High hydrostatic pressure effects in highly birefringent optical fibers

The effect of high hydrostatic pressure on polarization properties in highly birefringent (HB) optical fibers is experimentally evaluated up to 200 MPa. The results are discussed in terms of beat-length changes under high pressure. It is found that oscillatory behavior of the output signal exiting from the HB bow-tie fiber and monitored in the plane parallel to one of its own two principal axes can be attributed to a pressure-induced increase of beat-length parameter. This effect can be applied to sense high hydrostatic pressure using appropriately configured HB fiber, but it could be a disadvantage in underwater communication systems using HB fibers if these are not adequately protected.