Passive signal processing of in-line fiber etalon sensors for high strain-rate loading

This paper describes the development of a passively demodulated optical fiber sensor system capable of accommodating the high strain-rate events commonly encountered in applications involving stress wave propagation. This sensor system, which is based on in-line fiber etalon (ILFE) sensors and path-matched differential interferometry (PMDI), was tested experimentally at low frequency and strain-rates (time derivative of strain) up to (/spl sim/10/sup 7/ /spl mu//spl epsiv//s). For the present system, this strain-rate corresponds to a sensor phase bandwidth of approximately 100 kHz. Characterization tests using sensor gauge lengths ranging from 260 to 350 /spl mu/m showed that the sensor system had a minimum detectable phase of /spl sim/2 microrad//spl radic/HZ rms at 2 kHz which corresponds to /spl sim/0.8 n/spl epsiv///spl radic/Hz rms for 260 /spl mu/m-gauge length sensor.