Long-period fiber gratings as band-rejection filters

We present a new class of long-period fiber gratings that can be used as in-fiber, low-loss, band-rejection filters. Photoinduced periodic structures written in the core of standard communication-grade fibers couple light from the fundamental guided mode to forward propagating cladding modes and act as spectrally selective loss elements with insertion losses < 0.2 dB, barkreflections < -80 dB, polarization-mode-dispersions < 0.01 ps and polarization-dependent-losses < 0.02 dB.