Photonic transport networks based on optical paths

This paper describes the performances of a newly-developed experimental optical path cross-connect system (OPXC) based on the wavelength path scheme and its wavelength monitoring circuit. The OPXC system features high levels of modularity and expandability for switching components. Exploiting planar lightwave circuit (PLC) technologies, (8/spl times/16) delivery-and-coupling-type optical switches (DC-switch) are fabricated for the 320-Gbit/s throughput OPXC system which can accommodate 16 incoming and outgoing fibers. The average fiber-to-fiber insertion loss of the DC switch is 12.6 dB and its on/off ratio is 42.1 dB. Eight wavelength-division multiplexing (WDM) signals, directly intensity-modulated at 2.5 Gbit/s, are performed to be transported over 330 km from origin to destination node via a cross-connection node in the test-bed system which simulates a 5-node network. Additionally, a novel multiwavelength simultaneous monitoring circuit for the OPXC is proposed and its performance is demonstrated through experiments.

SUMMARY This paper proposes new switch architectures for hierarchical optical path cross-connect (HOXC) systems. The architectures allow incremental expansion of system scale in terms of the number of input/output fiber ports, wavebands, and optical paths per waveband. These features assure the cost-effective introduction of HOXCs even at the outset when traffic volume is not so large. Furthermore the effectiveness of the proposed switch architectures is demonstrated in a comparison with singlelayer OXCs (conventional OXCs). The results provide useful criteria for the introduction of HOXCs in terms of hardware scale. Broadband access including ADSL and FTTH is being rapidly adopted throughout the world and, as a result, traffic is continually increasing. The maximum number of WDM wavelengths per fiber now exceeds one hundred, and wavelength routing using ROADMs (Reconfigurable OADMs) is being widely adopted to develop cost-effective networks [1]. GMPLS controlled OXCs have also been used to create nation-wide testbeds [2]. Further traffic expansion is expected in the near future with the introduction of new broadband services including IP TV and high definition TV. This will result in a significant increase in the number of wavelength paths that are to be cross-connected at nodes, and hence optical node throughput needs to be greatly enhanced. To resolve this problem, the hierarchical optical path crossconnect (HOXC) [3]–[5] is being investigated; it can handle hierarchical bandwidth optical paths, wavelength paths and wavebands (WBs) which consist of multiple wavelength paths. Indeed, several studies have targeted the development of hierarchical optical path network design algorithms [6]– [9], these algorithms were shown to greatly lower network cost compared to conventional single-layer optical path networks for a wide range of traffic demand. Most of the works evaluated the effectiveness in terms of the total number of OXC and HOXC ports compared to those of single-layer OXCs. Another study [10] showed that an HOXC with nonuniform WB size can not only improve node throughput but also reduce cross-connect node cost. The key components needed to develop HOXCs are waveband multi/demultiplexers (WB MUX/DEMUX),

Optical networks that support high‐speed, low‐cost communication services are required. an optical path is proposed that utilizes wavelength multiplexing technology at the path layer of transport network layers. Optical path schemes, wavelength path (WP)/virtual wavelength path (VWP) that can realize optical path networks are also proposed. Although wavelengths are a resource in optical networks, the number of wavelengths required to construct an optical path network has not been evaluated.This paper describes a method of network protection using the optical path technique that enhances network reliability and proposes a method for establishing a restoration path that restores failed active paths in both WP and VWP schemes. Proposed herein is an optical path accommodation design to establish WPs or VWPs in a physical network considering the proposed restoration method. Furthermore, optical path networks are constructed by establishing WPs or VWPs on a physical network that has a regular structure and the number of wavelengths required in the network are evaluated. This evaluation makes it clear that the VWP scheme requires fewer wavelengths than the WP scheme.

