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【Objective】In order to realize intelligent cloud-light integration and to solve the problem of slow deploying optical transport network, the article provides a fast deployment method for end-to-end business of cross-domain and cross-vendor.【Methods】By analyzing current status of cross-domain and cross-vendor service deployment on the live network, we find and solve the problems of intelligent optical business integration of Software Defined Network (SDN) control system of the device manufacturer with Abstraction and Control of Traffic Engineered Networks (ACTN) and Software Defined Optical Transport Network (SDOTN) standards. The paper also proposes the methods and directions to improve the SDN management and control system of device manufacturers.【Results】Verified by testing, by optimizing and improving the Synchronous Digital Hierarchy (SDH) management and control system of device manufacturers, the efficiency of enabling end-to-end services within a domain can be improved. The intelligent one-click deployment of cross-domain end-to-end services can be implemented.【Conclusion】Proved by the test results, Optimizing and improving the SDN management and control system of equipment manufacturers is conducive to the service opening of intelligent cloud-light integration.

In order to solve the problems of high cost, low efficiency, and weak intelligence in the traditional operation and maintenance mode of optical transport networks, the research status and challenges of knowledge graph technology in the telecom industry were analyzed. Firstly, an intelligent operation and maintenance system architecture for optical transport networks based on knowledge graphs were proposed. Key technologies such as network state perception, knowledge graph construction, and open search capabilities were emphatically studied. Secondly, the application of intelligent cutover in a city branch of China Telecom was taken as an example, the application effect was analyzed, and the test showed that the cutover efficiency was improved by about 3 times. Finally, the development trend of intelligent operation and maintenance of optical transmission networks based on knowledge graphs was discussed.

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The evolution of optical networks is enabled by both technological and architectural advances with the goal of reducing operational and capital expenditure per transmitted bit. While the former one stimulates significant system capacity, the latter paves the way for reducing the effective traffic load in network so that more traffic can be carried. Accordingly, optical node architectures have been transitioning from optical-electrical-optical mode to all-optical one, leveraging the scalability and efficiency of fully optical cross-connecting. Conventional wisdom in designing and architecting such switching nodes is nevertheless rooted in the intuition that when an optical channel crossing an intermediate node, it should be maximally isolated from other optical channels in order to avoid interference which may result in degrading signal quality. Such long-established paradigm perceiving the interference of optical channels transiting at the same node as an adversarial factor and should therefore circumvent, albeit reasonable, may leave vast unexplored opportunities. Indeed, the rapid advances in all-optical signal processing technologies has brought opportunities to re-define the optical node architecture by upgrading its naive functionalities from simply add/drop and cross-connecting to proactively mixing optical channels in photonic domain. Specifically, all-optical channel aggregation and de-aggregation technologies have been remarkably advancing in recent years, permitting two or more optical channels at lower bit-rate and/or modulation formats could be all-optically aggregated to a single channel of higher-rate and/or higher-order modulation format and vice versa. Such evolutionary technique is poised to disrupt the existing ecosystem for optical network design and planning, and thus necessitates for a radical change to unlock new potentials. To that end, this paper presents a new paradigm for future optical networks, namely, optical-processing-enabled networks, which are powered by in-network all-optical mixing capability. We introduce the operational principle of optical channel aggregation (de-aggregation) and show how spectrally beneficial such innovative operations could yield by an illustrative example. Next, in order to maximize the aggregation opportunity, we present a mathematical model for optimal routing based on integer linear programming model. Numerical results on the realistic network topology COST239 are provided to quantify the spectral gain of aggregation-aware routing compared to the conventional one. [ABSTRACT FROM AUTHOR]

In the January 2022 issue of NTT Technical Review, we introduced the secure optical transport network for enabling secure optical transport even in the era of quantum computers. In this article, two concepts, cryptographic agility and Multi-Factor Security, which are key factors in the transition from current cryptographic techniques to quantum-resistant cryptographic techniques and need to be considered in the era of quantum computers, are explained, and our efforts to incorporate these concepts into secure optical transport networks (i.e., elastic-key-control technology and disaggregation technology for cryptographic processing) are introduced. [ABSTRACT FROM AUTHOR]

