DWDM Networks Research Articles

Impact of RoPP in Wavelength Conversion Inducing Nonlinearity and All-Optical 3R Regeneration for DWDM Networks

Impact of RoPP in Wavelength Conversion Inducing Nonlinearity and All-Optical 3R Regeneration for DWDM Networks

Enabling ultra-high bit rate transmission with CFBG as dispersion compensator in an OptiSpan 240 km DWDM network

Abstract In this paper, a dispersion compensation technique for an ultra-long haul optical network utilizing a chirped fiber Bragg grating (CFBG) is presented. A high bit-rate signal of 40 Gbps is inputted into each channel. The CFBG, employed for dispersion compensation, is positioned after demultiplexing, enabling effortless network upgrades. The grating parameters of the implemented CFBG are mathematically analyzed and optimized to counteract net dispersion of over 3153 ps/nm across the channel. The design is verified using the OptiSystem software, resulting in a successful transmission up to 240 km with an average Q-factor of 8.09, utilizing an amplification gain of 49.5 dB. Additionally, the achieved optical signal-to-noise ratio (OSNR) level using the symmetrical amplification technique surpasses the acceptable value, with an average bit error rate of 10−16.

Proactive Fault Localization and Alarm Correlation in DWDM Networks

Proactive Fault Localization and Alarm Correlation in DWDM Networks

XPM Induced Filter Free Multi-Wavelength Conversion Exploiting Hybrid Multiplexing Employing Sagnac Effect and Circulator in DWDM Networks

XPM Induced Filter Free Multi-Wavelength Conversion Exploiting Hybrid Multiplexing Employing Sagnac Effect and Circulator in DWDM Networks

Comparison of CD and CDC Technologies for Flex Grid DWDM Networks

Comparison of CD and CDC Technologies for Flex Grid DWDM Networks

Performance enhancement of duobinary modulation-based DWDM system using particle swarm optimization

Abstract The next-generation light wave communication DWDM networks can accommodate large number of channels to efficiently utilize the bandwidth (BW). However, in the deployment of DWDM system mixing of two or more waves limits the performance due to four wave mixing (FWM) nonlinearity in fiber. This article, presents improved performance analysis of DWDM using a proposed improved duobinary modulation (IDBM), modified duobinary modulation (MDBM) and duobinary modulation (DBM) model for mitigation of FWM nonlinearities has been estimated experimentally through interference of noise on optical signal, FWM efficiency, FWM power etc. In IDBM, a unit delay in addition to time delay parameter is also utilized for generation of electrical duobinary pulses. The parameters of both delay blocks are tuned through particle swarm optimization (PSO) technique to improve the performance. The overall proposed IDBM effectively decreases the FWM. The results obtained for IDBM in terms of Q-factor 8.9, OSNR 18 dB, FWM power −87 dBm and FWM efficiency −70 dB shows substantial improvement with the recommended IDBM technique in comparison to DBM and MDBM schemes.

Bifurcations and dispersive optical solitons for the nonlinear Schrödinger–Hirota equation in DWDM networks

The main purpose of this paper is to study the dynamical behaviors and optical solitons in DWDM networks with Schrödinger–Hirota equation. First of all, the Schrödinger–Hirota equation was converted into plane dynamical system by using the traveling wave transform and some other suitable transform, which has been analyzed in detail via the theory of bifurcations for dynamical system. As we can see, a range of new soliton solutions are obtained. Then, with the assistance of the complete discriminant system method and symbolic computation, some other optical soliton solutions are constructed, which include Jacobi elliptic function solutions, hyperbolic function solutions, rational function solutions, solitary wave solutions and trigonometric function solutions. In particular, it is worth noting that these optical soliton solutions may motivate us to explore new phenomena which may appear in this equation. Finally, two-dimensional and three-dimensional graphs are drawn by selecting some specific parameters.

Effects of ASE noise and dispersion chromatic on performance of DWDM networks using distributed Raman amplifiers

We investigate effects of amplified spontaneous emission noise (ASE), noise figure (NF) and dispersion chromatic on the performance of DWDM networks using distributed optical fiber Raman amplifiers (DRAs) in two different pump configurations, i.e., forward and backward pumping. We found that the pumping configurations, ASE noise, and dispersion play an important role in network performance improving since it reduces noise figure and bit error rate (BER) of the system. Simulation results show that the lowest bit error rate and noise figure when using forward pumping configuration. Moreover, we have also compared ASE noise powers of the simulation with these of the experiment, they are match.