Path layer technologies play a key role in the development of a powerful and failure resilient broadband integrated services digital network (B-ISDN). The authors discuss wavelength division multiplexing/frequency division multiplexing (WDM/FDM) techniques and demonstrate that optical paths can greatly enhance the path layer capability and, therefore, network performance. It is shown that effective network failure restoration can be achieved with optical paths. The applicability of the wavelength path (WP) technique to global area networks is revealed. WPs are applied to the national backbone network example to evaluate the required number of wavelengths and to identify optical cross-connect node requirements. A new optical path concept is proposed, i.e., the virtual wavelength path (VWP). In the VWP scheme, wavelengths are assigned on a link-by-link basis. The wavelength assigned to a wavelength path has only local significance. Significant benefits of the VWP such as the simplified path accommodation design within a transmission facility network and the reduced number of wavelengths needed, are elucidated. >

Lightwave networks realized through code division multiple access techniques are extensively studied to determine their ultimate capabilities. Here, these concepts are extended to network implementation by introducing an optical code division multiplexing (OCDM) multihop strategy using optical coding. It is shown that this approach is effective in scaling up existing wavelength division multiplexing (WDM) networks without a significant drain of the wavelength resources. The concept of a virtual optical code path (VOCP) is introduced within the transport layer of the network. It is demonstrated that this is a potential solution to wavelength path (WP) allocation problems which may plague WDM based transport networks of the future. Crucial to the VOCP concept is optical code conversion. The interplay between this added functionality and the optical cross-connect is highlighted; the optical cross-connect serves to establish VOCP/VWP (virtual wavelength path) in the hybrid transport layer. An example of optical code conversion is introduced. It is based on coherent OCDM principles in which bipolar phase-shift keyed (PSK) optical pulse sequences are used as the signature codes. Error-free code conversion using a four-chip optical encoder/decoder is successfully performed at 1.24 Gbit/s. The results show the feasibility of high bit rate OCDM transmission with optical code conversion.

The 5th generation of mobile communication system (5G) is expected to change the communication landscape by 2020. 5G will provide a unified platform for connecting billions of devices and offering a wide range of networking services. The use-cases and the disruptive capabilities of 5G will bring forward a number of challenges for both the wireless radio and wired part of a 5G network. The wired transport network, typically consisting of access and core domains, has to adopt tailored networking solutions satisfying differentiated quality of service requirements as envisioned in 5G. While optical transport technology has been prevalent in core segments, it is also perceived as a key enabler for the 5G access networks due to its very high capacity and low transmission delay. However, existing optical transport technologies are hindered by inflexibility, poor resource utilization, and high costs, and cannot be stretched to 5G scale. On the other hand, optical technologies have been going through a paradigm shift towards an elastic optical network that is considered as the promising solution for future high-speed transport networks. This paper outlines key challenges for the design of a flexible, programmable, and dynamic 5G transport network, and discusses the enabling technologies and directions to address these challenges.

In recent years and within the framework of its project “Algiers the metropolis”, Algiers has classified its transport network among its first concerns in order to compete with the other Mediterranean metropolises. However, the complexity of its territory, which is of a particular geological and geomorphological nature, represents a constraint for the proper distribution and management of its transport network. The complexity of its territory and of its transport network, leads us towards the systemic approach for the search of an adequacy between these two complex urban realities in order to find an effective and efficient tool of management and urban planning. The development of a set of indicators of sustainable mobility, as a result of this work, allowed us to find through an epistemological study of the literature on the two complex concepts to select and develop a list of Input and Output Indicators that are related to both territory and transport. Indeed, this list of sustainable mobility indicators will allow, on the one hand, in urban planning, a better match of the transport network to the Algerian territory and, on the other hand, the study of the effectiveness and efficiency of the present and future transport network.

With optical technology evolution, it becomes possible to perform all optical traffic grooming (AOTG) with a very fine granularity. In the context of flexible optical networking, AOTG paves the way to new possibilities in future transport networks. Finding the best trade-off between electrical and optical aggregation in intrinsically multi-layer transport networks is a complex challenge for operators. This paper compares CAPEX results and resource fill-in performances of electrical and optical aggregation solutions, through a real multilayer transport network case study.

