SIMULTANEOUS HYDROSTATIC PRESSURE AND TEMPERATURE MEASUREMENT EMPLOYING A LPO~-LPI 1 FIBER-OPTIC POLARIZATION-SENSITIVE

A fiber-optic LPol -LP11 polarization- sensitive intermodal interferometer is proposed to simul- taneously measure hydrostatic pressure and temperature using the same sensing element. In analogy to the case of strain sensing it was found that the experimental parameters Tp and TT describing the 27c phase shifts in the interferogram are significantly different for the X- and Y- polarizations of two polarization modes. This represents a fundamental phenomenon which can be put to use for simultaneous two-parameter sensing. The results obtained are found to be in agreement with a recently developed Muller-Stokes formalism describing polarization effects in the case of two-mode interference. Initial calibration of the two parameter simultaneous pressure-and-temperature sensor has also been performed up to 100 MPa using a primary pressure standard (deadweight tester Hanvood DWT-35). 1.