Image Number 2 for United States Patent #4182935.
Optical sensors may be arranged to give transmission or reflection of signals along optical fibers depending on the quantity to be measured. The outputs of several sensors may be simply multiplexed onto a single fiber (or pair) by putting a different delay line in series with each sensor. Similarly optical filters can be used separately or combined with the delay lines and/or space division multiplexing can be used to increase the number of sensors. Local frequency modulation of the sensors offer an additional means of multiplexing.