Optical channel monitor

Abstract

An optical channel monitor is provided that sequentially or selectively filters an optical channel(s)of light from a (WDM) optical input signaland senses predetermined parameters of the each filtered optical signal (e.g., channel power, channel presence, signal-noise-ratio). The OCMis a free-space optical device that includes a collimator assembly, a diffraction gratingand a mirror. A launch pigtail emits into free space the input signal through the collimator assemblyand onto the diffraction grating, which separates spatially each of the optical channelsof the collimated light, and reflects the separated channels of light onto the mirror. A λ/4 plateis disposed between the mirrorand the diffraction grating. The mirror reflects the separated light back through the λ/4 plateto the diffraction grating, which reflects the channels of light back through the collimating lens. The lensfocuses each separated channel of light (λ-λ) at a different focal point in space. One of the optical channelsis focused onto a receive pigtail, which then propagates to a photodetector. A pivoting mechanismpivots the diffraction gratingor mirrorabout a pivot pointto sequentially or selectively focus each optical channelto the receive pigtail. A position sensordetects the displacement of the diffraction gratingor mirror.