Dynamic optical filter having a spatial light modulator

Abstract

An dynamic optical filteris provided to selectively attenuate or filter a wavelength band(s) of light (i.e., optical channel(s)) or a group(s) of wavelength bands of an optical WDM input signalThe optical filter is controllable or programmable to selectively provide a desired filter function. The optical filterincludes a spatial light modulatorwhich comprises an array of micromirrorsthat effectively forms a two-dimensional diffraction grating mounted in a retro-reflecting configuration. Each optical channelis dispersed separately or overlappingly onto the array of micro-mirrorsalong a spectral axis or directionsuch that each optical channel or group of optical channels are spread over a plurality of micromirrors to effectively pixelate each of the optical channels or input signal. Each channelor group of channels may be selectively attenuated by flipping or tilting a selected number of micromirrors to thereby deflect a portion of the incident radiation away from the return optical path. The micro-mirrors operate in a digital manner by flipping between a first and second position in response to a control signalprovided by a controllerin accordance with an attenuation algorithm and an input commandThe switching algorithm may provide a bit (or pixel) map or look-up table indicative of the state of each of the micro-mirrorsof the array to selectively attenuate the input signal and provide a modified output signalat optical fiber