Efficient design of a Raman amplified wavelength division multiplexed communication network at 1330 nm

Abstract From the advent of communication, there has been a constant demand for increasing communication capacity. In optical communications, capacity can be increased by implementing more fibers or can be increased by using the same fiber to transmit more than one signal. The process is known as the wavelength division multiplexing or WDM. Channels placed closer to each other in the wavelength scale leads to the process of DWDM or dense WDM networks. But with so many channels transmitted together over minimum distances of 10 km, the power of each channel decreases significantly within the fiber, hence a Raman amplification system has been incorporated within the network. The whole system is designed at the 1300 nm optical window which has shown the least dispersion among the other optical windows. Results from simulating a 16 channel network with 8 optical pumps, where all are configured in co and counter propagating directions. They have shown good amount of gain, relatively low noise and good SNR over the whole communication band of channels rendering the system to be a faithful communication network.

Modeling and Minimizing Spontaneous Raman Scattering for QKD Secured DWDM Networks

Quantum key distribution (QKD) provides information-theoretic security based on quantum mechanics. Integrating QKD with classical data traffic by using wavelength division multiplexing (WDM) techniques in a single fibre is a cost-efficient way to improve security in legacy infrastructure. In such a system, the main noise source to the quantum channel is spontaneous Raman scattering (SRS) caused by the classical channels. In this letter we introduce a channel allocation strategy for both quantum and classical signals to minimize the SRS noise. A use case that quantum and classical channels co-exist in a dense WDM system is investigated. The results show >26% increase of achievable transmission distance for the QKD system when implementing the introduced channel allocation strategy. Moreover, a network updating plan is proposed, which provides a guideline to light the new wavelengths for classical communications while minimizing the SRS noise to quantum channels.

Modelling and Optimization of Multi-Service Optical Switching Networks with Threshold Management Mechanisms

DWDM networks make use of optical switching networks that allow light waves of multiple lengths to be serviced and provide the possibility of converting them appropriately. Research work on optical switching networks focuses on two main areas of interest: new non-blocking structures for optical switching networks and finding traffic characteristics of switching networks of the structures that are already well known. In practical design of switching nodes in optical networks, in many cases, the Clos switching networks are successfully used. Clos switching networks are also used in Elastic Optical Networks that can effectively manage allocation of resources to individual multi-service traffic streams. The research outcomes presented in this article deal with the problems of finding traffic characteristics in blocking optical switching networks with known structures. This article aims at presenting an analysis of the influence of traffic management threshold mechanisms on the traffic characteristics of multi-service blocking Clos switching networks that are used in the nodes of elastic optical networks as well as their influence on the traffic efficiency of network nodes. The analysis was carried out on the basis of research studies performed in a specially dedicated purpose-made simulation environment. The article presents a description of the simulation environment used in the experiments. The study was focused on the influence of the threshold mechanism, which is one of the most commonly used and elastic traffic management mechanisms, and on the traffic characteristics of switching networks that service different mixtures of multi-service Erlang, Engset and Pascal traffic streams. The conducted study validates the operational effectiveness and practicality of the application of the threshold mechanism to model traffic characteristics of nodes in an elastic optical network.

Coherent Optics Ready for Prime Time in Short-Haul Networks

Optical fiber transport is the key technology to enable the delivery of fast and affordable bandwidth for all services, such as 5G/mobile, business and residential broadband, cloud computing, and video transport. Coherent optics, a game-changer optical fiber transport technology, has completely transformed optical transmission systems and enabled a widespread upgrade and new deployment of DWDM networks to speeds of 100 Gb/s, 200 Gb/s, and 400 Gb/s per wavelength. Over the past decade, coherent optics has moved beyond its long-haul application origins and is now firmly entrenched in metro networks. 2020 marked the 10th anniversary of digital coherent optical technology being officially deployed in service providers' networks. Further development in CMOS processing, design simplification, and cost reduction of opto-electronic components, and the need for more efficient optical transport technologies have been factors driving coherent solutions into new market applications, specifically short-haul applications in edge and access networks. This migration model has been demonstrated in the optical industry before: the DWDM system technology started in long haul and subsequently migrating to metro and edge access; forward error correction encoding and decoding followed the same pattern. Benefiting from initial long-haul technology development, coherent optics for access networks is poised to follow the same natural progression.

