Optical waveguide grating filter

摘要

The isolation between stop and pass bands afforded by an optical fibre normally reflective Bragg grating (5) reflective over a waveband lambda 3 in an optical fibre (2) is enhanced by preceding it with two blazed Bragg gratings (3, 4) that are spectrally selectively mode coupling respectively over wavebands lambda 1 and lambda 2, where the lambda 3 waveband compasses the spectral waveband separating waveband lambda 1 from waveband lambda 2. The fibre is connected to an optical circulator (40) or one port of an optical 4-port 3dB coupler (50).