Special Issue "Optical Communications and Networks"

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Networks".

Deadline for manuscript submissions: closed (31 October 2019).

Special Issue Editor

Dr. Alberto Gatto
Website
Guest Editor
Department of Electronics, Information, and Bioengineering, Politecnico di Milano, 20133 Milano, Italy
Interests: optical communications systems, advanced modulation formats, innovative optical sources (VCSELs/RSOAs), Digital Signal Processing for optical transmitters/receivers, spatial division multiplexing systems, optical vortices
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Special Issue Information

Dear Colleagues,

The continuous growth of bandwidth demands in optical access networks, to support different data traffic types, including mobile backhaul and fronthaul, and the migration towards a more flexible, efficient and agile paradigm of optical metro networks, are posing new challenges, urgently requiring low-cost and power-efficient solutions. In the last few decades, optical communications reached maturity in intra-datacenters and long-haul scenarios, the former being based on simple Intensity Modulation/Direct Detection (IM/DD) multimode fiber optic systems and the latter exploiting digital coherent detection to drastically increase the spectral efficiency and, hence, the transported capacity of the core network segment. Different from intra-datacenter and long-haul transmissions, access and metro networks require innovative solutions, driving research on energy- and cost-efficient photonic technologies, in order to target both capacity enhancement and dynamic and heterogeneous data delivery in a cost-effective way.

The aim of this Special Issue is to gather the most recent developments and applications of optical communication systems, covering, but not limited to, the following scopes:

  • Optical access/metro networks scenarios;
  • Modulation formats for short/medium reach applications;
  • Flexible/agile optical networks;
  • Novel energy- and cost-effective photonics technologies for access/metro networks;
  • Spatial division multiplexing systems (few-mode fibers, multicore fibers);
  • Low-complexity Digital Signal Processing for short/medium reach transmissions.

Prof. Alberto Gatto
Guest Editor

Manuscript Submission Information

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Keywords

  • Optical access/metro networks
  • Flexible optical networks
  • Spatial division multiplexing systems
  • Advanced modulation formats (PAM, DMT, OFDM, QAM)
  • Intensity Modulation/Direct Detection
  • Coherent transmission/detection
  • Low-complexity DSP
  • Energy- and cost-effective photonics technologies
  • Optical sources for short/medium reach applications

Published Papers (16 papers)

