Showing papers on "Optical Transport Network published in 2002"

Ethernet passive optical network (EPON): building a next-generation optical access network

Abstract: This article describes Ethernet passive optical networks, an emerging local subscriber access architecture that combines low-cost point-to-multipoint fiber infrastructure with Ethernet. EPONs are designed to carry Ethernet frames at standard Ethernet rates. An EPON uses a single trunk fiber that extends from a central office to a passive optical splitter, which then fans out to multiple optical drop fibers connected to subscriber nodes. Other than the end terminating equipment, no component in the network requires electrical power, hence the term passive. Local carriers have long been interested in passive optical networks for the benefits they offer: minimal fiber infrastructure and no powering requirement in the outside plant. With Ethernet now emerging as the protocol of choice for carrying IP traffic in metro and access networks, EPON has emerged as a potential optimized architecture for fiber to the building and fiber to the home.

Traffic grooming in an optical WDM mesh network

Abstract: In wavelength-division multiplexing (WDM) optical networks, the bandwidth request of a traffic stream can be much lower than the capacity of a lightpath. Efficiently grooming low-speed connections onto high-capacity lightpaths will improve the network throughput and reduce the network cost. In WDM/SONET ring networks, it has been shown in the optical network literature that by carefully grooming the low-speed connection and using wavelength-division multiplexer (OADM) to perform the optical bypass at intermediate nodes, electronic ADMs can be saved and network cost will be reduced. In this study, we investigate the traffic-grooming problem in a WDM-based optical mesh topology network. Our objective is to improve the network throughput. We study the node architecture for a WDM mesh network with traffic-grooming capability. A mathematical formulation of the traffic-grooming problem is presented in this study and several fast heuristics are also proposed and evaluated.

Optical differential quadrature phase-shift key (oDQPSK) for high capacity optical transmission

Abstract: Signaling using oDQPSK offers great potential for application in 10 and 40 Gb/s DWDM transmission systems, offering increased spectral efficiency, relaxed dispersion management and improved PMD tolerance. Practical realization of encoder and decoder functionality through integration should lead to wide system application.

A Review of Traffic Grooming in WDM Optical Networks: Architectures and Challenges

Abstract: The transmission capacity of a link in today’s optical networks has increased significantly due to wavelength-division multiplexing (WDM) technology. The network performance is now mainly limited by the processing capability of the network elements, which are mainly electronic. By efficiently grooming low-speed traffic streams onto high-capacity optical channels, it is possible to minimize this electronic processing and eventually increase the network performance. Traffic grooming is an emerging topic that has been gaining more research and commercial attention. Most previous research on traffic grooming is mainly based on the ring network topology. It is expected that there will be much more interest on the mesh topology suitable for long-haul, widearea networks. This paper reviews most of the recent research work on traffic grooming in WDM ring and mesh networks. Various network and node architectures for different traffic -grooming scenarios are compared and discussed. * This work has been supported by the National Science Foundation (NSF) under Grant Nos. NCR-9508239 andANI-9805286, and by Sprint Advanced Technology Laboratories (ATL).

All-optical processing with molecular switches

Abstract: A gradual transition from electrical to optical networks is accompanying the rapid progress of telecommunication technology. The urge for enhanced transmission capacity and speed is dictating this trend. In fact, large volumes of data encoded on optical signals can be transported rapidly over long distances. Their propagation along specific routes across a communication network is ensured by a combination of optical fibers and optoelectronic switches. It is becoming apparent, however, that the interplay between the routing electrical stimulations and the traveling optical signals will not be able to support the terabit-per-second capacities that will be needed in the near future. Electrical inputs cannot handle the immense parallelism potentially possible with optical signals. Operating principles to control optical signals with optical signals must be developed. Molecular and supramolecular switches are promising candidates for the realization of innovative materials for information technology. Binary digits can be encoded in their chemical, electrical, or optical inputs and outputs to execute specific logic functions. We have developed a simple strategy to gate optical signals with optical signals by using a photoactive molecular switch. We have demonstrated that NAND, NOR, and NOT operations can be implemented exclusively with optical inputs and optical outputs coupling from one to three switching elements. Our remarkably simple approach to all-optical switching might lead to the development of a new generation of devices for digital processing and communication technology.

Optical packet switching in core networks: between vision and reality

Abstract: The research on optical packet switching (OPS) has witnessed considerable progress in the 1990s. We examine the future potential of OPS in the core network by discussing this switching approach and the current status of a number of its enabling technologies. Many of these technologies are still in the stage of research and experimentation. We see that optical packet switching may be deployed in the long-term future subject to satisfaction of three main conditions/developments. First, additional technological developments have to take place to overcome remaining implementation challenges while making OPS cost-effective to deploy. Second, a rational migration scenario of the network toward gradual deployment of packet-based optical switching approaches should exist. Finally, carriers have to become more interested in packet-based optical switching solutions.

