Polarization-resolved spatial characterization of birefringent fiber Bragg gratings

A method that enables polarization-resolved spatial characterization of fiber Bragg gratings is presented. The polarization-resolved reflection spectrum of the grating is measured using optical-frequency domain reflectometry. A polarization-resolved layer-peeling algorithm is used to compute the spatial pro. le, including the local birefringence and the local polarization-dependent index modulation. A strain-tuned distributed feedback fiber laser is used as source. With closed-loop control of the laser sweep, 0.14% maximum deviation from constant sweep rate is achieved, which is much better than commercial available tunable lasers. The polarization of the source is modulated synchronous with the laser sweep by passing the light through a three-armed Mach-Zehnder-type interferometer having different retardation. The method is used to investigate the polarization-dependence of the index modulation amplitude of a fiber Bragg grating. (c) 2006 Optical Society of America.