A novel dynamic LPFG gain equalizer written in a bend-insensitive fiber

The bending characteristics of the long-period fiber gratings (LPFG) induced by high-frequency CO2 laser pulses using a bend insensitive fiber is reported, for the first time, to our knowledge. The experimental results show that the resonant peak amplitude of the LPFG written in a bend insensitive fiber is quite sensitive to bending while its resonant wavelength is insensitive to bending at some circular orientations. In addition, the resonant peak amplitude of the LPFG written in a bend insensitive fiber has a much higher bend sensitivity than that written in a standard telecommunication fiber. Based on this finding, a novel all-fiber dynamic gain equalizer is proposed to flatten the gain of EDFAs by controlling the bend of the LPFG directly. The experimental results show that such a device would be a practical and simple approach to realize gain flattening of an EDFA with a high precision for gain flatness control.