MEMS: the path to large optical crossconnects

Abstract: Continuous growth in demand for optical network capacity and the sudden maturation of WDM technologies have fueled the development of long-haul optical network systems that transport tens to hundreds of wavelengths per fiber, with each wavelength modulated at 10 Gb/s or more. Micro-electromechanical systems devices are recognized to be the enabling technologies to build the next-generation cost-effective and reliable high-capacity optical crossconnects. While the promises of automatically reconfigurable networks and bit-rate-independent photonic switching are bright, the endeavor to develop a high-port-count MEMS-based OXC involves overcoming challenges in MEMS design and fabrication, optical packaging, and mirror control. Due to the interdependence of many design parameters, manufacturing tolerances, and performance requirements, careful trade-offs must be made in MEMS device design as well as system design. We provide an overview of the market demand, various design trade-offs, and multidisciplinary system considerations for building reliable and manufacturable large MEMS-based OXCs.

On double-link failure recovery in WDM optical networks

Abstract: Network survivability is a crucial requirement in high-speed optical networks. Typical approaches of providing survivability have considered the failure of a single component such as a link or a node. We consider a failure model in which any two links in the network may fail in an arbitrary order. Three loopback methods of recovering from double-link failures are presented. The first two methods require the identification of the failed links, while the third one does not. However, precomputing the backup paths for the third method is more difficult than for the first two. A heuristic algorithm that pre-computes backup paths for links is presented. Numerical results comparing the performance of our algorithm with other approaches suggests that it is possible to achieve 100% recovery from double-link failures with a modest increase in backup capacity.

Multichannel digital transmission in an optical network of communicating molecules.

Abstract: In present telecommunication networks, information transfer relies on the interplay of optical and electrical signals. Data are communicated optically but processed electronically. Methods to maintain the propagating signals solely at the optical level must be developed to overcome the transmission capacities and speed limits imposed by the electronic components. We have demonstrated that molecular switches can be used to gate optical signals in response to optical signals. We have realized a simple optical network consisting of three light sources, one cell containing a solution of three fluorescent molecules, one cell containing a solution of a three-state molecular switch and a detector. The light emitted by the three fluorophores is absorbed by the three states of the molecular switch. Using this simple operating principle, we have shown that multichannel digital transmission can be implemented on an ensemble of communicating molecules relying exclusively on the interplay of optical inputs and optical...

Data-centric optical networks and their survivability

Abstract: The explosive growth of data traffic-for example, due to the popularity of the Internet-poses important emerging network requirements on today's telecommunication networks. This paper describes how core networks will evolve to optical transport networks (OTNs), which are optimized for the transport of data traffic, resulting in an IP-directly-over-OTN paradigm. Special attention is paid to the survivability of such data-centric optical networks. This becomes increasingly crucial since more and more traffic is multiplexed onto a single fiber (e.g., 160/spl times/10 Gb/s), implying that a single cable cut can affect incredible large traffic volumes. In particular, this paper is tackling multilayer survivability problems, since a data-centric optical network consists of at least an IP and optical layer. In practice, this means that the questions "in which layer or layers should survivability be provided?" and "if multiple layers are chosen for this purpose, then how should this functionality in these layers be coordinated?" have to be answered. In addition to a theoretical study, some case studies are presented in order to illustrate the relevance of the described issues and to help in strategic planning decisions. Two case studies are studying the problem from a capacity viewpoint. Another case study presents simulations from a timing/throughput performance viewpoint.

Digital optical network architecture

Abstract: A digital optical network (DON) is a new approach to low-cost, more compact optical transmitter modules and optical receiver modules for deployment in optical transport networks (OTNs). One important aspect of a digital optical network is the incorporation in these modules of transmitter photonic integrated circuit (TxPIC) chips and receiver photonic integrated circuit (TxPIC) chips in lieu of discrete modulated sources and detector sources with discrete multiplexers or demultiplexers.

Contention resolution for optical burst switching networks using alternative routing

Abstract: Optical burst switching (OBS) is an approach to building very high capacity routing switches based on optical data paths and electronic control. Therefore, OBS is considered as a viable solution in the high-speed optical Internet backbone. In this paper, we propose an intra-class contention resolution scheme in optical burst switching networks by the enhanced alternative routing algorithm. The blocking probability of the proposed scheme is significantly reduced as compared with the general OBS while the additional delay due to the alternative path is smaller than 10% of the basic offset time.

Intelligent optical networking for multilayer survivability

Abstract: In recent years, telecommunication networks have faced explosive (IP) traffic growth. As traffic keeps growing, network reliability gains more and more importance. This article investigates to which extent switched connections and fast connection provisioning, typical for intelligent optical networks (IONs), can be used to provide resilience in an IP-over-optical multilayer network scenario. This solution, based on transport network flexibility, is compared with more traditional static multilayer resilience schemes in terms of cost (capacity) requirements and operational (dis)advantages.

Transport of signals over an optical fiber using analog RF multiplexing

Abstract: In a wireless communication network, a method for transporting signals between a base station hotel (400) and a remote cell site (402, 404, 406) allows multiple uplink and downlink signals to be communicated using a single optical fiber. In a preferred embodiment of the invention, an RF transport technique uses frequency translation to shift the common carrier frequencies of diversity and sector signals to distinct intermediate frequencies that are then combined, converted to an optical signal and transmitted over a single fiber. The RF transport technique also uses wavelength division multiplexing (WDM) to communicate both uplink and downlink signals over the same fiber. Reference clock signals are distributed to ensure accurate frequency translation at both ends of the link. Reference power signals are also transmitted in both uplink and downlink to help perform signal power equalization.

