Fiber optic cable carries information through pulses of laser light, which are transmitted at one end and received to be finally decoded at the other. The pulses are turned on and off at great speed. Multiple streams of information can be carried at the same time by using multiple different wavelengths—colors—of light. The equipment to create the laser pulses keeps getting faster, but the same old fiber can be used to transmit the light it creates. New equipment is just slipped into the network.
The capacity of a network to relay information is referred to as bandwidth. Lots of bandwidth allows lots of information to be carried. Fiber has a lot of advantages over copper wire and coax cable, because it’s easier to maintain and delivers far more bandwidth.
The three biggest advantages of fiber are:
- Signals travel a long distance inside fiber cable without degradation— 20 miles or more, under certain circumstances. In contrast, as the distance traveled by a signal in a strand of copper wire increases, the bandwidth decreases. Short lengths of coax, for instance—the lengths typically found in a small building—can carry 1 Gbps. That’s a thousand times more bandwidth than a typical broadband service using DSL over copper wire, and 200 times more than typical broadband over cable TV coax. But those speeds are impossible over distances much longer than those lengths. With fiber the distance equation is simple: the closer fiber gets to a building, the faster the data service available to the residents and businesses within that building. Service providers have been bringing fiber closer and closer for years… and now they’ve managed to bring it right inside to the end user.
- Fiber cable is thin. In fact, fiber can be made thinner than a human hair, and carried on a thin ribbon (or “microduct”) of hollow plastic tubing, only an eighth of an inch wide. A typical fiber configuration with about 200 super-thin strands is about the thickness of a single standard coax cable.... and that same fiber cable could theoretically carry all the information being sent on Earth at any one time today. The bottom line: Fiber can be ‘hidden’ easily on the surfaces of walls in old construction.
- Fiber networks are upgraded by changing the electronics responsible for creating the light pulses that travel along the fiber, not by replacing the fiber itself. The nonconductive fiber strand is amazingly reliable. Nothing hurts fiber except a physical cut, or the destruction of the building in which it’s been installed. Passive Optical Networks, or PON’s, are the most common type of network. They employ a minimum of electronics— in fact, between the provider’s central office and the users, there are no electronics at all. This vastly improves network reliability.
Bandwidth providers are increasingly bringing fiber optics all the way to customer premises. That technology, referred to as FTTH (for “fiber to the home”) or FTTP (for “fiber to the premises”) or FTTx (for “fiber to everyplace”) is the gold standard. But in cases where the population density is too low, or where high-quality coaxial or copper networks exist, it may make more sense under some circumstances to bring fiber only partway to the customer. The fiber is then connected to the existing copper for the last “jump” to users’ homes.
As time goes on, fiber is moved closer to customers to provide more bandwidth. That approach is called FTTN for “fiber to the neighborhood” or “fiber to the node,” or (for even greater bandwidth) "fiber to the curb" (FTTC). Today, the impending bandwidth demand is so large, and FTTH construction prices so reasonable, that going straight to FTTH makes more economic sense. Single-family homes comprise the easiest group to equip with FTTH. It wasn’t until 2006 that apartment building and other multiple-dwelling-unit (MDU) structures in the US started to be served with FTTH in appreciable numbers. MDU fiber service is already common in Europe and Asia, however, so there is no “technology risk” in specifying FTTH now, in any circumstance.
