Showing papers on "Optical Transport Network published in 2000"

WDM optical communication networks: progress and challenges

Abstract: While optical-transmission techniques have been researched for quite some time, optical "networking" studies have been conducted only over the past dozen years or so. The field has matured enormously over this time: many papers and Ph.D. dissertations have been produced, a number of prototypes and testbeds have been built, several books have been written, a large number of startups have been formed, and optical WDM technology is being deployed in the marketplace at a very rapid rate. The objective of this paper is to summarize the basic optical networking approaches, report on the WDM deployment strategies of two major US carriers, and outline the current research and development trends on WDM optical networks.

Survivability in optical networks

Abstract: Survivability, the ability of a network to withstand and recover from failures, is one of the most important requirements of networks. Its importance is magnified in fiber optic networks with throughputs on the order of gigabits and terabits per second. This article takes a look at the techniques used to achieve survivability in traditional optical networks, and how those techniques are evolving to make next-generation WDM networks survivable.

Dispersive multiplexing in multimode optical fiber

Abstract: Recently developed ideas in the field of wireless communications suggest that the presence of scattering can be used to enhance, rather than degrade, the total information capacity of a transmission system. This concept is applied to data transmission over multimode optical fiber, and the result is an optical multiplexing that can increase the capacity of such fiber. Experimental results demonstrate the feasibility of this approach. The technique may play an important role in future high-bandwidth local area networking applications.

Approaches to optical Internet packet switching

Abstract: Wavelength-division multiplexing is currently being deployed in telecommunications networks in order to satisfy the increased demand for capacity brought about by the explosion in Internet use. The most widely accepted network evolution prediction is via an extension of these initial predominantly point-to-point deployments, with limited system functionalities, into highly interconnected networks supporting circuit-switched paths. While current applications of WDM focus on relatively static usage of individual wavelength channels, optical switching technologies enable fast dynamic allocation of WDM channels. The challenge involves combining the advantages of these relatively coarse-grained WDM techniques with emerging optical switching capabilities to yield a high-throughput optical platform directly underpinning next-generation networks. One alternative longer-term strategy for network evolution employs optical packet switching, providing greater flexibility, functionality, and granularity. This article reviews progress on the definition of optical packet switching and routing networks capable of providing end-to-end optical paths and/or connectionless transport. To date the approaches proposed predominantly use fixed-duration optical packets with lower-bit-rate headers to facilitate processing at the network-node interfaces. Thus, the major advances toward the goal of developing an extensive optical packet-switched layer employing fixed-length packets are summarized, but initial concepts on the support of variable-length IP-like optical packets are also introduced. Particular strategies implementing the crucial optical buffering function at the switching nodes are described, motivated by the network functionalities required within the optical packet layer.

Optical layer survivability: a services perspective

Abstract: This article provides a perspective on optical layer protection and restoration based on the services offered by carriers using the optical layer. This is different from other viewpoints that provide a taxonomy of protection techniques in a more abstract fashion for the purposes of standardization. The latter viewpoints are mostly based on the classification adopted in the SONET/SDH standards. In contrast, taking a services-based view provides a way to distinguish between protection schemes based on implementation costs and the associated services enabled by the protection scheme.

Optical layer survivability-an implementation perspective

Abstract: This paper looks at several aspects of optical layer protection techniques from an implementation perspective. We discuss the factors that affect the complexity of optical protection schemes, such as supporting mesh instead of ring protection, handling low-priority traffic, and dealing with multiple types of failures. The paper also looks at how the client layer interacts with the optical layer with respect to protection, in terms of how client connections are mapped into the optical layer, and how protection schemes in both layers can work together in efficient ways. Finally, we describe several interesting optical protection implementations, focusing on the ones that are different from conventional SONET-like implementations.

IP over optical networks: architectural aspects

Abstract: The Internet transport infrastructure is moving toward a model of high-speed routers interconnected by intelligent optical core networks. A consensus is emerging in the industry on utilizing an IP-centric control plane within optical networks to support dynamic provisioning and restoration of lightpaths. At the same time, there are divergent views on how IP routers must interact with optical core networks to achieve end-to-end connectivity. This article describes the architectural alternatives for interconnecting IP routers over optical networks, considering the routing and signaling issues. Also, the application of IP-based protocols for dynamic provisioning and restoration of lightpaths, as well as the interworking of multivendor optical networks is described.