Combined SONET/SDH and OTN architecture

Abstract: Architecture for efficient processing of the evolving OTN transmission technology, standardized under ITU-T G.709, in conjunction with existing and emerging SONET/SDH protocol signals, standardized under ANSI T1.105/ITU-T G.707. The new architecture allows processing the SONET/SDH signals, and/or OTN signals, and/or SONET/SDH mapped into OTN signals more efficiently. The architecture further allows processing and multiplexing of lower order signals into a higher order signal such as quad OC-192 into OC-768 or quad OC-192 into OPU3 and OTU3. This architecture uses an embedded processor to process some of the signals' overhead in software, contributing to an additional level of flexibility in the processing. This architecture enables customization and allowing for future standard updates and upgrades. The architecture can be upgraded to SONET OC-3072, SDH STM-1024 and OTU4, which currently are not standardized. The architecture can also be used for the implementation of SONET OC-192 with OTN OTU2.

DWDM: Networks, Devices, and Technology

Abstract: Preface. Acknowledgments. List of Physical Constants. Introduction. 1. The Physics of Optical Components. 1.1. Introduction. 1.2. The Nature of Light. 1.2.1. The Wave Nature of Light. 1.2.2. The Particle Nature of Light. 1.2.3. Huygens-Fresnel Principle. 1.2.4. Interference. 1.2.5. Holography. 1.2.6. Optical Correlators and Storage. 1.2.7. Light Attributes. 1.3. Optical Materials. 1.3.1. Transparent Versus Opaque Matter. 1.3.2. Homogeneity and Heterogeneity. 1.3.3. Isotropy and Anisotropy. 1.3.4. Organic Materials. 1.3.5. Photochromaticity. 1.4. Light Meets Matter. 1.4.1. Reflection and Refraction: Snell's Law. 1.4.2. Critical Angle. 1.4.3. Antireflection. 1.4.4. Prisms and Superprisms. 1.4.5. Propagation of Light. 1.4.6. Diffraction. 1.4.7. Polarization. 1.4.8. Extinction Ratio. 1.4.9. Phase Shift. 1.4.10. Birefringence. 1.4.11. Material Dispersion. 1.4.12. Electro-Optic Effects. 1.4.13. Material Attributes. 1.5. The Fiber as an Optical Transmission Medium. 1.5.1. Composite Refractive Indices. 1.5.2. Fiber Modes. 1.5.3. Fiber Attenuation and Power Loss. 1.5.4. Fiber Birefringence. 1.5.5. Dispersion. 1.5.6. Spectral Broadening. 1.5.7. Self-Phase Modulation. 1.5.8. Self-Modulation or Modulation Instability. 1.5.9. Effect of Pulse Broadening on Bit Error Rate. 1.6. Nonlinear Phenomena. 1.6.1. Stimulated Raman Scattering. 1.6.2. Stimulated Brillouin Scattering. 1.6.3. Four-Wave Mixing. 1.6.4. Temporal FWM, Near-End and Far-End. 1.6.5. Impact of FWM on DWDM Transmission Systems. 1.6.6. Countermeasures to Reduce FWM. 1.7. Solitons. 1.8. Summary of Nonlinear Phenomena. 1.9. Factors that Affect Matter and Light. 1.10. Regarding Optical Fiber. 1.10.1. Ideal Fiber Versus Real Fiber. 1.10.2. The Evolving Bandwidth-Span Product. 1.10.3. Fiber Amplifiers and Spectral Continuum. 1.10.4. New Fibers. 1.10.5. How Strong Is Fiber? 1.11. Fiber Connectivity. 1.12. Optical PWBs. Exercises. References. Standards. 2. Optical Components. 2.1. Introduction. 2.1.1. Geometrical Optics. 2.1.2. Insertion Loss and Isolation. 2.1.3. Parameters Common to All Components. 2.2. Optical Filters. 2.2.1. Fabry-Perot Interferometer. 2.2.2. Dielectric Thin Film. 2.2.3. Diffraction Gratings. 2.2.4. Bragg Gratings. 2.2.5. Mach-Zehnder Interferometry. 2.2.6. Arrayed Waveguide Grating Filters. 2.2.7. Polarizing Filters. 2.2.8. Absorption Filters. 2.2.9. Acousto-Optic Tunable Filters. 2.2.10. Hybrid Filters. 2.2.11. Comparing Tunable Filters. 2.3. Optical Directional Couplers. 2.4. Optical Power Attenuators. 2.5. Polarizers and Rotators. 2.6. Beam Splitters. 2.7. Optical Isolators and Circulators. 2.8. Quarter-Wavelength and Half-Wavelength Plates. 2.9. Optical Multiplexers and Demultiplexers. 2.9.1. Prisms and Superprisms. 2.9.2. Gratings. 2.9.3. Mach-Zehnder Demultiplexer. 2.9.4. Arrayed Waveguide Grating Demultiplexers. 2.9.5. Channel Interleavers and Channel Splitters. 2.10. Optical Cross-Connects. 2.10.1. Free-Space Optical Switching. 2.10.2. Solid-State Cross-Connects. 2.10.3. Polymers and Inks. 2.10.4. Photochromic Materials. 2.10.5. Technologies and Switching Speeds. 2.11. Optical Add-Drop Multiplexers. 2.12. Optical Equalizers. 2.13. Light Sources. 2.13.1. Light-Emitting Diodes. 2.13.2. Lasers. 2.14. Laser Beams. 2.14.1. Gaussian Beams. 2.14.2. Near-Field and Far-Field Distribution. 2.14.3. Peak Wavelength. 2.14.4. Degree of Coherence. 2.14.5. Laser Safety. 2.15. Modulators. 2.15.1. Types of Modulators. 2.15.2. A Case: Amplitude Modulation. 2.15.3. Modulation and Bit Error Probabilities. 2.16. Photodetectors and Receivers. 2.16.1. The PIN Photodiode. 2.16.2. The APD Photodiode. 2.16.3. Photodetector Figure of Merit. 2.16.4. ITU-T Nominal Center Frequencies. 2.17. Optical Amplifiers. 2.17.1. Semiconductor Optical Amplifiers. 2.17.2. Rare Earth-Doped Fiber Optical Amplifiers. 2.17.3. Optical Parametric Amplifiers. 