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 its distance capability. Industrial plants use lots of fibre for 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.
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.
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.