Multiple wavelength signal processing technique for short gauge length interferometric fiber sensors

摘要

A low finesse fiber Fabry-Perot interferometric sensor is illuminated with five equally spaced axial modes from a multimode semiconductor laser diode source. The resulting intensity output is composed of five equally phase shifted optical frequencies, the intensities of which are used to determine the interferometric phase modulo 2 pi. This technique is shown to reduce the phase errors arising from multiply reflected beams, characteristic of the Fabry-Perot interferometer, by two orders of magnitude compared to techniques using two or three intensity outputs. The use of this technique is also shown to result in a reduction in cavity miscalibration errors when compared to previously reported signal processing techniques for Fabry-Perot interferometric sensors. The signal processing technique is demonstrated for temperature measurement where a 70 degree Celsius range and 0.07 degree Celsius resolution are obtained.