Architectural and technological issues for future optical Internet networks

Abstract: This article reports a review of the most significant issues related to network architectures and technologies which will enable the realization of future optical Internet networks. The design of such networks has to take into consideration the peculiar characteristics of Internet traffic. Several architectures have been proposed to provide optical networking solutions, based on wavelength-division multiplexing and compatible with the IP world. These architectures are presented briefly, and the main advantages and drawbacks are discussed. Furthermore, advanced network architectures are reported. In particular, two network paradigms are illustrated and discussed: the optical transparent packet network and optical burst switching. Finally, the key technologies are illustrated.

Optical routing of asynchronous, variable length packets

Abstract: We discuss the introduction/implementation of optical IP routers, then we introduce a novel scheduling algorithm incorporating void filling and aimed at optical routing of asynchronous, variable packet length packets. We describe its structure and discuss the complexity issues. Albeit introduced with the purpose of cancelling expensive optical synchronization, we argue that this approach represents the most viable all-optical approach for implementing packets-over-SONET (IP-centric scenario). We also present simulations under self-similar traffic conditions which point to the inefficiency of optical buffering to combat the effects of self-similarity, and we outline alternative strategies for proper buffer dimensioning.

Burst optical deflection routing protocol for wavelength routing WDM networks

Abstract: Given the significant progress made and the continuing advances expected in the optical networking technology, it becomes attractive to build a future Optical Internet that natively supports bursty IP datagrams. Burst switching WDM optical networks are touted as suitable network architectures for future Optical Internet backbones. However, the lack of optical processing capabilities results in increased burst blocking probability, which in turn leads to very limited network performance. Efficient contention resolution method is therefore necessary. Based on discussions of the state of the art of recent optical technologies, a burst optical deflection routing protocol is proposed. The idea of this approach is to use idle optical links as fiber delay lines for contention resolution. Simulation results show that the proposed protocol is available solution for effectively reducing the blocking probability and increasing the performance of burst switching WDM optical networks.

Optical power management in an optical network

Abstract: A system for managing signal power levels in an optical network. The optical network comprises a plurality of nodes having logic to receive and transmit optical signals over a plurality of network interconnections. The system includes a method wherein each of the nodes is provided configuration parameters, each of the nodes is configured based on the configuration parameters, power parameter information is exchanged between the nodes, at least some of the nodes are re-configured based on the power parameter information and the steps of exchanging power parameter information and re-configuring at least some of the nodes are repeated until the optical network is fully configured so that the optical signals have selected signal power levels.

Optical performance monitoring in reconfigurable WDM optical networks using subcarrier multiplexing

Abstract: Optical performance monitoring (OPM) is an important approach to determine the quality of optical channels within an optical core network without passing data through optoelectronic regeneration at the monitor points. Using this approach, the quality or "health" of signals can be determined at arbitrary points in a network without knowledge of the transport history of the data or the details of the transmission path. We report experimental results on the use of subcarrier multiplexing (SCM) to perform a variety of monitoring functions including chromatic dispersion monitoring, wavelength registration, power monitoring, and signal-to-noise ratio (SNR) monitoring.

A novel all-optical transport network with time-shared wavelength channels

Abstract: High-speed and high-capacity transport networks are necessary for providing future broadband services and multimedia applications. Optical networks, such as wavelength-routed networks and optical switching networks, are the most popular solutions. However, the limited electronic switching capability constrains the scalability of the multihop wavelength routed networks, while the difficulty and complexity of implementing efficient optical buffers and optical contention resolution schemes constrains the development of optical switching networks. This paper proposes a new architecture for the optical transport networks based on time-wavelength-space routers (TWSRs). The TWSR is equipped without optical buffers and optical contention resolution devices. A connection is established by constructing a time-slot based lightpath (ts-lightpath) between source TWSR and destination TWSR. The paper also proposes a heuristic algorithm for the problem of establishing the set of efficient ts-lightpaths for a given set of connection requests. The effectiveness of the proposed network architecture with the heuristic algorithm is demonstrated by simulation.

