There are three main topologies for fiber optic networking: linear (or point-to-point), ring, and passive star. The first is the simplest to set up but, especially in linear topologies with hubs, is also easy to bring down. As all of the important fibers in the linear connection are in one place, an environmental problem in the area of that connection could bring down the network.
The ring method is to connect the various hosts in a (conceptually) circular pattern. In this way, a single downed host does not hurt any communication but lag time for hosts adjacent to the downed host might be longer.
Sprint has built its network backbone in a ring architecture called four-fiber, bi-directional line switched ring (4F BLSR). This structure allows for fast error recovery (see figure 1 below).
The final method is called passive star. Each host has has a fiber running from its transmitter to a passive cylinder. The cylinder has fibers fused out of it to all hosts on the network. When a host wishes to communicate to an other host(s), the message is sent to the cylinder which automatically broadcasts the message to all the other hosts. While tremendously fault tolerant (as any host can go down without affecting the network) and fast, it's wasteful of bandwidth and limited by the size of the cylinder.
Last Modified: 3/15/00
By Brian Patterson and
Erin Quealy