Refined Spectral Regulation of Chirped Fiber Bragg Gratings

A novel technique is proposed for refining the spectral regulation of chirped fiber Bragg gratings (CFBGs) during the fabrication process, utilizing an ultraviolet (UV) laser with a chirped phase mask. By incorporating an additional phase into the Hamming window function, a new laser control function is generated. This supplementary phase directly enhances the waveform shift parameter and introduces an extra degree of freedom. Consequently, it becomes easier to accurately control the direct-current component in the photo-induced refractive index change during grating writing, leading to a more precise distribution of the refractive index gradient within the grating. The effectiveness of this method was validated through experiments conducted over a wide bandwidth of 20 nm for the CFBGs. The number of peaks from 1 to 4 were investigated, achieving a contrast of 40 dB. Extensive testing and verification were performed on the peak position shifts within the modulation bandwidth of numerous CFBGs. The results demonstrated that this new approach enables the fabrication of CFBGs with arbitrary waveform spectra. This technique significantly improves the optical performance and application value of CFBGs, offering a means to fabricate high-performance CFBGs using the UV mask method.