Future Optical Networks in a 10 Year Time Frame
06 Jun 2021-pp 1-3
TL;DR: In this article, the authors describe the evolution of the network over a time-scale of 10 years and cover the merger of photonics and electronics, optical switching, reliance on data-center technologies and architectural evolution.
Abstract: We describe the evolution of the network over a time-scale of 10 years. We cover the merger of photonics and electronics, optical switching, reliance on data-center technologies and architectural evolution.
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TL;DR: In this article , a hybrid erbium-doped fiber (EDF) and bismuth-decompositioned fiber (BDF) based optical amplifier (OA) was proposed for C+L optical networks.
Abstract: The ever increasing capacity demand on optical networks and the slowdown of improving spectral efficiency lead to the solution of utilizing more wavelength band in existing optical fibers. More and more operators will extend from C band to C+L bands, or plan to deploy C+L systems, and in future they may utilize more of other bands. This paper firstly discusses different optical layer architectures for multi-band system. Using optical components that can natively support multi-band is attractive to us, because in this way the multi-band system can be planned and operated similarly with the single-band system, which is customer friendly and potentially more economical. We address mainly three technical challenges in this paper. The first one is the wide-band fiber optical amplifier (OA). After a short review of recent research progress, we propose a hybrid erbium-doped fiber (EDF) and bismuth-doped fiber (BDF) based OA approach, and demonstrated single-stage amplification over 100 nm in extended C+L bands. The second challenge is the optical cross connect based on wavelength selective switch (WSS). It is not trivial to realize a C+L-band WSS while preventing the key optical parameters (filtering bandwidth, loss, channel isolation, etc.) to be degraded. We analyze different technical schemes, and propose an optical design based on an LCoS with a large panel size and a high-dispersion diffraction grating. The optical design and simulation on a 2×35 WSS reveals this approach can support 100-nm extended C+L spectrum and is promising for commercialization. The third challenge is the SRS induced WDM channel power inequality, which is more severe for multi-band system. We propose a solution by using OAs with a novel optical spectrum processor (OSP). Simulation and experiment showed that the power of the WDM channels can be equalized on a per span basis, which can prevent accumulation of stimulated Raman scattering (SRS) induced wavelength division multiplexing (WDM) channel power transfer and can meanwhile keep the optical signal to noise ratio (OSNR) of WDM channels well equalized.
24 citations
TL;DR: In this article, the authors formulate the access link capacity dimensioning problem as an optimization problem with a nested dynamic constraint satisfaction subproblem, and use the probability of fulfillment with regard to different traffic arrival rates as the performance measure and the performance-cost ratio as their optimization objective.
Abstract: Access links that connect cloud data centers or enterprise networks to public networks are important parts of the network infrastructure and make up considerable portions of overall network expenditures. When a customer network is connected to an overlaid elastic optical network, determining the capacity of the access link is difficult. Furthermore, access links carry mixed packet streams and circuit connections, each with different performance requirements. Additionally, traffic loads are time-varying and often exhibit diurnal patterns. In this study, we formulate the access link capacity dimensioning problem as an optimization problem with a nested dynamic constraint satisfaction subproblem. Instead of using hard performance measures, such as packet delays and blocking probabilities, we use the probability of fulfillment with regard to different traffic arrival rates as the performance measure and the performance–cost ratio as our optimization objective. Numerical results suggest that a 7.5% to 19.47% cost savings can be achieved if resources are shared between packet streams and circuit connections. And if resource preemptions are allowed, the delay performance for packet streams can be improved by 12% with more frequent preemptions. Our study provides useful insights into the planning and operation of access links.
3 citations
05 Oct 2022
TL;DR: In this article , a new architectural paradigm for future optical networks is introduced, inspired by the accelerated progresses in optical signal processing technologies and the integration of computing and communications, and highlight how this new architecture has the potential to shatter the status quo.
