15-02-2013, 02:47 PM
Fiber Optic Network
Fiber Optic Network.docx (Size: 38.72 KB / Downloads: 19)
In the telcos, singlemode fiber 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 fiber optics except the connection to the home. Fiber 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 fiber optics.
CATV companies "overbuild" with fiber. They lash fiber cable onto the aerial "hardline" coax used for the rest of the network or pull it in the same conduit underground. The fiber 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 fiber also gives them a return path which they use for Internet and telephone connections, increasing their revenue potential.
LANs (local area networks) use fiber 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 fiber offers higher bandwidth for future expansion. Most large corporate LANs use fiber backbones with copper wire to the desktop. Fiber to the desk can be cost effective if properly designed.
Lots of other networks use fiber. CCTV is often on fiber for it's distance capability. Industrial plants use lots of fiber 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. Airplanes use it for that reason too, but also like the lighterweightof fiber.
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'tno substitute for common sense here!
Fiber'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 fiber. 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 fiber, you only need passive patch panels locally to allow for moves. Upgrades are easy, since the fiber is only loafing at today's network speed!
Is Copper Really Cheaper Than Fiber?
When it comes to costs, fiber optics is always assumed to be much more expensive than copper cabling. Whatever you look at - cable, terminations or networking electronics - fiber costs more, although as copper gets faster (e.g. Cat 6) it gets more expensive, almost as much as fiber. So isn't it obvious that fiber networks are more expensive than copper? Maybe not! There is more to consider in making the decision.
Why Use Fiber?
If fiber is more expensive, why have all the telephone networks been converted to fiber? And why are all the CATV systems converting to fiber too? Are their networks that different? Is there something they know we don't? Telcos use fiber 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 fiber 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 fiber for economic reasons, but their cost justification requires adopting new network architectures to take advantage of fiber's strengths. A properly designed premises cabling network can also be less expensive when done in fiber instead of copper. There are several good examples of fiber being less expensive, so lets examine them.