PASSIVE SIGNAL-PROCESSING FOR A MINIATURE FABRY-PEROT INTERFEROMETRIC SENSOR WITH A MULTIMODE LASER-DIODE SOURCE

A passive signal-processing technique for addressing a miniature low-finesse fiber Fabry-Perot interferometric sensor with a multimode laser diode is reported. Two modes of a multimode laser diode separated by 3 nm are used to obtain quadrature outputs from an similar to 20-mu m cavity. Wavelength-division demultiplexing combined with digital signal processing is used to recover the measurand-induced phase change. The technique is demonstrated for the measurement of vibration. The signal-to-noise ratio is similar to 70 dB at 500 Hz for similar to pi/2 rad displacement of the mirror, which results in a minimum detectable signal of similar to 200 mu rad Hz(-1/2). A quantitative discussion of miscalibration and systematic errors is presented. (C) 1995 Optical Society of America