2.17.4. Raman Amplifiers. 2.17.5. Synergistic Amplification. 2.17.6. Stimulated Brillouin Scattering. 2.17.7. Amplification in the Low-Loss Spectral Range. 2.18. Wavelength Converters. 2.18.1. Cross-Gain Modulation. 2.18.2. Cross-Phase Modulation. 2.18.3. Four-Wave Mixing. 2.18.4. Optical Frequency Shifting. 2.19. Optical Phase-Locked Loops. 2.20. Ring Resonators. 2.21. Optical Attenuators. 2.22. Optical Signal-to-Noise Ratio. 2.22.1. Bit Error Rate. 2.22.2. BER and Eye Diagram. 2.23. New Materials and Components. 2.23.1. Optical Materials. 2.23.2. Hollow Fibers. 2.23.3. Lasers and Receivers. 2.23.4. Optical Cross-Connects. 2.23.5. Optical Memories. 2.23.6. Optical Integration. Exercises. References. Standards / 233 3. Communications Fundamentals. 3.1. Introduction. 3.2. Pulse Coded Modulation. 3.3. Loop Accessing Methods. 3.3.1. xDSL. 3.3.2. Other High-Speed Short-Reach Technologies. 3.4. Time Division Multiplexing Systems. 3.4.1. Access and Pair-Gain Systems. 3.4.2. Fiber-to-the-Home Technology. 3.4.3. Switching Systems. 3.4.4. Digital Cross-Connect Systems. 3.5. Getting Connected. 3.6. Data Systems. 3.6.1. The OSI Model. 3.6.2. Local Area Networks. 3.6.3. Packet Networks. 3.6.4. Frame Relay. 3.6.5. ATM. 3.6.6. Quality of Service. 3.7. SONET and SDH. 3.7.1. SONET Topologies. 3.7.2. SONET and SDH Rates. 3.7.3. SONET and SDH Frames. 3.7.4. Floating Frames and Pointers. 3.7.5. Overhead Definition. 3.7.6. Frequency Justification. 3.7.7. Path Overhead. 3.7.8. Maintenance. 3.7.9. Operations Communications Interface. 3.7.10. Interworking. 3.7.11. Next-Generation SONET. 3.8. Internet. 3.8.1. Voice over IP. 3.8.2. Fax over IP (FoIP). 3.8.3. ATM over SONET. 3.8.4. IP over SONET. 3.9. Optical Networks. 3.10. What Is a DWDM System and Network? Exercises. References. Standards. 4 .DWDM Systems. 4.1. Introduction. 4.2. DWDM Network Topologies-Review. 4.3. DWDM Systems and Network Layers. 4.3.1. DWDM and Standards. 4.3.2. Domains or Functions. 4.3.3. System Partitioning and Remoting. 4.4. Key Building Blocks of a DWDM System. 4.4.1. Transmitters and Receivers. 4.4.2. Optical Amplifiers and Regenerators. 4.4.3. Dispersion Compensating Solutions. 4.4.4. Optical Gain Equalizers. 4.4.5. Optical Wavelength Translators. 4.4.6. Timing. 4.4.7. Optical Switching. 4.4.8. Control Architectures and Controllers. 4.4.9. Interfaces. 4.5. Wavelength Management Strategy. 4.6. Equipment Sensing Strategy. 4.7. Fault Detection and Reporting Strategy. 4.7.1. Fault Detection on the Network Level. 4.7.2. Fault Detection Identifiers. 4.7.3. Overhead, Data, and Error Correction: The Digital Wrapper. 4.8. Power Strategy. 4.9. DWDM Systems by Network Layer. 4.9.1. Point-to-Point Systems. 4.9.2. Large Optical Cross-Connect Systems. 4.9.3. DWDM Metro Systems. 4.9.4. Access DWDM Systems and First/Last Mile. 4.10. Protected and Unprotected Systems. 4.11. Engineering DWDM Systems. 4.11.1. Parameters That Influence Optical Design. 4.11.2. ITU-T Recommended Frequencies. 4.11.3. Channel Capacity, Width, and Spacing. 4.11.4. Channel Bit Rate and Modulation. 4.11.5. Multichannel Frequency Stabilization. 4.11.6. BER and Channel Performance. 4.11.7. Channel Dispersion. 4.11.8. Power Launched. 4.11.9. Optical Amplification and Compensation. 4.11.10. The Fiber-Medium and Limitations. 4.11.11. Optical Power Budget. 4.11.12. Power Budget Calculations by Example. Conclusions. Exercises. References. Standards. 5. DWDM Networks. 5.1. Introduction. 5.1.1. Multiprotocol Label Switching. 5.1.2. MPlambdaS. 5.1.3. DiffServ, IntServ, and MPLS. 5.1.4. Optical Virtual Path Network. 5.1.5. Network Layers and Protection. 5.1.6. The Evolving Telecommunications Management Network. 5.2. The Optical Transport Network. 5.3. DWDM Network Topologies and Restoration Strategies. 5.3.1. Point-to-Point Topology. 5.3.2. Ring Topology. 5.3.3. Mesh Topology. 5.3.4. Ring-Mesh Networks. 5.4. Dispersion Management. 5.5. Bandwidth Management. 5.5.1. Wavelength Management. 5.5.2. Traffic Management. 5.5.3. Congestion Management. 5.6. Fiber Span Between Transmitter and Receiver. 5.7. Fault Management. 5.8. Network Security. 5.9. DWDM Network Issues. 5.9.1. Interoperability and Internetworking. 5.9.2. Optical Performance Monitoring. 5.9.3. Network Future-Proofing. 5.9.4. Wavelength Sharing. 5.9.5. IP/SONET over DWDM. 5.9.6. Maintenance. 5.9.7. DWDM Network Management. 5.10. Wireless DWDM Networks. Exercises. References. Standards. 6. Emerging Technologies. 6.1. Introduction. 6.2. Emerging Technologies. 6.2.1. Theory and New Materials. 6.2.2. Communications Components, Systems, and Networks. 6.2.3. Intelligent Homes. 6.2.4. Intelligent Transportation. 6.2.5. Intelligent Powering Systems. 6.3. Current Research. 6.3.1. Advanced Lasers. 6.3.2. Artificial Optical Materials. 6.3.3. Optical Cross-Connect. 6.3.4. Optical Memories and Variable Delay Lines. 6.3.5. Nonintrusive Optical Sensors. 6.4. Conclusion. References. Standards. Answers to Exercises. Acronyms. Index. About the Author.

