多波长光交叉连接节点的优化设计

在WDM光网络中，光交叉连接（OXC）节点的串扰是限制网络规模的关键因素，提高光开关的隔离度是降低OXC串扰的一条途径，文章比较了3种不同结构的光开关矩阵的串扰特性，在此基础上对OXC节点进行了优化设计，改进后的OXC节点的串扰性能大的改善，网络规模也因此而得到了极大地扩展。     

A novel integrated-optic WDM cross-connect for wide area all optical networks

The authors propose a novel design for an integrated-optic wavelength-division-multiplexing (WDM) cross-connect that can be used in routing network applications at various wavelengths. The device is based on integrating a two-dimensional array of Bragg diffraction cells at cross points of input/output (I/O) coplanar waveguides. The wavelength tuning of the individual Bragg cells can be chosen to produce a WDM cross-connect with any number of required I/O interconnections. These cross-connects have proved extremely useful in the design and deployment of wide-area/nationwide all-optical networks.<>     

High-level fluctuation tolerant optical receiver for optical packetswitch and WDM cross-connect

This paper proposes a high-level fluctuation tolerant optical receiver for optical packet switches and WDM cross-connects. We describe the tolerance of an experimental receiver to packet-level fluctuation and coherent crosstalk. The sensitivity of the experimental receiver was -26.9 dBm for the packet receiver configuration and -32.7 dBm for the WDM cross-connect configuration at the bit rate of 10 Gb/s. In the setup for level-fluctuating packet reception, the power-penalties of 1.1 and 4.6 dB were observed with 6 and 10 dB of fluctuation, respectively. As a WDM cross-connect, the sensitivity penalties of the receiver under the coherent crosstalk powers of -15 and -12 dB were 2.5 and 6.5 dB, respectively     

Large-capacity optical path cross-connect system for WDM photonictransport network

This paper demonstrates our previously developed large-capacity optical path cross-connect (OPXC) system. The major hurdles to be cleared are (1) establishment of a highly modular architecture that facilitates hardware design and upgrading and (2) the development of an OPXC demonstrator designed to achieve 320-Gbit/s throughput capacity. Due to the use of planar lightwave circuit technologies, compact size packaging for an 8×16 delivery-and-coupling type optical switch and an arrayed-waveguide grating for a wavelength-demultiplexer are achieved. The dense packaging of the four-channel optical regenerators (3-R function regenerator) makes it possible to realize a large-capacity OPXC that can offer high quality transmission and ensure robustness in terms of multiple node connection. Performance test results confirm the validity of the system design and the feasibility of 320-Gbit/s OPXC implementation     

Solid state optical space switches for network cross-connect andprotection applications

Network protection and reconfiguration is becoming increasingly important in fiber optic communications systems. This is driven by the intense traffic and high cost of lost high-data-rate optical connections. Optical cross-connects at the nodes in transmission systems are developing rapidly in response. A key optical component required for these applications is an optical space switch. Since the required timescale of network reconfiguration at the optical level is on the order of 50 ms to prevent electrical intervention. The optical space switching speed must be approximately 5 ms or faster. The demand created by these applications has motivated the development of a solid state optical space switch based on a novel planar-waveguide technology. This planar integrated optics technology relies on the thermo-optic effect in specialized optical polymer materials and results in reliable optical space switches without moving parts to wear out. This article reviews the state of the art in solid state optical space switches based on thermo-optic polymers and applications of these switches in network communication systems. The same polymer-based planar waveguide technology used to make the solid state optical space switches of today provides the basis for WDM devices. Electro-optic modulators, and devices integrating several functions (space switching, wavelength multiplexing, light generation and detection) in one component in the years to come     

Analytical model for a WDM optical cross-connect with limitedconversion capability

We introduce a general model for describing the connection setup in various wavelength-routing optical cross-connects with limited conversion capability. It enables us to determine if a given connection pattern can be supported, and to calculate the blocking performance of the cross-connects     

