Abstract

It is well known that the thermal sensitivity of an optical fiber sensor often appears as a parasitic effect. In the case of an intrinsic polarimetric pressure sensor, we have shown both theoretically and experimentaly [l] that the thermal sensitivity can be strongly reduced by performing a differential measurement. But in these experiments, the temperature variations are not available; the pressure variations are deduced from the measurement of the induced birefringence (X and Y axes) in a single mode fiber wrapped around an hollow cylinder. When an overpressure is applied in the cylinder, the induced strains are transmitted to the fiber an so the refractive indices are affected by the photoelastic effect. In a similar manner, an increase of the temperature induces strains in the cylinder and modifies also the index of refraction of the fiber. Moreover, because of partial reflections on the fiber end-faces, such a device can be considered as a dual PEROT-FABRY resonator. Thus two optical parameters depending on P and T can be obtained: the mean round trip phase Φ and the differential phase shift Ψ and simultaneous measurement may be performed [2]. In this paper the theory of the operation is described and the first results on a pressure-temperature sensor are presented.

© 1988 Optical Society of America