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Fiber Optics in Sensors and Contr ol Systems

FIGURE 3.38 Point-to-point data link. 163

FIGURE 3.39 Daisy chain data bus.

illustrated in Fig. 3.35 is such a system, providing multiple access
points from remote terminals to a programmable controller processor.
A system with several repeater points is vulnerable to the loss of any
repeater, and with it all downstream points, unless some optical
bypass scheme is utilized. Figures 3.38 and 3.39 exhibit such a scheme.

3.12.6.2 Ring Coupler
A preferred choice among several current fiber-optic system designs
is the token-passing ring structure.
Signals are passed around the ring, with each node serving to
amplify and retransmit. Care must be taken to provide for a node
becoming nonoperational. This is usually handled by using some
type of bypass switching technique, given that the system provides