Two-Stage n-PSK Partitioning Carrier Phase Recovery Scheme for Circular mQAM Coherent Optical Systems

Abstract

A novel two-stage n-PSK partitioning carrier phase recovery (CPR) scheme for circular multilevel quadrature amplitude modulation (C-mQAM) constellations is presented. The first stage of the algorithm provides an initial rough estimation of the received constellation, which is utilized in the second stage for CPR. The performance of the proposed algorithm is studied through extensive simulations at the forward error correction bit error rate targets of 3.8ˆ10´3 and 1ˆ10´2 and is compared with different CPR algorithms. A significant improvement in the combined linewidth symbol duration product (∆νT s ) tolerance is achieved compared to the single-stage n-PSK partitioning scheme. Superior performance in the ∆νT s tolerance compared to the blind phase search algorithm is also reported. The relative improvements with respect to other CPR schemes are also validated experimentally for a 28-Gbaud C-16QAM back-to-back transmission system. The computational complexity of the proposed CPR scheme is studied, and reduction factors of 24.5 | 30.1 and 59.1 | 63.3 are achieved for C-16QAM and C-64QAM, respectively, compared to single-stage BPS in the form of multipliers | adders.

Experimental Evaluation of Impairments in Unrepeatered DP-16QAM Link with Distributed Raman Amplification

“…By comparing the backward and bidirectional pumping schemes, we could observe a clear performance improvement around the optimum pump power, enabling the bidirectional pumping scheme to achieve a Q factor above the 8.5 dB HD-FEC limit after 200 km SSMF unrepeatered transmission. Moreover, it was observed that the BPS slightly outperformed DDPLL and QPSKP in mitigating the Raman-induced impairments, thanks to the accurate phase tracking capability at the high OSNR [27]. One should note that due to the experimental constraints, the power ratio between the forward and backward pump was fixed during this work; however, it is worth further investigation as an important aspect to draw a more generic conclusion.…”

“…For each pumping scheme, the phase noise and amplitude noise are measured as a function of the Raman pump power. Three different carrier phase recovery (CPR) algorithms are tested and compared for each transmission scenario: decision-directed phase-lock-loop (DDPLL) [24], two-stage feed-forward based on QPSK partitioning (QPSKP) with a sliding window average [25] and feed-forward based on blind phase search (BPS) [26,27]. This paper is organized as follows.…”

Intelligent Matching of the Control Voltage of Delay Line Interferometers for Differential Phase Shift Keying-Modulated Optical Signals

“…Because of the differences between phase retardations for different optical carrier frequencies, the spectral response should be tunable along the frequency axis while keeping the free spectral range (FSR) unchanged to match different channels in a dense wavelength division multiplexing (DWDM) system. As the development of digital processing technology continues, coherent detection methods based on high-speed analog-to-digital converters (ADC) and digital processors are being proposed [11][12][13][14][15][16]. Coherent detection provides better demodulation performance and high tolerance to chromatic dispersion and major nonlinear effects.…”