PASSIVE DEMODULATION OF MINIATURE FIBER-OPTIC-BASED INTERFEROMETRIC SENSORS USING A TIME-MULTIPLEXING TECHNIQUE

A passive demodulation technique suitable for interferometric interrogation of short optical cavities is described. It is based on time multiplexing of two low-finesse Fabry-Perot interferometers subject to the same measurand and with a differential optical phase of pi/2 (modulo 2-pi). Independently of the cavity length, two optical outputs in quadrature are generated, which permits signal reading free of fading. The concept is demonstrated for the measurement of vibration using a simple processing scheme.