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Photonics
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Coherent Optical Communications
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Coherent Optical Communications

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Optical Communication and Network".

Deadline for manuscript submissions: closed (15 December 2022) | Viewed by 11930

Special Issue Editor

Prof. Dr. Fady Elnahal

E-Mail Website
Guest Editor
1. Department of Electrical Engineering, Islamic University of Gaza, Gaza, Palestine
2. Connected Systems Group, School of Engineering, University of Warwick, Coventry, UK
Interests: coherent optical communication systems; applications of WDM components for data communications; guided-wave and free space optical systems and components; telecommunications switches

Special Issue Information

Dear Colleagues,

Coherent optical communications for data rates of 100Gbit/s and beyond have been extensively studied, primarily because high sensitivity of coherent receivers could extend the transmission distance. The demonstration of digital carrier phase estimation in coherent receivers has illuminated coherent optical communications. Spectrally efficient modulation techniques, known from wired or wireless communication systems, can be employed for coherent optical links. Moreover, since the phase information is preserved after detection, linear equalization methods can be used to compensate linear optical impairments, such as chromatic dispersion and polarization mode dispersion (PMD). In addition, advanced forward error correction (FEC) techniques can be applied to increase reach and robustness of optical communication systems.

This Special Issue on “Coherent Optical Communications” will welcome basic, methodological, and applied cutting-edge research contributions, as regular and review papers, dealing with:

  • Fundamentals of coherent transmission technology;
  • Multidimensional optimized optical modulation formats;
  • Spectrally efficient multiplexing for coherent systems;
  • Advances in detection and error correction techniques;
  • Digital equalization in coherent optical systems;
  • Implementation of high-speed digital coherent transceivers.

Prof. Dr. Fady Elnahal
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (6 papers)

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Editorial

Jump to: Research, Review

2 pages, 152 KiB  
Editorial
Special Issue on Coherent Optical Communications
by Fady I. El-Nahal
Photonics 2023, 10(6), 683; https://doi.org/10.3390/photonics10060683 - 12 Jun 2023
Viewed by 1094
Abstract
Coherent optical communications have emerged as a groundbreaking technology, enabling data rates of 100 Gbit/s and beyond [...] Full article
(This article belongs to the Special Issue Coherent Optical Communications)