Electrical ingress buffering and traffic aggregation for optical packet switching and their effect on TCP-level performance in optical mesh networks

Abstract: The wide deployment of wavelength-division multiplexing technology and new transmission techniques have resulted in significant increases in the transmission capacity in optical fibers, both in the number of wavelengths and the bandwidth of each wavelength channel. Meanwhile, the fast growth of the Internet demands more data switching capacity in the network in order to deliver high bandwidth to end users. Although the capacity of electronic routers has been increasing consistently in the past, optical switching appears to be a more cost-effective way to switch individual wavelengths. As the bit rate per wavelength channel continues to grow, optical subwavelength switching emerges as a new paradigm capable of dynamically delivering the vast bandwidth WDM offers. This article discusses one of such techniques, namely optical packet switching, and its performance perceived by end users in optical mesh networks. Specifically, our investigation reveals the benefit of using electrical ingress buffering and traffic aggregation to reduce packet-loss rate of optical packet-switched networks. Through simulation experiments, we present an evaluation of the network's TCP-level performance based on the proposed architecture.

Network diagnostic tool for an optical transport network

Abstract: A network diagnostic system is provided for an optical transport network having a plurality of network elements. The network diagnostic system includes at least one network element having a network diagnostic operation integrated therein and operable to perform the network diagnostic operation, thereby determining a network performance characteristic associated with the optical transport network; a wayside communication subsystem interconnecting the network elements residing in the optical transport network; and a network diagnostic device in data communication with the at least one network element and operable to initiate the network diagnostic operation at the network element.

A tutorial on optical networks

Abstract: In this half-day tutorial, we present the current state-of-the-art in optical networks. We begin by discussing the various optical devices used in optical networks. Then, we present wavelength-routed networks, which is currently the dominant architecture for optical networks. We discuss wavelength allocation policies, calculation of call blocking probabilities, and network optimization techniques. Subsequently, we focus on the various protocols that have been proposed for wavelength-routed networks. Specifically, we present a framework for IP over optical networks, MPLS, LDP, CR-LDP, and GMPLS. Next, we discuss optical packet switching and optical burst switching, two new emerging and highly promising technologies.

New transport services for next-generation SONET/SDH systems

Abstract: SONET/SDH systems have been the preferred transport technology over fiber optics for almost two decades now. Carriers have developed extensive expertise in operating, managing, and developing business models for these systems. Manufacturers' technical expertise in such systems has increased to a deep understanding of what transport over fiber is about. In short, SONET/SDH can be called a mature transport technology. Out of this mature expertise, new techniques for bettering transport over fiber services have appeared. These techniques are likely to considerably reshape the next generation of SONET/SDH systems in many aspects: new transport techniques, new transport services, new management systems and business models. We describe several new transport techniques, and discuss their impact on the creation of new transport services for next-generation SONET/SDH systems.

