Birefringence measurement under hydrostatic pressure utilizing twist-induced effects in highly birefringent fibers

A new method of birefringence measurement in highly birefringent bow-tie fibers under hydrostatic pressure up to 100 MPa is presented. The birefringence measurement method is based on twist-induced effects and has never been applied before in a high-pressure environment. The experiments were conducted using a specially designed pressure facility, which made it possible to simultaneously generate several mechanical. Perturbations, including twist and hydrostatic stress, and to investigate their effects on mode transmission in optical fibers. The results indicate that in the case of ECB single-mode bow-tie fibers, hydrostatic pressure up to 100 MPa decreased beat length with a mean coefficient of 1/L/sub Bo/|dL/sub Bdp|=0.170%/MPa what is in a very close agreement with our previous measurement based on Rayleigh scattering.