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Special Issue "Next-Generation Optical Communication: Components and Devices"

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A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E：Engineering and Technology".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 7428

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Special Issue Editors

Dr. Jiangbo Zhu

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Guest Editor

Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, UK
Interests: structured light; optical communications; integrated photonics; fiber optics

Dr. He Wen

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Guest Editor

School of Electronic Engineering, Beijing University of Posts & Telecommunications, Beijing 100876, China
Interests: optical communications; microwave photonics; optoelectronics; nonlinear optics

Special Issue Information

Dear Colleagues,

Ever-emerging services and applications, such as cloud computation, big data, and the Internet of things, have imposed an exponentially growing capacity demand on communication systems and networks on all layers. In particular, conventional single-mode fiber (SMF)-based optical communication technologies, such as wavelength-division multiplexing (WDM), time-division (TDM), and polarization-division (PDM), have confronted fundamental scalability limits. The last decade has seen various technologies emerge as possible solutions for next-generation optical communications for sustainable capacity growth, by exploiting the only known uncultivated degree of freedom of light—the space domain. Space- and mode-division multiplexing (SDM and MDM)-based optical-fiber, free-space, and underwater communications have been extensively investigated at both system and component levels. Multi-core, multi-mode, few-mode fibers (MCF, MMF, and FMF) and the variations as their combinations are explored as the main platforms for SDM and MDM fiber transmissions, while major challenges including optical amplification and inter-channel coupling remain to be fully addressed. In pursuit of other key components of high efficiency and scalability, especially spatial/modal (de)multiplexers, significant developments have been witnessed recently by introducing sophisticated structured light manipulation techniques, for example, photonic lantern, multi-plane light conversion (MPLC), log-polar and spiral transform based mode sorters, and inverse-design based optical mode converters. This Special Issue seeks to showcase research papers, communications, and review articles that focus on new developments in the design, modelling, fabrication, and application of SDM/MDM devices and components.

Dr. Jiangbo Zhu
Dr. He Wen
Guest Editors

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Keywords

optical communications
space-division multiplexing
mode-division multiplexing
multi-core fiber
multi-mode fiber
few-mode fiber
mode sorter
multi-plane light conversion
orbital angular momentum
linearly polarized modes
few-mode amplifiers
multicore fiber amplifier

Published Papers (6 papers)

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Research

Open AccessArticle

Free Space Optics Transmission Performance Enhancement for Sustaining 5G High Capacity Data Services

and

Micromachines 2022, 13(8), 1248; https://doi.org/10.3390/mi13081248 - 03 Aug 2022

Cited by 1 | Viewed by 925

Abstract

Enhanced bandwidth issues for 5G system are fruitfully resolved by organizing free space optics (FSO) communication frameworks. The high bandwidth, the maximum number of channel transmission requirements, and high data rate have been boosted during the last years because of the COVID-19 pandemic. The online services and digital applications have increased pressure on installed optical network models. In addition, the optical networks with high capacity transmission produce nonlinear distortions, which degrade system efficiency. This paper presents a mixed FSO and fiber network to tackle the factors of nonlinearities and enrich the system capacity and range. Furthermore, the issues related to radio frequency, FSO pointing, and co-channel interference are considered in this work. The theoretical and simulation structures are validated using advanced measuring parameters, such as bit error rate (BER), peak to average power ratio (PAPR), cumulative distribution function (CDF), and outage probability. The nonlinear factors are addressed successfully, and the capacity is developed from current models. Finally, the proposed model’s limitations and future direction are discussed in this paper. Full article

(This article belongs to the Special Issue Next-Generation Optical Communication: Components and Devices)

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Open AccessArticle

SOA Amplified 100 Gb/s/λ PAM-4 TDM-PON Supporting PR-30 Power Budget with >18 dB Dynamic Range

and

Micromachines 2022, 13(3), 342; https://doi.org/10.3390/mi13030342 - 22 Feb 2022

Cited by 1 | Viewed by 1116

Abstract

Semiconductor optical amplifier (SOA) is considered an excellent candidate for power amplification at O-band due to its low cost and small footprint. In passive optical networks (PONs), SOA is popular as a booster and pre-amplifier to improve the link power budget. However, whether as a booster or pre-amplifier, SOA will induce different degrees of nonlinearity when the output power is high, which degrades the transmission performance of the system and leads to a limited receiver dynamic range. In this paper, we experimentally demonstrate the feasibility of using SOA in both transmitter and receiver sides for power budget improvement in 100 Gb/s/λ four-level pulsed amplitude modulation (PAM-4) time division multiplexed PON (TDM-PON) system at O-band. For compensating the linear and nonlinear impairments induced by transceivers and SOA, a look-up-table (LUT) pre-compensation at the optical line terminal (OLT) side and a simple feed-forward equalizer (FFE) at the optical network unit (ONU) side are adopted for downstream transmission. For upstream transmission, a 2nd-order Volterra nonlinear equalizer (VNLE) is utilized at the OLT side, and no pre-compensation is used at the transmitter of the ONU, which releases the digital signal processing (DSP) pressure of ONUs in a multi-user scenario. For the soft-decision FEC (SD-FEC) threshold (1 × 10⁻²), the IEEE PR-30 power budget requirement is met, and >18 dB dynamic range is achieved in both 25 km downstream and upstream transmission. Full article

(This article belongs to the Special Issue Next-Generation Optical Communication: Components and Devices)

