Pilot-free common phase error estimation for CO-OFDM with improved spectral efficiency
TL;DR: An improved pilot free phase noise mitigation algorithm for CO-OFDM systems using weighted multi-level QPSK partitioning and Kalman filtering is proposed and an improvement in spectral efficiency is demonstrated.
Abstract: We propose an improved pilot free phase noise mitigation algorithm for CO-OFDM systems using weighted multi-level QPSK partitioning and Kalman filtering. Through extensive Monte Carlo simulations, we demonstrate an improvement in spectral efficiency of $>$
6% in case of 200 Gbps single channel and 1 Tbps multi channel 16QAM CO-OFDM transmission with blind carrier phase estimation. We also experimentally demonstrate the performance of the proposed algorithm against the standard pilot aided algorithm for the transmission of 120 Gbps 16QAM CO-OFDM at different noise levels.
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TL;DR: In this paper, the authors demonstrate superchannel transmission using CO-OFDM with higher cardinality QAM corresponding to total data rates up to 760 Gbps over 25 km fiber using optical carriers generated from an externally injection locked gain-switched comb source with linewidth ≈19 kHz.
Abstract: We experimentally demonstrate superchannel transmission using CO-OFDM with higher cardinality QAM corresponding to total data rates up to 760 Gbps over 25 km fiber using optical carriers generated from an externally injection locked gain-switched comb source with linewidth ≈19 kHz. Bandwidth re-configurability is demonstrated by operating the comb with different line spacing (20 GHz, 11 GHz) for the choice of (16-/32-/64-) QAM considered and we show the BER performance is within the SD-FEC limit. The system proposed can be used in any short reach application including DCIs and in access networks.
3 citations
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TL;DR: In this article, a CO-OFDM superchannel transmission over 25 km using optical carrier generated from an externally injected gain-switched comb source with linewidth ≈ 19 kHz was demonstrated.
Abstract: We experimentally demonstrate 608 Gbps CO-OFDM superchannel transmission over 25 km using optical carrier generated from an externally injected gain-switched comb source with linewidth ≈19 kHz. We show the BER performance is within the HD-FEC limit.
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TL;DR: A DWPT based CO-OFDM system with Wilcoxon Robust Extreme Learning Machine based pilot-free phase noise compensator using multi-level QPSK partitioning of 16-QAM has been proposed and the percentage improvement in performance and spectral efficiency over traditional pilot-aided techniques is 6 and 21 respectively.
Abstract: Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) system with Pilot-free phase noise compensator was introduced in order to accomplish the need of high spectral efficiency in the optical communication. In CO-OFDM system Discrete wavelet packet transforms (DWPTs) in place of Fast Fourier Transforms (FFTs) had attracted more attention since it has removed the need of cyclic prefix used to compensate fiber dispersion. In this paper, a DWPT based CO-OFDM system with Wilcoxon Robust Extreme Learning Machine based pilot-free phase noise compensator using multi-level QPSK partitioning of 16-QAM has been proposed. From the results of this work it has been seen that the percentage improvement in performance (in terms of Q-Factor) and spectral efficiency over traditional pilot-aided techniques is approximately 6 and 21 respectively. Moreover, this proposed work will comparatively reduce the overall system complexity.
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TL;DR: The effectiveness of the SOA-based phase conjugator to improve the link budget with a 100 km standard single mode fiber link for 20 GHz coherent OFDM signals, with QPSK and 16QAM modulations and a corresponding net bit-rate of 40 Gbps and 80 Gbps respectively is experimentally demonstrated.
Abstract: We study the use of nonlinear semiconductor optical amplifier (SOA) for generating optical phase conjugate towards compensation of distortions in short distance optical fiber transmission due to Kerr nonlinearity and chromatic dispersion in coherent multi-carrier lightwave signals. We experimentally demonstrate the effectiveness of the SOA-based phase conjugator to improve the link budget with a 100 km standard single mode fiber link for 20 GHz coherent OFDM signals, with QPSK and 16QAM modulations and a corresponding net bit-rate of 40 Gbps and 80 Gbps respectively. Mid-span spectral inversion scheme is employed where the optical phase conjugate is generated through a partially degenerate four-wave mixing process in a nonlinear SOA. We demonstrate a bit error rate performance within $2\times 10^{-2}$ for an average launched power of up to 12 dBm (9 dBm) for QPSK (16QAM) coherent OFDM signals, in a 100 km fiber link. We also investigate the possible improvement in link budget using numerical simulation for 16QAM and 64QAM CO-OFDM signals with the proposed scheme.
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References
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TL;DR: An exact analysis of orthogonal frequency-division multiplexing (OFDM) performance in the presence of phase noise and a general phase-noise suppression scheme which, by analytical and numerical results, proves to be quite effective in practice.
