Physical-layer security in evolving optical networks

Content caching is an effective technique that reduces network power consumption by reducing the path between users and requested video content. This paper examines the benefit of caching in an IP over WDM core network with respect to current and future networks. It compares the power savings due to caching in current implementations of optical networks to potential power savings when future optical network features are realized. Future optical core networks are considered with three major power efficiency improvements over current networks. First, network devices are equipped with sleep-mode capabilities where inactive parts of storage devices are put in low-power mode. Second, optical bypass is employed where intermediate IP routers are not engaged in traffic routing. Third, the power consumption of router ports is significantly reduced, consequently reducing the power consumption of transport. The results show that content caching is effective in reducing power consumption under both current and future optical networks, making caching a successful option for video delivery in the future Internet.

In future optical networks, versatile functionalities will be required for the optical network subsystems to fully utilize the spectral resources with low energy consumption. The key technologies are the spectral efficient MUX/DEMUX technique and flexible control of optical channels with high frequency granularity. An orthogonal frequency division multiplexing (OFDM) and Nyquist wavelength division multiplexing (N-WDM) are the most promising candidates of spectral efficient multiplexing techniques, and all-optical (AO) processing is expected to reduce the energy consumption. In an AO-OFDM systems, discrete Fourier transform (DFT) and inverse DFT (IDFT) are performed in optical domain by specially designed arrayed waveguide gratings (AWGs). In our experiment, 12.5 GHz spaced AO-OFDM system has been successfully demonstrated with no guard interval. In N-WDM systems, the Nyquist signal is generated by using carrier-suppressed return-to-zero (CS-RZ) signal and optical Nyquist filtering, which is achieved with two flat-top AWGs and optical interleaver, and the 25 Gbaud signals are successfully multiplexed in the experiment. Although both AO-OFDM and N-WDM can achieve the highest spectral efficiency, N-WDM is more suitable for flexible optical networks. This is because the N-WDM channels have less spectral overlap with the other channels than AO-OFDM, owing to its rectangular shaped compact spectrum. Therefore, N-WDM channel can be easily multiplexed and demultiplexed by optical filters. At an optical network node, channel defragmentation is indispensable technology to flexibly control the optical channels. We have experimentally demonstrated a format independent optical channel defragmentation with N-WDM signal. We believe these technologies are promising for future flexible optical networks.

Elastic optical network (EON) is a promising candidate for the next generation optical transport network because of its high spectrum efficiency and flexible spectrum allocation. However, to migrate from today’s dense wavelength division multiplexing (DWDM) network to EON, optical nodes such as reconfigurable optical add/drop multiplexers (ROADMs) should be replaced with the ones with expensive flexi-grid wavelength selective switches (WSSs). Thus, whether and how today’s optical network will be evolved to EON is still under debate. Meanwhile, with the technical maturity of optical super-channels that transmit bit rates at the level of 1 Tb/s, super-channels are expected to dominate the future optical transport network because of their attractiveness of high spectrum efficiency and superior cost effectiveness. In this paper, we propose a new quasi-coarse wavelength division multiplexing (Quasi-CWDM) optical network architecture that is compatible to today’s WDM network in spectrum operation, while still maintaining the flexibility of adaptation between the bit rate and the transparent reach of an optical super-channel, but not requiring expensive flexi-grid WSSs. Specifically, the Quasi-CWDM optical network employs large fixed frequency grids, whose spacing falls between the traditional CWDM and DWDM, e.g., 200 GHz or 400 GHz. To maintain the flexibility between the bit rate and the transparent reach of an optical super-channel, different modulation formats are chosen according to channel physical distances. To minimize network hardware cost and maximize carried user traffic demand, we develop a mixed integer linear programming (MILP) model and a heuristic algorithm that can efficiently groom upper-layer IP traffic onto the optical layer by optical super-channels. We compare the design based on the Quasi-CWDM network to those based on the DWDM network and the advanced EON. It is found that the proposed Quasi-CWDM network has a much lower hardware cost than the other two types of networks, while achieving spectrum efficiency close to EON.