Method for mapping and multiplexing constant bit rate signals into an optical transport network frame

Abstract: A method for mapping and multiplexing of constant bit rate (CBR) signals into optical transport network (OTN) frames is provided. The method, in addition, enables the transportation of data from a plurality of SONET/SDH clients through a single OTN frame. The preferred method thereby enables efficient adoption of SONET/SDH legacy equipment by OTN networks.

All fiber-optic neural network using coupled SOA based ring lasers

Abstract: An all-optical neural network is presented that is based on coupled lasers. Each laser in the network lases at a distinct wavelength, representing one neuron. The network status is determined by the wavelength of the network's light output. Inputs to the network are in the optical power domain. The nonlinear threshold function required for neural-network operation is achieved optically by interaction between the lasers. The behavior of the coupled lasers is explained by a simple laser model developed in the paper. In particular, the winner take all (WTA) neural-network behavior of a system of many lasers is described. An experimental system is implemented using single mode fiber optic components at wavelengths near 1550 nm. A number of functions are implemented to demonstrate the practicality of the new network. The neural network is particularly robust against input wavelength variations.

Hybrid hierarchical optical networks

Abstract: Hybrid hierarchical optical cross-connects enhance the performance/cost ratio of optical networks by providing transparent (optical) switching of sets of wavelengths (wavebands) in addition to opaque (electrical) switching of individual wavelengths. As network bandwidth gets cheaper, and the performance bottleneck moves to switching nodes, these systems provide an attractive scalable solution for next-generation optical networks. We describe key technological components (including flexible nonuniform wavebands) of hybrid hierarchical optical cross-connects and discuss their performance/cost implications.

Multifunctional intelligent optical modules based on planar lightwave circuits

Abstract: Since the bandwidth-intensive applications such as Internet access, electronic commerce, multimedia applications, and distributed computing are rapidly increasing the volume of telecommunication traffics, optical networks become an essential backbone of telecommunication networks. The optical networks have shown a superior performance/cost ratio for both long-haul and short-haul routes and the emerging dense wavelength division multiplexing and all-optical network technologies have promised a potential to improve speed, capacity and connectivity of telecommunication networks. The present invention provides a multifunctional intelligent optical module (IOM) by integrating a multitude of photonic, electronic, and micro mechanical elements into a single module. The multifunctional IOM is an integrated hybrid microsystem and it applicable to fast network provisioning, reliable protection switching, instant fault detection/correction, guaranteed quality-of-service, accurate optical performance monitoring, and efficient optical transmission engineering.

Network, switching apparatus and OTN frame processing method for use therein; its circuit and integrated circuit

Abstract: An OTN cross-connecting apparatus ( 100 ) constituting a second network is arranged on a boundary to a first network. The OTN framer ( 220 ) of a client interface card ( 200 ) mounted on the OTN cross-connecting apparatus ( 100 ) stores an SDH/SONET signal into an OTN frame on a non-interfering manner and, using the overhead of the second network OTN frame, controls and manages the apparatus and the network.

Method and apparatus for tunnelling data in a network

Abstract: A communications network including nodes which permit networks to be tunnelled across intermediate networks. The present invention has application, in particular, to SDH networks, SONET and OTN. The content of entities for transportation across an existing network are mapped into a series of subframes and are virtually concatenated across the network. Each subframe is assigned a sequence indicator, which allows the original entity to be assembled at a remote node.

