Low-coherent WDM reflectometry for accurate fiber length monitoring

A fiber-optic low-coherent reflectometer was developed to accurately monitor fiber length variation. A large lengthcoverage range was obtained by using a fiber Bragg grating array in a wavelength-division-multiplexing configuration. The polarization mismatch-induced signal fading was eliminated by applying a polarization spreading technique at the optical receiver and, therefore, no active polarization adjustment was necessary for long-term measurement.