- 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.
Additional reading on specific areas of cabling
installation: Premises
Cabling Installation, Outside
Plant (OSP) Cabling Installation
Read
more on installation.
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