Spectral decoding in fiber-optic interferometric sensors

Principles of white-light interferometric techniques are described in this paper. Different spectral decoding methods applied to low coherence interfe rometry are also presented. Among them one can distinguish: direct recoveri ng of an optical path difference with use of second interferometer as a spe ctrum analyzing device, several wavelength interrogation with use of a spec trometer or suitable narrow-band optical filters, and chromatic monitoring in a wider spectrum. The last decoding method was applied to test the perfo rmance of fiber optic interferometric pressure and temperature sensors. A d iffraction grating was used to monitor a wide part of the output spectrum. The phase shift induced by measurand changes in both sensors was determined with a fringe counting method.