Improved DSP algorithms for coherent 16-QAM transmission

Louchet, Hadrien; Kuzmin, Konstantin; Richter, André

doi:10.1109/ecoc.2008.4729195

Cited by 45 publications

(14 citation statements)

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“…The output signal reconstructed from a digital coherent receiver can be represented as r k = a k e j φ k + n k (8) where a k is the 16-QAM data symbol, φ k is the phase noise, and n k is the complex circularly symmetric additive white Gaussian noise (AWGN). The phase noise in the simulation was modeled as the Wiener process [6] …”

Section: Simulation Resultsmentioning

confidence: 99%

Carrier-Phase Estimation for 16-QAM Optical Coherent Systems Using QPSK Partitioning With Barycenter Approximation

Fatadin

Ives

Savory

2014

J. Lightwave Technol.

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This paper presents a hardware-efficient carrier phase estimator with high-linewidth tolerance for 16-QAM optical coherent systems. The laser phase noise is estimated using quaternary phase-shift keying (QPSK) partitioning complemented with a low complexity angle-based barycenter approximation as opposed to the classical Viterbi and Viterbi algorithm. The various stages necessary for partitioning and removing the modulation on the received symbols for carrier phase recovery are presented. We show that the phase offset in the middle ring for a 16-QAM constellation can be removed through a simple comparison with the symbols lying on the inner and outer rings of the constellation thus enabling all the symbols to be efficiently utilized for carrier phase recovery. We assess the performance of different filter structures for 16-QAM with filter half width 8 and 16. Simulation results demonstrate that combined linewidth symbol duration product Δν · T s of 10 −4 is tolerable at the target BER of 10 −2 and 10 −3 when using the barycenter algorithm. Finally, carrier phase recovery in a 16-QAM experiment is investigated to validate the performance of the proposed algorithm.Index Terms-Barycenter algorithm, carrier phase recovery, QPSK partitioning, quadrature amplitude modulation (QAM). 0733-8724

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Section: Simulation Resultsmentioning

confidence: 99%

Carrier-Phase Estimation for 16-QAM Optical Coherent Systems Using QPSK Partitioning With Barycenter Approximation

Fatadin

Ives

Savory

2014

J. Lightwave Technol.

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“…Thereafter, an enhanced CMA, the multiple moduli algorithm (MMA) was used. Previously applied to Square-16QAM [7], in this work the MMA was adapted to the Star-16QAM modulation format: only two levels corresponding to the two symbol amplitudes are distinguished. The MMA is applied to compensate for residual CD and polarization misalignment between the channels at the receiver side to reduce channel crosstalk.…”

Section: Equalization and Offline Ber Estimationmentioning

confidence: 99%

“…Using EDE after coherent detection, chromatic dispersion can effectively be compensated for in the frequency domain [3], while other transmission impairments (such as polarization cross-talk) are usually compensated in the time domain using blind channel equalization (BCE) techniques, such as the constant modulus algorithm (CMA). In this paper, an enhanced CMA is applied, which has already been investigated numerically for 16QAM in square constellation [7].…”

Section: Introductionmentioning

confidence: 99%

80 Gbit/s/λ̣ polarization multiplexed star-16QAM WDM transmission over 720 km SSMF with electronic distortion equalization

