Demonstration of the highly reliable Hikari router network based on a newly developed disjoint path selection scheme

Integration of multiprotocol label switching functions and multiprotocol lambda switching functions can enhance the throughput of IP networks and remove bottlenecks that are derived from electrical packet processing. To enhance the packet forwarding capability, NTT proposed a photonic MPLS concept that includes MP/spl lambda/S, and demonstrated IP, MPLS, and photonic MPLS integrated router systems called the photonic MPLS router. This router system is now called the Hikari router. The word Hikari is Japanese meaning beam, light, lightwave, optical, photonic, and sunshine. The amount of IP data traffic has grown remarkably. Massive IP routers and flexible route control mechanisms are now required to cope with the increased amount of traffic. The Hikari router can offer two solutions utilizing photonic switching technologies, and photonic network operation and management technologies. The first solution is utilizing photonic switching technologies realized using optical-switch-based crossconnect systems. The other solution is realized using the MPLS and MP/spl lambda/S signaling protocol and photonic network protection functions. In this article we report on the implementation of the Hikari router systems, propose a newly developed disjoint path selection scheme for generalized MPLS networks with shared risk link group constraints, and demonstrate the signaling protocol and network protection functions. The demonstration system achieves a distributed optical path set-up/tear-down protocol with an extended constraint-based routing label distribution protocol. Fast self-healing through automatic protection switching and a new restoration scheme are also implemented. These functions are successfully implemented, and the performance is verified on a demonstration network. The protection switching scheme achieves protection in less than 20 ms, and the optical path restoration scheme achieves restoration in less than 500 ms.     

通信网中电交换与光交换的协作运用

简单地介绍现时通信网中同时存在电交换和光交换两类设施和它们互相协作运用,以取得较好效果。文中对这两类交换作了比较,接着说明它们的协作运用。     

Picosecond switching dynamics of a bistable-wavelength-latchtwo-segment distributed feedback laser

The bistable-wavelength-latch operation of a two-segment distributed-feedback laser was observed and characterized. Short electrical trigger pulses were used to demonstrate mode power switching in less than 200 ps with only 450-ps delay between set and reset pulses. Spectrally resolved measurements show transient spectral broadening during the bistable wavelength switching. Fast laser wavelength switching is important for wavelength-division-multiplex photonic switching systems     

Photonic switching technology: component characteristics versusnetwork requirements

Components for switching in the optical domain offer substantially different characteristics than electronic switches. However, except in special cases these characteristics do not immediately map well onto the network requirements as currently perceived so that there remains great challenge in establishing a viable technology. A variety of photonic switching technologies are discussed in this context. They are: passive pathway switches with electrical control active-path optical switches with electrical control; optically controlled electronic logic; optically controlled optical logic; and wavelength routing technologies. Optimum component and technology choices are discussed     

A compact optical active connector: an optical interconnect modulewith an electrical connector interface

This paper describes a compact optical active connector that has both optical and electrical interfaces for an asynchronous-transfer-mode (ATM) switching system and high-speed computer network systems. This connector with an O/E or E/O conversion module can replace the conventional electrical-cable six-pin connector for an ordinary printed circuit board that has only an electrical interface. Our connector consists of a specially developed duplex MU-type submodule with photonic devices, an electrical connector, and integrated circuits (ICs). It can be used for 620-Mbps data transmission and has lower electromagnetic radiation noise than conventional connectors. Using optical active connectors to replace electrical-cable connectors will facilitate the introduction of high-throughput, large-capacity ATM switching systems, and next-generation local area network systems     

B-ISDN waits for photonics to deliver

A variety of photonic switching techniques have been studied from the viewpoint of expanding switching-mode throughput. The basic issue discussed is how the high bandwidths of optical devices can be applied to switching nodes. It is shown that a high time-domain bandwidth allows high-speed signal transmission without waveform distortion, a high frequency-domain bandwidth allows a system to accommodate a large number of channels, which results in a high-capacity system, and a high space-domain bandwidth allows high-density interconnections in free space and resolves the pin-out bottleneck of LSIs and multichip modules (MCMs). Photonic space-division switching, photonic ATM switching, photonic frequency-division switching, and photonic free-space switching methods are described     