In this paper we propose a unified model for dynamic bandwidth adaptation in future transport networks. It acts as an umbrella for both next generation SONET/SDH (NG-SONET/SDH) and even more general, networks with a GMPLS control plane. We adapt bandwidth in discrete steps by exploiting features of virtual concatenation and bundled links, respectively. Applying our model, we demonstrate its advantage in providing improved service quality in comparison to a scheduled provisioning scheme. We evaluate the adaptation granularity to provide a required quality of service for typical IP network traffic behavior in the access network. Furthermore we quantify in depth the impact of increasing access bandwidth at the network edge on signaling load in a transport network.

The introduction of optical technology in the path layer of the transport network is expected to allow scalable and modular networks to be realized. In this paper, different optical cross-connect architectures, based either on space division or wavelength division switching, are analyzed. A comparative investigation is accomplished considering three issues of primary importance: cross-connect modularity, complexity, and transmission performance. In particular, the transmission performance of a generic path through the network is evaluated by upgrading a previously published analytical model, so to more accurately take into account the in-band crosstalk arising in the cross-connect.

The plasmodium stage of the giant single-celled amoeboid organism Physarum polycephalum, or true slime mould, dynamically adapts its body plan in response to environmental stimuli, including nutrient location, temperature gradients, light exposure, and predatory threats. The construction and adaptation of the plasmodial transport network has been shown to be an efficient trade-off between minimising network distance and maximising connectivity. Optimisation of topology is also a desired trait in manufacturing and engineering, whereby the topology of an initially simple component is modified to minimise one or more properties (for example minimising the amount of substrate reduces the weight and material cost of the component) whilst maintaining other desired material properties within the component (for example strength under specific load points and conditions). Biologically inspired approaches to certain specific engineering challenges are well documented and successful. In this paper we explore at a more general level whether a cross-pollination can occur between Physarum computing and Topology Optimisation. Using an interdisciplinary modelling approach we explore whether the evolution of transport networks in a multi-agent model of Physarum has any similarities to networks formed by Topology Optimisation. We find that the Topology Optimisation method generates networks which are similar to the model slime mould networks. The Topology Optimisation networks correspond to higher regions of the Toussaint hierarchy of proximity graphs (i.e. more edges) whereas the model slime mould networks exhibit greater minimisation of network length. Since it is possible to adjust network connectivity in the multi-agent model via nutrient concentration we speculate that similar parametric adjustment may be possible to alter the connectivity of Topology Optimisation networks.

Routing and planning of working capacity and spare capacity in WDM networks were investigated. Joint optimization technique has been used and the problem has been formulated to restore the general failure scenarios. The difference between the cost for the restoration of one node failure and the cost for the restoration of one link failure is decreased as more wavelengths per fiber are used. The difference between the cost of virtual wavelength path (VWP) network and the cost of wavelength path (WP) network is increased as more wavelengths per fiber are used.

Chapter 3 - Optical Technologies in Passive Optical Access Networks

The past decade has witnessed the large shipments of Ethernet switches and IP routers. The wide availability of commodity Ethernet ASICs and the publicly open interoperable Ethernet/IP network standards have made Ethernet/IP equipment the preferred deployment option in the campus, data center, and mobile service operator’s 3G/4G LTE backhaul network. In this paper, we present an end-to-end Ethernet Transport Network (ETN) framework which features multi-service access, deterministic forwarding latency, hard traffic isolation, hierarchical traffic multiplexing, flexible and adjustable L1/L2/L3 forwarding, and multi-layer OAM mechanism. We envision ETN to be a unified solution for the future 5G mobile transport, metro, and data-center interconnects (DCI) network. In the end, we present the preliminary evaluation of our ETN prototype switch boxes implemented using commercial FPGAs and share our future vision for ETN evolution.

The mobile data traffic increase and the future connection of billions of Internet of Things (IoT) devices require operators to reshape the existing transport network architecture. Today, more than 50 % of Base-stations (BTS) are backhauled via radio. Radio technology can continue to play this vital role in future transport networks if it is able to evolve to cope with the new capacity level and latency requirements supporting the new 5G services. In this paper, a possible answer to this demand is provided, proposing a radio solution working in D-Band (130-170 GHz) and enabling a reconfigurable meshed network that can support the backhaul needs of future 5G and beyond networks.