Wavelength dependence of stress-induced time of flight variations

In this paper, we measured the stress-induced time of flight variations in silica-fibers for λ =0.67μm∼ 1.65μm. For measurements, the phase method was used to detect the phase change of the modulated wave propagating in a fiber with and without stress. It is found that the measured time of flight variations due to stress have clear wavelength dependence. It is very important to evaluate the photo-elastic constant as a basic constant of silica fibers. In this paper, we propose to evaluate the photo-elastic constant based on the measured stress-induced time of flight variations. Using this method, we evaluate the photo-elastic constant in a wide wavelength range (λ =0.44μm∼ 1.65μm). It is found that the evaluated photo-elastic constant has clear wavelength dependence. We also discuss the error of the proposed evaluation method and the origin of wavelength dependence of the photo-elastic constant.