Thermo-optically tunable band-rejection filters using mechanically formed long-period fiber gratings

We present tunable mechanically formed long-period fiber gratings whose resonance peaks are shifted by the thermo-optic effect of a medium surrounding the fiber cladding. A novel grating formation method and tuning principles that use periodically arrayed metal wire are described. The performance as an active gain equalizer of an erbium-doped fiber amplifier is also reported.