Traditional optical transport network is gradually becoming open and disaggregated, and the chimney-type single-vendor and single-domain management mode is also developing to the multi-vendor and multi-domain management mode with the penetration of software defined network (SDN) concept.Considering the equipment difference and protocol complexity of transport network, application of SDN management and control for transport network faces challenges.Firstly, the concept of grey-box was proposed, which was between black-box and white-box.Then, taking grey-box access OTN as an example, the key technologies of SDN unified management and control of access-type OTN were discussed, including management and control architecture, service template, automatic topology generation, automatic equipment online, remote upgrade of equipment, in-band DCN communication between different vendors, etc.Finally, the application of access-type OTN unified management and control system in real network was described.

Optical transport networks (OTNs) are widely used in backbone- and metro-area transmission networks to increase network transmission capacity. In the OTN, it is particularly crucial to rationally allocate routes and maximize network capacities. By employing deep reinforcement learning (DRL)- and software-defined networking (SDN)-based solutions, the capacity of optical networks can be effectively increased. However, because most DRL-based routing optimization methods have low sample usage and difficulty in coping with sudden network connectivity changes, converging in software-defined OTN scenarios is challenging. Additionally, the generalization ability of these methods is weak. This paper proposes an ensembles- and message-passing neural-network-based Deep Q-Network (EMDQN) method for optical network routing optimization to address this problem. To effectively explore the environment and improve agent performance, the multiple EMDQN agents select actions based on the highest upper-confidence bounds. Furthermore, the EMDQN agent captures the network's spatial feature information using a message passing neural network (MPNN)-based DRL policy network, which enables the DRL agent to have generalization capability. The experimental results show that the EMDQN algorithm proposed in this paper performs better in terms of convergence. EMDQN effectively improves the throughput rate and link utilization of optical networks and has better generalization capabilities. [ABSTRACT FROM AUTHOR]

The age of acceleration is taking place, driven by the revolutionary digital transformation creating basically a digital version of the physical world. Massive amount of data has thus been generated ranging from wearable devices monitoring our physical health every single millisecond to autonomous vehicles generating an order of magnitude of Terabytes hourly to even astronomical activities producing an order of Exabytes on a daily basis and then ultra-broadband Internet comes into play, moving such data to the cloud. As a result, Internet traffic has been experiencing explosive growth and in this context, optical transport networks forming the backbone of the Internet are pushed for transformation in system capacity. While the intuitive solution of deploying multiple fibers can address the pressing demand for increased capacity, doing so does not bring improvements in economic of scales with respect to cost, power consumption and spectral efficiency. This necessitates for a complementary approach so that the fiber capacity could be utilized in a more efficient manner. Indeed, optical-processing-enabled network has been emerging as a new architectural paradigm to attain greater fiber capacity thanks to permitting the superposition of in-transit lightpaths at intermediate nodes for optical signal processing purposes. In this paper, we focus on innovative techniques, that is, photonic network coding and partial protection, to reduce the effective traffic load for optical transport networks adopting optical-processing-enabled architecture. Specifically, the application of photonic network coding is investigated by upgrading the functionalities of intermediate nodes with all-optical processing (i.e., encoding and decoding) capabilities. Besides, partial protection relying on the premise of providing just enough bandwidth in case of failure events is exploited for saving the redundant protection capacity. That it takes two to tango, combining photonic network coding and partial protection therefore bring to light new opportunities and challenges. In mining such new avenue, we present insights on how to derive compounding gains to maximize spectral efficiency via a case study. [ABSTRACT FROM AUTHOR]

The evolution beyond 5G towards 6G will accelerate the transformations begun by 5G to deploy new approaches to define delivery services. The network should be accessible anywhere, always-on and with the guarantee performances. This poses new challenges to the transport network that should assure available connectivity among the functions at different levels of granularity. The transport network should be so flexible to guarantee on-demand the connectivity among the processing functions that automatically will be required and, at the same time, should assure extreme performance. Optical network and Dense Wavelength Division Multiplexing technology are relevant candidates to match high bandwidth and low latency, but new challenges are required to assure the suitable cost and size for the wireless access networks. The current optical technology, suitable used in aggregation and long-haul transport network, cannot be simply downsized to be used in the access area, but novel paradigm should be considered for the optics as well. Integrated photonics seems a promising direction to realize low cost and low size optical components for the transport network. Moreover, this technology enables a certain level of remote tunability and reconfiguration of optical equipment that allow to simplify and reduce cost of installation in field and operation of the transport network. In this paper relevant optical components for transport networks are analyzed using the integrated photonics to assess the technology challenges. [ABSTRACT FROM AUTHOR]

