Optical Communications, 2nd Edition

8.7 OPTICAL CIRCUIT SWITCHED NETWORKS

The alternative to addressed waveforms for achieving multiple accessing in networks is the use of circuit switching. Rather than depend on recognizeable addresses to separate channels, the network instead directly switches the optical paths to complete a link between a receiver and transmitter.

A circuit switched network is obtained by placing on–off switches (some-times called optical shutters) in the fiber paths interconnecting the receiver to the star distribution, as shown in Figure 8.17. The switch can be physically located at the star output or at the receiver input. By externally switching off the undesired channels, a direct link is maintained to the desired channel, ideally with no crosstalk interference. The switching can be converted upon command so that any receiver can be connected to any transmitter, while blocking off the other channels.

Each shutter in Figure 8.17 is separately accessible by a control signal.

Figure 8.17. Implementation of shutter switches in space switching network.

Figure 8.18. Spatial light modulator (SLM) shutter switch.

Several popular ways can be used to accomplish the shutter operation. One is by the use of spatial light modulators (SLM) in Figure 8.18. These devices correspond to a matrix of pixels, in ...