Tensile strain dependence of Brillouin frequency shift in silicaoptical fibers

Brillouin frequency shift in a single-mode optical fiber has been measured as a function of tensile strain. The strain coefficient of normalized Brillouin frequency shift C≡(dv_B/ dϵ)/v_B is found to be 4.4 for silica fibers. This result shows the potential of Brillouin spectroscopy to evaluate tensile strain in the fiber with the strain resolution of about 2×10^-4. The origin of the large strain coefficient is discussed