Extending the researches on wavelength switched optical networks (WSON), efficient integration of the novel optical packet switching network and wavelength switching-based optical circuit switching network technologies which offers both best-effort packet delivery and QoS guaranteed lightpath services has been being studied. In addition, researches on the optical-layer transparent data processing, such as all-optical wavelength multicasting, all-optical 3R regeneration, etc, are conducted simultaneously. It is believed that future innovative optical network services (INSes) would be built on these novel future-proof technologies, and foster colorful applications in the new generation networks. Before the wide applications of INS in different fields, there would be a foreseeable strong requirement for INS firstly posed by pioneer grid applications, e.g., e-science, e-government, and e-banking, etc, which would require the high-performance underlying networks. Our research here is motivated to glue the optical networks and grid applications by integrating lightpath, geographically distributed INS systems and grid resources (e.g., computers, storages, instruments, etc.), and finally offering an easy-to-use high performance networked grid computing environment-optical grid network (OGN) to user applications. In this paper, we introduce our research activities of a distributed optical grid network infrastructure (OGNI), and the creation of the future easy-to-use INS based on OGNI. The proposals have been validated through fieldtrial experiments over a developed WSON testbed.

This paper studies the overall energy consumption of a pan-European optical transport network for three different time periods: today and in five and ten years from now. In each time period the pan-European network was dimensioned using traffic predictions based on realistic data generated by the optical networking roadmap developed in the framework of the European project Building the Future Optical Network in Europe—BONE. A wavelength routed wavelength division multiplexed optical network based on either transparent or opaque node architectures was examined considering exclusively either 10 Gbit/s or 40 Gbit/s per channel data rates. The results manifest that transparent optical networking technologies are expected to provide significant energy savings of the order of 35% to 55%. It was also shown that the migration towards higher data rates, i.e., from 10 Gbit/s to 40 Gbit/s, is assisting in improving the overall energy efficiency of the network.

The traffic carried by core optical networks grows at a steady but remarkable pace of 30-40% year-over-year. Optical transmissions and networking advancements continue to satisfy the traffic requirements by delivering the content over the network infrastructure in a cost and energy efficient manner. Such core optical networks serve the information traffic demands in a dynamic way, in response to requirements for shifting of traffics demands, both temporally (day/night) and spatially (business district/residential). However as we are approaching fundamental spectral efficiency limits of singlemode fibers, the scientific community is pursuing recently the development of an innovative, all-optical network architecture introducing the spatial degree of freedom when designing/operating future transport networks. Spacedivision- multiplexing through the use of bundled single mode fibers, and/or multi-core fibers and/or few-mode fibers can offer up to 100-fold capacity increase in future optical networks. The EU INSPACE project is working on the development of a complete spatial-spectral flexible optical networking solution, offering the network ultra-high capacity, flexibility and energy efficiency required to meet the challenges of delivering exponentially growing traffic demands in the internet over the next twenty years. In this paper we will present the motivation and main research activities of the INSPACE consortium towards the realization of the overall project solution.

Aiming at the working mechanism of optical backbone network, based on the theory of complex network, the invulnerability evaluation index of optical backbone network is extracted from the physical topology of optical backbone network and the degree of bandwidth satisfaction, finally, the invulnerability evaluation model of optical backbone network is established. At the same time, the evaluation model is verified and analyzed with specific cases, through the comparison of 4 types of attack, the results show that the number of deliberate point attacks ( $DP$ ) is 16.7% lower than that of random point attacks ( $RP$ ) when the critical collapse state of the network is reached, and the number of deliberate edge attacks ( $DE$ ) is at least 10.4% lower than that of random edge attacks ( $RE$ ). Therefore, evaluating the importance of nodes and edges and strengthening the protection of key nodes and edges can help optical network effectively resist external attacks and significantly improve the anti-damage ability of optical network, which provides theoretical support for the anti-damage evaluation of optical network and has certain practical significance for the upgrade and reconstruction of optical network.

