Retrieval of the refractive-index distributions of fiber gratings with complex Bragg reflection measurements

Summary form only given. The Bragg reflection characteristics of a fiber grating, including intensity and phase, are controlled by its longitudinal refractive-index distribution, i.e., the local grating period and the depth of effective index modulation. Therefore, the retrieval of the longitudinal index distribution is crucially important for controlling the characteristics of a fiber grating. We report our results of reconstructing the index distributions of a uniform and an apodized chirped fiber grating. The procedures include the measurements of their complex Bragg reflection spectra with a balanced Michelson interferometer and the execution of a simple retrieving algorithm. With the procedures, we can retrieve index profiles of fiber gratings with any apodization, chirping or DC structures.