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Research

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Open AccessArticle
Iterative Decoding of LDPC-Based Product Codes and FPGA-Based Performance Evaluation
Electronics 2020, 9(1), 122; https://doi.org/10.3390/electronics9010122 - 08 Jan 2020
Abstract
Low-density parity-check (LDPC) codes have the potential for applications in future high throughput optical communications due to their significant error correction capability and the parallel decoding. However, they are not able to satisfy the very low bit error rate (BER) requirement due to [...] Read more.
Low-density parity-check (LDPC) codes have the potential for applications in future high throughput optical communications due to their significant error correction capability and the parallel decoding. However, they are not able to satisfy the very low bit error rate (BER) requirement due to the error floor phenomenon. In this paper, we propose a low-complexity iterative decoding scheme for product codes consisting of very high rate outer codes and LDPC codes. The outer codes aim at eliminating the residual error floor of LDPC codes with quite low implementation costs. Furthermore, considering the long simulation time of computer simulation for evaluating very low BER, the hardware platform is built to accelerate the evaluation of the proposed iterative decoding methods. Simultaneously, the fixed-point effects of the decoding algorithms are also be evaluated. The experimental results show that the iterative decoding of the product codes can achieve a quite low bit error rate. The evaluation using field programmable gate array (FPGA) also proves that product codes with LDPC codes and high-rate algebraic codes can achieve a good trade-off between complexity and throughput. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
A Radio over Fiber System with Simultaneous Wireless Multi-Mode Operation Based on a Multi-Wavelength Optical Comb and Pulse-Shaped 4QAM-OFDM
Electronics 2019, 8(10), 1064; https://doi.org/10.3390/electronics8101064 - 20 Sep 2019
Cited by 3
Abstract
In this paper, we propose a radio over fiber transmission system with simultaneous wireless multi-mode operation based on multi-wavelength optical comb and pulse shaping. This study is an initial attempt to accomplish simultaneous wireless multi-mode operation on a single optical carrier. A multi-wavelength [...] Read more.
In this paper, we propose a radio over fiber transmission system with simultaneous wireless multi-mode operation based on multi-wavelength optical comb and pulse shaping. This study is an initial attempt to accomplish simultaneous wireless multi-mode operation on a single optical carrier. A multi-wavelength optical comb with 13 flat optical wavelengths and space of 10 GHz is achieved by utilizing radio frequency (RF)-optics modulation and parameter configuration. The central station contains four adjacent optical wavelengths separated from the multi-wavelength optical comb by a wavelength division multiplexer, that one is modulated by 4QAM-OFDM signals with an up-converted carrier frequency of 5 GHz. The signals modulated with a single-sideband can be obtained by employing pulse shaping. The single-sideband optical signals are combined with the other three optical wavelengths and then transmitted over a standard single-mode fiber with a length of 50 km. In this arrangement, we can obtain several wireless carriers with frequencies of 5 GHz, 25 GHz, 45 GHz, and 65 GHz by direct detection. These wireless carriers are used for wireless transmission between the RF remote units and the mobile terminals. Additionally, in the radio frequency (RF) remote unit, we have three pure optical sources that can be utilized for the uplink transmission. With single channel and direct optoelectronic modulation, the optical and wireless communication with 10 Gbps can be accomplished in the whole process of system network transmission. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Efficiency Tests of DBA Algorithms in XG-PON
Electronics 2019, 8(7), 762; https://doi.org/10.3390/electronics8070762 - 08 Jul 2019
Cited by 3
Abstract
Sophisticated dynamic bandwidth allocation (DBA) algorithms can dramatically improve or worsen throughput and delay in whole networks. It is very important to choose the right DBA algorithm. Our work tests static assignment and three DBA algorithms, namely GigaPON Access Network DBA, Hybrid Reporting [...] Read more.
Sophisticated dynamic bandwidth allocation (DBA) algorithms can dramatically improve or worsen throughput and delay in whole networks. It is very important to choose the right DBA algorithm. Our work tests static assignment and three DBA algorithms, namely GigaPON Access Network DBA, Hybrid Reporting Allocation, and modified Max–Min Fair. All tests were made on our simulator of ten-gigabit passive optical network DBA specially developed for testing DBA algorithms. The tests verify delay of each optical network unit and amount of waste with bandwidth. This paper describes how the used DBA algorithms work and the processes involved in DBA algorithms. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Application for GPON Frame Analysis
Electronics 2019, 8(6), 700; https://doi.org/10.3390/electronics8060700 - 21 Jun 2019
Cited by 5
Abstract
This article presents a design of a database model used to gather and analyze data frames transmitted over gigabit passive optical network (GPON) in the downstream direction. An issue with this kind of system is the difficulty in analyzing a transmission on the [...] Read more.
This article presents a design of a database model used to gather and analyze data frames transmitted over gigabit passive optical network (GPON) in the downstream direction. An issue with this kind of system is the difficulty in analyzing a transmission on the optical part which is caused by the difference among devices using Ethernet frames technology and passive optical network technology with usage gigabit encapsulation method. In this article, a principle of the downstream direction is described. Next, the design of the database model for the analysis of transmitted data is discussed. Based on the design and implementation of the database, a script capable of processing data gathered by a programmable network card is proposed. The script for physical layer operation, admission, and maintenance (PLOAM) messages analysis is written in the Python programming language. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Compact and Low Crosstalk Echelle Grating Demultiplexer on Silicon-On-Insulator Technology
Electronics 2019, 8(6), 687; https://doi.org/10.3390/electronics8060687 - 18 Jun 2019
Cited by 3
Abstract
We report on the design of an ultra-compact integrated wavelength demultiplexer in echelle configuration for the optical O-band realized on silicon-on-insulator technology. The device has four channels with channel spacing of 800 GHz and a small footprint of 260 × 83 μm2 [...] Read more.
We report on the design of an ultra-compact integrated wavelength demultiplexer in echelle configuration for the optical O-band realized on silicon-on-insulator technology. The device has four channels with channel spacing of 800 GHz and a small footprint of 260 × 83 μm2. Channel crosstalk lower than −28 dB across the four channels is experimentally demonstrated along with insertion losses of −1.5 dB. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Performance Enhancement Methods for the Distributed Acoustic Sensors Based on Frequency Division Multiplexing
Electronics 2019, 8(6), 617; https://doi.org/10.3390/electronics8060617 - 31 May 2019
Cited by 2
Abstract
The last years have witnessed the wide application of Distributed Acoustic Sensor (DAS) systems in several fields, such as submarine cable monitoring, seismic wave detection, structural health monitoring, etc. Due to their distributed measurement ability and high sensitivity, DAS systems can be employed [...] Read more.
