Fiber Fabry-Perot Interferometer for Measurement of Gas Pressure and Temperature

A fiber Fabry-Perot interferometer (FPI) is proposed and demonstrated for the measurement of gas pressure and temperature. The interferometer is fabricated by fusion splicing a short segment of capillary tube to a standard single mode fiber (SMF), followed by inserting a glass microsphere into the tube, the air gap between the SMF end face and the glass microsphere then forms a fiber FPI. Due to the additional reflection occurred on the rear surfaces of the microsphere, the reflection spectrum of the device is a three-beam interference pattern. Owing to the dependence of refractive index of gas on the pressure applied and the thermal-optical effect of glass microsphere, different dips in the interference fringe pattern exhibit different responses to the changes in gas pressure and temperature, which enables a simultaneous gas pressure and temperature sensing. The proposed device has the advantages of compact size, robust structure, easy fabrication, high gas pressure sensitivity, and supporting of range tunable operation.