Abstract: Among various aspects in optical network architectures, handling transit traffic at intermediate nodes represents a defining characteristic for classification. In this context, the transition from the first generation of optical-electrical-optical mode to the second generation of optical-bypass marked a paradigm shift in redesigning optical transport networks towards greater network efficiency. Optical-bypass operation has then become the de facto approach adopted by the majority of carriers in both metro and backbone networks. However, in optical-bypass network, the fact that in-transit lightpaths crossing a common intermediate node must be separated in either time, frequency or spatial domain to avoid adversarial interference appears to be a critical shortcoming as the interaction of such lightpaths in optical domain may result in efficient computing and/or signal processing operations for saving spectral resources. Inspired by the accelerated progresses in optical signal processing technologies and the integration of computing and communications, we introduce in this paper a new architectural paradigm for future optical networks and highlight how this new architecture has the potential to shatter the status quo. Indeed, our proposal is centered on exploiting the superposition of in-transit lightpaths at intermediate nodes to generate more spectrally efficient lightpaths and how to harness this opportunity from network design perspectives. We present two case studies featuring optical aggregation and optical XOR encoding to demonstrate the merit of optical-processing-enabled operation compared to its counterpart, optical-bypass. Preliminary results on realistic network typologies are provided, revealing that a spectral saving up to 30% could be achieved thanks to adopting optical-processing network.
References
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TL;DR: In this paper, the potential and challenges of fiber-optic multi-band transmission (MBT) covering the ITU-T optical bands O(rightarrow$ ǫ ) were discussed.
Abstract: Fiber-optic multi-band transmission (MBT) aims at exploiting the low-loss spectral windows of single-mode fibers (SMFs) for data transport, expanding by $\sim\!11\times$ the available bandwidth of C-band line systems and by $\sim\!5\times$ C+L-band line systems’. MBT offers a high potential for cost-efficient throughput upgrades of optical networks, even in absence of available dark-fibers, as it utilizes more efficiently the existing infrastructures. This represents the main advantage compared to approaches such as multi-mode/-core fibers or spatial division multiplexing. Furthermore, the industrial trend is clear: the first commercial C $+$ L-band systems are entering the market and research has moved toward the neighboring S-band. This article discusses the potential and challenges of MBT covering the ITU-T optical bands O $\rightarrow$ L. MBT performance is assessed by addressing the generalized SNR (GSNR) including both the linear and non-linear fiber propagation effects. Non-linear fiber propagation is taken into account by computing the generated non-linear interference by using the generalized Gaussian-noise (GGN) model, which takes into account the interaction of non-linear fiber propagation with stimulated Raman scattering (SRS), and in general considers wavelength-dependent fiber parameters. For linear effects, we hypothesize typical components’ figures and discussion on components’ limitations, such as transceivers,’ amplifiers’ and filters’ are not part of this work. We focus on assessing the transmission throughput that is realistic to achieve by using feasible multi-band components without specific optimizations and implementation discussion. So, results are meant to address the potential throughput scaling by turning-on excess fiber transmission bands. As transmission fiber, we focus exclusively on the ITU-T G.652.D, since it is the most widely deployed fiber type worldwide and the mostly suitable to multi-band transmission, thanks to its ultra-wide low-loss single-mode high-dispersion spectral region. Similar analyses could be carried out for other single-mode fiber types. We estimate a total single-fiber throughput of 450 Tb/s over a distance of 50 km and 220 Tb/s over regional distances of 600 km: $\sim\!10\times$ and 8× more than C-band transmission respectively and $\sim\!2.5\times$ more than full C+L.
179 citations
TL;DR: A robust numerical approach is developed for calculating the key rate for arbitrary discrete-variable QKD protocols that will allow researchers to study ‘unstructured' protocols, that is, those that lack symmetry.
