Adaptive digital equalization in the presence of chromatic dispersion, PMD, and phase noise in coherent fiber optic systems

Crivelli, D.E.; Carter, H.S.; Hueda, Mario R.

doi:10.1109/glocom.2004.1378465

Cited by 36 publications

(53 citation statements)

References 31 publications

(23 reference statements)

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“…This is certainly possible, since the sequence is, after all, a function of the sequence . As an example, in the case of a PSK alphabet, the symbol-by-symbol asynchronous strategy (17), (18) can be equivalently expressed as (taking also into account that and that according to the differential encoding rule) [23] (21) where (22) In this way, an explicit differential decoding is not necessary.…”

Section: Asynchronous Detection Strategy and Asynchronous Filter Amentioning

confidence: 99%

“…The described symbol-by-symbol asynchronous detection strategies (17), (18), and (17)- (19) and the updating rule (20) can be equivalently expressed as a function of the information symbols . This is certainly possible, since the sequence is, after all, a function of the sequence .…”

Section: Asynchronous Detection Strategy and Asynchronous Filter Amentioning

confidence: 99%

“…Notice that this FFE also performs the compensation for a constant phase shift, possibly introduced by transmit and receive lasers, which is implicit in the knowledge of the channel impulse response . Hence, an explicit phase estimation, such as that used in [17], is not necessary, at least when phase noise is absent (i.e., assuming that the transmit and receive lasers only introduce a constant phase shift). The FFE structure is shown in Fig.…”

Section: A Two-dimensional Fractionally-spaced Ffementioning

confidence: 99%

“…In both figures, we considered the case of a FFE alone, and in this case its coefficients are adjusted every symbol time to follow the phase variations, and the cases when a PLL or the asynchronous strategy (17), (18) are employed. The PLL equivalent bandwidth and the value of for the asynchronous strategy (17), (18), have been optimized for every value of the lasers linewidth. As previously mentioned, the asynchronous strategy exhibits an impressive robustness and is immune from the occurrence of losses of lock which on the contrary affect the PLL.…”

Section: B Robustness To Phase Noisementioning

confidence: 99%

“…First of all, we consider the asynchronous detection strategy (17), (18) and assess its robustness to an uncompensated frequency offset. To this purpose, we consider the QPSK modulation, although similar considerations also hold for the 16-QAM.…”

Section: Frequency Estimation and Compensationmentioning

confidence: 99%

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Robust Multilevel Coherent Optical Systems With Linear Processing at the Receiver

Colavolpe

Foggi

Forestieri

et al. 2009

J. Lightwave Technol.

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Abstract-This paper investigates optical coherent systems based on polarization multiplexing and high-order modulations such as phase-shift keying (PSK) signals and quadrature amplitude modulations (QAM). It is shown that a simple linear receiver processing is sufficient to perfectly demultiplex the two transmitted streams and to perfectly compensate for group velocity dispersion (GVD) and polarization mode dispersion (PMD). In addition, in the presence of a strong phase noise of the lasers at the transmitter and receiver, a symbol-by-symbol detector with decision feedback is able to considerably improve the receiver robustness with a limited complexity increase. We will also discuss the channel estimation and the receiver adaptivity to time-varying channel conditions as well as the problem of the frequency acquisition and tracking. Finally, a new two-dimensional (polarization/time) differential encoding rule is proposed to overcome a polarization-ambiguity problem. In the numerical results, the receiver performance will be assessed versus the receiver complexity.Index Terms-Electrical equalization, group velocity dispersion (GVD), intersymbol interference (ISI), optical coherent transmission systems, phase-shift keying (PSK), polarization mode dispersion (PMD), quadrature amplitude modulation (QAM).

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Section: Asynchronous Detection Strategy and Asynchronous Filter Amentioning

confidence: 99%

Section: Asynchronous Detection Strategy and Asynchronous Filter Amentioning

confidence: 99%

Section: A Two-dimensional Fractionally-spaced Ffementioning

confidence: 99%

Section: B Robustness To Phase Noisementioning

confidence: 99%

Section: Frequency Estimation and Compensationmentioning

confidence: 99%

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Robust Multilevel Coherent Optical Systems With Linear Processing at the Receiver

Colavolpe

Foggi

Forestieri

et al. 2009

J. Lightwave Technol.

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Error-Backpropagation-Based Background Calibration of TI-ADC for Adaptively Equalized Digital Communication Receivers