Network automation is the current challenge that operators face to accelerate end-to-end service delivery and improve network operations in the context of rapidly growing capacity needs. Optical networks have long been built using vendors’ turn-key solutions, resulting in complexity for the operator to automate its multi-vendor networks in a consistent way. Questioning the vendors’ lock-in in disaggregating the optical transmission systems (i.e., splitting the system into parts, where each part can be provided by a different vendor) provides advantages (e.g., cost) but also additional complexity. Openness and standardization appear as key for these multi-vendor scenarios. The path is not easy, but it is not a matter of choice: opening and interoperability are obligations that we face because of the need for automation. The journey that we detail in this paper is the one that we think will be sustainable from our side. The opposite, i.e., continue building vendors’ silos and staking per-vendor specialized applications, is not sustainable. We propose a step-by-step approach, starting with the non-disaggregated situation, followed by partial and full disaggregation architectures to the last evolution towards data centric networking. We present and discuss implementations that Orange has been contributing to and identify some gaps the industry should address. We show that current works in the communities of open source, open initiatives, and standardization bodies are addressing all these steps, and in this respect can accelerate the deployment of automation solutions in current and future optical transport networks.

Growing concerns regarding the scalability of current optical networks as well as IP-based networks are driving two important trends. One trend is a shift from the current rigid optical networks to spectrally efficient elastic optical networks with a flexible bandwidth and adaptive channel spacing. The other trend is IP traffic offloading to a lower layer yielding benefits that are potentially cost-effective and power-efficient. This article presents a novel multiflow optical transponder (OTP) that enables more efficient IP optical networking. A multiflow OTP allows client data flows that arrive from a single client interface to be mapped to multiple optical flows. In cooperation with the emerging spectrally efficient elastic optical path networking technology, multiflow OTPs can provide multiple optical connections from a single OTP to multiple OTPs. IP traffic offloading to an elastic optical path layer architecture and the effect of introducing multiflow OTPs (i.e., the potential reduction in the number of router interfaces and considerable potential for cost savings) are discussed. These benefits are brought about by increasing the number of directly connected router pairs while keeping router-to-optical-node interconnections simple. A novel optical virtual private line service based on multiflow OTPs that supports multiple optical connections from a single customer site to multiple customer sites with capacity adjustment is also discussed.

Optical networks are the backbone of today’s high-speed communication systems, but they can be attacked in many ways. Hackers might use advanced methods like wormhole attacks, Sybil attacks, or single-point failures to disrupt or take control of the network. Most current security systems rely on complex math to protect data. But with the development of quantum computers, those systems are no longer fully safe. Quantum computers could break these protections easily in the future. This problem can be solved by integrating two powerful technologies: Quantum Key Distribution (QKD) and blockchain This combination is called quantum-secured blockchain. This system removes the need for older, potentially breakable digital signatures, and instead uses methods that are resistant to quantum computer attacks. They also rely on new quantum materials and nanomaterials, which help in making better light sources, reducing signal loss and storing quantum information more reliably. AI and machine learning are now being used to speed up the discovery of these advanced materials such as superconductors, quantum dots and special optical fibers that are required to make the technology practical and scalable. This paper explains the different types of attacks that can occur in optical networks and the ways to protect optical networks using quantum-secured blockchain along. It gives the introduction to blockchain technology along with its security weaknesses, and then focuses on Quantum Key Distribution (QKD), which can make blockchain much stronger against attacks from powerful quantum computers. It also provides an overview of how quantum-secured blockchain works to secure optical communication networks.