We review a series of innovative optical network technologies for 5G and beyond mobile networks, enabling high-throughput mobile any-haul (x-haul) via wavelength-division multiplexing, bandwidth-efficient mobile front-haul via hybrid digital-analog radio-over-fiber, Shannon-limit-approaching long-haul transmission for core networks via advanced coding and probabilistic constellation shaping, low-latency 50-Gb/s passive optical network for cost-effective x-haul traffic aggregation, and service-enabling optical transport network capable of bandwidth-guaranteed network slicing with fine granularity. The vision and main application scenarios of the 5th generation fixed network (F5G) are also discussed. With its capability to support enhanced fixed broadband, guaranteed reliable experience, full fiber connection, energy-efficient broadband communication, real-time broadband communication, and harmonized communication and sensing, F5G is well positioned to not only support mobile networks, but also complement them to jointly meet the ever-increasing communication demands in the era of 5G and 6G. [ABSTRACT FROM AUTHOR]

Traditional optical transport network is gradually becoming open and disaggregated, and the chimney-type single-vendor and single-domain management mode is also developing to the multi-vendor and multi-domain management mode with the penetration of software defined network (SDN) concept. Considering the equipment difference and protocol complexity of transport network, application of SDN management and control for transport network faces challenges. Firstly, the concept of grey-box was proposed, which was between black-box and white-box. Then, taking grey-box access OTN as an example, the key technologies of SDN unified management and control of access-type OTN were discussed, including management and control architecture, service template, automatic topology generation, automatic equipment online, remote upgrade of equipment, in-band DCN communication between different vendors, etc. Finally, the application of access-type OTN unified management and control system in real network was described. [ABSTRACT FROM AUTHOR]

Optical transport networks (OTNs) are widely used in backbone- and metro-area transmission networks to increase network transmission capacity. In the OTN, it is particularly crucial to rationally allocate routes and maximize network capacities. By employing deep reinforcement learning (DRL)- and software-defined networking (SDN)-based solutions, the capacity of optical networks can be effectively increased. However, because most DRL-based routing optimization methods have low sample usage and difficulty in coping with sudden network connectivity changes, converging in software-defined OTN scenarios is challenging. Additionally, the generalization ability of these methods is weak. This paper proposes an ensembles- and message-passing neural-network-based Deep Q-Network (EMDQN) method for optical network routing optimization to address this problem. To effectively explore the environment and improve agent performance, the multiple EMDQN agents select actions based on the highest upper-confidence bounds. Furthermore, the EMDQN agent captures the network’s spatial feature information using a message passing neural network (MPNN)-based DRL policy network, which enables the DRL agent to have generalization capability. The experimental results show that the EMDQN algorithm proposed in this paper performs better in terms of convergence. EMDQN effectively improves the throughput rate and link utilization of optical networks and has better generalization capabilities.

In this paper, a 420 km Optical transport network (OTN) transmission system of 8 × 100 Gbit/s signals was achieved with amplifier combination of a low cost second order Raman amplifier and an enhanced remotely pump amplifier. The second order Raman amplifier consist of a commercial first order Raman amplifier and two auxiliary lasers which is completely controlled by the first order Raman amplifier. The total link budget is 84 dB with a power margin of more than 4 dB. The new amplifier structure increased the link power budget by 6.5 dB and OSNR by 1.4 dB on average.

