Showing papers on "Optical Transport Network published in 1990"

Fiber network survivability

Abstract: At the transport layer in interoffice and interexchange networks, shared protection rings (SPRINGS) interconnected at matched nodes can provide 100% restoration in milliseconds after cable cuts and central office failures. The author introduces the SPRING and explains how its capacity advantage over other ring configurations enables it to be the most economical solution in more applications. Transport restoration technologies-1+1 diversity, digital crossconnect systems, and SPRINGS-in interoffice and interexchange environments are compared. A representative network study is presented to justify the choice of SPRINGs and matched nodes for the target architecture. Recommendations on how to evolve today's asynchronous networks in preparation for a fully survivable SONET ring-based network are also provided. Generic ring planning guidelines and network examples are presented to demonstrate how today's networks can be evolved to provide end-to-end survivable SONET transport. An approach to ring-based network design that simplifies the planning process and minimizes network cost is provided. >

Wavelength domain optical network techniques

Abstract: Optical network technology will soon allow wavelength-multiplexed optical channels to be carried to multiple terminals, giving rise to new broadband network architectures and protocols. Two stages of evolution are anticipated, with transmission-only structures appearing first and networks with optical switching appearing later. Some basic transmission considerations relating to system operation over wide optical bandwidths for both local and longer distance networks are reviewed, and the present status of experimental optical networks and the components they use are discussed. >

Linear lightwave networks: how far can they go?

Abstract: A novel type of lightwave network architecture that is based on establishing controllable, optically transparent paths among network users is described. The objective is to provide optical connections on demand. These connections would support a high degree of flexibility, including user-chosen modulation formats and bit rates, for large numbers of user stations (e.g., 100000) using mesh-type topologies that are spread over geographical areas that may extend to diameters of several thousand kilometers. The networks in question perform only linear operations on optical signals, essentially operating as a dynamically controlled 'ether' within which light beams are selectively directed between prescribed source-destination pairs. Because these linear lightwave networks are controllable, they are capable of being reconfigured in response to changing load conditions or component failures. >

Feasibility study of a high-speed SONET self-healing ring architecture in future interoffice networks

Abstract: The economic feasibility of using SONET self-healing-ring (SHR) architecture in survivable interoffice fiber networks is studied. The model used is discussed, and the selection criterion for the candidate area in this study, the SHR cost model, the hubbing network cost model, the network survivability measure, and the network growth model are described. Results of two case studies based on a metropolitan local access and transport area (LATA) network are discussed. One involves a single- and the other a dual-homing interoffice network. Sensitivity analysis and network impact results are highlighted. >

Optically-processed routing for fast packet switching

Abstract: Electronic routing control of photonic switches is considered. The types of network architectures and routing strategies that the authors think are best-suited to optical processing are proposed, and a generic optical routing processor is described. Address-encoding schemes for optically controlling a photonic switching node are presented. The results of several experiments that have demonstrated optical control of a photonic switching node are reported. Potential applications of these photonic switching architectures are described. >

Asynchronous optical communication system

Abstract: An asynchronous time-division multiplex optical communication system comprises: a switching network, user transmitter circuits, user receiver circuits and broadcast servers connected by optical lines to the switching network. The switching network comprises an optical spectro-time-division switching network, a control processor unit and a clock unit. The spectro-time-division switching network is connected optically to the user transmitter circuits, to the user receiver circuits, to the broadcast servers and to control transmitter, signalling transmitter, control receiver and signalling receiver circuits of the control processor unit. The clock unit is connected by a first line to the switching network and by a second line to the control processor unit which is connected by a control bus to the spectro-time-division switching network. The system uses conjointly a first set of optical frequencies for transmission and a second set optical frequencies for switching.