Connection setup and traffic aggregation in IP-based Elastic Optical Networks (EON)

To overcome the challenges of the increased IP traffic volume on the Internet, the IP/MPLS-based fixed grid DWDM network structure was proposed, which makes the interaction between both the IP layer and the optical wavelength routed fixed DWDM layer applicable. However, the deployment of this architecture was not only expensive, but power-consuming. The emerging optical Flexgrid networks technology is nowadays suggested to be the potential candidate for future optical transport networks. This is because it provides extremely flexible and spectrally effective resources utilisation. Therefore, it has attracted the attention of network operators, optical networks equipment manufacturers and the wider research and development society. In this research work, we propose a novel multilayer routing scheme for an IP/MPLS-based optical Flex-grid network, which is based on the protocol suite defined by the GMPLS architecture. Furthermore, we evaluate its behaviour in an online dynamic traffic scenario.

Machine Learning Algorithms for Prediction of the Quality of Transmission in Optical Networks.

Increasing demand in the backbone Dense Wavelength Division (DWDM) Multiplexing network traffic prompts an introduction of new solutions that allow increasing the transmission speed without significant increase of the service cost. In order to achieve this objective simpler and faster, DWDM network reconfiguration procedures are needed. A key problem that is intrinsically related to network reconfiguration is that of the quality of transmission assessment. Thus, in this contribution a Machine Learning (ML) based method for an assessment of the quality of transmission is proposed. The proposed ML methods use a database, which was created only on the basis of information that is available to a DWDM network operator via the DWDM network control plane. Several types of ML classifiers are proposed and their performance is tested and compared for two real DWDM network topologies. The results obtained are promising and motivate further research.

On The Possibility of Improving the Reliability of Communication in Fiber Optic Systems with Spectral Compaction

In the article, the authors present a concrete example of a block diagram of a signal transmission device at WDM. Operation of this device with the representation of plots of pulse diagram of operation at standard characteristics of services and evaluation of their quality indicators depending on the fault tolerance in the whole system under study. Recommendations for practical use in various types of network topology are given. Spectral compaction technologies such as CWDM, DWDM, HDWDM, principles of construction of these technologies, as well as advantages and disadvantages are considered. The functional schemes of the signal transmission device and the functional scheme of the optical transceiver and the principle of operation of these devices are given. The frequency plan for CWDM systems is defined by ITU G. 694.2. The scope of CWDM technology is urban networks with a distance of up to 50 km. The advantage of this type of WDM systems is low (compared to other types) the cost of equipment due to lower requirements for the constituent equipment of the fiber optic network. The frequency plan for DWDM systems is defined by ITU G. 694.1. The field of application — backbone network. This kind of WDM systems has higher requirements for components than CWDM (radiation source spectrum width, source temperature stabilization, etc.). The impetus for the rapid development of DWDM networks was given by the appearance of inexpensive and efficient fiber erbium amplifiers (EDFA) operating in the range from 1525 to 1565 nm (the third window of transparency of quartz fiber). For simplicity, the model is limited to a frequency plan DWDM with a step of 100 GHz, and CWDM has eight main channels in the range of 1470-1610 nm. The calculations of reliability indicators of the basic version and the modified version of the signal transmission device are given.

Tunable quantum dot lasers grown directly on silicon

Tunable semiconductor lasers are often listed in critical technology road maps for future dense-wavelength-division-multiplexing (DWDM) systems and high-performance computing systems, and they are increasingly demanded in long-haul, metropolitan, and access networks. The capability to produce such lasers directly on silicon (Si) could boost the use of Si photonics and facilitate the adoption of optical data transmission even at the chip scale. Moreover, just the use of Si as a cheap and large-diameter substrate for device production is very advantageous, as the fabrication can take advantage of the highly optimized processing techniques and economy of scale enabled by decades of development in Si microelectronics. Here, we report a tunable single-wavelength quantum dot (QD) laser directly grown on Si. The high carrier confinement and a real dot density of QDs provide reduced sensitivity to crystalline defects, which allows for exceptional lasing performance even in lattice-mismatched material systems. The discrete density of states of dots yields unique gain properties that show promise for improved device performance and new functionalities relative to the quantum well counterparts, including high temperature stability, low threshold operation, reduced sidewall recombination, and isolator-free stability. We implement a simple, integrable architecture to achieve over 45 dB side-mode-suppression-ratio without involving regrowth steps or subwavelength grating lithography. Under continuous-wave electrical injection at room temperature, we achieved a 16 nm tuning range with output powers of over 2.7 mW per tuning wavelength. This work represents a step towards using III–V/Si epitaxy to form efficient, easily manufacturable on-chip Si light sources for not only DWDM networks, but also spectroscopy, biosensors, and many other emerging applications.