Optical multi-domain transport networks are often controlled by a hierarchical distributed architecture of controllers. Optimal placement of these controllers is very important for efficient management and control. Traditional SDN controller placement methods focus mostly on controller placement in datacenter networks. But the problem of virtualized controller placement for multi-domain transport networks needs to be solved in the context of geographically distributed heterogeneous multi-domain networks. In this context, edge datacenters have enabled network operators to place virtualized controller instances closer to users, besides providing more candidate locations for controller placement. In this study, we propose a dynamic controller placement method for optical transport networks that considers the heterogeneity of optical controllers, resource limitations at edge hosting locations, and latency requirements. We also propose a machine-learning framework that helps the controller placement algorithm with proactive prediction (instead of traditional reactive threshold-based approach). Simulation studies, considering practical scenarios and temporal variation of load, show significant cost savings compared to traditional placement approaches. [ABSTRACT FROM AUTHOR]

Photonic Integrated Circuits allow to meet the increasing demand of communication systems for internet which is growing at about 40% per year. This growth is driven mainly by increasing video traffic in the internet network. This growth is now further accelerated by mobile access, with video clients shipping on an all smart phones and tablets, enabling video to be consumed more conveniently via network connections anywhere and anytime. This paper reviews several material platform of photonic integrated circuits a compares their performance. This paper also describes the new approaches in the design and fabrication of optical transceivers based on photonic integrated circuits for next terabit era.

Optical fiber communication system is one of the core supporting systems of the modern internet age.Firstly,major recent technological advances in optical fiber communication system were summarized.Then,the driving forces for its future development in the emerging cloud era,the future challenges and opportunities that it faced were analyzed.With the consideration of these challenges and opportunities,the future evolution paths in key areas such as optical fiber communication system overall network architectures,core network technologies,metro network technologies,access network technologiesand novel software-defined optical transport network technologies in the upcoming cloud erawere described,aiming to support future generations of internet,data center interconnect,internet of things and 5G mobile network,as well as the smart home and smart city initiativesmore effectively.

Traditional dense wavelength division multiplexing (DWDM) technology is no longer enough to meet the extensive growth in the demand of bandwidth in an efficient and effective manner under the fixed grid environment. Thus, a technology is needed to overcome the challenges raised by the ever-increasing demand of bandwidth in an effective manner with efficient utilization of spectral resources. To solve this problem, an elastic optical network (EON) paradigm comes into existence. It uses a flexible grid technology that removes the limitations of fixed grid DWDM technology and increases the channel capacity to meet current bandwidth demand with proper utilization of optical spectrum. We present the evolution of EON from the DWDM network. We have discussed the main components and characteristics of EON that includes superchannel and sliceable bandwidth variable transponder (SBVT). Thereafter, we discuss the different modulation and transmission techniques used in EON. Next, we present the recently proposed architectures of SBVT followed by its applications. Lastly, we have discussed various subcarrier generation techniques in brief. [ABSTRACT FROM AUTHOR]

A low-complexity soft-decision concatenated FEC scheme, consisting of an inner LDPC code and an outer staircase code, is proposed. The inner code is tasked with reducing the bit error probability below the outer-code threshold. The concatenated code is obtained by optimizing the degree distribution of the inner-code ensemble to minimize estimated data-flow, for various choices of outer staircase codes. A key feature that emerges from this optimization is that it pays to leave some inner codeword bits completely uncoded, thereby greatly reducing a significant portion of the decoding complexity. The tradeoff between required signal-to-noise ratio and decoding complexity of the designed codes is characterized by a Pareto frontier. Computer simulations of the resulting codes reveals that the net coding-gains of existing designs can be achieved with up to 71% reduction in complexity. A hardware-friendly quasi-cyclic construction is given for the inner codes, which can realize an energy-efficient decoder implementation, and even further complexity reductions via a layered message-passing decoder schedule. [ABSTRACT FROM AUTHOR]

Photonic Integrated Circuits allow to meet the increasing demand of communication systems for internet which is growing at about 40% per year. This growth is driven mainly by increasing video traffic in the internet network. This growth is now further accelerated by mobile access, with video clients shipping on all smart phones and tablets, enabling video to be consumed more conveniently via network connections anywhere and anytime. This paper reviews several material platform of photonic integrated circuits and compares their performance. This paper also describes the new approaches in the design andfabrication of optical transceivers based on photonic integrated circuits for next terabit era. [ABSTRACT FROM AUTHOR]

As a converged technology, the packet enhanced optical transport network（POTN/PE-OTN）technology is able to meet the rapidly growing demand for bandwidth and multi-service bearing with differentiated quality of services. The statuses of POTN/PE-OTN technology standards were introduced. The architecture of POTN/PE-OTN equipment and the possible implementations were analyzed. The architecture of networking with POTN/PE-OTN technology in the metropolitan area network was discussed.