The design of a TDMA system for passive optical networks

Abstract: The authors describe the design methodology and implementation details of a time-division multiple access (TDMA) system which has been developed to allow point to multipoint operation of passive optical networks. This TDMA bit transport system transparently handles the multiplexing and control functions required for passive splitting optical networks. The system is generic and, with relatively simple interfacing, applicable to switching systems worldwide. The design has been implemented in ASIC (application-specific integrated circuit) technology for a forthcoming UK field trial of fiber in the subscriber loop. >

A B-ISDN local distribution system based on a passive optical network

Abstract: An experimental system that transports ATM (asynchronous transfer mode) cells through a passive optical local network (APON) is described. It distributes a 155.52 Mb/s ATM stream from an ATM node to 64 customer ends, synchronizing return cells to interleave at the exchange. A variant of the Orwell protocol is used for bandwidth control. Key features demonstrated are clock phase alignment and an exchange optical receiver design to realize a practical system. APON provides dialog service to those smaller customers that cannot be economically served using dedicated point-to-point links, permitting early economic deployment of ATM to smaller, or start up customers. >

A broadband access network based on optical signal processing: the photonic highway

Abstract: A broadband access network, the photonic highway, which is based on optical signal processing (OSP) and consists of photonic access nodes (PANs), which process optical signals directly, is discussed. Each PAN has an optical drop/insert function. The authors focus on the configuration of the fiber network and access nodes and describe its application to a metropolitan area network (MAN) and a CATV distribution network. They also describe the basic experiments conducted to verify the proposed architecture using newly developed bistable laser diodes. >

Optical fibre data network

Abstract: In an all-optical data network, a plurality of subscriber stations are to be able to communicate with one another bidirectionally via the same optical waveguide and only one type of electro-optical circuit arrangement is to be used. The optical amplifiers (OVn, OVn+1, ...) incorporated in the optical waveguide network are equipped with additional input and output circuits for electric signals and are set up for the operating modes "Optical amplification/simultaneous reception signal conversion/transmission signal conversion". They are located at the subscriber terminal stations and replace the optical couplers and different opto-electronic components found in conventional networks. In the lasers in the optical amplifiers (OVn, OVn+1, ...), the optical strip line conductor also operates bidirectionally. The optical waveguide network does not therefore need to be designed as a closed ring and can be extended as required. Use as a local area network, processor bus system etc.

Free-space optical implementation of a feed forward crossbar network.

Abstract: The crossbar network has been a popular topology for proposed guided wave optical switching systems as well as for proposed free-space optical switching and computing systems. However, these crossbar system proposals suffer from fundamental problems that may limit the overall size of the network. A new implementation of a free-space optical crossbar network (the feed forward crossbar network) is proposed which may be able to overcome these problems. One-dimensional and two-dimensional implementations are described. The resulting optical interconnections in both implementations are space-invariant interconnections, so the optical hardware requirements are minimal.

A distributed wavelength switching architecture for the TPON local network

Abstract: Passive optical networks offer economic Provision Of telephony and low-dain-rate services over optical fibre. Upgrading of these networks by WDM will also bring the possibility of broadband access to customers, and with it the need for broad band switching to interconnect customers in the local network. A distributed switching architecture is proposed for reducing the component quantities needed to implement a local broadband exchange The architecture consists of three stages of switching, The first and third stages of which are distributed throughout the passive optical networks using wavelength routing technique, with only the middle stage implemented in the exchange, using either optical space or wavelength switching. When space switching is employed in the exchange, the distributed architecture almost halves the number of crosspoints, and when wavelength switching is used laser and regenerator numbers are reduced by 40%, compared with die conventional architecture of centralised switching.

Cost projections for fiber in the loop

Abstract: A forecast is provided of the cost of realizing an all-fiber network. It is based on the successful histories of fiber penetration into the trunk and feeder networks and is intended to help build a framework against which local or regional strategies for network evolution can be tested. Starting with the early trend data for fiber to the home (FTTH), the pattern for the complete conversion of the lop network to fiber is estimated. No attempt has been made to factor in the impact that greater demand for broadband, particularly in the business sector, may have in accelerating the process; the impact of unforeseen new technologies in reducing costs; or the effect of the European and Asian markets in driving down costs. The results do, however, suggest a smooth transition to broadband as part of the normal improvement and evolution of the network, with a time-frame consistent with other views on the evolution of broadband. >

