Multimode fiber-optic Mach-Zehnder interferometer and its use in temperature measurement.

A fiber-optic Mach-Zehnder interferometer with multimode fibers has been constructed, in which the fringe shift is detected by a spatial filtering detector. In this interferometer, throughput is much greater than in interferometers using single-mode fibers, but speckles disturb detection of the fringe shift. We have overcome this disadvantage by computer software; the interferometer measured temperature and a sensitivity of 72.3 +/- 1.2 fringes/ degrees C . m was obtained.