Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

We report the observation of abnormal spectral evolution in regenerated fiber Bragg gratings in hydrogenated B-Ge-codoped and standard telecom fiber with UV overexposure. The behavior of this new type of regenerated grating, which we have designated type IA, contrasts with that of the previously reported type IIA grating in nonhydrogenated fiber by exhibiting a large redshift in Bragg wavelength with increasing exposure of as much as 18 nm from a strong (16-dB) regenerated grating in B-Ge fiber.