Photonic local/metropolitan area network

Abstract: With this invention, collisions of optical packets in local area networks are avoided. Briefly, each branch of a local area network topology, such as a star, a ring or a bus is provided with an optical path having two substantially parallel optical fibers which can be selectively configured to form either a direct straight through path or a loop-back path. Prior to advancing a packet to the next occurring branch, a test is made to determine if it is occupied. If it is not occupied, the packet is advanced along one of the opitcal fibers of the optical path. If it is occupied, then the two optical fibers are rapidly configured to form a loop-back path and the packet travels around the loop-back path, again and again as required until the danger of a collison with a preceding packet no longer exists.

A packet compression/decompression approach for very high speed optical networks

Abstract: A technique to produce time-compressed optical packets for transmission over an ultra-high-speed optical network is proposed and analytically studied. The technique employs two recirculating optical loops per network node, one to optically compress a fully formatted electronic packet for transmission onto the network and one to electronically expand such a packet upon reception. Depending upon the specific parameters chosen, loss of optical power is shown to limit the packet size to the range of several tens of bits. Despite the significant spontaneous emission noise which is thereby produced, it is shown possible to maintain a bit error rate of 10/sup -9/ and a link margin of 15-30 dB over a wide range of conditions. Finally, compression/expansion techniques are shown to introduce a new network phenomenon which prohibits a node from accessing (both for transmission and reception) two or more time slots within a contiguous group of slots of number equal to the compression ratio. >

Plans and considerations for SONET deployment

Abstract: A perspective is given from the local exchange carrier (LEC) viewpoint on the advantages of deploying SONET (synchronous optical network), the rate at which SONET will be deployed, some typical early applications and architectures, and the role SONET will play in the evolution of the LEC network of the future. The SONET deployment timeline and capabilities are examined. Aspects of SONET architecture are discussed, namely, the access network, the interoffice transport-network, and SONET operations and control. New network capabilities and services and evolution to broadband are considered. >

Line capacity expansion schemes in photonic switching

Abstract: Design considerations for capacity expansion are described, and requirements for photonic switch matrices, optical memories, and tunable-wavelength filters are examined. The present status of photonic switching devices and system experiments is discussed, covering space-, wavelength-, and time-division switches. Hybrid switching systems and coherent optical detection are considered as examples of system technology that will facilitate line capacity expansion. >

Introducing SONET into the local exchange carrier network

Abstract: The synchronous optical network (SONET) is discussed from the perspective of the transition from the existing network to the desired SONET. The existing network and environment and the desired network are described. The means by which the local exchange carriers will migrate to SONET are discussed. >

An optical backplane for high performance switches

Abstract: We have demonstrated an optical backplane which provides high speed bit-synchronous digital data interconnection for a variety of applications, including high performance time division switching and packet switching. In addition to discussing architectures and technologies for optical backplanes, we will describe a prototype digital time division switch and its optical backplane to aid in understanding these new technologies and their implications on switching. Our optical backplane is an optical fiber-based design in which all components are targeted for high speed over very short (10s of meters maximum) distances at the lowest possible cost. The new components developed include specialty fibers, high performance short wavelength active devices, low-cost molded plastic optical backplane connectors, and a new low-cost polymeric resin-filled optical coupler technology for splitting and combining optical signals. The passive components are designed to support a large range of interconnection speeds so that only active devices need be changed to optimize cost/performance for a particular application. The optical bus architecture resembles an electrical passive bus in which circuit boards can be inserted and removed without interrupting the bus or causing bus errors. The resulting optical backplane can be used to provide inherently electromagnetic interference free backplane communication which does not depend on costly shielding and grounding techniques. Other advantages include equipment size reduction, reduced requirements for quality of power, and inherent lightning and power-cross protection. Our prototype optical backplane-based switch demonstrates that optical technology can provide cost reduction of conventional telephony switching equipment and provides the opportunity to design much higher bandwidth busses than can be implemented with conventional electrical technology. When such optical bussing technologies are applied to a telephony switch, higher port densities and wider distribution options are possible. Optical busses can extend busses not only between shelves within a cabinet but may also be used between cabinets. Our prototype switch uses high numerical aperture, large diameter, step-index optical waveguides which have a smaller bandwidth-distance product than fibers typically used for tele-communications. These waveguides were used to give us a much broader spectrum of optical component design choices, while still maintaining relatively high bandwidths over the limited distances required for interconnecting circuit packs within switching equipment.

