Phase reconstruction from reflectivity in fiber Bragg gratings

It is shown that a recently proposed phase-retrieval technique for Bragg gr atings [Opt. Lett. 22, 93 (1997); J. Lightwave Technol. 15, 1314 (1997)] is not well suited for gratings with imperfections. The reconstructed group d elay is in many cases not a more accurate estimate than the simulated group delay of the perfect, designed grating, independently of how small the err ors in the grating structure are. The error in the group delay may be espec ially large near the zeros in the reflection spectrum. (C) 1999 Optical Soc iety of America.