Mitigation of Transmitter Impairment with 4×2 WL MIMO Equalizer Embedding Preliminary CPR

Sato, Masaki; Noguchi, Hidemi; Matsui, Junichiro; Abe, Jun-ichi; Gabory, Emmanuel Le Taillandier de

doi:10.1364/ofc.2022.m1h.5

Cited by 3 publications

(5 citation statements)

References 3 publications

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“…These indicate the PF MIMO AEQ is a promising technique for future high-information-rate optical receivers in practical applications. APPENDIX A DERIVATION OF (4,5) This appendix explains a derivation of (4,5). First, the inverse process of the signal transmission can be represented by cascaded multiplication of complex four-dimensional matrices and a vector:…”

Section: Discussionmentioning

confidence: 99%

“…As digital coherent systems have developed, it has been found that MIMO AEQs can compensate for electrical signal in-phase/quadrature (IQ) impairments in the transmitter and receiver, alongside those caused by polarization-related effects in the transmission line, by increasing their internal degrees of freedom (DOFs) [1][2][3][4][5]. Here, IQ impairments refer to IQ skew, IQ imbalance (including those caused by electrical signal reflection) and IQ crosstalk, which reportedly can be limiting factors of high-information-rate transmissions [1][2][3][4][5][6]. Typical examples of such AEQs are complex 4×2 MIMO AEQs (or widely linear AEQ) [2] and 8×2 MIMO AEQs [1].…”

Section: Introductionmentioning

confidence: 99%

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Partial Freezing for MIMO Adaptive Equalizers: Precise Demodulation in Dynamic Environments

Kawai

Nakamura

Takahashi

et al. 2023

J. Lightwave Technol.

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We propose partially frozen (PF) multiple-input multiple-output (MIMO) adaptive equalizers (AEQs). By increasing the degrees of freedom (DOFs) of widely used complex 2×2 MIMO AEQs, complex 4×2 and 8×2 MIMO AEQs can cope with various signal impairments that occur within a transmitter and receiver, such as in-phase/quadrature (IQ) skew and IQ imbalance. Although precise signal demodulation with such MIMO AEQs are useful for enhancing the information rate of a transmission even to reach beyond 1 Tb/s, the increase in internal DOFs ultimately comes with a decrease in the speed of tracking polarization fluctuations and an increase in computational complexity, which are problematic for efficient demodulation in a dynamic environment. To solve this, as the speed of fluctuation in the state of polarization (SOP) of the signal is much faster than those of impairments within the transmitter and receiver, PF MIMO AEQs reduce effective DOFs by separating each DOF corresponding to the SOP, transmitter, and receiver, then freezing unnecessary updates of transmitter and receiver DOFs. In this paper, we describe the principle and show the results of numerical simulations and experiments with 128-Gbaud quadrature phase shift keying (QPSK) signals under IQ impairments. PF MIMO AEQs increased the tracking speed of the 8×2 MIMO AEQ, enabling the tracking of polarization fluctuations of over 11 Mrad/s (faster than fluctuation induced by lightning strikes) with less computational complexity than the conventional configuration. This method is a promising solution for high-speed data transmissions in dynamic environments.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Partial Freezing for MIMO Adaptive Equalizers: Precise Demodulation in Dynamic Environments

Kawai

Nakamura

Takahashi

et al. 2023

J. Lightwave Technol.

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show abstract

“…[4] notes that a second stage of CPR after the Tx compensation filter is expected to prevent the degradation. In addition, the placement of CPR after the MIMO equalizer in the proposed method can prevent it [5].…”

Section: Wl Mimo Equalizer With Independent Complex Filtering On Iq S...mentioning

confidence: 99%

“…As the symbol rate increases, the signal-quality impact of linear impairments such as various IQ imbalances, either frequency dependent or independent, becomes more significant in proportion to the modulation order. Accordingly, several transceiver impairment mitigation techniques featuring digital signal processing (DSP) have been proposed, for both factory calibration [2] and adaptive equalization at the coherent receiver [3][4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…To mitigate Tx impairment, a 2×2 real-IQ multiple-input multiple-output (MIMO) equalizer for signals after carrier phase recovery (CPR) has been proposed [4]. We have also proposed a 4×2 widely linear (WL) MIMO equalizer embedding preliminary CPR [5]. This equalizer first compensates for carrier phase error and then compensates simultaneously for polarization rotation and Tx impairments.…”

Section: Introductionmentioning

confidence: 99%

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Transceiver Impairment Mitigation by 8×2 Widely Linear MIMO Equalizer With Independent Complex Filtering on IQ Signals

et al. 2022

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High-order modulation formats with high symbol rates are promising candidates for meeting the growing traffic requirements of digital coherent transmission. In using these modulation formats, the impact of transceiver impairment on the signal quality becomes significant. In this paper, we propose an 8×2 widely linear (WL) multiple-input multiple-output (MIMO) equalizer with independent complex filtering on IQ signals to mitigate linear transceiver impairments. Furthermore, we extend the equalizer for digital subcarrier (SC) multiplexing. Accordingly, a 16×4 WL MIMO equalizer is also proposed to mitigate linear transceiver impairments, through application to a pair of SC inputs. Experimental results show that, for transmission of a 58-GBaud polarization-multiplexing 64 quadrature amplitude modulation (PM-64QAM) single-carrier signal, the proposed method effectively compensates for various receiver impairments and also mitigates transmitter (Tx) impairments. Q-penalties of 0.1 dB up to a 10-ps skew, 2.5-dB gain imbalance, 7.2-degree phase error, and -15-dB crosstalk in Tx were achieved for 100-km standard single-mode fiber transmission. Moreover, for a 29-GBaud PM-64QAM dual-SC signal, the proposed 16×4 WL MIMO equalizer shows transceiver impairment mitigation performance similar to that in the singlecarrier case, even though dual-SC transmission is less tolerant of laser phase noise.

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High Spectral Efficiency Probabilistically Shaped PDM 1024-QAM Transmission System

Shi,

Gao,

Han

et al. 2023

2023 Opto-Electronics and Communications Conference (OECC)

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Mitigation of Transmitter Impairment with 4×2 WL MIMO Equalizer Embedding Preliminary CPR

Abstract: Transmitter impairment mitigation for 58-GBaud PM-64QAM with 4×2 WL MIMO embedding preliminary CPR was demonstrated over 100 km SSMF. Q-penalties of 0.1 dB with 14 ps IQ skew and 10 degree phase error were achieved.

Cited by 3 publications

References 3 publications

Partial Freezing for MIMO Adaptive Equalizers: Precise Demodulation in Dynamic Environments

Partial Freezing for MIMO Adaptive Equalizers: Precise Demodulation in Dynamic Environments

Transceiver Impairment Mitigation by 8×2 Widely Linear MIMO Equalizer With Independent Complex Filtering on IQ Signals

High Spectral Efficiency Probabilistically Shaped PDM 1024-QAM Transmission System

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