In this paper, we have proposed a generalized large-scale optical cross-connect (OXC) architecture utilizing waveband selective switches (WBSS) for realizing future cost-effective, bandwidth-abundant and flexible optical networks. The developed architecture implements multiple WBSSs for each incoming fiber and small size wavelength selective switches (WSSs) for dropping optical paths while simply deploying 1´2 WSSs or 1´2 optical couplers for realizing the adding function. Thanks to the use of WBSSs, which are more cost-effective and simpler devices, the developed architecture enables a significant hardware scale reduction. The WBSS-based OXC, however, suffers from a limited routing capability, which relies on the inner node parameter (i.e., the WBSS number per input fiber) and the waveband granularity of WBSSs. We, therefore, evaluate the hardware scale requirement of our developed architecture in comparison with that of conventional WSS-based OXC. It is verified that a substantial hardware scale reduction can be achieved by using the proposed architecture, especially for high port count OXCs or when applying coarser granular WBSSs. Moreover, we also assess the performance of dynamic optical networks based on the proposed OXC. Numerical simulations show that the network offers a substantial necessary hardware scale reduction at the cost of a small performance offset comparing to that of the network using conventional WSS-based OXC.

Metaheuristic hybridizations for the regenerator placement and dimensioning problem in sub-wavelength switching optical networks

The ongoing evolution of optical networks towards autonomous systems supporting high-performance services beyond 5G requires advanced functionalities for automated security management. To cope with evolving threat landscape, security diagnostic approaches should be able to detect and identify the nature not only of existing attack techniques, but also those hitherto unknown or insufficiently represented. Machine Learning (ML)-based algorithms perform well when identifying known attack types, but cannot guarantee precise identification of unknown attacks. This makes Root Cause Analysis (RCA) crucial for enabling timely attack response when human intervention is unavoidable. We address these challenges by establishing an ML-based framework for security assessment and analyzing RCA alternatives for physical-layer attacks. We first scrutinize different Network Management System (NMS) architectures and the corresponding security assessment capabilities. We then investigate the applicability of supervised and unsupervised learning (SL and UL) approaches for RCA and propose a novel UL-based RCA algorithm called Distance-Based Root Cause Analysis (DB-RCA). The framework’s applicability and performance for autonomous optical network security management is validated on an experimental physical-layer security dataset, assessing the benefits and drawbacks of the SL- and UL-based RCA. Besides confirming that SL-based approaches can provide precise RCA output for known attack types upon training, we show that the proposed UL-based RCA approach offers meaningful insight into the anomalies caused by novel attack types, thus supporting the human security officers in advancing the physical-layer security diagnostics.

An energy-efficient optical access network scheme based on sub-band grouping and allocating is proposed and studied for the digital filter multiple access adopted passive optical network (DFMA-PON). In this scheme, sub-bands generated in digital sdomain are grouped as band groups and properly allocated for optical network unit (ONU) transmissions to reduce the transmission time. Based on this, longer sleeping time can be provided to each ONU, and some more energy can be saved. Numerical evaluations indicate that comparing with basic DFMA-PON, significant energy is saved by the proposed scheme, and a promoted energy saving performance can be achieved by properly arranging the number of sub-bands assigned in a band group. Furthermore, the technology improvement and its impact on the performance of the scheme are also investigated. It is demonstrated that comparing with the conventional network, the proposed scheme possesses prominent energy saving potential. It can be considered as a potential solution for future energy-efficient optical access network.

Widely available broadband services in the Internet require high capacity access networks. Only optical networking is able to efficiently provide the huge bandwidth required by multimedia applications. Distributed applications such as Video-Conferencing, HDTV, VOD and Distance Learning are increasingly common and produce a large amount of data traffic, typically between several terminals. Multicast is a bandwidth-efficient technique for one-to-many or many-to-many communications, and will be indispensable for serving multimedia applications in future optical access networks. These applications require robust and reliable connections as well as the satisfaction of QoS criteria. In this chapter, several access network architectures and related multicast routing methods are analyzed. Overall network performance and dependability are the focus of our analysis.