Optical Networks: Third Generation Transport Systems

Abstract: Preface. 1. Introduction. Three Generations of Digital Transport Networks. All Features Are Not Yet Available. Optical Fiber Capacity. A Brief Introduction to WDM and TDM. Combining WDM and TDM. The Optical Marketplace. The Local Loop Bottleneck Must Be Solved. Expansion of Network Capacity. Wireless Optical Systems. Key Optical Nodes. Key Terms for the Cross-connect. Other Key Terms. Another Look at the Optical Node. Evolution of Optical Systems. Key Attributes of Optical Fiber. Summary. 2. The Telecommunications Infrastructure. The Local Connections. The Backbone Connections. The Digital Multiplexing Hierarchy. The Digital Signaling Hierarchies. T1 or DS1 T3 or DS3? The Layered Protocol Model in the Transport Network. Considerations for Interworking Layer 1, Layer 2, and Layer 3 Networks. Summary. 3. Characteristics of Optical Fiber. The Basics. The Wavelength. The Basic Components. The Source of the Signal. The Detector. Structure of the Fiber. Angles. Fiber Types. Key Performance Properties of Fiber. Attenuation. Amplifier Spontaneous Emission (ASE). Chromatic Dispersion. Polarization-mode Dispersion (PMD). Lasers. Summary. 4. Timing and Synchronization. Timing and Synchronization in Digital Networks. Effect of a Timing Error. The Clocking Signal. Types of Timing in Networks. The Synchronous Clock Hierarchy. Timing Variations. Frequency Accuracy. Methods of Clock Exchange. Free-Running. Line-Timed. Loop-Timed. External. Through-Timed. Distribution of Timing Using SONET and DS1. Timing Downstream Devices. The Building Integrated Timing Supply (BITS). Synchronization Status Messages (SSMs) and Timing Loops. Summary. 5. SONET and SDH. How SONET and SDH Came into Being. Participation by ITU-T. Reasons for Success of SONET/SDH. The SONET Multiplexing Hierarchy. SONET and SDH Multiplexing Structure. The SONET/SDH Frame Structure. Rationale for the 51.840 Mbit/s Envelope. Overhead and User Areas in the Envelope. SONET and SDH Functional Components. SONET and SDH Problem Detection. Locating and Adjusting Payload with Pointers. Virtual Tributaries in More Detail. Virtual Tributaries and Virtual Containers. The Overhead Bytes. SONET and SDH Concatenation. Summary. 6. Architecture of Optical Transport Networks (OTNs). The Digital Wrapper. Control Planes. In-band and Out-of-band Control Signaling. An In-band Signal on an O/O/O PXC. Importance of Multiplexing and Multiplexing Hierarchies. Current Digital Transport Hierarchy. SONET Multiplexing Hierarchy. SDH Multiplexing Hierarchy. Revised SDH Transport Hierarchy. Key Indexes and Other Terms. The New Optical Transport and Digital Transport Hierarchy. ODUk Mapping and Multiplexing. The OTN Layered Model. Another View. Full Functionality Stack: OTM-n.m. Reduced Functionality Stack: OTM-nr.m and OTM-0.r. Encapsulation and Decapsulation Operations. Generic Framing Procedure (GFP). Summary. 7. Wavelength Division Multiplexing (WDM). The WDM Operation. Dense Wave Division Multiplexing (DWDM). TDM and WDM Topologies. Relationship of WDM to SONET/SDH. Erbium-doped Fiber (EDF). WDM Amplifiers. Gain Flatness. Add-Drop Multiplexers. WADM Input and Output Ports. WDM Cross-connects. Wavelength Continuity Property. Example of DWDM Wavelength Plan. Average Versus Maximum Span Loss and Chromatic Dispersion. Higher Dispersion for DWDM. Tunable DWDM Lasers. Summary. 8. Network Topologies and Protection Schemes. The Non-negotiable Requirement: Robust Networks. Diversity in the Network: Which Control Plane? Line and Path Protection Switching. Types of Topologies. Working and Protection Fibers. Point-to-Point Topology. 1:N Protection Channel Sharing. Optical Channel Concatenation. Bi-directional Line-Switched Ring (BLSR). Protection Switching on Four-Fiber BLSR. Meshed Topologies. Passive Optical Networks (PONs). Optical Ethernets and Ethernet PONs. Ethernet in the Wide Area Backbone? Metro Optical Networking. Summary. 9. MPLS and Optical Networks. What IS Label Switching? Reasons for Using Label Switching. The Forwarding Equivalence Class (FEC). Scalability and Granularity: Labels and Wavelengths. Types of MPLS Nodes. Label Distribution and Binding. Methods for Label Distribution. Label Swapping and Traffic Forwarding. MPLS Support of Virtual Private Networks (VPNs). MPLS Traffic Engineering (TE). Traffic Oriented or Resource Oriented Performance. Traffic Trunks, Traffic Flows, and Label Switched Paths. LDP, CR-LDP, RSVP-TE, and OSPF (Extensions) for TE Support. Multiprotocol Lambda Switching (MPlS). Relationships of OXC and MPLS Operations. MPLS and Optical Wavelength Correlation. Failure of the Optical Connection. MPLS and Optical TE Similarities. Possibilities for the MPlS Network. Control and Data Planes Interworking. Summary. 10. Architecture of IP and MPLS-based Optical Transport Networks. IP, MPLS, and Optical Control Planes. The Internet Control and Data Planes. The MPLS Control and Data Planes. The Optical Control and Data Planes. Interworking the Three Control Planes. Management of the Planes. Diverse Views on Control Planes' Interworkings. A Framework for IP over Optical Networks. Two General Models. Domain Services Model. Unified Service Model. Interconnections for IP over Optical. An Opposing View. Which Approaches to Use? Generalized MPLS (GMPLS) Use in Optical Networks. Considerations for Interworking Layer 1 Lambdas and Layer 2 Labels. Examples of GMPLS Operations. Suggested Labels for the Wavelengths. Bi-directional LSPs in Optical Networks. Link Protection. The Next Horizon: GMPLS Extensions for G.709. Technology Independent Part. Technology Dependent Part. OTM Overhead Signal (OOS). Transparency. G.709 Label Space. OCh Label Space. Applications. ODUk General Communication Channel (GCC). A More Immediate Horizon: GMPLS with SONET and SDH. Traffic Parameters. Summary. 11. The Link Management Protocol (LMP). Keep the Optical Link Up and Running. What is Managed. Data-bearing Links. Clarification of Terms. Basic Functions of LMP. LMP Messages. LMP Message Header. LMP TLVs. The Fields in the LMP Messages. Control Channel Management. Parameter Negotiation. The Hello Protocol. Link Property Correlation. Link Connectivity Verification. Fault Management. Extending LMP Operations for Optical Link Systems (OLSs). Link Summarization. Fault Management. Trace Monitoring. Summary. 12. Optical Routers: Switching in Optical Internets. The State of the Art in Optical Switching. Order of Preferences in Switching Implementations. Clarification of Key Terms. One Aftermath of September 11: Increasing Load on the Transport Networks. Evolution of Switching Technologies. The Speeds of Electronics and Photonics. An Optical Router. The Control Element. Optical Switching Technologies. Optical Resources. MicroElectroMechanical Systems (MEMS). Protecting the Label Switched Path. Protection of the Optical Switched Path (OSP). Correlating the Wavelength OSP with the MPLS LSP. Setting up the OSPs and LSPs Between Nodes H, I, and J. Setting Up a Protection Path Between Nodes H, G, and J. Recovery and Use of Protection Path. Expanding the Roles of Nodes G and I. Nesting the LSPs and OSPs. Topology Choices for a Node Failure. Plane Coupling and De-coupling. Some End-to-End Wavelengths and Some Node-to-Node Wavelengths. Granularity of Labels vs. Wavelength Support. Approach to the Problem of LSP and OSP Interworking. MEMS and Optical Switching Re-examined. Thermo-optic Switches. Bubble Switches. Summary. 13. ASON Operations at the User Network Interface (UNI) and the Network-to-Network Interface (NNI). Objectives of the ASON. The UNI and the NNI. Managing the Optical Bandwidth in the ASON. The General Approach to Optical Bandwidth Management. IETF Optical Carrier Framework for the UNI. Focus on OC-48/STM-16 and Above. UNI-SR (Subrates). Types of Connections. Connection Attributes. Identification Attributes. Connection Characteristic Attributes. Routing Constraints Attributes. The Network-to-Network Interface (NNI). NNI Signaling Requirements. Neighbor Discovery. NNI Topology and Resource Distribution Protocol. NNI Protocol Mechanisms. UNI and NNI Signaling Services. Summary. 14. ATM vs. IP in Optical Internets. IP over ATM over SONET. The OSI and Internet Layered Models. Placement of Core Protocols. PPP and L2TP. ATM in the SONET/SDH Payload Envelope. PPP in the SONET Payload Envelope. Prevalent Approach in Today's Internets. Encapsulation/Framing Rules. ATM and Frame Relay Framing Formats. Encapsulation Field Values. Encapsulation Options with SNAP. The PPP Packet. The ATM vs. IP Debate. Overhead of IP and ATM. Is the ATM Overhead Tolerable? Three Encapsulation Methods. Method 1: Conventional Approach. Method 2: Lightweight PPP. Method 3: Eliminating ATM. Summary. 15. Optical Internets: Evolving to a 3G Architecture. Migration to IP Optical Networking. IP and the Optical Backbone. Example of IP and l Forwarding. IP Subnets. Support of Non-optical Nodes. Placing MPLS into the Picture. Putting It Together. IP Routing Table. MPLS Cross-connect Table: Interface A. Optical Cross-connect Table: Interface A. Optical Cross-connect Table: Interface B.

