High fidelity, pitch-by-pitch grating inscription in free-standing single-mode optical fiber

A pitch-by-pitch grating inscription method that allows both high laser intensity and long-exposure dosage when inscribing each pitch is demonstrated. Based on slit beam-profiling, proposed scheme does not require oil-immersion-based beam distortion compensation techniques for inscription into free-standing single-mode fiber. High grating fringe visibility inscription is achieved for 1.07μm-period structure in single-mode fiber even though each grating pitch are individually defined by 50msec-long laser exposure.