Advanced Digital Signal Processing for High Spectral Efficiency Multidimensional Transmission
Doctoral thesis, 2024
Modern coherent optical communication systems utilize all available physical dimensions for data modulation. In general, independent modulation and signal processing are performed in coherent systems, leaving a performance gap to the Shannon limit. This thesis focuses on advanced digital signal processing to achieve joint encoding and joint processing systems with high spectral efficiency (SE).
First, we investigate the low-complexity and practical digital predistortion approaches to eliminate the nonlinear transmitter distortion, which is one dominant impairment for the high-SE transponder. Joint processing of multiple wavelength channels in the receiver can eliminate the linear and nonlinear interchannel interference in long-haul superchannel systems. Using the frequency-locked received channels provided by the comb-based superchannel and receiver, two joint processing schemes are studied. We investigate the performance of multichannel equalization, which cancels linear interchannel crosstalk and reduces the guard bands, in the long-haul transmission constrained by the amplified spontaneous emission noise. In addition, we propose a perturbative-based compensation to eliminate both self-phase modulation and cross-phase modulation caused by the interference wavelength channels.
Multidimensional (MD) Vononoi constellations generated by a structured geometric shaping method provide shaping gain over conventional quadrature amplitude modulation (QAM) and have low-complexity encoding and decoding algorithms, which are suitable for high-SE applications. The use of MD formats closes the gap to the theoretical Shannon limit. By employing a 24-dimensional VC with a record constellation size of 7.9×10^28 and lookup table based predistortion, we present a 12.2 bit/s/Hz C-band transmission over 40 km single-mode fiber and have the first experimental demonstration of a significant MD shaping gain over QAM formats in the soft-decision coded system.
First, we investigate the low-complexity and practical digital predistortion approaches to eliminate the nonlinear transmitter distortion, which is one dominant impairment for the high-SE transponder. Joint processing of multiple wavelength channels in the receiver can eliminate the linear and nonlinear interchannel interference in long-haul superchannel systems. Using the frequency-locked received channels provided by the comb-based superchannel and receiver, two joint processing schemes are studied. We investigate the performance of multichannel equalization, which cancels linear interchannel crosstalk and reduces the guard bands, in the long-haul transmission constrained by the amplified spontaneous emission noise. In addition, we propose a perturbative-based compensation to eliminate both self-phase modulation and cross-phase modulation caused by the interference wavelength channels.
Multidimensional (MD) Vononoi constellations generated by a structured geometric shaping method provide shaping gain over conventional quadrature amplitude modulation (QAM) and have low-complexity encoding and decoding algorithms, which are suitable for high-SE applications. The use of MD formats closes the gap to the theoretical Shannon limit. By employing a 24-dimensional VC with a record constellation size of 7.9×10^28 and lookup table based predistortion, we present a 12.2 bit/s/Hz C-band transmission over 40 km single-mode fiber and have the first experimental demonstration of a significant MD shaping gain over QAM formats in the soft-decision coded system.
multidimensional format
frequency comb
superchannel
Coherent communication
signal processing
wideband transmission
Kollektorn, Kemivägen 9, Chalmers
Opponent: Prof. Georg Rademacher, Institute of Electrical and Optical Communications, University of Stuttgart, Germany
Author
Zonglong He
Chalmers, Microtechnology and Nanoscience (MC2), Photonics
12.2 bit/s/Hz C-band Transmission with High-Gain Low-Complexity 24-Dimensional Geometric Shaping
Journal of Lightwave Technology,;Vol. 42(2024)p. 4829-4836
Journal article
Inter-Channel Interference Cancellation for Long-Haul Superchannel System
Journal of Lightwave Technology,;Vol. 42(2024)p. 48-56
Journal article
Periodicity-Enabled Size Reduction of Symbol Based Predistortion for High-Order QAM
Journal of Lightwave Technology,;Vol. 40(2022)p. 6168-6178
Journal article
Over-the-fiber Digital Predistortion Using Reinforcement Learning
2021 European Conference on Optical Communication, ECOC 2021,;(2021)
Paper in proceeding
Perturbation based Joint SPM and XPM Compensation for Superchannel System
IEEE Photonics Technology Letters,;Vol. In Press(2024)
Journal article
Coherent optical communication systems are one of the most important components in the Internet infrastructure, providing a high-speed global connection for a wide range of services such as big data, online video, messaging, and online computer game. Today, to meet the demand for fast-growing data traffic, coherent fiber-optic systems modulate the information of the amplitude, phase, time, polarization, wavelength, and even space of the optical light to achieve high total throughput. As the current available hardware, spectral and fiber resources are limited, it is of importance to improve the spectral efficiency, i.e. the achievable information rate per frequency unit, and thus boost the overall capacity. In current systems, independent data is modulated in each dimension and no multichannel processing is performed in the receiver, leaving an unknown full capacity for the fiber communication.
In this thesis we focus on high-spectral-efficiency multidimensional transmission, in which joint encoding and processing is performed, to exploit the full fiber capacity. The advanced digital signal processing such as pre-compensation and multichannel equalization is investigated for their ability to cancel transceiver and channel impairments, which preserves the shaping gain from the multidimensional modulation formats. The goal of this study is to utilize all the available physical dimensions for more energy-efficient data transmission and support future high-capacity fiber networks.
In this thesis we focus on high-spectral-efficiency multidimensional transmission, in which joint encoding and processing is performed, to exploit the full fiber capacity. The advanced digital signal processing such as pre-compensation and multichannel equalization is investigated for their ability to cancel transceiver and channel impairments, which preserves the shaping gain from the multidimensional modulation formats. The goal of this study is to utilize all the available physical dimensions for more energy-efficient data transmission and support future high-capacity fiber networks.
Coupled fiber optic channels
Swedish Research Council (VR) (2019-04078), 2019-12-01 -- 2023-11-30.
Unlocking the Full-dimensional Fiber Capacity
Knut and Alice Wallenberg Foundation (KAW 2018.0090), 2019-07-01 -- 2024-06-30.
Communications over bursty optical channels
Swedish Research Council (VR) (2021-03709), 2022-01-01 -- 2025-12-31.
Areas of Advance
Information and Communication Technology
Subject Categories
Signal Processing
ISBN
978-91-8103-054-9
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5512
Publisher
Chalmers
Kollektorn, Kemivägen 9, Chalmers
Opponent: Prof. Georg Rademacher, Institute of Electrical and Optical Communications, University of Stuttgart, Germany