A novel distributed photonic switch

Abstract: This paper presents a novel distributed shared medium photonic switch applicable to optical broadband local and metropolitan area networks. This switch supports a hierarchical star topology and adopts an hybrid FDM/TDM multiplexing scheme with a total capacity in the 5-20 Gbit/s range. An extension of OSI reference model to optical multi-channel operation is proposed using a new Medium Access Control (MAC) protocol and a distributed network management scheme characterized by a semipermanent frequency assignment. Interconnection of several stars in an hierarchical multi-star topology is also discussed.

Photonic switching for ATM networks

Abstract: A tera-BPS throughput ATM cell switch requires an efficient combination of high photanic bandwidths and high electronic intelligence. Thispaper discusses the design principles necessary for an effective photonic cell switch; a two-layer structure of photonics and electronics; a cell-by-cell synchronous operation, a simpple optical layer, A modular structure and an electronic routing control that is well-matched with the optical layer. A novel Cell switched architecture based on a two-layered detouring, hypercube network is described and some related results are presented for an experimental 2-Gbps 8-line system using a tree structured space switch made from high-speed LiNbO/sub 3/ directional coupler switches. The throughput estimates suggest that 6.6-Tbps photonic systems will be possible in the future.

An optical multiaccess network with optical collision detection and optical frequency addressing

Abstract: An optical frequency addressing carrier sense multiaccess (CSMA) network with optical collision detection (CD) is proposed. In this network, traffic is routed through many optical frequency division multiplexing (FDM) virtual transmission lines to nodes defined by optical carrier wave frequencies, and collision between optical signals having a large power level difference can be monitored by optical signal processing. Numerical results on the packet transmission delay characteristics are presented and compared to those for a conventional TDM (time division multiplexing)-based CSMA/CD. It is shown that the FDM CSMA/CD scheme achieves a shorter transmission delay time, even with higher traffic loads. An optical collision detection circuit using self-delay homodyne detection is also proposed. This novel circuit is expected to obtain more than 15 dB and is suitable for large-area applications. >

Design of compact transceiver optical systems for optical intersatellite links

Abstract: In optical communication links between GEO satellites, all optical beam control functions required for the transceiver may be realized without using external gimbals. Configuration of such a transceiver internal optical system can be designed considering the satellite dynamics in orbit. This paper presents a design of the transceiver internal optical systems, taking into account the accuracy of satellite station-keeping and attitude control as well as an orbital separation. An experimental optics was constructed on the basis of the results for a bidirectional link between satellites separated by about 60 deg in orbit. The attitude control accuracy of + or - 0.1 deg and the satellite station-keeping of + or - 0.1 deg were assumed. It can be utilized to develop a variety of beam-controlling schemes.

Application of a service-independent architecture

Abstract: The period since ISS'87 has seen a great deal of industry wide activity on the requirements, design and standardization of the Intelligent Network. Although there are many outstanding issues to be resolved before a consensus is achieved on Intelligent Network Architecture and its evolution, there has been a convergence of thinking on the role of the Intelligent Network, on its major elements, and on the associated design considerations, including compatibility with the existing network.

