Design and fabrication of flat-band long-period grating

A method to realize the practical flat-band long-period fiber grating (LPG) fabrication is proposed. Based on the results obtained from the layer-peeling method, we have analyzed the structure of the designed flat-band LPG. We found that the designed LPG is an apodized LPG with sinc-like envelope and a constant period, while there exists a /spl pi/ phase shift at each zero point of the apodization profile. For the first time, a flat-band LPG is realized in fabrication. The experimental result shows a good match with our theoretical analysis.