Measuring the structure of highly reflecting fiber Bragg gratings

We demonstrate a new technique that enables us to measure the structure of highly reflecting fiber Bragg gratings. The impulse response function is measured from both sides of the grating using a low-coherence spectral interferometry technique. An inverse scattering algorithm is used to extract the refractive-index profiles from the measured impulse responses. The reconstruction of the grating is performed by combining the refractive-index profiles, measured from both sides of the grating. The transfer function of the optical spectrum analyzer is measured, and used to correct the measured results. The interrogation of an apodized grating with a reflectivity of 99.91% is demonstrated.