The last years have witnessed the wide application of Distributed Acoustic Sensor (DAS) systems in several fields, such as submarine cable monitoring, seismic wave detection, structural health monitoring, etc. Due to their distributed measurement ability and high sensitivity, DAS systems can be employed as a promising tool for the phase sensitive optical time domain reflectometry (Φ-OTDR). However, it is also well-known that the traditional Φ-OTDR system suffers from Rayleigh backscattering (RBS) fading effects, which induce dead zones in the measurement results. Worse still, in practice it is difficult to achieve the optimum matching between spatial resolution (SR) and signal to noise ratio (SNR). Further, the overall frequency response range (FRR) of the traditional Φ-OTDR is commonly limited by the length of the fiber in order to prevent RBS signals from overlapping with each other. Additionally, it is usually difficult to reconstruct high frequency vibration signals accurately for long range monitoring. Aiming at solving these problems, we introduce frequency division multiplexing (FDM) that makes it easier to improve the system performance with less system structure changes. We propose several novel Φ-OTDR schemes based on Frequency Division Multiplexing (FDM) technology to solve the above problems. Experimental results showed that the distortion induced by fading effects could be suppressed to 1.26%; when the SR of Φ-OTDR is consistent with the length of the vibration region, the SNR of the sensing system is improved by 3 dB compared to the average SNR with different SRs; vibration frequencies up to 440 kHz have been detected along 330 m artificial microstructures. Thus, the proposed sensing system offers a promising solution for the performance enhancement of DAS systems that could achieve high SNR, broadband FRR and dead zone-free measurements at the same time. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
An Analytical Cost-Optimal Cloudlet Placement Framework over Fiber-Wireless Networks with Quasi-Convex Latency Constraint
Electronics 2019, 8(4), 404; https://doi.org/10.3390/electronics8040404 - 05 Apr 2019
Cited by 5
Abstract
To meet the low-latency constraints arising from future smart mobile devices, Internet-of-Things, and 5G applications, major interest is currently given to the integration of centralized cloud computing and distributed edge computing infrastructures to deliver higher performance and reliability to edge devices in accessing [...] Read more.
To meet the low-latency constraints arising from future smart mobile devices, Internet-of-Things, and 5G applications, major interest is currently given to the integration of centralized cloud computing and distributed edge computing infrastructures to deliver higher performance and reliability to edge devices in accessing mobile cloud services. The three-tier network architecture arising from cloud, cloudlet, and edge-devices can handle miscellaneous latency requirements for both latency-sensitive and latency-tolerant applications more efficiently than conventional two-tier networks. In this paper, we primarily focus on the static cloudlet network planning problem and propose an analytical hybrid cost-optimization framework for optimal cloudlet placement. We formulate this problem as a convex optimization problem and solve by using Karush-Kuhn-Tucker (KKT) conditions, and show that this framework can be evaluated without any scalability issues observed with integer programming based frameworks for large datasets. Moreover, we derive user-friendly closed form expressions that provide a first-hand estimation of cloudlet deployment cost depending on a few important network parameters like split-ratio, population density, and network bandwidth. Finally, we also show that the optimal solution of this analytical framework can be considered as a tight lower bound of the optimal solutions of integer programming based frameworks and makes a better cloudlet installation cost estimation compared to other existing frameworks. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Performance Analysis of Bandwidth Allocation Based on Dynamic User Priority for Indoor Visible Light Communication Ultra-Dense Networks
Electronics 2019, 8(3), 276; https://doi.org/10.3390/electronics8030276 - 02 Mar 2019
Abstract
Focusing on the high user density in visible light communication ultra-dense networks (VLC-UDNs), this paper proposes a resource allocation method based on dynamic user priority (DUP). Firstly, this paper establishes the DUP model, which realizes a multi-dimensional measurement for differences of users. Considering [...] Read more.
Focusing on the high user density in visible light communication ultra-dense networks (VLC-UDNs), this paper proposes a resource allocation method based on dynamic user priority (DUP). Firstly, this paper establishes the DUP model, which realizes a multi-dimensional measurement for differences of users. Considering the variety of network environments, we dynamically select multiple features of users and achieve the calculation of DUP by fuzzy logic (FL). Secondly, the throughput-maximizing resource allocation (TMRA) scheme with user priority guarantee is proposed. Thirdly, the lower bound of the proposed DUP-TMRA is derived. Simulation results show that the proposed multi-dimensional DUP model outperforms the conventional one-dimensional DUP model and fixed priority model. In addition, the proposed TMRA scheme outperforms the conventional proportion allocation scheme. Finally, in comparisons of system throughput, the proposed DUP-TMRA achieves 4% performance improvement against the conventional required data rate proportion allocation (RPA) method. In comparisons of fairness, DUP achieves the modest performance. In comparisons of satisfaction, when the average blocking probability is higher than 0.45, the proposed DUP-TMRA improves the proportion of satisfied users against the conventional RPA method by up to 17.5%. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
QoS-Based DWBA Algorithm for NG-EPON
Electronics 2019, 8(2), 230; https://doi.org/10.3390/electronics8020230 - 18 Feb 2019
Cited by 4
Abstract
The next-generation Ethernet passive optical network (NG-EPON) is basically classified into two architectures on the basis of the wavelength sharing by the optical network units (ONUs). The single scheduling domain (SSD) and multi-scheduling domain (MSD) EPON are the two different design architectures for [...] Read more.
The next-generation Ethernet passive optical network (NG-EPON) is basically classified into two architectures on the basis of the wavelength sharing by the optical network units (ONUs). The single scheduling domain (SSD) and multi-scheduling domain (MSD) EPON are the two different design architectures for NG-EPON. A vital task in NG-EPON is to design dynamic wavelength bandwidth allocation (DWBA) algorithms that can meet the future demands of the network subscribers. A number of DWBA algorithms have been designed for time and wavelength division multiplex (TWDM) EPON. The existing DWBA algorithms for TWDM-EPON could be used in MSD-EPON by making necessary parametric changes. The design and implementation of new DWBA algorithms for MSD-EPON are still required specifically. In this paper, we have proposed a quality of service (QoS)-based DWBA algorithm for NG-EPON. We have comparatively analyzed our proposed DWBA with the existing algorithms like earlier finished time (EFT), weighted bipartite matching (WBM), and earlier finished time with void filling (EFT-VF). The results show that our proposed DWBA algorithm performs better as compared to EFT, WBM, and EFT-VF on the basis of average packet delay and average completion time for NG-EPON. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Design of XOR Photonic Gate using Highly Nonlinear Fiber
Electronics 2019, 8(2), 215; https://doi.org/10.3390/electronics8020215 - 15 Feb 2019
