Strain and Temperature Discrimination Using High Birefringence Fiber Sagnac Interferometer With Enhanced Sensitivities

Discrimination between the strain and temperature variations based on the Sagnac interferometer is newly proposed and demonstrated with much improved properties. It is achieved by containing five sections of high birefringence fibers (HBFs) in the Sagnac interferometer-three of them spliced together act as the compact sensing head and the other two are isolated from the strain and temperature changes. By properly setting all the HBF lengths and relative orientations of their primary polarization axes, the strain and temperature sensitivity coefficients of the two wavelength dips generated due to the Sagnac interference may be greatly enhanced with the effectively reduced cross sensitivity.