Group-delay ripple reduction in step-chirped fiber Bragg gratings by using laser-beam written step-chirped phase masks

Step-chirped phase masks for step-chirped fiber Bragg gratings (FBGs) were fabricated by employing a new writing strategy, in which the beam is able to scan a step-chirped pattern all at once or continuously. This new writing strategy was realized by using a raster scan-type laser-beam writing system. Linearly and nonlinearly step-chirped FBGs, fabricated by using these masks, show very low group-delay ripple characteristics, which means that the masks have fewer stitching errors than conventional step-chirped masks.