Showing papers on "Optical Transport Network published in 1998"

Transparent optical packet switching: network architecture and demonstrators in the KEOPS project

Abstract: This paper reviews the work carried out in the ACTS KEOPS (Keys to Optical Packet Switching) project, describing the results obtained to date. The main objective of the project is the definition, development, and assessment of optical packet switching and routing networks, capable of providing transparency to the payload bit rate, using optical packets of fixed duration and low bit rate headers in order to enable easier processing at the network/node interfaces. The feasibility of the KEOPS concept is assessed by modeling, laboratory experiments, and testbed implementation of optical packet switching nodes and network/node interfacing blocks, including a fully equipped demonstrator. The demonstration relies on advanced optoelectronic components, developed within the project, which are described.

Nonlinear Optical Communication Networks

Abstract: Optical Fiber Propagation Optical Amplifiers Optical Transmission Systems Soliton Optical Communications Repeaterless Systems Long Distance TDM Transmission WDM Optically Amplified Systems Transmission in All-Optical Networks Appendices Index

Architectures and technologies for high-speed optical data networks

Abstract: Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper discusses architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented stresses WDM aware Internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple quality-of-service (QoS) levels, and truly flexible bandwidth-on-demand. The paper gives an overview of an ultrahigh-speed TDM network architecture and describes recent key technology developments such as high-speed sources, switches, buffers, and rate converters.

Code division multiplexing lightwave networks based upon optical code conversion

Abstract: 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.

Wavelength-division multiplexing in passive optical networks

Abstract: An optical line termination (OLT) device (12) generates a plurality of optical signals having different respective wavelengths (λ1, λ2), each optical signal carrying data, and wavelength-division-multiplexes the optical signals. A plurality of optical network units (ONUs 14 1 -14 5) are connected to the OLT device (12) by way of a passive optical network (6) so as to receive the wavelength-division-multiplexed optical signals. Each ONU (14) has a wavelength selection unit operable in dependence upon control information sent from the OLT (12) to the ONU (14) concerned by way of the passive optical network (6) to select one of the optical signals of the plurality, and also has a detector for processing the selected optical signal to derive therefrom the data carried thereby. The control information may be included in the data-carrying optical signals themselves as overhead information, or may be sent separately by another optical signal that is wavelength-division multiplexed with the data-carrying optical signals. Such an arrangement can enable the downstream capacity of the passive optical network to be shared flexibly by the different optical receivers.

Optical networking

Abstract: Optical networking, as embodied by dense wavelength division multiplexing (DWDM) and optical amplification, has revolutionized long-distance transport and has resulted in capacity expansion, cost reduction, and operations simplification. Extension to more wavelengths, emergence of reconfigurable wavelength add/drop and other optical network elements (NEs), as well as cost reduction of optical amplifiers and laser devices, are pushing the revolution into the local and metropolitan networks. Traffic generated in any format, such as SONET/SDH, asynchronous transfer mode (ATM), and plesiochronous digital hierarchy (PDH), with bit rates ranging from 45 Mb/s to 10 Gb/s, can be economically transported and routed optically without resorting to time division multiplexing (TDM). In this paper, we describe the latest advances in optical NEs and applications in the public and private networks. In addition, we discuss how optical networking creates flexibility in sharing existing fiber inventory between service providers. We present an example of how optical networking is capable of meeting the emerging demand for high-capacity clear-channel end-user services, a demand that TDM systems cannot meet. Finally, we discuss future directions and optical layer restoration as a prime target of network evolution.

Experimental demonstration of bipolar optical CDMA system using a balanced transmitter and complementary spectral encoding

Abstract: We demonstrate a novel balanced differential optical transmitter for spectrally encoded optical code-division multiple-access (CDMA) systems. The proposed structure is suitable for making optical signaling bipolar using complementary spectral encoding. An optical CDMA link with a pair of programmable transmitter and receiver is tested at the OC-3 transmission speed (155 Mb/s) for single-channel transmission. Unmatched code rejection is also demonstrated.

