Fiber optic monitor for measuring vibration and acceleration of a load object

摘要

A vibration sensor 24 is disclosed which uses a piezoelectric crystal 26 to electrically modulate the phase of a laser beam using a phase modulator 28 producing a linearly phase modulated light beam. A DC bias can be provided by a battery 60 while a photocell 64 can provide the DC bias along with a calibration signal. The sensitivity of the sensor 24 can be doubled by passing the light beam through the sensor 24 twice using a reflector 74. By routing optical fibers 20, 22 and 31 carrying a reference beam and a sensing beam along the same physical path mechanical stress effect noise can be removed.