An experimental study on the effects of high hydrostatic pressure of as much as 100 MPa on mode propagation in a highly birefringent two-mode bow-tie fiber is presented. Hydrostatic pressure is found to produce a large phase shift between both orthogonal polarizations in fundamental and second-order modes and also between the two lowest-order spatial modes in the highly birefringent two-mode bow-tie fiber. The pressure-induced effects are expressed in terms of birefringence changes and pressure phase sensitivity, both described by the experimental parameter Tp. The results indicate that pressure phase sensitivity between the two spatial modes, ~1.3 rad/MPa-m, is approximately one order lower than for polarization modes.
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