A symmetric-structure CDMA-PON system and its implementation

Abstract: A code-division multiple-access (CDMA) passive optical network is proposed as an optical access network system to satisfy the subscriber's increasing data traffic. A CDMA scheme is used not only for delivering multiple channels to as many remote units, but also for suppressing optical beat noise. In this study, a beat noise environment is analyzed and a transceiver structure to efficiently increase the reverse link rate is suggested. Fundamental experimental results are provided to show its validity.

Optical communication system, optical communication unit, and optical transceiving package

Abstract: Cost-reduction in an optical communication unit is achieved by using spectrum-sliced modulated broadband light for transmitting upstream signals, instead of using laser light. An optical communication system includes at least one pair of optical communication units that each has a bi-directional network interface in which physical bit rates of transmission signals and reception signals are identical, an optical transmitter, and an optical receiver, and that performs bi-directional transmissions via at least one optical fiber. One optical communication unit includes a physical bit rate down-converter that lowers the physical bit rate of transmission signals from the bi-directional network interface and outputs to the optical transmitter, and the other optical communication unit includes a physical bit rate up-converter that raises the physical bit rate of signals received by the optical receiver and outputs to the bi-directional network interface. These optical communication units are also applicable to wavelength-division multiplexing systems.

Optical fiber protection switch

Abstract: An optical fiber protection switch that performs automatic protection switching. The optical fiber protection switch performs span and ring switching at the optical layer, thereby negating the need for SONET ADMs to perform the switching at the SONET layer. The optical fiber protection switch includes span switches and ring switches arranged to provide span and ring switching, respectively. The span switches and ring switches are implemented using 2×2 optical switches, for a total of eight 2×2 optical switches in the optical fiber protection switch. The system described herein may utilize SONET terminals and/or ATM switches in a WDM environment to support capacity increases while providing the ring and span switching functionality. A network switching element providing transparent, self-healing optical 4-fiber BLSR (OBLSR/4) is realized by using the optical fiber protection switch described herein.