Fabrication of high reflection UV written fiber Bragg gratings

The experimental results that fiber Bragg gratings with a peak reflectivity up to 98% have been fabricated by 248nm KrF excimer laser irradiated on untreated B/Ge co-doped fibers through a zero-order null phase mask was reported. The growth of the fiber gratings was monitored by a white light source and an optical spectrum analyzer during the grating formation. The grating length is 15mm. The fiber has a 4μm core diameter and NA=0.14. The 3dB bandwidth of the fiber grating reflector is less than 0.4nm and the side-lobes of the grating reflection spectra are almost ideally suppressed.