Multi-Modulus Blind Equalizations for Coherent Quadrature Duobinary Spectrum Shaped PM-QPSK Digital Signal Processing

Abstract

A novel digital signal processing (DSP) scheme for quadrature duobinary (QDB) spectrum shaped polarization multiplexed quadrature phase shift keying (PM-QPSK) based on multi-modulus blind equalizations (MMBE) is proposed and demonstrated with both simulation and experimental results. The key algorithms for this novel digital signal processing scheme include the cascaded multi-modulus algorithm (CMMA) for blind polarization de-multiplexing, multi-modulus QPSK partitioning frequency offset estimation (FOE) and two stage carrier phase recovery (CPR) with maximum likelihood phase estimation. The final signal is detected by maximum-likelihood sequence detection (MLSD) for data BER measurement. It shows that CMMA have better frequency response performance compared with CMA for noise compression. The performances of FOE and CPR are also investigated with different spectrum shaping bandwidth, group size and laser linewidth. Finally, the feasibility of the proposed digital signal processing scheme is demonstrated by the experiment of 112 Gb/s QDB spectrum shaped PM-QPSK signal with a 25 GHz bandwidth waveshaper for Nyquist WDM channels.

A Fast Converge Dual-Mode Modified Constant Norm Blind Equalization Algorithm

“…In the underwater communication, the envelope of the transmit signal is always changeless such as PSK. CMA is based on the characteristic and is very suitable for the equalization of this kind of signal (Zhang, Yu and Chi, 2013;Li, 2015;Zhang, Chen and Hanzo, 2014). In the coherent underwater acoustic communication, the transmitting signal waveform has constant envelope, such as PSK (phase-shift keying) signal.…”

Transmission and reception of Quad-Carrier QPSK-OFDM signal with blind equalization and overhead-free operation

“…For the phase recovery, Viterbi algorithm is utilized to cancel the phase noise of QPSK signal after 4-point FFT. For the CMMA algorithm, we only select the inner three rings/radii for the error signal calculation to increase equalizer robustness [10,11], which is the same as CMMA algorithm for 9-QAM signal [12,13]. We also analyze the PAPR of Quad-Carrier QPSK-OFDM signal and traditional QPSK-OFDM signal.…”

“…At receiver, after optical to electrical (O/E) conversion, a digital filter is used to separate the 4-subcarrier, and then DSP is applied for each subcarrier [9]. 4-subcarrier OFDM signal shows as a 25-QAM signal in the time domain, and it can be blindly equalized with cascaded multi-modulus algorithm (CMMA) equalization in the time domain [10][11][12][13]. With the blind equalization, channel estimation and equalization, FOE, and phase recovery can be implemented without TS and pilot tones.…”

Analysis of Performance for 100 Gbit/s Dual-Polarization QPSK Modulation Format System

“…In Ref. [13], 40 Gbit/s QPSK signal polarization multiplexing transmission was used in single-mode fiber (SMF) for 100 km, signals received are processed via A/D conversion offline DSP. In 2008, the Nortel research team reported a coherent optical communication experiment, which is a milestone.…”