Showing papers on "Optical Transport Network published in 1999"

Multiwavelength Optical Networks: A Layered Approach

Abstract: From the Publisher: Written by leading authorities in optical networking, this book explores wide area wavelength-division multiplexing now that commercial deployment is at hand. After an overview of the enabling technology, the authors focus on methodologies for network analysis, control, design, and protection from a layered multiwavelength network architecture point of view. Procedures for network control and design are covered for each category of network and are illustrated with examples. The emphasis here is on the fundamental role of available network resources - optical spectrum, fiber topology, and switching node and access station functionality - in determining network performance.

Free-space micromachined optical switches for optical networking

Abstract: Fiber-optic switches with high port count have emerged as leading candidates for deployment in future optical transport networks, where restoration and provisioning in the optical layer will become increasingly important. This paper reviews the principle and performance of free-space micromachined optical switches (FS-MOS) featuring free-rotating hinged micromirrors. A single-chip FS-MOS that implements the critical function of bridging-essential for restoration in core optical networks is also proposed and demonstrated. The scalability of FS-MOS devices, and the dependence of their insertion losses on mirror-angle, are estimated theoretically. Simulation results suggest that the FS-MOS approach holds considerable promise for being expandable to the port-count values that will be needed in future core-transport lightwave networks.

Hierarchical optical path cross-connect systems for large scale WDM networks

Abstract: Hierarchical optical path architecture consisting of wavelength-division multiplexing (WDM) bands and channels are suitable for large-scale WDM backbone networks. A hierarchical optical path crossconnect system (OPXC) using a matrix WDM scheme is proposed as a reliable and economical high-performance node architecture.

Optical Code Division Multiplexing (OCDM) and Its Applications to Photonic Networks

Abstract: Optical code division multiplexing (OCDM) is the other class of multiplexing techniques than time division multiplexing (TDM), wavelength division multiplexing (WDM) and space division multiplexing (SDM). OCDM has been proposed in mid ’70s. It has been long since OCDM remains outside the mainstream of research community of optical communications, however, possible scarcity of the wavelength resource in future photonic networks, the simple access protocol as well as versatility of optical codes motivate recent growth of OCDM research activities. In this paper, first, fundamentals of OCDM concept are presented, highlighting optical encoding and optical time gate detection which realize time spreading/despreading. Next, current research activities of OCDM are reviewed by focusing particularly on the optical implementations and the proof-of-concept experiments. It is devoted to three categories; high bit rate pointto-point transmissions, gigabit multiple access, followed by optical path networks using optical code. Finally, future issues are briefly summarized. key words: optical communications, code division multiplexing, wireless CDMA, multiple access, optical network

Optical signal quality monitor using direct Q-factor measurement

Abstract: In photonic networks, different types of signal formats such as synchronous digital hierarchy, plesiochronous digital hierarchy, and synchronous optical network are included. Therefore, an optical signal-quality monitoring scheme that is independent of the signal format is indispensable. This letter proposes a novel scheme to accomplish this. This method derives the standard deviation and the mean value of the marks/spaces rail of an eye pattern, and calculates the Q-factor. Computer simulation results confirm the applicability of the new technique.

Packet optical networks for high-speed TCP-IP backbones

Abstract: This article presents a new proposal for TCP-IP backbone implementation based on optical packet switching technology. The proposed network architecture merges the flexibility in resource management of packet switching with the high capacity offered by full optical technology.

Nondegenerate buffers: an approach for building large optical memories

Abstract: We describe a new methodology for analyzing optical buffers with nonuniform distribution of the delay lines, the nondegenerate buffers. Coupled with an intelligent scheduling algorithm, it features improved system performance leading to more efficient and larger optical buffers. We demonstrate that the concept under bursty, both time-slotted and asynchronous traffic conditions, can lead to a sizable reduction in buffer depth requirements compared to conventional solutions.

Optical scale communications network having a full meshed optical core transport network

Abstract: A fully meshed telecommunications network based on an optical core transport network having a plurality of optical nodes is described. An electronic edge switch is connected to an optical node and dedicated channels are established between all the possible pairs of electronic edge switches through their associated optical nodes and the optical core transport network. Connection paths are set up using a channel or channels between a pair of electronic edge switches which perform major functions concerning connection routes, including rate regulation, path establishment, etc.

