Patent ID: 8707138

Claim:
A method of blind demultiplexing a polarization diversity multiplex signal in a coherent receiver, deriving x-polarization samples r X (n) and orthogonal y-polarization samples r Y (n) of the received polarization diversity multiplex signal, calculating complex filter functions of a multidimensional equalizer between the x-polarization samples r X (n), y-polarization samples r y (n) and output x-signal samples z x (n), y-signal samples z y (n) representing optical signals received as the polarization diversity multiplex signal, the method comprising: calculating at least one error correction factor derived from the x-signal samples and y-signal samples z x (n), z y (n) output from the equalizer by deriving averaged correlation factors according to: ρ xy (n) [k ]=(1−ε)·ρ xy (n−1) [k]+ε·z x [n]z y *[n−k]; k= 0 , . . . , k max ρ yx (n) [k ]=(1−ε)·ρ yx (n−1) [k]+ε·z y [n]z x *[n−k]; k= 0 , . . . , k max, with k=0, . . . , k max being a corrlation delay time variable; and deriving error correction factors according to: η x (n) =−ρ xy (n) [k x ]·z y [n−k x ] for k x =argmax{ρ xy ( k )}; k= 0 , . . . , k max , η y (n) =−ρ yx (n) [k y ]·z x [n−k y ] for k y =argmax{ρ yx ( k )}; k= 0 , . . . , k max , calculating correction values from the at least one error correction factor multiplied by an update factor and by an x-polarization sample or a y-polarization sample; calculating corrected filter coefficients by adding the correction values to filter coefficients of the complex filter functions; and wherein n is a time instant, ρ is a correlation factor, k=0, 1, . . . , k max is a correlation delay time variable and ε is a forgetting factor.