Freund

Louchet

Gruner

et al. 2009

2009 14th OptoElectronics and Communications Conference

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For the first time, 80/40 Gbit/s/O Star-16QAM WDM transmission with/without polarization multiplexing has been demonstrated over 720/1200 km SSMF on a 50 GHz frequency grid applying enhanced techniques for electronic distortion equalization. IntroductionHigher-order optical modulation formats in combination with coherent detection and electronic distortion equalization (EDE) are key emerging technologies paving the way to 100 Gb-Ethernet and highest spectral efficiency as they lead to a reduction of symbol rate and spectral width per WDM channel. Transmission over long distances using higher-order modulation and coherent detection was already demonstrated for quadrature phase shift keying (QPSK) [1] and 8-ary phase shift keying (8PSK) [2,4]. In this paper, long-haul WDM transmission of 16-ary quadrature amplitude modulation in star constellation, Star-16QAM, is investigated for transmission spans without inline dispersion compensation. When applying Star-16QAM, the spectral efficiency can theoretically be increased 4-fold without, and 8-fold with polarization multiplexing (PM), respectively. Data rates of 80 Gbit/s per wavelength can be generated by using PM Star-16QAM requiring a symbol rate of only 10 Gbaud. Generation and transmission of the Square-16QAM format have been already demonstrated by using multilevel driving signals and a single stage IQmodulator [5] or by using an integrated solution of a quad-parallel Mach-Zehnder modulator (MZM) [6]. At this stage, main challenges of these solutions are the generation of the high quality driving signals for the IQmodulator as well as the performance of the integrated quad-parallel MZM. In this paper we demonstrate generation of Star-16QAM by using binary driving signals only based on state of the art modulators as well as WDM transmission over 720/1200 km SSMF on a 50 GHz frequency grid with/without polarization multiplexing. Using EDE after coherent detection, chromatic dispersion can effectively be compensated for in the frequency domain [3], while other transmission impairments (such as polarization cross-talk) are usually compensated in the time domain using blind channel equalization (BCE) techniques, such as the constant modulus algorithm (CMA). In this paper,

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“…The first one is based on a decision directed feedback loop [8]- [10]. Laser linewidth tolerance of this method is not very promising because the estimation of phase depends on the previous set of data symbols instead of the current one, hence making this algorithm complex at the implementation level [11], [12].…”

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confidence: 99%

Multistage Carrier Phase Estimation Algorithms for Phase Noise Mitigation in 64-Quadrature Amplitude Modulation Optical Systems

Bilal

Fludger

Curri

et al. 2014

J. Lightwave Technol.

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Two novel low-complexity multistage digital feedforward carrier phase estimation algorithms for 64-ary quadrature amplitude modulation (QAM) are proposed and analyzed by numerical simulations. The first stage is composed of a Viterbi and Viterbi block, based on either the standard quadrature phase shift keying (QPSK) partitioning algorithm using only Class-1 symbols or a modified QPSK partitioning scheme utilizing both Class-1 and outer most triangle-edge symbols. The second stage applies the Viterbi and Viterbi algorithm after a 64-QAM-to-QPSK transformation, while the subsequent stages iterate a maximum likelihood estimation algorithm for phase estimation. All proposed techniques are characterized by a high tolerance to laser phase noise: with an optical signal-to-noise ratio penalty of 1 dB at bit error rate of 10 −2 , the proposed schemes can tolerate a linewidth times symbol duration product (Δν · T s ) equal to 5.6 × 10 −5 and 7.1 × 10 −5 , respectively. At 32 Gbaud, all of the above linewidth requirements can be met using commercial tunable lasers. The proposed schemes achieve a similar linewidth tolerance with a reduced implementation complexity with respect to algorithms based on the blind phase search method.Index Terms-Bit error rate (BER), carrier phase recovery, maximum likelihood estimation (MLE), quadrature amplitude modulation (QAM), 64-QAM-QPSK transformation, triangle edge (TE) symbols, Viterbi and Viterbi algorithm.

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Improved DSP algorithms for coherent 16-QAM transmission

Cited by 45 publications

References 1 publication

Carrier-Phase Estimation for 16-QAM Optical Coherent Systems Using QPSK Partitioning With Barycenter Approximation

Carrier-Phase Estimation for 16-QAM Optical Coherent Systems Using QPSK Partitioning With Barycenter Approximation

80 Gbit/s/λ̣ polarization multiplexed star-16QAM WDM transmission over 720 km SSMF with electronic distortion equalization

Multistage Carrier Phase Estimation Algorithms for Phase Noise Mitigation in 64-Quadrature Amplitude Modulation Optical Systems

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