Connection system for optical redundancy

Abstract: A redundant optical connection system is manufactured in specially prepared form to allow optical connections to be made at a later step. In response to information specifying which of the optical sources are functional, further structure may be activated or introduced into the connection system which guides optical energy to optical outputs from only those of the sources that are functional. In one aspect of the invention, the preliminary form includes primary guiding structures coupling each of a plurality of primary optical sources to a respective application structure, and a secondary guiding structure coupled to a secondary optical source and terminating without yet coupling to any application structure. If the information indicates that one of the primary optical sources in non-functional, then structure can be added or activated which transfers optical energy from the secondary guiding structure into the primary guiding structure corresponding to the non-functional source. In another aspect of the invention, the preliminary form includes a material having N optical sources and more than N output guiding structures. A gap region is provided in the material between the outputs of the optical sources and the inputs of the output guiding structures. Additional guiding structures are later formed or activated in response to the information, to guide optical energy to the inputs of the output guiding structures from only functional ones of the optical sources.

Fast restoration in a mesh network of optical cross-connects

Abstract: This paper proposes a distributed restoration method for mesh networks of optical cross-connects (OXCs) that is competitive with SONET ring restoration speeds. This approach is especially adapted to OXCs with optic fabrics where electronic signal performance or fault detection is available only at add/drop ports.

Connection management for wavelength-routed WDM networks

Abstract: In wavelength-routed WDM networks, a control mechanism is required to set up and take down all-optical connections. Upon the arrival of a connection request, this mechanism must be able to select a route, assign a wavelength to the connection, and configure the appropriate optical switches in the network. The mechanism must also be able to provide updates to reflect which wavelengths are currently being used on each link so that the nodes may make informed routing decisions. We investigate and compare different distributed control mechanisms for establishing all-optical connections in a wavelength-routed WDM network.

Method and apparatus for providing loss equalization and adjustment in a fiber optic network

Abstract: Loss equalization is provided in an optical communications network. Included in a optical communications network are a number of optical switches which include various elements for the routing of optical signals. The optical paths through the switches may introduce loss into the signals which causes the strengths of the various signals transmitted over the plurality of lines to be different. Measurements of the optical signals may be taken at both the entry and the exit of the optical switch. Through this measurement, losses through the paths are measured. This information may then be used to adjust the routing devices within the optical switch to equalize the losses occurring along the paths. Measurements may also be taken at various points in the optical network to determine losses introduced by components such as splices or amplifiers. Equalization for these losses can also be made through the routing devices of the optical switch.

WDM burst switching for petabit capacity routers

Abstract: WDM burst switching is an approach to building very high capacity routing switches based on optical data paths and electronic control. Burst switches assign user data bursts to channels in WDM links on-the-fly in order to provide efficient statistical multiplexing of high rate data channels. The overall system architecture is designed to facilitate the introduction of optical switching components as they become more highly integrated. At the same time it exploits the sophistication of modern electronic processing to perform the routing and higher level control operations needed in realistic, large scale networks.

A novel switching paradigm for buffer-less WDM networks

Abstract: Optical burst switching (OBS) is proposed to efficiently support IP over wavelength-division multiplexing (WDM). We describe various OBS protocols and in particular, one that can achieve high bandwidth utilization and low blocking probability in bufferless optical networks.

Self-healing optical network

Abstract: A self-healing optical network carrying traffic between first and second optical linear terminals (NODE A, NODE B, NODE C, NODE D). The self-healing optical network including first, second, and third optical switching units (210, 216, 226, 232), first, second, and third spare optical channels (214, 220, 222, 228), and a working optical channel (212, 218, 224, 230). The first, second, and third optical switching units are coupled in a ring configuration using said first, second, and third spare optical channels. The first and second optical switching units are coupled by the first spare optical channel and by the working optical channel. The first and second optical switching units each direct the traffic between the first and second optical linear terminals along the working optical channel or along the second and third spare optical channels in the event the working optical channel is not available.

Reconfigurable optical wireless

Abstract: We propose a natural step in freespace optical communications that is wireless. Namely, we propose the use of inertialess optical scanners as the agile free space light routing method within a multi-user free-space optical wireless network to realize all-optical advanced wireless networking. For instance, optical intersatellite links can use the highly accurate and fast beam pointing capabilities of the scanner to enhance the tradeoff between link distance and data rates.

A practical vision for optical transport networking

Abstract: Optical transport networks (OTNs) will quickly evolve from dense wavelength division multiplexed (DWDM) remedies for capacity exhaust to scalable and robust optical networking applications catering to a wide variety of client signals with equally varied service requirements. This paper presents a practical vision for OTN evolution, placing it in the context of other networking trends. It also provides a brief introduction to the papers presented in this issue, which together provide a view of Lucent Technologies' Network Vision for a cost-effective, survivable, and flexible broadband optical networking infrastructure.