Large-scale WDM star-based photonic ATM switches

This paper describes the large-scale photonic asynchronous transfer mode (ATM) switching systems being developed in NTT Laboratories. It uses wavelength division multiplexing (WDM) techniques to attack 1 TB/s throughput. The architecture is a simple star with modular structure and effectively combines optical WDM techniques and electrical control circuits. Recent achievements in important key technologies leading to the realization of large-scale photonic ATM switches based on the architecture are described. We show that we can obtain a 320 Gb/s system that can tolerate the polarization and wavelength dependencies of optical devices. Our experiments using rack-mounted prototypes demonstrate the feasibility of our architecture. The experiments showed stable system operation and high-speed WDM switching capability up to the total optical bandwidth of 12.8 nm, as well as successful 10 Gb/s 4×4 broadcast-and-select and 2.5 Gb/s 16×16 wavelength-routing switch operations     

Payload-envelope detection and label-detection integrated photonic circuit for asynchronous variable-length optical-packet switching with 40-gb/s RZ payloads and 10-gb/s NRZ labels

A photonic integrated circuit that performs 40-Gb/s payload-envelope detection (PED) and 10-Gb/s label detection for asynchronous variable-length optical-packet switching is demonstrated. The circuit consists of an InP photonic integrated device combined with electronic GaAs and InP devices on a carrier. Asynchronous variable-length optical packets with 40-Gb/s return-to-zero (RZ) payloads and 10-Gb/s non-RZ (NRZ) labels are processed by the circuit. The circuit outputs a PED electrical signal that represents the temporal location of the payload and a 10-Gb/s electrical signal representing the optical label. The optical label is detected error free. The PED signal has a rise/fall time of 3-ns and 150-ps jitter. The PED signal was also used to erase and rewrite the optical labels error free.     

Photonic fast packet switching

Several approaches to photonic fast packet switching systems are presented. The wavelength-, time-, code-, and space-division approaches, including free-space photonic fast packet switching, are discussed. These approaches to photonic fast packet switching systems show that the research in this area is still in its infancy. Among various solutions, those based on a wavelength-division transport network and an electronic controller are most mature     

光交换技术谈

论述了在全光通信网络技术中将发挥重要作用的光交换技术 ,比较详细地介绍空分光交换、时分光交换、波分光交换、ATM光交换、码分光交换、自由空间光交换和复合型光交换等 7种光交换技术 ,并对光交换技术的市场和技术发展前景进行了描述。     

Photonic switching fabrics

The strengths and limitations of the photonic technology are reviewed, beginning with the temporal bandwidth limitations of photonic devices and then focusing on spatial bandwidth, commonly referred to as the parallelism of optics, and how it can be used in photonic fabrics. Some of the proposed photonic switching fabrics that are based on guided-wave devices are discussed, comprising switching fabrics based on space channels, using directional couplers and optical amplifiers, and those based on time channels. The latter include active reconfigurable fabrics based on TDM, time-slot interchangers, and universal time slots, in addition to passive shared media fabrics. Some of the switching fabrics that have been proposed using wavelength channels are outlined, and multidimensional fabrics are briefly reviewed. Photonic switching fabrics based on free-space devices are described, covering free-space relational switching fabrics, the basic hardware required for digital free-space optical fabrics, and digital free-space switching fabrics     

Bipartite graph design principle for photonic switching systems

Several attributes of a bipartite graph are exploited in designing switching systems. First, in a network based on bipartite graphs, no two paths are allowed to intersect at a vertex. This attribute is used to design a directional coupler-based photonic switching network with very low crosstalk. Since crosstalk is the most limiting factor in constructing a large directional-coupler-based photonic switching network, crosstalk reduction on the device and architecture levels is an important design issue. Secondly, broadcast, which is an intrinsic property of a bipartite graph (the same is always true with a crossbar representation), is used in designing multiconnection switching networks. Thirdly, it is shown that the nonplanar nature of bipartite graphs makes them well suited for designing three-dimensional free-space-transmission photonic switching systems     

Studies on semiconductor optical amplifiers for line capacityexpansion in photonic space-division switching system

