Influence of birefringence dispersion on a distributed stress sensor using birefringent optical fiber

Distributed stress sensor with a white-light scanning interferometer is used to detect stress distribution by analyzing polarization mode coupling caused by forces exerted on PMFs (polarization maintaining fibers). In measurement of polarization coupling, the birefringence in sensing fiber is usually considered to be wavelength independent. Sensitivity and spatial resolution of the distributed stress sensor are constant for a given optical source spectrum. In practical measurement, however, the birefringence in PMFs is related with optical wavelength. In other words, birefringence dispersion exists in PMFs. Due to birefringence dispersion, the relationship between stress and coupling strength varies with different positions of external forces, and spatial resolution of the distributed stress sensor descends obviously with transmitted distance. In this paper, influences of external-force positions and optical source spectrum on distributed stress sensor are analyzed in consideration of birefringence dispersion and validated with experiments. A method for compensating birefringence dispersion in the sensing system is proposed in the end.