多波长光传送网的保护

介绍了多波长光传送网的一些基本优点,并和ＳＤＨ网络作了简单的对比,详细介绍了多波长光传送网的保护和故障恢复,特别是光环形网的保护倒换和故障恢复功能,最后对系统性能检测和保护判据的确定作了简单的论述。     

Asymmetric sampled grating laser array for a multiwavelength WDM source

We propose a multiwavelength laser array associated with asymmetric sampled grating lasers. The laser was designed to operate at the first-order reflection of a sampled grating with the aid of an index shifter. A four-channel laser array with 400-GHz wavelength spacing was fabricated and its operation at designed wavelengths was confirmed. Individual lasers showed a threshold current of 11-17 mA and slope efficiency of around 0.18 W/A. A high side-mode suppression ratio over 39 dB was observed as well.     

Mini-slot TDM WDM optical networks

In recent years, optical transport networks have evolved from interconnected SONET/WDM ring networks to mesh-based optical WDM networks. Time-slot wavelength switching is to aggregate the lower rate traffic at the time-slot level into a wavelength in order to improve bandwidth utilization. With the advancement of fiber-optics technologies, continual increase of fiber bandwidth and number of wavelengths in each fiber, it is possible to divide a wavelength in a fiber into time-slots, and further divide a time-slot into mini-slots so that the fiber bandwidth can be more efficiently utilized. This article proposes a router architecture with an electronic system controller to support optical data transfer at the mini-slot(s) of a time-slot in a wavelength for each hop of a route. The proposed router architecture performs optical circuit switching and does not use any wavelength converter. Each node in the mini-slot TDM WDM optical network consists of the proposed router architecture. Three different network topologies are used to demonstrate the effectiveness and behavior of this type of network in terms of blocking probability and throughput.     

WDM cross-connect architectures with reduced complexity

With the arrival of wavelength division multiplexed (WDM) systems carrying large numbers of wavelength channels, it appears that new cross-connect architectures that allow large numbers of wavelength channels to cross-connect at the wavelength granularity level are required. We propose a number of such architectures. The different architectures are compared in terms of complexity, cost, loss, crosstalk and filter narrowing. An analysis of the various nonblocking properties of such cross-connects is also described     

WDM Ethernet passive optical networks

WDM EPONs not only allow for cautious pay-as-you-grow upgrades of single-channel TDM EPONs but also avoid linearly increasing polling cycle times for an increasing number of ONUS. In this article, we first provide a comprehensive overview of the state of the art of TDM EPONs and recently reported dynamic bandwidth allocation algorithms, including decentralized scheduling schemes. After reviewing previous work on WDM EPONs, we address the requirements of WDM upgraded EPONs and make recommendations on an evolutionary WDM upgrade at the architecture, protocol, and dynamic bandwidth allocation algorithm levels, taking backward compatibility with MPCP and future-proofness against arbitrary WDM ONU structures into account. We describe and compare online and offline scheduling paradigms for WDM EPONs. Our simulation results indicate that online scheduling can achieve lower delays, especially at high loads. We outline areas of future research on WDM EPONs.     

N/spl times/N multiwavelength optical cross-connect based on tunable fiber Bragg gratings

We propose a highly channel-scalable multiwavelength optical cross-connect (OXC) based on tunable fiber Bragg gratings (TFBGs), which is suited for metropolitan or access networks. N/spl times/N OXC of this architecture is constructed by cascading independently operating routing modules, and each routing module consists of fiber Bragg gratings (FBGs) with fixed center wavelength and a TFBG-based N/spl times/N routing block. The group velocity dispersion (GVD) and intraband crosstalk (IXT) are the main signal-degrading factors arising from the operation of the proposed OXC, and the effectiveness of each factor is individually investigated numerically for 10-Gb/s nonreturn-to-zero (NRZ) systems. Then, a routing experiment of the proposed OXC is carried out in a 3/spl times/3 routing block configuration, using OC-192 signals with channel spacing of 0.8 nm. Finally, the installable size of the proposed OXC and network scale are estimated by resorting to a comprehensive numerical simulation of 10-Gb/s NRZ signal transmission.     