Photonic space-division switching system for broadband services

Abstract: A practical 32-line photonic space-division switching system a fabricated using the world first 8x8 polarization independent LiNbO3 matrix switches. Owing to their polarization independence, the switching system can employ ordinary single-made optical fibers for subscriber access lines, which greatly contributes to make a photonic switching system practical and competent for broadband communications services. A three-stage switching network, with specially designed optical matrix switches in the third stage, is developed to provide HDTV- program distribution services as well as TV phone services. The overall insertion loss and crosstalk characteristics of the matrix switches, and the feasibility of the system is proved. The constructed 32-fine photonic switching system is now successfully operating. To extend the line capacity so over one hundred laser diode optical amplifier employment is investigated as well. Some 128-line switching networks including one optical amplifier stage are presented and requirements for optical amplifier gain and matrix switch insertion loss to implement the networks are clearly indicated. Those requirements are almost within reach of the current intensive research activities on the LiNbO3 matrix switches and laser diode amplifiers. Owing to the experiment and investigations described above, it is concluded that a practical 128 more line photonic switching system can be fabricated in the near future.

Impact of new transmission technologies on the network architecture, network management and economics

Abstract: Present telecommunication networks in various European countries are generally divided, depending on the size of the country, in three or four hierarchical levels in order to efficiently handle the traffic volume. This architecture is based upon available technology in the past, where many small local exchanges are used to compensate the relatively high cost of transmission systems. Due to the digitalization of the network in the last decade and new developments in transmission technology (e.g. optical fiber) the transmission costs decreased strongly. In addition there is an increasing demand for leased circuits (up to 2 Mbit/s) requiring sophisticated cross-connect systems. The paper discusses the influence of the emerging Synchronous Digital Hierarchy (SDM on the network structure and presents a first costs economic comparison with the current plesiochronous transmission network.

Planning a SONET network

Abstract: The author examines the transition from today's asynchronous network to tomorrow's advanced all-SONET (synchronous optical network) network. Network planning studies have identified three phases in the development of a SONET network: initial SONET entry, SONET penetration, and the introduction of new broadband services. The author presents the results of studies conducted to establish deployment strategies and triggers which guarantee the maximum benefit from SONET at each phase of its deployment. The S/DMS product family, which is specifically designed to capture these benefits in a multivendor environment, is discussed. It is noted that the planning guidelines provided should assist operating company and interexchange planners in deploying SONET cost-effectively, establishing a SONET infrastructure quickly, and growing the network to trigger and accommodate a variety of new broadband services. >

Photorefractive optical neural network

Abstract: An account is given of the self-pumped optical neural network (SPONN) fine-grained optical architecture, which features massive parallelism and much higher interconnectivity than either bus-oriented or hypercube electronic architectures. Connections among neurons are implemented by SPONN as sets of angularly and spatially multiplexed volume phase gratings. The mapping of neural-network models onto the SPONN architecture occurs without the need for neuron-multiplexing or dealing with electronic parallel computers'' bottlenecks, greatly simplifying programming.

Computer systems employing reconfigurable board-to-board free-space optical interconnections: COSINE-1 and -2

Abstract: Parallel-processing computer systems using reconfigurable board-to-board free-space optical interconnections, called COSINE-1 and -2, are presented. In COSINE-1, 36 transputer-accommodated boards are connected by optical links comprised of collimated optical beams and optical fibers. The 144*144 crossbar interconnections are manually rearranged by operating beam couplers which couple the fiber ends to the optical beams. The system was tested for a computer graphic machine, and no degradation of performance was observed in spite of mechanical tremors. COSINE-2 uses an optical Benes switch which can electrically control the interconnection network topology. Since the interconnection state is electrically changed during the system operation, the processor can be used more efficiently. A 16-channel prototype optical switch was constructed and tested. >

An experimental photonic ATM switching system using an InP semiconductor optical switch

Abstract: A prototype of a photonic ATM (asynchronous transfer mode) switching system is fabricated and evaluated. It uses a space-division-type optical switch array for switching optical signals. Each of its highways contains two 1.2-Gb/s signals (wavelength division multiplexed), and it has 4*4 optical switch ports. It can realize a total capacity of 9.6 Gb/s. An optical signal format and retiming architecture for bit and cell synchronization are proposed. Measurements of basic characteristics have been made. >