We propose a novel frequency-domain adaptive equalizer in digital coherent optical receivers, which can reduce computational complexity of the conventional time-domain adaptive equalizer based on finite-impulse-response (FIR) filters. The proposed equalizer can operate on the input sequence sampled by free-running analog-to-digital converters (ADCs) at the rate of two samples per symbol; therefore, the arbitrary initial sampling phase of ADCs can be adjusted so that the best symbol-spaced sequence is produced. The equalizer can also be configured in the butterfly structure, which enables demultiplexing of polarization tributaries apart from equalization of linear transmission impairments. The performance of the proposed equalization scheme is verified by 40-Gbits/s dual-polarization quadrature phase-shift keying (QPSK) transmission experiments.
© 2011 OSA
DSP complexity of mode-division multiplexed receivers
Beril Inan, Bernhard Spinnler, Filipe Ferreira, Dirk van den Borne, Adriana Lobato, Susmita Adhikari, Vincent A. J. M. Sleiffer, Maxim Kuschnerov, Norbert Hanik, and Sander L. Jansen
Opt. Express 20(10) 10859-10869 (2012)
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