Patent ID: 8805208
Filing Date: 2014-08-12
Classification: H04B,H04L

Abstract:
1. An optical receiver system comprising: a coherent receiver for receiving a polarization multiplexed optical signal and providing a first plurality of outputs in response to a first polarization of said optical signal and a second plurality of outputs in response to a second polarization of said optical signal; and a digital signal processor (DSP) configured to apply a modified constant modulus algorithm (CMA) to a first digital signal established in response to said first plurality of outputs and a second digital signal established in response to said second plurality of outputs to provide first and second digital outputs representative of a first polarization state of said optical signal at which data is modulated and a second polarization state of said optical signal at which data is modulated, said modified CMA comprising a plurality of sub-equalizer filters, each of said sub-equalizer filters comprising a plurality of delays for producing successively delayed versions of said input signal and a plurality of multipliers, each of said multipliers multiplying said input signal or an associated one of said delayed versions of said input signal with an associated filter coefficient to produce an associated tap weight product, said tap weight products being summed to provide an output for said equalizer, said plurality of sub-equalizers comprising a first sub-equalizer and a second sub-equalizer, each of said filter coefficients for said first sub-equalizer being determined by said modified CMA as the sum of a first component and a second component, said first component being determined using a previous filter coefficient for said first-sub-equalizer and an update gradient for said first sub-equalizer modified by a function of a coupling coefficient, said second component being determined using a filter coefficient of said second sub-equalizer and an update gradient of said second sub-equalizer modified by a function of said coupling coefficient.