Impact of refractive index DC disturbance on time delay characteristics for sampling fiber gratings

Based on the coupled mode equations (CMEs), sampling fiber grating with direct current (DC) refractivity index disturbance was analyzed. The theoretical model of changing grating phase and period was given. Through transfer matrix method (TMM), influence of this disturbance on grating delay characteristic was simulated and analyzed. It was proved that disturbance lies in no-grating region make little influence on characteristics of sampled grating. Using a uniform phase mask and two pieces of amplitude mask to carry two exposures, a sampled chirped grating was produced and tested in experiments.