Fiber Bragg Grating (FBG)

Abstract

The fiber Bragg grating (FBG) is one of the key elements in the established and emerging fields of optical communication systems. In order to fasten the FBG inscription speed, it is desirable to enhance the photosensitivity of standard silica fibers. The FBG acts as a band-pass filter at the reflection port and a band-rejection filter at the transmission port. Such interferometric effect usually exhibits very narrow bandwidth characteristics of filters. The spatially modulation of light intensity, which is essential for FBG inscription, is set up by using a phase mask. The phase mask is a silica plate transparent to UV-radiation, and one of its surfaces is etched with a relief grating. Advanced structures such as apodized FBGs and chirped FBGs can also be fabricated by using the phase mask technique. Complex gratings such as chirped FBGs and phase-shifted gratings could also be fabricated by the phase mask method.