Effects of the phase shift split on phase-shifted fiber Bragg gratings

摘要

In proximity side-writing fiber Bragg gratings (FBGs) using a phase shifted phase mask, the phase shift in the phase mask is split into two half-amplitude phase shifts. The effects of the phase-shift split on FBGs is investigated. A FBG with a split pi-phase shift is modeled as two cascaded and tightly coupled grating-based FabryPerot filters. A compact expression of its reflectivity spectrum is obtained showing spectral asymmetry errors and a shift of the transmission peak. Our numerical results are in good agreement with previous experimental results. These effects decrease with increasing FBG length and become negligible for gratings more than a few millimeters long. (c) 2006 Optical Society of America.