Bit-rate transparent WDM optical communication system with remodulators

Abstract: The present invention provides improved compatibility between optical transmitters of various data rates and WDM optical communication systems. In the present invention, optical remodulators are configured to receive an optical signal, separate the information from that optical signal into N information streams (where N is a whole number greater than or equal to 2), and place the information onto N optical channels within the channel plan of a WDM optical system. Alternatively, the present invention provides optical remodulators configured to receive N optical signals, combine the information from the N optical signals, and place the information onto a single output optical channel having a wavelength within the channel plan of a WDN optical system.

Hybrid wavelength-interchanging cross-connect

Abstract: A wavelength-interchanging cross-connect for a wavelength-division multiplexing (WDM) optical communication system including both transparent optical paths and opaque paths through an electronic switching network, such as a high-speed digital cross-connect switch (DCS), including matching opto-electronic conversions of the data signal. All optical switching is performed on the input and output sides, for example, by mechanically actuated fiber switches. The DCS, receiving optical inputs from the input optical switches and providing optical outputs to the output optical switches, performs switching in the electrical domain and can perform wavelength conversion of the signals passing through it. The DCS also provides for access to electrical add/drop lines for interfacing to a client. The transparent optical path, which can be either direct or through an optical switch, transfers a signal without regard to its format from the input to the output of the switching system. An algorithm is available for setting up the required connection through the different components.

All-optical buffering of 40-Gb/s data packets

Abstract: Ultrafast slotted, time-division-multiplexed (TDM) multiaccess networks will utilize optical buffers at user nodes to hold data packets until they are transmitted and to hold received packets until they are demultiplexed or rate converted. We demonstrate the loading and unloading of a compensating optical fiber loop buffer storing packets of 40-Gb/s data for over 300 circulations.

Layered switch architectures for high-capacity optical transport networks

Abstract: We propose and analyze layered switch architectures that possess high design flexibility, greatly reduced switch size, and high expandability. The improvement in loss and crosstalk due to the reduced switch size is also discussed. Theoretical models have been developed to compute the network blocking probability using these architectures. Low blocking probability and high network utilization are achieved because of the capability of communication between layers in adjacent switches. The results show that the proposed layered switch architectures are very attractive for high-capacity optical transport networks.

Optical monitoring apparatus and method for network provisioning and maintenance

Abstract: Optical-to-electrical and electrical-to-optical signal conversion is substantially eliminated for performance of monitoring and maintenance functions within a wavelength-division-multiplexed optical network having a Network Control Element by detecting optical intensities of signals conveyed over wavelength channels at the optical layer. Values associated with the detected optical intensities are generated and conveyed to the Network Control Element. The Network Control element analyzes these values for the purposes of fault detection, channel power monitoring, channel signal to noise ratio determinations, channel continuity checks, and network provisioning.

Opportunities for optical protection and restoration

Abstract: Summary form only given. Experimentation with optical switching technology by various telecom companies for healing an optical network in the face of equipment and fiber failures has made headlines recently. This talk attempts to check whether such optical protection and restoration (optical recovery henceforth) makes practical sense, given similar mechanisms that are already available at the higher layers (e.g., SONET/SDH or ATM). We then discuss the implications of various network parameters on the implementation of optical recovery.

Toward wide-scale all-optical transparent networking: the ACTS optical pan-European network (OPEN) project

Abstract: The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N/spl times/10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4/spl times/4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s.

Asynchronous digital optical regeneration and networks

Abstract: This paper outlines the concept of the asynchronous digital optical network, which is aimed to combine the advantages, and overcome the drawbacks, of existing approaches to photonic networking. The network is based on digital optical transmission and processing, which offers the prospect of almost infinite scalability. Optical transmission throughout the network is in burst mode, using a standard digital optical signal format. The main defining feature of the asynchronous network is that the network nodes (in which the optical processing and routing take place) do not share global synchronization at the bit level. Instead, the nodes each operate with independent bit-level clocks. This approach removes the architectural constraints found in synchronous networks. An essential component of the network is the asynchronous digital optical regenerator. Various design and performance aspects of this new type of regenerator are analyzed.