Abstract: We provide an exact analysis of orthogonal frequency-division multiplexing (OFDM) performance in the presence of phase noise Unlike most methods which assume small phase noise, we examine the general case for any phase noise levels After deriving a closed-form expression for the signal-to-noise-plus-interference ratio (SINR), we exhibit the effects of phase noise by precisely expressing the OFDM system performance as a function of its critical parameters This helps in understanding the meaning of small phase noise and how it reflects on the proper parameters selection of a specific OFDM system In order to combat phase noise, we also provide in this paper a general phase-noise suppression scheme, which, by analytical and numerical results, proves to be quite effective in practice
339 citations
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Proceedings Article•
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TL;DR: In this paper, the authors demonstrate the generation of a 1.2-Tb/s NGI-CO-OFDM superchannel comprising of 24 frequency-locked 12.5GHz spaced PDM-QPSK carriers, and transmit it over 72×100-km of ultra-large-area fiber, achieving 3.7b /s/Hz channel spectral efficiency.
Abstract: We demonstrate the generation of a novel 1.2-Tb/s NGI-CO-OFDM superchannel comprising of 24 frequency-locked 12.5-GHz spaced PDM-QPSK carriers, and transmit it over 72×100-km of ultra-large-area fiber, achieving 3.7-b/s/Hz channel spectral-efficiency (SE) and a record SE-distance product of 27,000-km·b/s/Hz.
264 citations
"Pilot-free common phase error estim..." refers background in this paper
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TL;DR: In this paper, the optical OFDM architectures are reviewed, and their performance under various system conditions are compared and compared with alternative technologies, and the challenges in the implementation of optical ONDM are also discussed.
Abstract: Orthogonal frequency division multiplexing (OFDM) is a widely used modulation/multiplexing technology in wireless and data communications. Leveraging recent advances in high-speed complementary metal-oxide semiconductor (CMOS) technologies and optical modulation and detection technologies, optical OFDM at a 40Gb/s or even a 100Gb/s information rate becomes feasible. At the optical transmitter, OFDM is realized by a digital signal processor (DSP) using inverse fast Fourier transformation (iFFT) with subsequent digital-to-analog conversion and Cartesian electro-optic modulation. At the receiver, the signal optical field is first reconstructed, e.g., by coherent detection. Then reverse signal processing is applied to recover the original data. OFDM enables efficient compensation of transmission effects such as chromatic dispersion and polarization mode dispersion that often are prohibiting impairments to cost-effective realization of high-speed optical transport systems. In light of the emerging demand for a 100+ Gb/s data rate in future optical transport systems, optical OFDM is considered to be a promising enabling technology. In this paper, the optical OFDM architectures will be reviewed, and their performance under various system conditions will be discussed and compared with alternative technologies. The challenges in the implementation of optical OFDM will also be discussed.
58 citations
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TL;DR: The feasibility of zero-overhead laser phase noise compensation (PNC) for long-haul coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission systems, using the decision-directed phase equalizer (DDPE), and the complexity of DDPE versus CE is analyzed in terms of the number of required complex multiplications per bit.
Abstract: We report and investigate the feasibility of zero-overhead laser phase noise compensation (PNC) for long-haul coherent optical orthogonal frequency division multiplexing (CO-OFDM) transmission systems, using the decision-directed phase equalizer (DDPE). DDPE updates the equalization parameters on a symbol-by-symbol basis after an initial decision making stage and retrieves an estimation of the phase noise value by extracting and averaging the phase drift of all OFDM sub-channels. Subsequently, a second equalization is performed by using the estimated phase noise value which is followed by a final decision making stage. We numerically compare the performance of DDPE and the CO-OFDM conventional equalizer (CE) for different laser linewidth values after transmission over 2000 km of uncompensated single-mode fiber (SMF) at 40 Gb/s and investigate the effect of fiber nonlinearity and amplified spontaneous emission (ASE) noise on the received signal quality. Furthermore, we analytically analyze the complexity of DDPE versus CE in terms of the number of required complex multiplications per bit.
48 citations
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TL;DR: The carrier phase recovery for 16-ary quadrature amplitude modulation (16-QAM) optical coherent systems using the quaternary phase-shift keying (QPSK) partitioning with sliding window averaging and differential decoding with the impact of analog-to-digital converter (ADC) resolution is investigated.
Abstract: This letter presents the carrier phase recovery for 16-ary quadrature amplitude modulation (16-QAM) optical coherent systems using the quaternary phase-shift keying (QPSK) partitioning with sliding window averaging and differential decoding. We assess the increase in linewidth tolerance achievable with sliding window averaging as opposed to block averaging. Simulation results demonstrate that combined linewidth symbol duration product, Δv · Ts, 10-4 is tolerable at the target bit error ratio (BER) of 10-2 and 10-3 for a penalty of 0.6 and 0.8 dB, respectively, compared with the theoretical limit with differential decoding. The impact of analog-to-digital converter (ADC) resolution on the performance of the QPSK partitioning algorithm is also investigated. Finally, the performance of the algorithm using the measured phase noise for a distributed feedback (DFB) laser is presented for different values of Δv · Ts. We show that for Δv · Ts > 10-4, the penalty of block averaging is > 0.5 dB with respect to sliding window averaging at the target BER of 10-3 with the measured phase noise. The degradation associated with block averaging at the target BER of 10-2 is shown to be less significant compared to sliding window averaging.
30 citations
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