Getting Started in Fiber Optics
- You need tools, test
equipment and - most of all - training!
This guide will help you get
started by providing very basic information (we will also point
you to more advanced studies) and demonstrating that you don't
need to break the bank to break into the field.
- What is "Fiber Optics"?
And a short history.
- It's the communications technology
that works by sending signals down hair thin strands of glass
fiber (and sometimes plastic fiber.) It began about 30 years
ago in the R&D labs (Corning, Bell Labs, ITT UK, etc.) and
was first installed in Chicago in 1976. By the early 1980s, fiber
networks connected the major cities on each coast.
- By the mid-80s, fiber was replacing
all the telco copper, microwave and satellite links. In the 90s,
CATV discovered fiber and used it first to enhance the reliability
of their networks, a big problem. Along the way, the discovered
they could offer phone and Internet service on that same fiber
and greatly enlarged their markets. Now, even fiber to the home (FTTH) is cost effective.
- Computers and LANs started using
fiber about the same time as the telcos. Industrial links were
among the first as the noise immunity of fiber and its distance
capability make it ideal for the factory floor. Mainframe storage
networks came next, the predecessors of today's fiber SANs (storage
- Other applications developed
too: aircraft, ship and automobile data busses, CCTV for security,
even links for consumer digital stereo!
- Today fiber optics is either
the dominant medium or a logical choice for every communication
Which Fiber Optics?
Whenever you read an article
or talk to someone about fiber optics, you need to know the point
of view of the writer. Fiber optics, you see, is not all the
same. Is the writer discussing "outside plant" fiber
optics as used in telephone networks or CATV. Or is the article
about "premises" fiber optics as found in buildings
Just like "wire" which can mean lots of different things
- power, security, HVAC, CCTV, LAN or telephone - fiber optics
is not all the same. And this can be a big source of confusion
to the novice. Lets define our terms.
Outside Plant (OSP)
Telephone companies, CATV and the Internet all use lots of fiber
optics, most of which is outside buildings. It hangs from poles,
is buried underground, pulled through conduit or is even submerged
underwater. Most of it goes relatively long distances, from a
few thousand feet to hundreds of miles.
Outside plant installations are all singlemode fiber (we'll define
the fiber types in the next chapter), and cables often have very
high fiber counts, up to 288 fibers. Cable designs are optimized
for resisting moisture and rodent damage. Installation requires
special pullers or plows, and even trailers to carry giant spools
Long distances mean cables are spliced together, since cables
are not longer than about 4 km (2.5 miles), and most splices
are by fusion splicing. Connectors (SC, ST or FC styles) on factory
made pigtails are spliced onto the end of the cable. After installation,
every fiber and every splice is tested with an OTDR.
If this sounds like big bucks, you are right! The installer usually
has a temperature controlled van or trailer for splicing and/or
a bucket truck. Investments in fusion splicers and OTDRs can
add up to over $100,000 alone.
Contractors doing outside plant work are few and far between.
Most outside plant telephone installs are done by the telco themselves,
while a small number of large, specialized installers do CATV
By contrast, premises cabling- cabling installed in a building
or campus - involves short lengths, rarely longer than a few
hundred feet, with 2 to 48 fibers per cable typically. The fiber
is mostly multimode, except for the enlightened user who installs
hybrid cable with both multimode and singlemode fibers.
Splicing is practically unknown in premises applications. 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
Most connectors are ST style with a few SCs here and there. Termination
is by installing connectors directly on the ends of the fibers,
primarily using adhesive technology or occasionally some other
variety of termination method. Testing is done by a source and
meter, but every installer should have a flashlight type 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 for LANs too!)
probably has an investment of less than $2,000 in tools and test
There are thousands of cabling installers who do fiber optic
work. They've found out it isn't "rocket science,"
and their small initial investment in training, tools and test
equipment is rapidly paid back.
Few installers do both outside plant and premises cabling. The
companies that do are usually very large and often have separate
divisions doing each with different personnel. Most contractors
do nothing but premises cabling.
Fiber vs Copper you may be surprised by who wins
If you are already terminating
copper wire then you are well along in learning to install fiber.
Twenty five years ago, fiber was just
being introduced and required PhD's from Bell Labs to install
it while copper wire was easy to install. Today it is often the
opposite. Because fiber is so powerful, at today's network speeds
fiber is hardly working hard at all and can look to the future
of ten gigabit speeds with confidence. Copper on the other hand,
can handle gigabit Ethernet but only if it is carefully installed
and tested with very expensive test equipment and components.
Even the experts have to be very careful because it has little
Also, if you are currently working
with copper, you also have to know that LAN copper cable is delicate.
