Open AccessPhase noise tolerance study in coherent optical circular QAM transmissions with Viterbi-Viterbi carrier phase estimation
Author(s) -
Sebastian Ortega Zafra,
Xiaodan Pang,
Gunnar Jacobsen,
Sergei Popov,
Sergey Sergeyev
Publication year - 2014
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.22.030579
Subject(s) - quadrature amplitude modulation , viterbi algorithm , phase noise , computer science , laser linewidth , minimum shift keying , modulation (music) , electronic engineering , phase modulation , phase shift keying , qam , optics , algorithm , bit error rate , telecommunications , physics , channel (broadcasting) , engineering , acoustics , decoding methods , laser
We present a performance evaluation of a non-conventional approach to implement phase noise tolerant optical systems with multilevel modulation formats. The performance of normalized Viterbi-Viterbi carrier phase estimation (V-V CPE) is investigated in detail for circular m-level quadrature amplitude modulation (C-mQAM) signals. The intrinsic property of C-mQAM constellation points with a uniform phase separation allows a straightforward employment of V-V CPE without the need to adapt constellation. Compared with conventional feed-forward CPE for square QAM signals, the simulated results show an enhanced tolerance of linewidth symbol duration product (ΔνTs) at a low sensitivity penalty by using feed-forward CPE structure with C-mQAM. This scheme can be easily upgraded to higher order modulations without inducing considerable complexity.