Research

Jump to: Editorial, Review

13 pages, 854 KiB  
Article
Optical Properties Analysis of Scattering Media Based on GI-OCT Imaging
by Decai Huyan, Nofel Lagrosas and Tatsuo Shiina
Photonics 2023, 10(2), 146; https://doi.org/10.3390/photonics10020146 - 31 Jan 2023
Cited by 3 | Viewed by 1710
Abstract
An optical coherence tomography (OCT) system based on the ghost imaging (GI) technique is developed for correctly imaging in scattering media. Usually, the scattering in the media leads to a decrease in the signal-to-noise ratio of the reconstructed image. This problem can be [...] Read more.
An optical coherence tomography (OCT) system based on the ghost imaging (GI) technique is developed for correctly imaging in scattering media. Usually, the scattering in the media leads to a decrease in the signal-to-noise ratio of the reconstructed image. This problem can be solved by using ghost imaging-OCT(GI-OCT), but the number of patterns required for GI reconstruction depends on the concentration of the scattering media. Therefore, studying the relationship between the intensity distribution in reconstructed images and the optical properties of scattering media is essential. In this study, image reconstruction is carried out in scattering media with a concentration of 0.0% to 1.4%, diluted from processed milk. Using the structural similarity index method (SSIM) to analyze the reconstruction condition, it is found that the target image can be reconstructed correctly when the SSIM value is more than 0.7. By analyzing the intensity distribution of the reconstructed image, the results show that the extinction coefficient of the scattering media is negatively correlated with the contrast of the reconstructed image and positively correlated with the scattering intensity. Their correlation coefficients are −0.94 and 0.99, respectively. Full article
(This article belongs to the Special Issue Coherent Optical Communications)
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12 pages, 4566 KiB  
Article
Multi-Level Phase Noise Model for CO-OFDM Spatial-Division Multiplexed Transmission
by Guozhou Jiang and Liu Yang
Photonics 2023, 10(1), 8; https://doi.org/10.3390/photonics10010008 - 23 Dec 2022
Cited by 1 | Viewed by 1407
Abstract
Spatial division multiplexed (SDM) transmission systems with coherence communication technology have become an important issue in meeting the demands for the capacity of fiber. However, research on the phase noise from lasers is mainly focused on single-channel systems or single-carrier SDM systems. In [...] Read more.
Spatial division multiplexed (SDM) transmission systems with coherence communication technology have become an important issue in meeting the demands for the capacity of fiber. However, research on the phase noise from lasers is mainly focused on single-channel systems or single-carrier SDM systems. In this paper, a phase noise model comprising common laser phase noise, in addition to the core phase drifts induced by the SDM, is introduced and analyzed for a coherence orthogonal frequency-division multiplexing (CO-OFDM) spatial-division multiplexed transmission (SDM) system. Based on the phase noise model, the applicability of the blind phase search algorithm and the pilot-aided phase estimation algorithm is discussed and demonstrated via simulation. The results show that these two algorithms can work well when considering combined laser linewidths with core phase drifts for CO-OFDM 7-core multi-core fiber (MCF). The results mean that with the SDM phase noise model, phase noise estimation in other cores can be transferred from one core to lower the complexity with the help of the model. This research provides a proper application of the phase noise analysis of large-capacity optical communication based on a weak-coupled MCF. Full article
(This article belongs to the Special Issue Coherent Optical Communications)
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17 pages, 3987 KiB  
Article
An Effective Method for Enhancing Heterodyne Efficiency by Comparing the Effect of Degree of Polarization on an Uplink Path and a Downlink Path
by Zhenkun Tan, Jiao Wang, Yingxiu Kong, Sichen Lei and Pengfei Wu
Photonics 2022, 9(11), 798; https://doi.org/10.3390/photonics9110798 - 25 Oct 2022
Cited by 1 | Viewed by 1192
Abstract
By analyzing the effect of the degree of polarization (DoP) of the partially coherent Gaussian Schell-model (GSM) beam on a heterodyne system of an uplink path and a downlink path, we developed an innovative and noteworthy theory according to which σsy (signal [...] Read more.
By analyzing the effect of the degree of polarization (DoP) of the partially coherent Gaussian Schell-model (GSM) beam on a heterodyne system of an uplink path and a downlink path, we developed an innovative and noteworthy theory according to which σsy (signal beam waist radius in the y direction component) and δSyy (coherence length of the signal beam in the yy direction component) had a more significant impact on heterodyne efficiency and DoP than the turbulence term on uplink and downlink paths. Namely, the DoP and heterodyne efficiency of an uplink path are higher than that of a downlink path when σsy > 0.02 m or δSyy ≥ 0.03 m. This innovative rule provides an efficient way for increasing the heterodyne efficiency of a signal beam propagating along an uplink or a downlink path channel in satellite-ground communication links in free-space optical heterodyne detection communication. Full article
(This article belongs to the Special Issue Coherent Optical Communications)
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15 pages, 2571 KiB  
Article
Blind Carrier Phase Recovery Using Extended Kalman Filtering in Probabilistically Shaped Coherent Systems
by Shiqun Zhang, Jiarun Yan and Zhiping Huang
Photonics 2022, 9(10), 719; https://doi.org/10.3390/photonics9100719 - 2 Oct 2022
Cited by 2 | Viewed by 1566
Abstract
In this paper, we propose an Extended Kalman Filtering with phase noise reconstruction (EKF-PC) scheme to enhance the carrier recovery capability for probabilistic shaping of coherent optical communication systems with various shaping factors. We first investigate the weights of the shaping factor and [...] Read more.
In this paper, we propose an Extended Kalman Filtering with phase noise reconstruction (EKF-PC) scheme to enhance the carrier recovery capability for probabilistic shaping of coherent optical communication systems with various shaping factors. We first investigate the weights of the shaping factor and the noise rejection window length of EKF-PC for PS-64QAM at a fixed signal-to-noise ratio (SNR). After that, we jointly optimize the shaping factor and the noise rejection window length to obtain the maximum achievable information rate at a variety of SNRs. Then, we numerically analyze the carrier recovery performance of the EKF-PC for different linewidths and SF conditions. Finally, we conduct simulation experiments to compare EKF-PC, PCPE, and other currently available Kalman CPE algorithms with the SFs of 0.02, 0.025, 0.03, and 0.035 under back-to-back (B2B) scenarios. The experimental results show that EKF-PC obtains an average SNR improvement of 0.13–0.5 dB compared to PCPE and an average performance improvement of 0.5–1 dB compared to other Kalman algorithms. Full article
(This article belongs to the Special Issue Coherent Optical Communications)
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Review

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15 pages, 895 KiB  
Review
Recent Advances in Coherent Optical Communications for Short-Reach: Phase Retrieval Methods
by Abdullah S. Karar, Abdul Rahman El Falou, Julien Moussa H. Barakat, Zeynep Nilhan Gürkan and Kangping Zhong
Photonics 2023, 10(3), 308; https://doi.org/10.3390/photonics10030308 - 13 Mar 2023
Cited by 9 | Viewed by 4206
Abstract
Short-reach transmission systems traditionally utilize intensity modulation (IM) at the transmitter and direct detection (DD) at the receiver due to their cost-effectiveness, small footprint, and low power consumption. However, with the exponential increase in bandwidth demand, coherent optical communication systems have become necessary [...] Read more.
Short-reach transmission systems traditionally utilize intensity modulation (IM) at the transmitter and direct detection (DD) at the receiver due to their cost-effectiveness, small footprint, and low power consumption. However, with the exponential increase in bandwidth demand, coherent optical communication systems have become necessary for long-haul distances, requiring application-specific integrated circuits (ASIC) and advanced digital signal processing (DSP) algorithms coupled with high-speed digital-to-analog and analog-to-digital converters to achieve Tbit/s speeds. As coherent technology matures, it will eventually become feasible for short-reach transmission. In this context, self-coherent systems have emerged as an intermediary solution, offering advantages over traditional IM/DD systems. While comprehensive review studies exist on self-coherent transceivers, they do not cover recent advances in phase retrieval methods for short-reach optical communications. This review article highlights recent developments in cost-effective self-coherent detection for short-reach systems through comparing the benefits of single sideband (SSB) transmission and Kramers-Kronig detection to carrier-assisted phase retrieval, the Gerchberg-Saxton (GS) algorithm, and the transport of intensity equation (TIE) method. Full article
(This article belongs to the Special Issue Coherent Optical Communications)
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