Evolution of optical transport technologies: from SONET/SDH to WDM

Abstract: It took roughly 10 years for the transport network industry to migrate from PDH to SONET. As this technology swap comes to an end, WDM technology is dawning, promising to revolutionize the network industry, with the possibility of transport bit rates above 10 Gb/s as well as transparency to signal encodings. However, a new wave of equipment upgrade is unlikely to happen as current SONET equipment is just beginning to pay off for its large investment. Thus, in years to come, SONET technology, the current standard for optical fiber access, will have to make room for WDM technology in a gradual way. On its part, WDM equipment must be developed to be backward compatible with SONET technology. This article discusses the requirements and issues involved in making WDM technology interoperable with SONET legacy equipment, as well as the evolution path toward a transparent optical transport network.

A next-generation optical regional access network

Abstract: We describe an optical regional access network which combines electronic IP routing with intelligent networking functionality of the optical WDM layer. The optical WDM layer provides such networking functions as network logical topology reconfiguration, optical flow switching to offload traffic and bypass IP routers, wavelength routing of signals, protection switching and restoration in the optical domain, and flexible network service provisioning by reconfigurable wavelength connectivity. We discuss key enabling technologies for the WDM layer and describe their limitations. The symbiosis of electronic and optical WDM networking functions also allows support for heterogeneous format traffic and will enable efficient gigabit-per-second user access in next-generation Internet networks.

Multi-purpose optical fiber access network

Abstract: The present invention relates to an optical fiber access network, and more particularly, to a multi-purpose optical fiber access network capable of accepting all services provided by hybrid wireline/wireless access network. According to the present invention, in an optical fiber access network of double star structure where a central office/headend and several optical network units are connected through a splitting/combining device, a multi-purpose optical fiber access network capable of accepting not only wired telephone service, wired CATV and wired data service but also various kinds of wireless services including LMDS, WLL, PCS and so forth, in which LMDS local wireless base station is located in a place adjacent to the splitting/combining device, WLL local wireless base station is located in a place adjacent to the splitting/combining device, optical network unit connects the conventional wired network composed of said optical fiber access network, twisted pair and coaxial cable, telephone service, data service and CATV service are provided through the optical network unit and PCS local wireless base station is located in a place adjacent to the optical network unit, is provided.

Making use of a two stage multiplexing scheme in a WDM network

Abstract: The paper explores the implications of using a two stage optical multiplexing scheme in optical WDM nodes. This allows to keep bands of adjacent wavelengths intact, thereby reducing the cost of multiplexing, increasing the number of hops and simplifying network management.

A novel optical label swapping technique using erasable optical single-sideband subcarrier label

Abstract: To support optical multiprotocol label switching (MPLS) technology in an optical network, we have demonstrated subcarrier label swapping in a 96.2 km, three-node experiment, by using optical single-sideband modulation and an optical notch filter. At each intermediate switching node, an old subcarrier label can be suppressed by 25 dB, while the 2.5 Gb/s payload experienced only 2 dB loss.

Optical fiber network having increased channel capacity

Abstract: Optical communication system apparatus and methods of operating an optical communications system is described. The system advantageously may utilize existing optical fiber networks and provide significantly increased channel capacity. In accordance with one aspect of the invention the system apparatus provides for a plurality of communications channels and a processor unit receives requests for allocation of one or more channels from a node coupled to the optical communications system. The system apparatus dynamically allocates one or more channels selected from unused channels.

Optical data networking

Abstract: We challenge current thinking about IP over WDM by outlining a path to optical data networking that includes multiple data networking protocols coupled with a protocol-neutral optical networking infrastructure. Included is a discussion of the diversity of data networking protocols and network architectures for optical data networking.

Photonic node, photonic nodes for transmission and reception, and method of restoring traffic upon occurrence of link failure in optical path network

Abstract: The present invention relates to a technology of an IP node for transferring IP packets accommodated in a wavelength division multiplexing optical signal. The optical IP node of the present invention includes a space switch unit supplied with a wavelength division multiplexing optical signal and a packet with another node destination and generating an optical signal with the self node destination and multiplexing the optical signal with another node destination and an optical signal caused by the packet together and generating the multiplexed signal, link failure detecting unit connected to an input side and an output side of the space switch unit, detecting link failure and generating a detection signal, an OAM packet transmitting unit for generating a monitoring packet at a predetermined time interval, and a traffic restoration control unit connected to the link failure detecting unit, selecting each optical signal depending on the wavelength in response to reception of the detection signal, switching the optical path and generating the optical signal. Each of the optical IP nodes carries out optical path switching on the wavelength division multiplexing optical signal and assignment of an IP packet to be transmitted to an optical signal and switching of the assignment. Thus, the number of optical wavelengths utilized for transmission can be reduced and the size of the optical IP node can be made small.

