Networks
In the telcos, singlemode fibre
is used to connect long distance switches, central offices and
SLCs (subscriber loop carriers, small switches in pedestals in
subdivisions or office parks or in the basement of a larger building).
Practically every telco's network is now fibre optics except
the connection to the home. Fibre to the home is not yet cost
effective - especially since most homes do not want (nor are
willing to pay) for the high speed services that would justify
fibre optics.
CATV companies "overbuild" with fibre. They lash fibre
cable onto the aerial "hardline" coax used for the
rest of the network or pull it in the same conduit underground.
The fibre allows them to break their network into smaller service
areas that prevent large numbers of customers from being affected
in an outage, making for better service and customer relations.
The fibre also gives them a return path which they use for Internet
and telephone connections, increasing their revenue potential.
LANs (local area networks) use fibre optics primarily in the
backbone but increasingly to the desk. The LAN backbone often
needs longer distance than copper cable (Cat 5/5e/6) can provide
and of course, the fibre offers higher bandwidth for future expansion.
Most large corporate LANs use fibre backbones with copper wire
to the desktop. Fibre to the desk can be cost effective if properly
designed.
Lots of other networks use Fibre. CCTV is often on fibre for
it's distance capability. Industrial plants use lots of fibre
or distance and noise immunity. Utilities use it for network
management, liking its immunity to noise also. The military uses
it because it's hard to tap or jam. Aeroplanes use it for that
reason too, but also like the lighter weight of fibre.
Designing Cable Networks
I guess this is too big a topic for a overview! But we'll pass
along some hints to make life easier. First and foremost, visit
the work site and check it out thoroughly. Know the "standards"
but use common sense in designing the installation. Don't cut
corners which may affect performance or reliability. Consider
what are the possible problems and work around or prevent them.
There ain't no substitute for common sense here!
Fibre's extra distance capability makes it possible to do things
not possible with copper wire. For example, you can install all
the electronics for a network in one communications closet for
a building and run straight to the desktop with fibre. With copper,
you can only go about 90 meters (less than 300 feet), so you
need to keep the electronics close to the desk. With fibre, you
only need passive patch panels locally to allow for moves. Upgrades
are easy, since the fibre is only loafing at today's network
speed!
Is Copper Really Cheaper Than
Fibre?
When it comes to costs, Fibre optics is always assumed to be
much more expensive than copper cabling. Whatever you look at
- cable, terminations or networking electronics - fibre costs
more, although as copper gets faster (e.g. Cat 6) it gets more
expensive, almost as much as fibre. So isn't it obvious that
Fibre networks are more expensive than copper? Maybe not! There
is more to consider in making the decision.
Why Use Fibre?
If fibre is more expensive, why have all the telephone networks
been converted to Fibre? And why are all the CATV systems converting
to fibre too? Are their networks that different? Is there something
they know we don't?
Telcos use fibre to connect all their central offices and long
distance switches because it has thousands of times the bandwidth
of copper wire and can carry signals hundreds of times further
before needing a repeater. The CATV companies use Fibre because
it give them greater reliability and the opportunity to offer
new services, like phone service and Internet connections. 
Both telcos and CATV operators use fibre for economic reasons,
but their cost justification requires adopting new network architectures
to take advantage of fibre's strengths. A properly designed premises
cabling network can also be less expensive when done in fibre
instead of copper. There are several good examples of fibre being
less expensive, so lets examine them.
Industrial Networks
In an industrial environment, electromagnetic interference (EMI)
is often a big problem. Motors, relays, welders and other industrial
equipment generate a tremendous amount of electrical noise that
can cause major problems with copper cabling, especially unshielded
cable like Cat 5. In order to run copper cable in an industrial
environment, it is often necessary to pull it through conduit
to provide adequate shielding.
With fibre optics, you have complete immunity to EMI. You only
need to choose a cable type that is rugged enough for the installation,
with breakout cable being a good choice for it's heavy-duty construction.
The fibre optic cable can be installed easily from point to point,
passing right next to major sources of EMI with no effect. Conversion
from copper networks is easy with media converters, gadgets that
convert most types of systems to fibre optics. Even with the
cost of the media converters, the fibre optic network will be
less than copper run in conduit.
Long Cable Runs
Most networks are designed around structured cabling installed
per EIA/TIA 568 standards. This standard calls for 90 meters
(295 feet) of permanently installed unshielded twisted pair (UTP)
cable and 10 meters (33 feet) of patchcords. But suppose you
need to connect two buildings or more? The distance often exceeds
the 90 meters by the time you include the runs between the buildings
plus what you need inside each building.
By the time you buy special aerial or underground waterproof
copper cable and repeaters, you will usually spend more than
if you bought some outside plant Fibre optic cable and a couple
of inexpensive media converters. It's guaranteed cheaper if you
go more than two links (180 meters.)
Centralised Fibre LANs
When most contractors and end users look at fibre optics versus
Cat 5e cabling for a LAN, they compare the same old copper LAN
with Fibre directly replacing the copper links. The fibre optic
cable is a bit more expensive than Cat 5e and terminations are
a little more too, but the big difference is the electronics
which are $200 or more per link extra for fibre.
However, the real difference comes if you use a Centralised Fibre
optic network - shown on the right of the diagram above. Since
fibre does not have the 90 meter distance limitation of UTP cable,
you can place all electronics in one location in or near the
computer room. The telecom closet is only used for passive connection
of backbone fibre optic cables, so no power, UPS, ground or air
conditioning is needed. These auxiliary services, necessary with
Cat 5 hubs, cost a tremendous amount of money in each closet.
In addition, having all the fibre optic hubs in one location
means better utilisation of the hardware, with fewer unused ports.
Since ports in modular hubs must be added in modules of 8 or
16, it's not uncommon with a hub in a telecom closet to have
many of the ports in a module empty . With a Centralised Fibre
System, you can add modules more efficiently as you are supporting
many more desktop locations but need never have more than a one
module with open ports.
High Speed Networking
It was over a year after Gigabit Ethernet (GbE) became available
on fibre optics that it finally become available on Cat 5e. It
took another couple of years before GbE on copper became significantly
less expensive. In order to get GbE to work over Cat 5e, the
electronics must be very complicated, and consequently as expensive
as fibre. A newer version is in the wings, awaiting a Cat 6 standard,
but that means the version running over Cat 5e will be obsolete
before it even gets started! Finally, we went to a major distributor's
seminar on advanced cabling recently and the copper marketing
guy told us to go fibre for GbE.
Bottom Line
So when it comes to costs, looking at the cabling component costs
may not be a good way to analyse total network costs. Consider
the total system and you may find fibre looks a lot more attractive.