WDM光网络中的业务量疏导

波分复用（WDM）技术在主干传送网中巳广泛应用，WDM光网络的研究进展也非常迅速，光网络中的业务量疏导定义为复用、解复用和交换低速率业务流到大容量的光路中的行为。介绍了WDM光网络的业务量疏导的重要性，研究方法及其最新研究进展情况。     

WDM网络波带交换算法分析

主要介绍了WDM光网络中的波带交换(Waveband Switching)问题的基本概念、技术特点.并分析了研究波带交换问题与波长路由问题(RWA)的不同之处,总结了波带交换算法常用的分析和研究方法.     

Polarization independent dilated WDM cross-connect on InP

A four wavelength 2×2 optical wavelength-division-multiplexed cross-connect with dilated switches is reported. The device is monolithically integrated on InP and consist of two eight-channel PHASAR's combined with 16 electrooptic Mach-Zehnder interferometer switches. On-chip loss is less than -17 dB and crosstalk is better than -20 dB     

Protection interoperability for WDM optical networks

The failure of a single optical link or node in a wavelength division multiplexing (WDM) network may cause the simultaneous failure of several optical channels. In some cases, this simultaneity may make it impossible for the higher level (SONET or IP) to restore service. This occurs when the higher level is not aware of the internal details of network design at the WDM level. We call this phenomenon “failure propagation.” We analyze three types of failure propagation, called “bottleneck,” “connectivity,” and “multiple groups.” Then we present a solution based on the definition of appropriate requirements at network design and a WDM channel placement algorithm, protection interoperability for WDM (PIW). Our method does not require the higher level to be aware of WDM internals, but still avoids the three types of failure propagation mentioned above. We finally show the result on various network examples     

Design protection for WDM optical networks

With wavelength division multiplexing (WDM) networks the failure of a single link or component may cause the simultaneous failure of several optical channels, potentially making impossible restoration by rerouting directly in higher layers directly using the optical network (SDH, ATM, internal protocol (IP)). To address this, we introduce the concept of design protection, which aims at making such failure propagations impossible. We present the disjoint alternate path (DAP) algorithm which places optical channels in order to maximize design protection. We show the result on various network examples     

Provisioning algorithms for WDM optical networks

This paper concerns connection provisioning for optical networks employing wavelength division multiplexing. A heuristic algorithm is developed and numerically studied for routing and wavelength assignment of a set of static connection requests. The algorithm runs much faster than the optimum solution of this problem. An adaptation of the algorithm is proposed to design restorable networks which can handle a specified set of failures. The proposed algorithm is based on taking all failures into consideration simultaneously, and performs better than developing independent designs for each failure     

Lightpath restoration in WDM optical networks

Optical networks employing wavelength-division multiplexing and wavelength routing are potential candidates for future wide area networks. Because these networks are prone to component failures and carry a large volume of traffic, maintaining a high level of service availability is an important issue. This article discusses providing tolerance capability to the optical layer in WDM-based transport networks. It presents a survey on restoration schemes available in the literature, explains the operation of these schemes, and discusses their performance.     

Scalability of optical multiwavelength switching networks:crosstalk analysis

The scalability of optical multiwavelength switching networks with respect to bit rate, number of wavelength channels per fiber, and number of inputs/outputs per optical node is examined. The limits considered here are those imposed by the combination of interferometric crosstalk, optical noise accumulation, and optical amplifier gain saturation. An analytical model that combines these effects is described. For the class of optical cross-connects examined, the number of first- and second-order crosstalk contributions per node for different node architectures and node sizes is derived. The results show that with a carefully designed optical cross-connect architecture, it should be possible to construct a fairly large meshed all-optical network (more than ten nodes in diameter with 32 inputs/outputs per node and 32 wavelengths per fiber) if the crosstalk of optical space switches, multiplexers, and demultiplexers is about -30 dB