Adaptive Boundaries Scheme for Cycle-Slip Mitigation in C-mQAM Coherent Systems
We propose a method for cycle-slip mitigation in circular multilevel quadrature amplitude modulation (C-mQAM) coherent optical systems, with constellation rotational asymmetry, based on an adaptive boundaries approach. The impact of cycle-slips in C-mQAM coming from Viterbi-Viterbi algorithm limits...
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Veröffentlicht in: | IEEE photonics technology letters 2015-10, Vol.27 (20), p.2154-2157 |
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Sprache: | eng |
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Zusammenfassung: | We propose a method for cycle-slip mitigation in circular multilevel quadrature amplitude modulation (C-mQAM) coherent optical systems, with constellation rotational asymmetry, based on an adaptive boundaries approach. The impact of cycle-slips in C-mQAM coming from Viterbi-Viterbi algorithm limits the phase noise tolerance. By introducing adaptive boundaries and a differential coding scheme, the ambiguity of asymmetrical rotation of constellation can be effectively removed. Performance of the proposed method is evaluated for a C-16QAM and C-64QAM for various laser linewidths. Results show a noticeable improvement in linewidth symbol duration product (Δν · TS) tolerance compared with the previous studies on C-mQAM and mQAM constellations. The Δν · TS tolerance reaches 4 × 10 -4 and 1.1 × 10 -4 for C-16QAM and C-64QAM, respectively, for 1 dB penalty at a symbol error rate of 10 -3 . |
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ISSN: | 1041-1135 1941-0174 1941-0174 |
DOI: | 10.1109/LPT.2015.2455234 |