Due to the emergence of high-bitrate application, the cross stratum optimization (CSO) using the path computation element (PCE) has recently stimulated the interest by network operators. With large-scale growth and high complexity of optical transport networks, especially deploying with data centers, how to realize CSO more effectively, accurately and practically will become the research focus. Based on our previous works about the CSO, this paper presents a CSO-oriented software defined multi-domain and multi-layer optical transport networks (SDMOTN) architecture deploying with data centers. The proposed architecture can enable joint optimization of optical networks and application stratum resources, and enhance the service accommodation and the data center responsiveness to end-to-end service demands. Moreover, a novel dynamic global load balancing strategy (DGLB) with dynamic resource rating method for CSO is presented based on the proposed architecture. The overall feasibility and efficiency of the SDMOTN architecture with DGLB strategy are experimentally demonstrated and quantitatively compared with four strategies by experiments on our optical as a service (OaaS) testbed with 1000 virtual nodes. [ABSTRACT FROM AUTHOR]

A concatenated soft-decision forward error correction (FEC) scheme consisting of an inner low-density generator-matrix (LDGM) code and an outer staircase code is proposed. The soft-decision LDGM code is used for error reduction, while the majority of bit errors are corrected by the low-complexity hard-decision staircase code. Decoding complexity of the concatenated code is quantified by a score based on the number of edges in the LDGM code Tanner graph, the number of decoding iterations, and the number of staircase code decoding operations. The inner LDGM ensemble is designed by solving an optimization problem, which minimizes the product of the average node degree and an estimate of the required number of decoding iterations. A search procedure is used to find the inner and outer code pair with lowest complexity. The design procedure results in a Pareto-frontier characterization of the tradeoff between net coding gain and complexity for the concatenated code. Simulations of code designs at \text20\% overhead showed that the proposed scheme achieves net coding gains equivalent to existing soft-decision FEC solutions, with up to \text57\% reduction in complexity. [ABSTRACT FROM PUBLISHER]

In this paper we propose a new sliceable bandwidth variable transponder (SBVT) architecture with the separate analysis on the transmitter and receiver section. In transmission section we propose a distance module (DM) which is a programmable module. It divides a data stream/main stream (which employs a super-channel) into sub-stream and assigned modulation technique to each sub-stream based on their light path distance detailing the concept of sub-channel. In this paper, we have also proposed an algorithm for the distance module. Next we propose a modulation and transmission module (M&TM), where, planar light wave circuit (PLC) is used for enabling three modulation techniques (PM-16QAM, PM-QPSK and PM-BPSK). Finally, we propose the receiving section, which is designed to support three modulation techniques. It consists of two demodulator circuits, one for PM-16QAM/PM-QPSK and the other for PM-BPSK. In this proposed work, we focus on the multi-mode interference (MMI) devices (MMI coupler and MMI splitter) because of their photonic integration technology which is necessary for the implementation of SBVT. Lastly, we propose an elastic optical node architecture which removes the limitations of previously discussed node architecture for long distance communication. [ABSTRACT FROM AUTHOR]

In this paper, we analyze benefits of photonic integration-based sliceable transponders (sliceable photonics) compared to discrete optics transponder-based solutions (CFP/CFP2-C form-factor pluggable) in metro and long-haul networks. The metrics considered for comparison include the number of transponders, bandwidth use and power utilization. We assumed an OTN-based network with QPSK and 16QAM modulation schemes for both the scenarios. We observed that sliceable photonics is much more advantageous than discrete transponder optics in both metro and long-haul networks. We also compared the effect of modulation schemes on the efficiency of the network by comparing QPSK and 16QAM in discrete transponder optics and show that 16QAM in discrete transponder optics makes the network more inefficient. [ABSTRACT FROM AUTHOR]

The development of packet enhanced optical transport network（POTN／PE-OTN）technology was put forward to meet the rapid growth of bandwidth demanding and multi-service providing. The features and development status of POTN／PE-OTN technology were introduced. The main application scenarios of POTN／PE-OTN technology in the MAN were analyzed. And the possible technical solutions were also explored.