Experimental investigation and digital compensation of DGD for 112 Gb/s PDM-QPSK clock recovery

Darko Zibar, Julio Cesar R. F. de Olivera, Vittor Bedotti Ribeiro, Alberto Paradisi, Julio C. Diniz, Knud J. Larsen, Idelfonso Tafur Monroy

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For asynchronous sampled systems such as Polarization Division Multiplexed Quadrature Phase Shift Keying, (PDM-QPSK), phase and frequency of the sampling clock is typically not synchronized to the data symbols. Therefore, timing adjustment, so called clock recovery and interpolation, must be performed in digital domain prior to signal demodulation in order to avoid cycle slips. For the first time, the impact of first order PMD, (DGD), is experimentally investigated and quantified for 112 Gb/s PDM-QPSK signal. We experimentally show that the combined effect of polarization mixing and first order PMD can significantly affect the performance of the timing error detector gain, even for moderate values leading to system outage. We propose and experimentally demonstrate a novel digital adaptive timing error detector is robust to polarization mixing and DGD. The proposed timing error detector algorithm combines the Gardner timing error detector algorithm with an adaptive structure based on gradient method.
Original languageEnglish
JournalOptics Express
Issue number26
Pages (from-to)B429-B439
Publication statusPublished - 2011

Bibliographical note

This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-26-B429. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.

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