Cited by 1
Abstract
In this paper, a comprehensive design and simulation of an all-photonic XOR logic gate is proposed. The design is based on the third-order Kerr nonlinear effect in highly nonlinear fiber, i.e., utilizing the self-phase and cross-phase modulations phenomena. This work presents the first [...] Read more.
In this paper, a comprehensive design and simulation of an all-photonic XOR logic gate is proposed. The design is based on the third-order Kerr nonlinear effect in highly nonlinear fiber, i.e., utilizing the self-phase and cross-phase modulations phenomena. This work presents the first photonic logic gate based on highly nonlinear fiber component only that achieves a data rate of 20 Gbps. Moreover, the design is based on two input binary bit sequences, narrow pulsed by a Gaussian distribution as 8-bit incoming data streams. Also, optical cross connectors with different coupling coefficients are used to generate pump and probe signals and tuneable optical band pass filters are leveraged to perform the logic gate functionalities. Remarkable performance outcomes are concluded from the eye pattern diagram and bit error rate analyzers. Simulation results show that the proposed XOR optical logic gate design is achieved at very low power penalties, low bit error rates, a significant Q-factor, and high extinction ratios as compared to existing methods. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
A New Type of AODF Based on an Imitation of the Weft Insertion of a Rapier Loom
Electronics 2019, 8(2), 157; https://doi.org/10.3390/electronics8020157 - 01 Feb 2019
Cited by 1
Abstract
The main distribution frame (MDF) is an important component between the user and the operator that supplies a telecommunication service and is the only layer in the seven-layer communication architecture that is not fully automated. In this paper, a cross-connect method for simulating [...] Read more.
The main distribution frame (MDF) is an important component between the user and the operator that supplies a telecommunication service and is the only layer in the seven-layer communication architecture that is not fully automated. In this paper, a cross-connect method for simulating the rapier picking of a rapier loom (shuttleless loom) is proposed to imitate the shedding and the picking action to achieve quick switching. Using the designed “shedding device” and “picking device”, a model prototype of the automatic optical distribution frame (AODF) was constructed and tested for verification. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Demand Forecasting DBA Algorithm for Reducing Packet Delay with Efficient Bandwidth Allocation in XG-PON
Electronics 2019, 8(2), 147; https://doi.org/10.3390/electronics8020147 - 31 Jan 2019
Cited by 10
Abstract
In a typical 10G-Passive Optical Network (XG-PON), the propagation delay between the Optical Network Unit (ONU) and Optical Line Terminal (OLT) is about 0.3 ms. With a frame size of 125 μs, this amounts to three frames of data in the upstream and [...] Read more.
In a typical 10G-Passive Optical Network (XG-PON), the propagation delay between the Optical Network Unit (ONU) and Optical Line Terminal (OLT) is about 0.3 ms. With a frame size of 125 μs, this amounts to three frames of data in the upstream and three frames of data in the downstream. Assuming no processing delays, the grants for any bandwidth requests reach the ONU after six frames in this request-grant cycle. Often, during this six-frame delay, the queue situation is changed drastically, as much, more data would arrive in the queue. As a result, the queued data that is delayed loses its significance due to its real-time nature. Unfortunately, almost all dynamic bandwidth allocation (DBA) algorithms follow this request-grant cycle and hence lacking in their performance. This paper introduces a novel approach for bandwidth allocation, called Demand Forecasting DBA (DF-DBA), which predicts ONU’s future demands by statistical modelling of the demand patterns and tends to fulfil the predicted demands just in time, which results in reduced delay. Simulation results indicate that the proposed technique out-performs previous DBAs, such as GigaPON access network (GIANT) and round robin (RR) employing the request-grant cycle in terms of Throughput and Packet delivery ratio (PDR). Circular buffers are introduced in statistical predictions, which produce the least delay for this novel DF-DBA. This paper, hence, opens up a new horizon of research in which researchers may come up with better statistical models to brew better and better results for Passive optical networks. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Model for the Prediction of Rain Attenuation Affecting Free Space Optical Links
Electronics 2018, 7(12), 407; https://doi.org/10.3390/electronics7120407 - 07 Dec 2018
Cited by 8
Abstract
A model for the prediction of the attenuation induced by rain on free space optical (FSO) links is presented. The proposed methodology is developed, starting from the accurate simulation of the interaction between FSO links (path length up to 5 km) and precipitation [...] Read more.
A model for the prediction of the attenuation induced by rain on free space optical (FSO) links is presented. The proposed methodology is developed, starting from the accurate simulation of the interaction between FSO links (path length up to 5 km) and precipitation maps, from which analytical expressions are then proposed. The model is simple as it only receives the local rainfall statistics for the site of interest as the input, but it is also accurate, as it takes into account the dependence of the attenuation on the drop size distribution (DSD), as well as multiple scattering effects associated with rain, which contributes to reducing the overall predicted attenuation. The proposed model represents a useful tool to dimension FSO links in areas where fog is negligible, i.e., where rain has the highest impact on the link performance. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Open AccessArticle
Label Stacking Scenarios in Hybrid Wavelength and Code-Switched GMPLS Networks
Electronics 2018, 7(10), 251; https://doi.org/10.3390/electronics7100251 - 14 Oct 2018
Cited by 4
Abstract
Multi-protocol label switching (MPLS) is a promising solution to implement high-speed internet protocol (IP) networks by reducing the layer number. To meet the increasing demand for data traffic, optical packet switching (OPS) is integrated under IP to provide high bandwidth to end users. [...] Read more.
Multi-protocol label switching (MPLS) is a promising solution to implement high-speed internet protocol (IP) networks by reducing the layer number. To meet the increasing demand for data traffic, optical packet switching (OPS) is integrated under IP to provide high bandwidth to end users. Generalized MPLS (GMPLS) is perfectly compatible with the routing algorithm in IP/MPLS as it supports packet-switching functions. In this paper, we investigate the label stacking scenarios in GMPLS networks. In GMPLS, label stacking is done to reduce the node complexity by appending multiple labels to a single packet. Wavelength-division multiplexing (WDM) and optical code-division multiplexing (OCDM) signals have been widely used as identifying labels. As the labels can be permutated among the wavelengths or code dimensions, the structure of a label stack can be varied. However, studies on the relationship between label stacking scenarios and network performance are limited. To investigate this issue, we propose three label stacking models: sequential code distribution; sequential wavelength distribution, and random label distribution. The simulation results show that the sequential wavelength assignment, wherein the labels are uniformly distributed among the wavelengths, exhibits the best system performance in terms of the label-error rate (LER). Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Review

