Transform domain techniques for adaptive crosstalk cancellation in dense wavelength division multiplexing (WDM) optical networks

A filter bank structure least mean-squares (LMS) algorithm is proposed to cancel received linear crosstalk in dense wavelength division multiplexing (WDM) networks. A new filter bank structure utilizing the time varying LMS algorithm was simulated which decreased the convergence time by a factor of four compared to standard LMS. The algorithm uses a modified generalized sidelobe canceller architecture to implement a signal subspace decomposition. The rapid convergence reported comes with a modest increase in computational burden. Analysis and simulations show that with the addition of a few photodetectors, channel spacing requirements can be reduced by over 50%. Simulations using a demodulator with Gaussian bandpass characteristics show that a 2.5 dB signal-to-crosstalk ratio can be increased to over 35 dB