The problems associated with introducing traveling wave amplifiers (TWAs) to photonic space-division (SD) switching systems are examined. Experiments were carried out to clarify the TWA noise effect and interference between cascaded TWAs, using about 10-dB gain TWA modules. Possibility of a 128-line photonic SD switching system, using current polarization-independent LiNbO₃ 8×8 switch matrices, has been shown through the experiments. The possible line capacity value of the photonic SD switching system with TWAs is examined theoretically. It is shown that the expected line capacity value for such a switching system exceeds 10³     

光交换技术的现状及发展趋势

光交换技术是未来全光网络（AON）中的关键技术。本文论述了光交换技术的现状及发展趋势，并对我国发展光交换技术提出个人的建议。     

Optical cross-connect system incorporated with newly developedoperation and management system

The optical cross-connect (OXC) system described in this paper increases the operation flexibility and reliability of the trunk-line optical networks used for data communication. It features an OXC node comprised of a photonic switching network and a conventional electric switching network that are connected hierarchically. The operation and management scheme proposed for this OXC system uses the concept of an optical path and an optical section. The OXC system allows hitless network reconfiguration by switching the photonic switches gradually and without interference effects. An experimental OXC network showed that a broken optical path is restored, by rerouting, within 50 ms. Experiments using a LiNbO₃ 8×8 photonic switch matrix also showed that the OXC system provides photonic hitless switching. These results confirm the feasibility of flexibly reconfigurable and fast-restorable OXC systems     

A wavelength-tunable duplex integrated light source for fastwavelength switching

A new monolithically integrated opto-electronic device has been developed for fast wavelength switching in photonic packet switching. The integrated device, called a tunable duplex integrated light source comprises two distributed Bragg reflector lasers (DBR-LDs), two electroabsorption optical switches, a Y-shaped waveguide coupler, an electroabsorption modulator, and two thermal drift compensators (TDCs). The tuning range of the DBR-LDs is 3 nm, and the wavelength switching time of the optical switches is estimated to be 60 ps including a 50 ps rise time for the electrical pulse generator. The wavelength of a 10 Gb/s NRZ-modulated optical signal is switched without bit loss. Thermal crosstalk between the DBR-LDs, and wavelength drift of the DBR-LDs, which is due to a thermal transient, are effectively suppressed by thermal-drift-compensation operation using the TDCs     

High-dimensionality shared-medium photonic switch

A space-division photonic switch which has the potential to achieve high dimensionality is presented. The proposed switch, which resembles a collapsed network, does not use optical crosspoints; rather a dedicated path is provided for all input/output port connections on a common high-bandwidth transmission medium. This eliminates the restrictions imposed by 2×2 switching elements in classical space-division switching fabrics. The demonstration of a fully connected 120×120 space-division time-multiplexed photonic switch is reported. The dimensionality and blocking performance of a shared-medium photonic switch that uses time-multiplexing is analyzed     

Communication network needs and technologies-a place for photonicswitching?

Projects the potential for photonic switching and control in networks by reviewing historic trends in technology and system development, analyzing application needs as a source of requirements on the technologies, and characterizing the limitations of competing electronic and photonic technologies for performing these functions. The author concludes that `all optical' switching systems concepts are in their infancy and are one to two decades away from any real usage. Such optical structures will by then most likely involve radically different concepts from electronic switches, as opposed to being photonic analogs of switching elements. Deployment of more limited application photonic subsystems in hybrid electrooptical structures are, however, distinct possibilities in earlier time frames     

Blocking performance with crosstalk consideration of the photonicswitching networks based on electrooptical directional couplers

Crosstalk is a fundamental task in electrooptical directional coupler-based photonic switching systems. A good design must balance the amount of hardware and the level of crosstalk. In this paper, we study the tradeoff between these two parameters in designing Banyan-type photonic switching systems based on electrooptical directional couplers. We develop a novel simulation technique that can significantly reduce the simulation time     

Wavelength routing-based photonic packet buffers and theirapplications in photonic packet switching systems

Photonic packet buffers are essential components in photonic packet switching systems. We present a wavelength routing-based photonic packet buffer based on a state-of-the-art arrayed-waveguide grating (AWG) multiplexer. We show how this new packet buffer can be effectively used in the implementation of photonic packet switching systems. We also propose and examine two different photonic packet switch architectures