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Open AccessFeature PaperReview
Sliceable BVT Evolution Towards Programmable Multi-Tb/s Networking
Electronics 2019, 8(12), 1476; https://doi.org/10.3390/electronics8121476 - 04 Dec 2019
Cited by 2
Abstract
The sliceable bandwidth variable transceiver (S-BVT) is a key element in addressing the challenges and evolution of optical networks, and supporting the ever-increasing traffic volume, speed, and dynamicity driven by novel and broadband services and applications. Multiple designs and configurations are possible and [...] Read more.
The sliceable bandwidth variable transceiver (S-BVT) is a key element in addressing the challenges and evolution of optical networks, and supporting the ever-increasing traffic volume, speed, and dynamicity driven by novel and broadband services and applications. Multiple designs and configurations are possible and are evolving towards supporting multi-Tb/s networking, thanks to the adoption of advanced and more mature photonic technologies. In this work, we review and analyze alternative S-BVT design architecture options that target different network segments and applications. We specifically focus on S-BVTs based on multicarrier modulation (MCM), which provide a wide range of granularity and more flexible spectral manipulation. A detailed description of the main elements in an S-BVT and their characteristics is provided in order to give design guidelines. The performance in a real testbed network is also reported, comparing a set of S-BVT configurations that adopt different technologies. Finally, an extensive discussion of the described architecture, functionalities, and results, including programmability aspects, is provided in view of S-BVT evolution towards future optical network requirements and needs. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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Other