Abstract: Quantum key distribution (QKD) allows for communication with security guaranteed by quantum theory. The main theoretical problem in QKD is to calculate the secret key rate for a given protocol. Analytical formulas are known for protocols with symmetries, since symmetry simplifies the analysis. However, experimental imperfections break symmetries, hence the effect of imperfections on key rates is difficult to estimate. Furthermore, it is an interesting question whether (intentionally) asymmetric protocols could outperform symmetric ones. Here we develop a robust numerical approach for calculating the key rate for arbitrary discrete-variable QKD protocols. Ultimately this will allow researchers to study 'unstructured' protocols, that is, those that lack symmetry. Our approach relies on transforming the key rate calculation to the dual optimization problem, which markedly reduces the number of parameters and hence the calculation time. We illustrate our method by investigating some unstructured protocols for which the key rate was previously unknown.
143 citations
TL;DR: In this article, an accurate, closed-form expression for the nonlinear interference power in coherent optical transmission systems in the presence of inter-channel stimulated Raman scattering (ISRS) is derived.
Abstract: An accurate, closed-form expression evaluating the nonlinear interference (NLI) power in coherent optical transmission systems in the presence of inter-channel stimulated Raman scattering (ISRS) is derived. The analytical result enables a rapid estimate of the signal-to-noise ratio and avoids the need for integral evaluations and split-step simulations. The formula also provides a new insight into the underlying parameter dependence of ISRS on the NLI. Additionally, it accounts for the dispersion slope and arbitrary launch power distributions including variably loaded fiber spans. The latter enables real-time modeling of optical mesh networks. The results is applicable for lumped amplified, dispersion unmanaged, and ultra-wideband transmission systems. The accuracy of the closed-form expression is compared to numerical integration of the ISRS Gaussian noise model and split-step simulations in a point-to-point transmission, as well as in a mesh optical network scenario.
104 citations
TL;DR: The experimental transmission of quantum digital signatures over channel losses of up to 42.8 ± 1.2 dB in a link comprised of 90 km of installed fiber with additional optical attenuation introduced to simulate longer distances is reported.
Abstract: Ensuring the integrity and transferability of digital messages is an important challenge in modern communications. Although purely mathematical approaches exist, they usually rely on the computational complexity of certain functions, in which case there is no guarantee of long-term security. Alternatively, quantum digital signatures offer security guaranteed by the physical laws of quantum mechanics. Prior experimental demonstrations of quantum digital signatures in optical fiber have typically been limited to operation over short distances and/or operated in a laboratory environment. Here we report the experimental transmission of quantum digital signatures over channel losses of up to 42.8 ± 1.2 dB in a link comprised of 90 km of installed fiber with additional optical attenuation introduced to simulate longer distances. The channel loss of 42.8 ± 1.2 dB corresponds to an equivalent distance of 134.2 ± 3.8 km and this represents the longest effective distance and highest channel loss that quantum digital signatures have been shown to operate over to date. Our theoretical model indicates that this represents close to the maximum possible channel attenuation for this quantum digital signature protocol, defined as the loss for which the signal rate is comparable to the dark count rate of the detectors.
51 citations
TL;DR: The authors attempt to cover issues that are essential for the practical deployment of optical packet and burst switched networks and highlight promising research directions that are likely to facilitate such deployments.
Abstract: Over the past several years, a significant amount of research has been conducted in the areas of optical packet switching (OPS) and optical burst switching (OBS). This research has been motivated by the need for techniques that are capable of supporting the demanding requirements of emerging dynamic high-bandwidth network applications in a flexible and efficient manner. Although optical packet and burst switching have yet to be widely deployed in commercial settings, recent research progress indicates that such deployments are not infeasible in the near future. The authors review the literature on OPS and OBS. Basic concepts are discussed and an overview of current and emerging research issues and challenges for optical packet and burst switched networks is presented. The authors attempt to cover issues that are essential for the practical deployment of such networks and highlight promising research directions that are likely to facilitate such deployments.
46 citations