Simultaneous hydrostatic pressure and temperature measurement employing an LP/sub 01/-LP/sub 11/ fiber-optic polarization-sensitive intermodal interferometer

A fiber-optic LP/sub 01/-LP/sub 11/ polarization-sensitive intermodal interferometer is proposed to simultaneously 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 T/sub P/ and T/sub T/ describing the 2/spl pi/ 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 by means of spatial Stokes parameters. Initial calibration of the two-parameter simultaneous pressure-and-temperature sensor has been performed up to 100 MPa using a primary pressure standard (deadweight tester Harwood DWT-35).>