It only has a 25 pound pulling tension limit and kinks will ruin
the high speed performance. With fiber - even though it's glass
fiber - it has more strength and greater tolerance to abuse than
copper wire. (What do you think gives the strength to your "fiberglass"
OK, you might say, I can buy
everything you've said so far, but isn't fiber more expensive?
Telcos and CATV operators use fiber because it's much cheaper.
They optimize their network to take advantage of fiber's speed
and distance advantages. In LANs, you need to follow the new
EIA/TIA 568 B.3 standard to optimize the fiber usage, and then
it can be cheaper than copper. How about test equipment? Guess
again Fiber optic test equipment costs lots less than Cat
5e/6 testers. See Networks where we will
show you how the setup for a fiber network has some surprising
The Secret To Success In Fiber
Optics Is Training!
You wouldn't try to drive a truck or fly a plane without taking
lessons. Likewise for improving your golf or tennis game. Well,
the secret to fiber optics is training too. With some basic knowledge
and hands-on practice gained in a training course, fiber is pretty
easy to install.
Where to get training?
Well, you can start right here, of course! But this guide is
only designed to get you started and you should have "hands-on"
training leading to a recognized certification program to be
qualified to install fiber. First, check the VDV
Works website for information on advanced training and organizations
that offer training. Also check the website of the Fiber Optic
Association at http://www.TheFOA.org. for the leading fiber optic
certification program in the industry. Finally, take advantage
of the training offered by manufacturers and distributors whenever
you can, often this training is free or cheap! (but limited to
the equipment being "pushed" of course.)
See the section
on training at the end for more
Most of what we call standards are voluntary standards, created
by industry groups to insure product compatibility. They are
not "codes" or actual laws that you must follow to
be in compliance with local ordinances.
Standards like EIA/TIA 568 ( from the Electronic Industries
Alliance/ Telecommunications Industry Association) which covers
all of the things you need to know to install a standard premises
cabling network are good guidelines for designs, but just guidelines
- they are not mandatory. Standards for fiber optic components
and testing have been set by several groups, but most in the
US follow the EIA/TIA developed FOTP's (fiber optic test procedures)
for testing. Some of the EIA procedures are also called OFSTP
(optical fiber system test procedures) like OFSTP-14 for the
installed cable plant.
Standards for optical power measurements are set by NIST (the
US National Institute of Standards and Technology)
The only common mandatory standard is the NEC 770 (National Electrical
Code). The NEC specifies fire prevention
standards for fiber optic cables. If a cable doesn't have
a NEC rating - don't install it - it won't pass inspection!
A complete listing of the EIA/TIA
standards is on the website
of The Fiber Optic Association. Information on the EIA/TIA standards
can be found on the website of most of he suppliers of structured
Before we get started - Safety
You might think that eye damage
from working with lasers would be the big concern in fiber optic
installations. The reality is that high power lasers burning
holes in metal or burning off warts mostly have little relevance
to your typical fiber optic installation. Optical sources used
in fiber optics are of much lower power levels (The exception
is high power DWDM or CATV systems). Of course, you should always
be careful with your eyes, especially when using a fiber optic
microscope. NEVER look into a fiber unless you know no light
is present - use a power meter to check it - and anyway, the
light is in the infrared and you can't see anything anyway!
The real safety lecture
will always be about small scraps of glass cleaved off the ends
of the fibers being terminated or spliced. These scraps are very
dangerous! The cleaved ends are extremely sharp and can easily
penetrate your skin. If they get into your eyes, they are very
hard to flush out. Don't even think about what happens if you
eat one. Safety glasses are a must!
Always follow these rules when
working with fiber.
1. Dispose of all scraps properly.
2. Always use a properly marked container to dispose of later
and work on a black pad which makes the slivers of glass easier
3. Do not drop them on the floor where they will stick in carpets
or shoes and be carried elsewhere.
4. Do not eat or drink anywhere near the work area.
Fiber optic splicing and termination
use various chemical adhesives and cleaners as part of the processes.
Follow the instructions for use carefully. Remember, even simple
isopropyl alcohol, used as a cleaner, is flammable.
Zero Tolerance for Dirt
With fiber optics, our tolerance
to dirt is near zero. Airborne particles are about the size of
the core of SM fiber- they absorb lots of light and may scratch
connectors if not removed! Dirt on connectors is the biggest
cause of scratches on polished connectors and high loss measurements!
1. Try to work in a clean area.
Avoid working around heating outlets, as they blow dust all over
2. Always keep dust caps on connectors, bulkhead splices, patch
panels or anything else that is going to have a connection made
3. Use lint free pads and isopropyl alcohol to clean the connectors.
4. Ferrules on the connectors/cables used for testing will get
dirty by scraping off the material of the alignment sleeve in
the splice bushing - creating a 1-2 dB attenuator. You can see
the front edge of the connector ferrule getting black! Use the
metal or ceramic alignment sleeve bulkheads only for testing.