Gigabit ethernet interface to synchronous optical network (SONET) ring

Abstract: A method and apparatus for routing data packets via a synchronous optical (SONET) network from devices connected to a local area network to devices connected to other local area networks. At each transport node in the SONET network the data packets are unloaded from SONET payloads and requeued for transmission on an output path. This allows for easy resolution of contention between devices transmitting at the same time and avoids pre-assigning SONET channels. Source and destination address information from the data packets can be used to route the data packets through the SONET network. A time-to-live indicator can be used to find the shortest path to a destination address in a SONET ring network or any bi-directional ring network.

Optical communication network apparatus and optical switching network

Abstract: An optical communication network node apparatus including input terminals 111 to 11n, 1:2 optical branch units 121 to 12n, a pass-through optical switching network d101, 2:1 optical connectors 151 to 15n, output terminals 171 to 17n, a drop optical switching network 102, output interfaces 13-1 to 13-mn, input interfaces 14-1 to 14-mn and an insert optical switching network. Accordingly, in the optical communication network node apparatus, various types of optical switching networks are separated from one another and each optical switching network supports only a necessary switching state, so that the number of optical switch elements can be reduced.

Optical communication node and wavelength division multiplexing optical transmission device having ring structure comprising the optical communication nodes

Abstract: A device comprises a plurality of nodes and four optical transmission lines of clockwise and counter-clockwise working operation lines and clockwise and counter-clockwise stand-by lines which connect the nodes in form of a ring. Each node is provided with first and second terminal sections including a receiver and transmitter, with a first optical path switch for switching the optical path between four output terminals of the counter-clockwise working operation and stand-by optical transmission lines, the second terminal section, and output terminal of a first stand-by line, and four input terminals of the clockwise operation and stand-by optical transmission lines, first terminal sections, and a second stand-by line. Each node is also provided with a second optical path switch for switching the optical path between four output terminals of clockwise operation and stand-by optical transmission lines, and first terminal section, and output terminal of the second stand-by path, and four input terminals of the counter-clockwise working operation and stand-by optical transmission lines, second terminal section, and input terminal of the first stand-by path.

Wavelength division multiplexed optical networks

Abstract: Arrayed waveguide grating routers are used to form 1×N demultiplexers and N×1 multiplexers to form channel drop modules in a WDM optical network. The demultiplexer and the multiplexer are interconnected by optical waveguides in which are inserted optical switches provided by MEMs devices that can be used to reflect incident optical signals backwards for dropping channels or to both transmit and reflect incident optical signals to drop and detect channels.

Architectural considerations of radio-on-fiber millimeter-wave wireless access systems

Abstract: Several system architectures of radio-on-fiber millimeter-wave wireless uplink and downlink are assessed from both technical and economical viewpoints. Technically, comparisons are made by focusing on the optical MM-wave generation and transport techniques. In the economical assessment, the cost of the base station (BS) is of primary concern. Overall evaluation may suggest that the external modulation based system architecture is the most promising, followed by the one using an optical transceiver.

Optical subscriber network system

Abstract: In an optical subscriber network system which connects plural optical network units to an optical service unit using passive optical elements through an optical transmission line, the optical transmission line is duplexed with a lower cost. The optical service unit and the optical network units each have plural transmission-reception portions the wavelengths of which are different from each other, and the inputs and outputs of the plural transmission-reception portions are multiplexed with the wavelengths (WDM) into a single optical transmission line to form a pseudo redundant communication path between the optical service unit and the optical network units. The communication which uses a certain wavelength between the optical service unit and the optical network units is active, and the communication which uses another wavelength is a standby. When the active communication has a fault, a switchover operation to the standby communication is performed. The communication path using plural wavelengths between the optical service unit and the optical network units can select either the function of “with redundancy” or “without redundancy” or “enhanced line speed”, depending on subscribers' demands.

Dynamically assignable optical signal access control apparatus

Abstract: An optical signal access apparatus responds to variations in network traffic by dynamically assigning the number of wavelengths at originating and terminating optical signal access apparatus. A controller of an optical signal access apparatus monitors network traffic by checking the occupancy level (or other parameters) of data buffers and determines therefrom the number of optical signals that should be allocated to handle the network traffic from those buffers. When the optical signal access apparatus is part of a router it can be used to control traffic at the router as well as on the links between the routers of an optical network.