Solis¹,

Reyes²,

Morero

et al. 2022

IEEE Access

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A novel background calibration technique for Time-Interleaved Analog-to-Digital Converters (TI-ADCs) is presented in this paper. This technique is applicable to equalized digital communication receivers. As shown in the literature, in a digital receiver it is possible to treat the TI-ADC errors as part of the communication channel and take advantage of the adaptive equalizer to compensate them. Therefore calibration becomes an integral part of channel equalization. No special purpose analog or digital calibration blocks or algorithms are required. However, there is a large class of receivers where the equalization technique cannot be directly applied because other signal processing blocks are located between the TI-ADC and the equalizer. The technique presented here generalizes earlier works to this class of receivers. The error backpropagation algorithm, traditionally used in machine learning, is applied to the error computed at the receiver slicer and used to adapt an auxiliary equalizer adjacent to the TI-ADC, called the Compensation Equalizer (CE). Simulations using a dual polarization optical coherent receiver model demonstrate accurate and robust mismatch compensation across different application scenarios. Several Quadrature Amplitude Modulation (QAM) schemes are tested in simulations and experimentally. Measurements on an emulation platform which includes an 8 bit, 4 GS/s TI-ADC prototype chip fabricated in 130nm CMOS technology, show an almost ideal mitigation of the impact of the mismatches on the receiver performance when 64-QAM and 256-QAM schemes are tested. INDEX TERMS Background calibration, error backpropagation, optical coherent receiver, TI-ADC, TI-ADC mismatch calibration. I. INTRODUCTION T HIS paper proposes a novel background calibration technique for Time-Interleaved Analog-to-Digital Converters (TI-ADCs) used in equalized digital communication receivers. It generalizes a previously proposed technique [1]-[3]. Current and emerging digital receivers for ultra highspeed communication systems [4]-[10] require large bandwidth, high sampling rate ADCs. Please see [11] and references therein for a recent review of interleaving techniques for high speed data converters. The TI-ADC has been the technique predominantly used to meet the demanding sampling rate and bandwidth requirements of high-speed transceivers [12], [13]. The per-formance of TI-ADCs is affected by mismatches among the interleaves [14], [15]. Mismatches of sampling time, gain, bandwidth, as well as DC offset, are the most common impairments. Many calibration techniques have been proposed in the literature. Please see [16]-[41] and references therein for a thorough review and discussion. Calibration techniques for general purpose TI-ADCs in general require dedicated calibration blocks and algorithms. On the other hand, several authors [1]-[3] have shown that in the special case of an equalized digital receiver, it is possible to treat the TI-ADC errors as integral part of the communication channel and take advantage of the already ex...

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Adaptive Digital Compensation of Analog Impairments in Frequency Interleaved ADC for Next-Generation High-Speed Communication Receivers

Passetti,

Morero,

Reyes

et al. 2023

IEEE Access

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This paper presents an adaptive background compensation technique designed to address analog impairments in frequency-interleaved analog-to-digital converters. Frequency interleaving has been proposed as a solution to the bandwidth bottleneck of data converters in high-speed digital communication receivers, including those deployed in coherent optical transmission systems. The proposed technique combines an adaptive multiple-input multiple-output equalizer with the well-established backpropagation algorithm commonly utilized in machine learning. Unlike previous proposals, the new algorithm (i) compensates the linear impairments in the analog-front-end of the receiver (e.g., mismatches of track-and-hold and trans-impedance amplifier frequency responses, time skews, quadrature imbalance in electrical carriers, etc.), and (ii) maximizes the signal-to-noise ratio at the decision point of the receiver without requiring estimation of the channel parameters. The proposed background compensation scheme is thoroughly investigated in a dual-polarization coherent optical receiver with 16-QAM operating at ∼200 GBd (i.e., ∼1.6 Tbps). Numerical results show the excellent performance and high robustness of the new background compensation algorithm. These features, combined with its low implementation complexity, will pave the way for the deployment of commercial transceivers with bandwidths of 100 GHz and beyond.INDEX TERMS Background calibration, frequency interleaved ADCs, high-speed optical receiver I. INTRODUCTION

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Adaptive digital equalization in the presence of chromatic dispersion, PMD, and phase noise in coherent fiber optic systems

Cited by 36 publications

References 31 publications

Robust Multilevel Coherent Optical Systems With Linear Processing at the Receiver

Robust Multilevel Coherent Optical Systems With Linear Processing at the Receiver

Error-Backpropagation-Based Background Calibration of TI-ADC for Adaptively Equalized Digital Communication Receivers

Adaptive Digital Compensation of Analog Impairments in Frequency Interleaved ADC for Next-Generation High-Speed Communication Receivers

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