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Open AccessArticle

3 × 40 Gbit/s All-Optical Logic Operation Based on Low-Loss Triple-Mode Silicon Waveguide

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Micromachines 2022, 13(1), 90; https://doi.org/10.3390/mi13010090 - 07 Jan 2022

Viewed by 867

Abstract

Information capacity of single-mode fiber communication systems face fundamental limitations imposed by optical nonlinearities. Spatial division multiplexing (SDM) offers a new dimension for upgrading fiber communication systems. Many enabling integrated devices, such as mode multiplexers and multimode bending with low crosstalk, have been developed. On the other hand, all-optical signal processing (AOSP) can avoid optical to electrical to optical (O–E–O) conversion, which may potentially allow for a low cost and green operation for large-scale signal processing applications. In this paper, we show that the system performance of AOSP can be pushed further by benefiting from the existing technologies developed in spatial mode multiplexing (SDM). By identifying key technologies to balance the impacts from mode-dependent loss, crosstalk and nonlinearities, three-channel 40 Gbit/s optical logic operations are demonstrated using the first three spatial modes in a single multimode waveguide. The fabricated device has a broadband four-wave mixing operation bandwidth (>20 nm) as well as high conversion efficiency (>−20 dB) for all spatial modes, showing the potential for a large-scale signal processing capacity with the combination of wavelength division multiplexing (WDM) and SDM in the future. Full article

(This article belongs to the Special Issue Next-Generation Optical Communication: Components and Devices)

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Open AccessArticle

Bandwidth Tunable Optical Bandpass Filter Based on Parity-Time Symmetry

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Micromachines 2022, 13(1), 89; https://doi.org/10.3390/mi13010089 - 07 Jan 2022

Cited by 4 | Viewed by 1129

Abstract

A chip-scale tunable optical filter is indispensable to meeting the demand for reconfigurability in wavelength division multiplexing systems, channel routing, and switching, etc. Here, we propose a new scheme of bandwidth tunable band-pass filters based on a parity-time (PT) symmetric coupled microresonator system. Large bandwidth tunability is realized on the basis of the tuning of the relative resonant frequency between coupled rings and by making use of the concept of the exception point (EP) in the PT symmetric systems. Theoretical investigations show that the bandwidth tuning range depends on the intrinsic loss of the microresonators, as well as on the loss contrast between the two cavities. Our proof-of-concept device confirms the tunability and shows a bandwidth tuning range from 21 GHz to 49 GHz, with an extinction ratio larger than 15 dB. The discrepancy between theory and experiment is due to the non-optimized design of the coupling coefficients, as well as to fabrication errors. Our design based on PT symmetry shows a distinct route towards the realization of tunable band-pass filters, providing new ways to explore non-Hermitian light manipulation in conventional integrated devices. Full article

(This article belongs to the Special Issue Next-Generation Optical Communication: Components and Devices)

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Open AccessArticle

Generating Different Polarized Multiple Vortex Beams at Different Frequencies from Laminated Meta-Surface Lenses

Pengfei Gao

and

Rui Yang

Micromachines 2022, 13(1), 61; https://doi.org/10.3390/mi13010061 - 30 Dec 2021

Cited by 3 | Viewed by 987

Abstract

We demonstrate the generation of multiple orbital angular momentum (OAM) vortex beams with different radiating states at different frequencies through a laminated meta-surface lens consisting of a dual polarized meta-array interconnected with a frequency selective meta-array. The co-linearly polarized (LP) waves from the source can directly penetrate the meta-surface lens to form multiple OAM vortex beams at one frequency. On the other hand, the meta-surface lens will be capable of releasing the cross-LP counterparts at another frequency with high-efficient polarization conversions to have multiple OAM vortex radiations with different radiating directions and vortex modes. Our design, using laminated meta-surface lens to synthesize multiple OAM vortex beams with orthogonal polarizations at different frequencies, should pave the way for building up more advanced vortex beam communication system with expanded diversity of the meta-device. Full article

(This article belongs to the Special Issue Next-Generation Optical Communication: Components and Devices)

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Open AccessArticle

An Improved End-to-End Autoencoder Based on Reinforcement Learning by Using Decision Tree for Optical Transceivers

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Micromachines 2022, 13(1), 31; https://doi.org/10.3390/mi13010031 - 27 Dec 2021

Viewed by 1503

Abstract

In this paper, an improved end-to-end autoencoder based on reinforcement learning by using Decision Tree for optical transceivers is proposed and experimentally demonstrated. Transmitters and receivers are considered as an asymmetrical autoencoder combining a deep neural network and the Adaboost algorithm. Experimental results show that 48 Gb/s with 7% hard-decision forward error correction (HD-FEC) threshold under 65 km standard single mode fiber (SSMF) is achieved with proposed scheme. Moreover, we further experimentally study the Tree depth and the number of Decision Tree, which are the two main factors affecting the bit error rate performance. Experimental research afterwards showed that the effect from the number of Decision Tree as 30 on bit error rate (BER) flattens out under 48 Gb/s for the fiber range from 25 km and 75 km SSMF, and the influence of Tree depth on BER appears to be a gentle point when Tree Depth is 5, which is defined as the optimal depth point for aforementioned fiber range. Compared to the autoencoder based on a Fully-Connected Neural Network, our algorithm uses addition operations instead of multiplication operations, which can reduce computational complexity from 10⁸ to 10⁷ in multiplication and 10⁶ to 10⁸ in addition on the training phase. Full article

(This article belongs to the Special Issue Next-Generation Optical Communication: Components and Devices)

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