pectral characteristics of chirped fiber Bragg gratings in large-mode-area fibers

A matrix method is extended to solve the multimode coupling differential equations, and thereby the spectral characteristics of the chirped Bragg gratings in large-mode-area fibers (LMA FBGs) are studied theoretically. Unlike those of Bragg gratings in single mode optical fibers (SM FBGs), the reflection spectra of chirped LMA FBGs contain self-coupling and co-coupling peaks of the existing modes. For the chirped LMA FBGs, the reflectivity decreases and the reflection peaks split. These splits can be improved on some degree by Gaussian apodization function.