Optical switching speed requirements for terabit/second packet over WDM networks

Abstract: Optical dynamics requirement for packet-over-WDM networks is analyzed. Optimization among optical switching speed, global resource availability, and local queuing considerations is performed, yielding multiterabit/second throughput capability by employing submicrosecond switching technology.

Bidirectional wdm optical communication system with bidirectional optical service channels

Abstract: The present invention provides a bidirectional wavelength division multiplexed optical communication system having bidirectional optical service channels. The bidirectional WDM optical communication system includes a bidirectional optical waveguide configured to carry a bidirectional optical communication signal comprising counterpropagating WDM optical signals. Each WDM optical signal includes plural optical channels and an optical service channel. A bidirectional optical add-drop multiplexer optically communicates with the waveguide. A first optical service channel selector optically communicates with the first bidirectional optical add-drop multiplexer input/output port. The first optical service channel selector is configured to separate the first optical service channel from the first WDM optical communication signal such that the first WDM signal enters the first input/output port of the bidirectional optical add-drop multiplexer and the first optical service channel is routed to a service channel module. Similarly, a second optical service channel selector optically communicates with the second input/output port of the bidirectional optical add-drop multiplexer and routes the second optical service channel to a service channel module. The bidirectional WDM optical communication system may advantageously by deployed in metropolitan networks requiring high volumes of add-drop multiplexing.

IP-centric control and management of optical transport networks

Abstract: Previous techniques for the management and control of optical transport networks are proving inadequate in today's rapidly evolving multivendor environments. This article examines the issues and challenges involved in developing a standardized optical network control plane. The control of optical transport networks is decomposed into provisioning models, a circuit provisioning process based on signaling, a neighbor and service discovery process, and a topology and resource discovery process. Unique properties and challenges of optical transport networks are explained in the context of these functions.

MEMS-based optical bench

Abstract: An optical bench that provides a core component for a communication system that performs all of the necessary switching, adding, dropping, and manipulating of optical signals entirely in the optical domain. The optical bench comprises a dispersive optical element and a spatial light modulator. Various devices that are useful in the field of optical communication can be produced using the optical bench apparatus as a core component, with the addition of other components to the optical bench. Exemplary optical communication devices that can be built using the optical bench include optical add/drop multiplexers (OADM), Dense Wavelength Division Multiplexing (DWDM) routers, tunable filters, tunable laser sources, optical cross connects, and the like.

Optical networking assembly

Abstract: An optical network assembly includes a planar lightguide circuit (PLC) and a filtering device. A PLC can have at least two optical paths for propagating optical energy. The PLC can be designed to channel optical energy with its optical paths towards the filtering device in order to separate the optical energy into at least two beams, where a first beam can contain a first information channel and a second beam can contain a second information channel. The filtering device can be attached directly to the PLC or it can be attached directly to an optical waveguide that is also connected to the PLC. The optical waveguide can either feed optical energy to or propagate optical energy away from the PLC. Multiple optical waveguides can be attached to a PLC to feed optical energy into and away from the PLC. The PLC, filtering device, and optical waveguide can form the building blocks to more complex optical network architectures.

Optical plug-type connection

Abstract: In an optical plug-type connection between two optical conductors having an optical terminal which receives an optical plug-type member, an electrical connection is provided for verifying that the optical plug-type connection has been made and/or released. This verification reduces the likelihood of an optical plug-type connection being erroneously acquired in the network management system and, thus, significantly reduces problems in locating errors in the optical communication system.

Parallel optical interconnects

Abstract: Summary form only given. Due to the increasing demand for high-bandwidth applications, multi-processor systems and communication systems are demanding very low cost, high-bandwidth optical interconnects. We present results on a 12-channel parallel optical link module (PONI Project) with each channel operating at a bit rate up to 2.5 GBd providing an aggregate bit rate up to 30 GBd. Each parallel optical link module is either a 12-channel transmitter module or a 12-channel receiver module with dimensions of 35 mm/spl times/16 mm/spl times/10 mm.