Rings

Written on 2:31 PM by ooe

Rings are used extensively in core and metropolitan networks because they offer a means of interconnecting a number of nodes (cities, towns) in a way that enables large capacities to be transported with resilience. The opto-electronic technology is the same as that needed for point-to-point unless WDM is involved. If a route fails another route can be found by sending traffic in the opposite direction round the ring as shown in.

The amount of fibre needed is considerably less than point-to-point networks, however there may be more civil works involved in serving a community as two fibre entry points are needed if strict route diversity is required. Furthermore if the ring is to be used to provide resilience, two optical paths and two sets of transceivers are needed to offer loop-back protection which increases the cost. Without loop back protection a unidirectional ring is vulnerable, as a single failure causes all of the traffic to be lost.