Dispersive solitons in optical fibers and DWDM networks with Schrödinger–Hirota equation

This paper secures dispersive solitons in polarization-preserving fibers, birefringent fibers and DWDM networks. The extended simplest equation approach analyzes the governing Schrödinger–Hirota equation. A wide spectrum of soliton solutions is yielded.

DHbLP: A Novel Technique for Survivability in Optical Networks

Abstract Dense Wavelength-Division Multiplexing (DWDM) optical networks meet ever-increasing bandwidth demand of internet applications. Network failure results in massive information loss particularly in networks carrying a huge volume of data. Survivability techniques ensure uninterrupted network functioning even in case of failure. Research in the domain of DWDM network survivability has contributed toward the development of protection and restoration techniques to provide resilience in optical networks. In this paper, basic concept of protection and restoration in optical networks has been introduced followed by review and analysis of existing routing and survivability techniques. It is observed that a trade-off among network performance parameters exists for any survivability scheme. A novel scheme, Dynamic Hybrid Technique based on Failure Location and Traffic Priority (DHbLP) adaptable to Quality of Service (QoS) demands, has been proposed. DHbLP is tested for one of the possible failure scenarios in the standard National Science Foundation NETwork (NSFNET) and it is observed that this technique improves network performance in terms of throughput and blocking probability.

Compensation of the Fluctuations of Differential Delay for Frequency Transfer in DWDM Networks.

This paper investigates the possibility of improving the stability of radio-frequency transfer in telecommunication dense wavelength division multiplexing fiber-optic networks. As it has been identified, the dispersion compensation fibers (DCFs), frequently used in these networks, cause substantial differential delay, whose temperature-induced fluctuations have the most significant impact on the deterioration of the stability of the frequency transfer. The authors present a method that allows achieving significant improvement in the long-term stability of the frequency transfer. The developed method is based on modeling the impact of DCFs with the help of remotely accessible temperature sensors factory installed by the manufactures in DCF modules. The effectiveness of the proposed solution has been tested on three different long-haul routes (up to 1550 km), set up in the operational Polish National Research and Education Network.

Machine Learning Models for Estimating Quality of Transmission in DWDM Networks

It is estimated that 5G and the Internet of Things (IoT) will impact traffic, both in volume and dynamicity, at unprecedented rates. Thus, to cost-efficiently accommodate these challenging requirements, optical networks must become more responsive to changes impacting the traffic and network state as well as operate more closely to optimality. In this context, knowledge-defined networking (KDN) promises to play a paramount role in improving network flexibility and automation. KDN is a solution that introduces reasoning processes and machine learning techniques into the control plane of the network, enabling it to operate autonomously and faster. One of the key aspects in this environment is the accurate validation of lightpaths. Accurate lightpath validation demands running computationally intensive performance models, which can be time-consuming and impact time-critical applications (e.g., optical channel restoration). This work evaluates the effectiveness of various machine learning models when used to predict the quality of transmission (QoT) of an unestablished lightpath, speeding up the process of lightpath provisioning. Three network scenarios to efficiently generate the knowledge database used to train the models are proposed as well as an overview of the mostused machine learning models. The considered models are: K-nearest neighbors, logistic regression, support vector machines, and artificial neural networks. Results showthat, in general, allmachine learningmodels are able to correctly predict the QoTofmore than 90% of the lightpaths. However, the artificial neural networks (ANN) model is the model presenting better generalization, being able to correctly predict the QoT of almost 99.9% of the lightpaths. Moreover, ANN is able to estimate the residual margin of a lightpath with an average error of only 0.4 dB.