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Open AccessLetter
Two-Code Keying and Code Conversion for Optical Buffer Design in Optical Packet Switching Networks
Electronics 2019, 8(10), 1117; https://doi.org/10.3390/electronics8101117 - 03 Oct 2019
Cited by 2
Abstract
Buffering management is a crucial function in current optical packet switching (OPS) networks. To avoid packet blocking due to competition for the same switched path, optical buffering is required to queue packets after a router makes the forwarding decision. In this paper, the [...] Read more.
Buffering management is a crucial function in current optical packet switching (OPS) networks. To avoid packet blocking due to competition for the same switched path, optical buffering is required to queue packets after a router makes the forwarding decision. In this paper, the author proposed a buffering scheme based on optical code-division multiple access (OCDMA), where each packet is encoded with an optical signature code. An optical coding technique combining spectral-amplitude coding (SAC) and two-code keying (TCK) is introduced to advance the buffering performance regarding packet loss probability. In TCK, the payload bits “1” and “0” of a stored packet are respectively converted to a SAC signal and its complementarity. As the Hamming distance between the coding signals of bits “1” and “0” is extended, the existing drawback that the OCDMA-based buffer capacity is limited by the decoder noise increased with the number of queued SAC packets is resolved. Moreover, an encoder consisting of a fiber Bragg grating (FBG) array is applied for simplifying the system design. A SAC signal and its complementary counterpart can be generated simultaneously without the need of an extra encoder. Full article
(This article belongs to the Special Issue Optical Communications and Networks)
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