Temperature sensing by mode-mode interference in birefringent optical fibers.

Fiber-optic sensors are described that utilize the mode-mode interference of the two orthogonal linear polarizations of the HE(11), mode in strongly birefringent single-mode fibers. The sensitivities of various versions of these one-fiber interferometers are calculated. When fibers with high internal stress are used, the temperature sensitivity is reduced by only a factor of 50 compared with that of two-fiber interferometers while the pressure sensitivity is reduced by 7.3 x 10(3). Thus the cross sensitivity is reduced by a factor of 150.