Optical line switching system

Abstract: An approach for performing fault recovery in an optical communications network is disclosed. An optical switch is connected to working optical fibers and protection optical fibers, which carry WDM (wave division multiplexing) optical signals. The optical switches possess functionality to switch over the optical signals among the working optical fibers and the protection optical fibers. The optical switch includes dual unit optical switches that have a common driving mechanism. The common driving mechanism is configured to perform simultaneously switching operation of the unit optical switches to alter a switching state of the optical switch. Monitoring devices are distributed throughout the node to monitor the transmitted optical signals over the optical fibers, and to output monitoring signals that indicate one or more faults in these optical fibers. In response to the monitoring signals, a control device outputs control signals to the optical switches to effect an optical protection scheme.

Optical transmission system including optical restoration

Abstract: An optical communications system employs a plurality of optical nodes interconnected in a ring configuration by at least two optical transmission media, for example, optical fiber. The at least two optical transmission media, in this example, provide optical service transmission capacity and optical protection transmission capacity. Efficient restoration of optical communications between optical nodes in the ring, after an optical transmission media failure, is realized by employing a relatively simple and efficient optical switch matrix having a first number of possible switching states and, then, by utilizing only a second number of the switching states fewer than the first number to switch optically from the optical service transmission capacity of the failed or faulted optical transmission media to the optical protection transmission capacity of another optical transmission media. Optical switching states of the optical switch matrix are blocked that are not actively used for switching from the active optical service capacity of the faulted optical transmission media to the standby optical protection capacity of the other optical transmission media. Use of this relatively simple optical switch matrix allows for the bulk switching of the optical wavelengths as contrasted with the one-to-one switching of the optical wavelengths used in prior arrangements.

Single and double distributed optical amplifier fiber bus networks with wavelength-division multiplexing for photonic sensors.

Abstract: Two different optical fiber bus networks are compared and demonstrated experimentally as means of gathering information from four wavelength-division-multiplexed photonic sensors. Both topologies include distributed amplification, which allows one to overcome the limitation in the maximum number of sensors that can be multiplexed in a single structure. Results obtained with a dual-bus topology are compared with those achieved with a single-bus network.

Apparatus and method for providing optical channel overhead in optical transport networks

Abstract: Optical channel overhead information for individual optical channels is transported in a message based channel on an optical supervisory channel. Specifically, this is realized by obtaining performance monitoring, and/or performance measurement, and/or operations, and/or administration, and/or maintenance information, and/or the like for the individual ones of one or more optical channels, formatting the obtained information into a message for each individual optical channel and inserting the resulting message(s) into an optical supervisory channel to be transported on the OTN. In one embodiment of the invention, particular overhead information is formatted into a message and controllably inserted into the optical supervisory channel at a prescribed optical network element to be transported on the OTN. In another embodiment of the invention, particular overhead information is formatted into a message and controllably inserted into the optical supervisory channel at a prescribed optical network element to be transported on the OTN to a node including the capability to insert the overhead information into channel associated optical channel overhead to be transported to a network element at which it may be removed. Additionally, overhead information transported in channel associated optical channel overhead may be extracted, formatted into a message and inserted in a message based channel in the OSC. The OSC transports the optical channel overhead to a particular node not equipped for associated overhead insertion or removal, where it is extracted form the OSC and used as desired.

Ring architecture for an optical satellite communication network with passive optical routing

Abstract: A node for satellite system communications between a ground station and a satellite includes a fiber optic bus on the satellite. An optical drop is coupled to the bus. The optical drop resolves an optical signal destined to the given satellite from the optical bus. An uplink and downlink receive and transmit communications from a ground terminal. A router is coupled to the optical drop and the uplink and downlink. An address reader and a table are used by the router to determine the destination of the received RF signals. The received RF signals are converted to optical signals by an optical source. The optical source has a wavelength that corresponds with the destination satellite. The optical signals are transmitted to an adjacent satellite by an optical transmitter such as a transmitting telescope.