Architectural and engineering issues for building an optical Internet

Abstract: Recent developments in high density Wave Division Multiplexing fiber systems allows for the deployment of a dedicated optical Internet network for large volume backbone pipes that does not require an underlying multi-service SONET/SDH and ATM transport protocol. Some intrinsic characteristics of Internet traffic such as its self similar nature, server bound congestion, routing and data asymmetry allow for highly optimized traffic engineered networks using individual wavelengths. By transmitting GigaBit Ethernet or SONET/SDH frames natively over WDM wavelengths that directly interconnect high performance routers the original concept of the Internet as an intrinsically survivable datagram network is possible. Traffic engineering, restoral, protection and bandwidth management of the network must now be carried out at the IP layer and so new routing or switching protocols such as MPLS that allow for uni- directional paths with fast restoral and protection at the IP layer become essential for a reliable production network. The deployment of high density WDM municipal and campus networks also gives carriers and ISPs the flexibility to offer customers as integrated and seamless set of optical Internet services.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Fiber distribution shelf assembly for a fiber administration system having integral line tracing capabilities

Abstract: A fiber administration system and improved components for use in a fiber administration system. The fiber administration system includes at least one fiber distribution shelve that supports a plurality of optical connection ports. Each of the optical connection ports contains a sensor for detecting the presence of an optical coupling in that optical connection port. A systems controller is coupled to the sensor of each of the optical connection ports. Accordingly, the systems controller can automatically determine from the sensors whether or not an optical coupling is present in each of the optical connection ports.

A novel optical-path supervisory scheme for optical cross connects in all-optical transport networks

Abstract: We propose and demonstrate a novel and effective supervisory scheme to monitor the optical-path routing at the optical cross connects in all-optical transport networks. Any error in optical-path routing due to failure in the cross connect can be detected without tapping off the power at the data wavelengths, and no dedicated monitoring light source is required. The scheme supports in-service surveillance. It can facilitate the network management in the optical layer of all-optical and reconfigurable transport networks.

Optical subscriber network system and fault supervising method for optical subscriber network system

Abstract: The invention provides an optical subscriber network system which can secure dual construction of optical transmission/reception sections of optical network units, specification of a failed faulty point in optical transmission lines and reception circuits of the optical network units and regular timing transmission of upstream data. The optical subscriber network system has a passive optical network construction wherein a plurality of network units are accommodated in a station apparatus through an optical transmission line using a passive optical element, and includes bypass transmission lines for mutual supervision control between the network units. A network unit mutual supervision control signal is communicated between the network units through the bypass transmission lines. The network unit mutual supervision control information received by each of the network units is transmitted to the station apparatus through the optical transmission line so that a fault is supervised based on the network unit mutual supervision control information by the station apparatus.

All-optical regeneration

Abstract: Different optical signal regeneration techniques are reviewed. Fibre or semiconductor based devices are addressed and compared, and 2R or 3R schemes are discussed. We briefly review 2R (reshaping repeater) and 3R (retiming reshaping repeater) optical regeneration schemes, based on different technologies which could be promising for high speed optical signal processing, and also try to compare these new optical approaches with well known optoelectronic schemes.

Fundamental limits of optical transparency

Abstract: Summary form only given. Network management is complicated by transparency in that there is no simple way to assure that signals entering or leaving a node are valid. One can envisage monitoring optical power or signal-to-noise ratio, but these analog measurements will not detect pulse distortion arising from nonlinearity and dispersion, for example. When performance is found to be degraded at an endpoint of a connection, there is no simple way to determine in what part of the network the degradation occurred.

Key building blocks for high-capacity WDM photonic transport networks

Abstract: The objective of this paper is to give an overview of the different studies we have performed at the research level regarding the design and implementation of a photonic wavelength division multiplexing (WDM) layer providing transparent transport services to client layers (SONET/SDH, ATM, etc.). Such a network requires a number of enabling factors to be assessed in order to become a reality. Among these factors are the availability of high-capacity WDM transmission systems and efficient optical routing nodes based on mature technology, the design of robust networks optimizing the utilization of resources, and the development of a management system in accordance with presently applied standards for transport networks. We review our achievements in these different fields.