Abstract

Coherence multiplexing has been proposed as a means of accessing an array of fiber-optic interferometric sensors.¹ This paper reports the application of this technique to multiplexing binary encoded data. This application was evaluated in the experiment shown in Fig. 1 where the coherence multiplexer consisted of an array of interferometers (each of a different length) which shared a common path. Each Interferometer consisted of two arms, a sensor arm and a reference arm, which were equal in length. The sensor arms shared a single fiber which connected the interferometers with a pair of collimating objective lenses, choppers and mirrors separated from the fiber ends by different distances, thus providing a different delay for the reflection from each mirror. The source was a multimode laser diode with an optical power output of 2.5 mW. The reference arms consisted of a parallel array of delay lines in series with a single-phase modulator which imposed a sinusoidal phase carrier on each interferometer. Thus a detector tuned to the carrier frequency detected only power reflected from one channel by envelope detecting and low-pass filtering the ac signal from the photodiode.

© 1987 Optical Society of America