Metro optical networking

Abstract: Today's telecommunication networks support an ever-increasing mixture of statistical and deterministic data traffic. Current networks rely on time division multiplexing (TDM) hierarchy, originally invented to be the most efficient multiplexing technique possible for 64-kb/s voice, but this architecture is not particularly suited to statistical data traffic. A router or ATM switch can connect into a dense wavelength division multiplexing (DWDM) transport network by mapping packets or cells directly onto a wavelength without the intervening use of a SONET or SDH TDM. In effect, a TDM can be replaced with an optical DWDM, which can increase bandwidth utilization, facilitate networking, and reduce cost. DWDM can defer or completely eliminate the need for extra fiber, which is especially significant for providers who have a fiber-exhaustion problem, and it can easily coexist with today's SONET/SDH networks or with older fiber-optic terminals (FOTs) operating on asynchronous protocols. DWDM has already revolutionized the telecommunication industry by providing the infrastructure for long-haul optical networks. As the DWDM revolution moves into the metropolitan interoffice (IOF) and access networks, it will rely on the optical add/drop multiplexer (OADM) as its fundamental network element for metro optical networking. In this paper, we examine the market needs for metro optical networking; introduce the concept, network topology, and architectures for metro optical rings; and describe the key requirements that address the needs of service providers. We also discuss the components of the network and review the general requirements that will enable the next step in the evolution — extending the DWDM ring architecture to business access customers. Metro optical networking represents a unique opportunity for service providers to begin deploying a data-centric high-bandwidth services infrastructure.

Optical transmission system and method using an optical carrier drop/add transceiver

Abstract: An optical carrier drop/add transmission system and method using a same optical carrier to both drop traffic from an optical network and to add traffic to the optical network. An optical carrier signal is received by a transceiver and is subsequently split into a first and second optical signal. The first optical signal can be converted into an electrical signal for processing by the subscriber (i.e., data out). The electrical signal corresponding to the first optical signal is additionally inverted by the transceiver. The inverted electrical signal is subsequently modulated with the second optical signal in order to create a nominally flat signal (“optical chalkboard”). The subscriber's data is then modulated onto the flat signal and sent across the optical network. As a consequence, the network subscriber controls the format and protocols of the data traffic on the optical network, while the optical network service provider controls the optical carrier wavelengths, which are of primary concern to maintain organization and efficiency on the optical network.

Scalable add/drop architecture for lightwave communication system

Abstract: A scalable, reconfigurable, and cost-effective add/drop arrangement is provided which enables a wavelength division multiplexed (WDM) system to be upgraded to accommodate new or changing add/drop requirements without disruptions in existing service. The add/drop arrangement is based on a modular architecture wherein one or more modular optical routing devices are coupled in an optical fiber path to facilitate the selective adding/dropping of individual optical channels and to facilitate in-service upgrades without disrupting existing transmissions in the optical fiber path. In an exemplary embodiment, at least two directional optical transfer devices, such as optical circulators, are coupled to a drop path for dropping optical channels from the WDM signal, an add path for receiving optical channels to be added to the WDM signal, and a common path between the directional optical transfer devices. In the common path, at least one optical routing module is employed which is capable of receiving the WDM signal at an input and routing or otherwise switching the WDM signal to outputs, each of which can be coupled to one or more wavlength-selective modules. Each wavelength-selective module can be configured with an arrangement of optical filters, such as fiber gratings, and optical switches to facilitate the selective adding and dropping of one or more individual optical channels. Importantly, the optical routing module includes additional outputs for coupling to additional optical routing modules, additional wavelength-selective modules, and other components in order to accommodate changing add/drop requirements, which is an anticipated characteristic especially of metropolitan optical networks.

Channel provisioning for higher-layer protocols in WDM networks

Abstract: Recent developments in optical WDM technology have opened up many new challenges and opportunities for network designers. The availability of increasingly advanced optical devices, such as add-drop-multiplexers and wavelength routers/cross- connects, is pushing this technology beyond simple point-to- point deployment and more towards applications in end-to-end networking. These trends will require more advanced network control features in order to take full advantage of the optical fiber bandwidth. Although much work has been done on static WDM network provisioning, the issue of lightpath channel control in practical network environments needs further investigation. New protocols are required to provision channels for various higher-layer protocols, and these schemes must make efficient use of key network resources such as wavelengths and switching/conversion capacity. Optical channel survivability is also an important concern and various types of schemes can be envisioned.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

System for dealing with faults in an optical link

Abstract: A system for dealing with faults in wavelength division multiplexed (WDM) optical communications between two terminals connected by at least two optical fibers monitors the status of communications over both optical fibers. If both optical fibers are operating normally, a first set of channels is routed over the first optical fiber and a second set of channels (which is mutually exclusive of the first set of channels) is routed over the second optical fiber. However, if a fault is detected in either optical fiber, the first terminal combines the first and second sets of channels and routes the combined channels over the remaining optical fiber to the second terminal. The second terminal separates the combined channels to recreate the first and second sets of channels. Wavelength slicers can be used to multiplex and demultiplex the channels at both terminals. This architecture allows the first and second sets of channels to be interdigitally spaced.