wireless devices like smart cell phones, desktop wiring is becoming
less common and multiple wireless access points more widely deployed.
Many telecom rooms (which used to be called telecom "closets" before
they became filled with LAN electronics, still contain large amounts of
copper (blue in the photo below) and fiber (orange.)
Telecom room with copper and fiber connecting network electronics
- Since the advent of Gigabit Ethernet which uses
VCSEL lasers for their high modulation speed, an old fiber design from
1980, 50/125 fiber (OM2), which is more compatible with lasers than
62.5/125, has become the fiber of choice for most LAN installations.
Manufacturers have further developed 50/125 fiber into "laser
optimized" fiber (OM3) that has higher bandwidth capability and is the
ideal choice for current installations. Manufacturers are working on even higher performance 50/125 fiber (perhaps to be called OM4) for 40
or even 100 Gb/s networks. Still, many users install hybrid cables with
both OM3 and singlemode fibers in backbones since SM fiber is cheap and
provides virtually infinite bandwidth for currently unknown future uses.
 Fiber and Copper Cables in Cable Trays
Premises
cables can be installed in cable trays, conduit, innerduct or special
types of cable hooks. Installation of the cable must be carefully done
to prevent snagging and kinking the cable as it is pulled among the
numerous hazards in a typical building installation. Fiber optic cables
should not be mixed with copper cables as the heavier copper cables can
stress the fiber cables. Sometimes the fiber is hung below cable trays
to protect it from masses of copper. Vertical cable runs are common in
buildings. Vertical cables are preferably installed by dropping the
cable down rather than pulling them up, using proper hangers and
service loops to prevent stressing cables.
SANs
or storage area networks in data centers are another popular fiber
application. At 10 Gb/s, UTP transceivers consume vast amounts of
power, 4-10 times more than fiber transceivers, so most data centers
use coax for short links and fiber for over 10 meters. Data centers
often run cables under the floor. Most false floor systems include
cable trays for fiber optic cables. An armored indoor cables is
sometimes used in underfloor applications to protect the fiber from
crushing by other cables.
 Underfloor fiber optic cable in tray
CCTV Cameras
Security
systems use lots of fiber. Airports and many public buildings have CCTV
cameras located too remotely for coax connections without repeaters, so media
converters or fiber-compatible cameras are used. Where security is
important, like airports, cables are usually run in metal conduit where
fiber's small size is a big advantage. Fiber bandwidth allows
multiplexing many cameras onto one fiber too. Most security systems
offer fiber options or can be easily converted with a commercial media
converter. Fiber can even be used for a perimeter intrusion sensor.
 CCTV camera in Boston "Big Dig" tunnel
 Aerial CCTV camera installation
Industrial
applications of fiber are widespread. Fiber's distance and bandwidth
capability is less an issue here, but immunity to noise and ruggedness
is very important. Data gathering and machine control (especially
robots) are big applications. Power controls are another important
application. For protection, cables are often run in metal conduit where
fiber's small size is another big advantage.
Premises Installation
- Common to all premises
applications is short links compared to OSP. LANs typically have links
shorter than 300m. Industrial systems are similarly sized. Even
security cameras run only 1-2Km typically, except some links at major
airports.
Splicing is practically unknown in premises applications. Building cables are generally installed in one piece. Cables
between buildings can be bought with double jackets, PE for outside
plant protection over PVC for building applications requiring
flame retardant cable jackets, so cables can be run continuously
between buildings. Today's connectors often have lower loss than
splices, and patch panels give more flexibility for moves, adds
and changes.
Premises
fiber optic cable is usually tight buffer cable. Simplex or zipcord
cable is used for some applications where only one or two fibers are
needed. Backbone cables, which may contain 24-96 fibers, are usually
distribution style cables. Smaller fiber counts and harsh (e.g.
industrial) environments often require more rugged cables like breakout
designs. All cables installed indoors must be rated for flammability
per the NEC, CEC or similar safety organizations worldwide. More on cables: 1, 2.
Most connectors are SC or ST style with LCs becoming more popular since
most transceivers of Gb/s speeds and above use LCs. Termination is
usually by installing connectors directly on the ends of the fibers,
primarily using adhesive or prepolished splice techniques. Testing is
done by a source and meter, but every installer should have a
flashlight type fiber tracer to check fiber continuity and connection.
Unlike the outside plant technician, the premises cabler (who is often
also installing the power cable and Cat 5/5e/6/6A for LANs too!) only
needs a termination kit and OLTS or source and power meter test kit.
