Open AccessFeed-forward frequency offset estimation for 32-QAM optical coherent detection
Author(s) -
Fei Xiao,
Jianing Lu,
Songnian Fu,
Cong Xie,
Ming Tang,
Jinwen Tian,
Deming Liu
Publication year - 2017
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.25.008828
Subject(s) - fast fourier transform , quadrature amplitude modulation , frequency offset , computer science , phase shift keying , qam , offset (computer science) , bit error rate , signal to noise ratio (imaging) , optics , telecommunications , electronic engineering , algorithm , orthogonal frequency division multiplexing , physics , engineering , decoding methods , channel (broadcasting) , programming language
Due to the non-rectangular distribution of the constellation points, traditional fast Fourier transform based frequency offset estimation (FFT-FOE) is no longer suitable for 32-QAM signal. Here, we report a modified FFT-FOE technique by selecting and digitally amplifying the inner QPSK ring of 32-QAM after the adaptive equalization, which is defined as QPSK-selection assisted FFT-FOE. Simulation results show that no FOE error occurs with a FFT size of only 512 symbols, when the signal-to-noise ratio (SNR) is above 17.5 dB using our proposed FOE technique. However, the error probability of traditional FFT-FOE scheme for 32-QAM is always intolerant. Finally, our proposed FOE scheme functions well for 10 Gbaud dual polarization (DP)-32-QAM signal to reach 20% forward error correction (FEC) threshold of BER=2×10 -2 , under the scenario of back-to-back (B2B) transmission.