Title :
Spectrally Efficient Quadrature Duobinary Coherent Systems With Symbol-Rate Digital Signal Processing
Author :
Li, Jianqiang ; Tao, Zhenning ; Zhang, Huijian ; Yan, Weizhen ; Hoshida, Takeshi ; Rasmussen, Jens C.
Author_Institution :
Fujitsu R&D Center, Beijing, China
fDate :
4/15/2011 12:00:00 AM
Abstract :
An enhanced digital coherent receiver including a novel blind equalization approach and maximum-likelihood sequence detection (MLSD) is proposed for dual-polarization quadrature duobinary (DP-QDB) systems. In virtue of the compact spectrum of DP-QDB signals approaching Nyquist limit, the equalization is implemented at symbol rate, which relaxes the demand on the sampling speed of analog-to-digital converters (ADCs). The proposed symbol-rate receiver is verified by 43 Gb/s experiments in the presence of chromatic dispersion and polarization-mode dispersion. This paper also investigates the tolerances to narrowband optical filtering, ADC sampling phase, duobinary-generating filter bandwidth, laser linewidth, and carrier frequency offset. Detailed modulation format comparisons are made among DP-QDB, DP-quadrature-phase-shift keying (QPSK), DP-8 quadrature amplitude modulation (QAM), and DP-16QAM. It is shown that DP-QDB with MLSD well trades off major requirements on advanced modulation formats.
Keywords :
analogue-digital conversion; blind equalisers; light polarisation; maximum likelihood estimation; optical dispersion; optical filters; optical information processing; optical receivers; quadrature amplitude modulation; quadrature phase shift keying; Nyquist limit; analog-to-digital converters; bit rate 43 Gbit/s; blind equalization approach; carrier frequency offset; chromatic dispersion; digital coherent receiver; dual-polarization quadrature duobinary systems; duobinary-generating filter bandwidth; laser linewidth; maximum likelihood estimation; modulation format; narrowband optical filtering; polarization-mode dispersion; quadrature amplitude modulation; quadrature-phase-shift keying; sampling phase; sequence detection; symbol-rate digital signal processing; symbol-rate receiver; Coherent detection; high spectral efficiency; optical communications; quadrature duobinary (QDB);
Journal_Title :
Lightwave Technology, Journal of
DOI :
10.1109/JLT.2011.2105461