The premises installer probably has an investment of less than $2,000
in tools and test equipment.
- The Installers
There are thousands of cabling installers who do fiber optic
work. They've found out it isn't "rocket science,"
and their initial investment in training, tools and test
equipment is rapidly paid back.
Few installers do both outside plant and premises cabling because of the difference in the applications. The
companies that do both are usually very large and often have separate
divisions doing each with different personnel. Most contractors
do nothing but premises cabling.
Fiber Optic Cable Plant Installation
Fiber
optic cable may be installed indoors or outdoors using several
different installation processes. Outdoor cable may be direct
buried, pulled or blown into conduit or innerduct, or installed
aerially between poles. Indoor cables can be installed in raceways,
cable trays above ceilings or under floors, placed in hangers, pulled
into conduit or innerduct or blown though special ducts with compressed
gas. The actual installation process will depend on the nature of the
installation and the type of cable being used.
Since there are so many types of
fiber optic cable and so many different applications, it is hard to
cover each application in detail. However there are some general rules
that should be followed:
Safety
Safety
on the job site
must be the number one concern of everyone - installers, supervisors,
owners, etc. Besides the usual safety issues for construction,
generally covered under OSHA rules, fiber optics adds concerns for eye
safety, chemicals, sparks from fusion splicing, disposal of fiber
shards and more. Before beginning any installation, safety rules should
be posted on the job site and reviewed with all onsite personnel.
Chemical MSDS (material safety data sheets) for any hazardous
substances should be available from the supervisor. All
personnel must wear the usual construction safety gear plus everyone
must wear eye protection whenever working with fiber. Here are safety rules for fiber optics.
Training
All
personnel involved in any fiber optic installation must be properly
trained and familiar with the tools, components and processes to be use
during the installation. Training must also include all safety
procedures. An installer should never use the job site to learn new
products or techniques. Test equipment should be checked for proper
operation, including condition of reference cables, charge level of
batteries and tested to ensure proper measurements can be made.
Personnel should have proof of basic knowledge, skills and abilities
(KSAs) such as the FOA CFOT certification.
Pre-Installation
No
installation should begin until there is a complete design, all
equipment and components have been chosen, the cable routing is
determined and any permits or coordination with other groups is ready.
Cable documentation should be started before installation so the
installation is properly documented and ready for labelling and
recording test data. Documentation will facilitate installation, allow planning for upgrades and provide data needed for restoration.
Components must be ordered and delivered to the job site before
installation can begin. Relevant
personnel who will be affected by the install, for example those
located in the installation area or who may lose communications
services, must be notified. If the installation takes more than one day, arrange security to guard the equipment and components left on the construction site.
More on fiber optic network design.
REMEMBER:
Safety rules should be posted on the job site(s) and reviewed with all
supervisors, installation personnel and any affected parties.
During The Installation
Inspect
all installation workmanship during the installation itself so any
problems can be identified and solved before they become major issues. Daily
supervisors and installers should review processes, progress on the job
and test data. All affected personnel should receive immediate notification of problems and solutions, shortages, etc.
Be
careful when installating cables to avoid stress, hazards that may snag
cables and kink them or installing cables where heavier cables may be
placed on top of them.
Bundling cables for neatness is fine, but
be careful using cable ties. Tightening them can put harmful stress on
the fibers (or pairs in UTP copper cables), so hand tighten them and
cut off the excess length. Even better, use soft "hook and loop" ties
that can be reopened to move cables.
Safety and Building Codes
All
installations must follow building and fire codes for safety. All
components must be appropriately rated for the application (premsies or
OSP) and properly installed. Indoor applications require rated
fire-retardant components and firestopping at walls or floor
penetrations. All metal components of a cabling system must be properly
grounded and bonded. Documentation should include all issues required
by building codes.
The National Electrical code now requries removal
of all "abandoned" cabling as a fire hazard. This should be considered
as part of the planning of an installation as cable removal should be
done first if possible to avoid interference with newer cables.
After completion of cable plant installation
Inspect
the workmanship of all parts of the installation. This includes visual
inspection of the work site for neat installation workmanship and reviewing test data on cable plant. Appropriate personnel should set
up and test the communications system that will operate over the fiber
optic cable plant to ensure it is proper for that system.
Before the job is completed, it is important to update and complete documentation and the restoration plan. Cable and component remainders should be stored along with the restoration plan and documentation in case of future network outages requiring cable plant restoration.
Read more on installation.
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