Design of a Two-layer Scalable Wavelength Routing Optical Interconnection Network

In this paper, a two-layer scalable wavelength routing optical interconnection network is presented. The top layer of the network is a multi-wavelength bi-directional optical bus which has high-bandwidth and low-latency; the sub-layer of the network is single-wavelength synchronous pipelined ring which has low communication latency and high-scalability. The way to implement the optical system of the network is put forward, and the synchronous pipelined optical interconnect ring is designed and implemented.     

Use of WDM technique in SDH networks

This paper proposes the introduction of the multiwavelength technique in the three layers of a SDH-based network. In the trunk layer, wavelength division multiplexing (WDM) takes advantage of the optical parallelism in a single fiber. Cross-connection can be achieved either passively (i.e., with tunable filters) or by means of wavelength converters. The latter solution, which offers high flexibility, was implemented in a 4 × 4 optical routing element. In the junction network the feasibility of a three-station WDM self-healing ring was demonstrated. Finally, in the access network, synchronous burst access and time and wavelength division multiplexing (T/WDM) switching is proposed to offer service flexibility to the subscribers.     

具有旋转连接功能的双层光互连网络设计

在设计的双层光互连网络中,上层网络是星型连接,依靠数字路由结点进行通信.单通道最大传输速率为1.4 Gbps,数字路由结点吞吐率大于10 Gbps,底层为网络接口卡和结点机连成的环形网,峰值传输速率为1.056 Gbps.在底层网络中个别结点机与传感器之间配置有光纤旋转连接器,可传输动态数据.经计算,环网内最大通信延迟时间小于5.292 μs,互连网络的平均通信延迟时间为11.03 μs,环形网络的最大数据传输带宽为50 Mbit/s.     

光互连技术在信号处理中的某些应用

叙述了近年来在天津大学研究及开发光互连网络的情况。这些研究围绕着解决信号传输中的延迟和通信带宽,开展的研究工作有：完成包括64个处理器的光电混合处理器阵列系统;giga—bit／s机群系统光互连链路;在链路中采用时分复用技术(TDM),实现了“虚拟并行传输”;在链路中设计了硬件路由功能,并组成光环网;在网络系统中实现波长路由,并建立了波长路由双环网,采用该技术可以避免路由延迟;在光互连网络中应用了MEMS光开关,实现了星型一环形二级结构;用同步光传输技术实现了多通道数据传输卡。     

光梯度力驱动的纳米硅基光开关

通过一道光改变另一道光的传输路线是光子集成网络中重要而长远的目标, 然而, 由于硅材料的光学非线性较弱, 在硅材料上实现开关的全光控制难以实现. 因此本文提出了一种由光梯度力驱动的纳米硅基光开关, 实现了硅基光开关的全光控制. 该光开关由一个部分悬空的微环谐振器和一个交叉波导结构构成, 当通入一道控制光时, 悬空的微环谐振器在光梯度力的作用下发生弯曲, 微环谐振器的谐振波长随之发生变化, 从而实现光信号的传输路线发生改变. 该光开关利用纳米光子制造技术在标准绝缘体上硅晶圆上制造, 实验数据得出其最小消光比为10.67 dB, 最大串扰为 -11.01 dB, 开关时间分别为180 ns和170 ns. 该光开关具有尺寸小, 响应速度快, 低损耗和可拓展等优点, 在片上集成光路、高速信号处理以及下一代光纤通信网络中具有潜在应用.     

基于光纤光栅波长路由的光纤自愈网

介绍了一种基于光纤光栅波长路由的全光双纤单向自愈环网,环内四节点具有16×10Gbit/s的传输能力。利用啁啾光纤光栅(CFBG)的波长可选择特性,实现了分布式的上下话路和波长选择功能,同时有效地补偿了传输色散。网络管理参照了网络管理协议(SNMP)的网络管理模型,通过对网络的重要参数进行实时监测来控制网络运行。实验结果表明,当环上任一处光缆发生故障时,通信业务能够自动恢复,恢复时间小于50ms,可实现网络的快速自愈,符合ITU-T G.841的建议规定。     

Design and Implementation of a Virtual Multi-channel Optical Ring

The hardware and the communication protocol of a scalable optical ring have been designed. A hardware routing has been achieved on the network interface card to minimize data packet communication latency and a simplified communication protocol has been designed to reduce communication overheads. To reduce the data packet blocking probability and have a more efficient usage of the data link layer bandwidth, a virtual multi-channel transmission mechanism has been achieved. The network supports a maximum of 16 virtual channels for each physical data link. Time slots can be dynamically assigned to each virtual channel. Zero wait time has been achieved for the switching between different virtual channels.     

Design and Implementation of a Virtual Multi-channel Optical Ring

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High Speed All-Optical Data Distribution Network

This article describes the performance and capabilities of an all-optical network featuring low latency, high speed file transfer between serially connected optical nodes. A basic component of the network is a network interface card (NIC) implemented through a unique planar lightwave circuit (PLC) that performs add/drop data and optical signal amplification. The network uses a linear bus topology with nodes in a “T” configuration, as described in the text. The signal is sent optically (hence, no latency) to all nodes via wavelength division multiplexing (WDM), with each node receiver tuned to wavelength of choice via an optical de-multiplexer. Each “T” node routes a portion of the signal to/from the bus through optical couplers, embedded in the network interface card (NIC), to each of the 1 through n computers.     

ATMOS (ATM optical switching)—system perspective

The expected traffic growth from new broadband services will require network capacities that can be beneficially provided by optical WDM transport networks. Optical packet techniques are essential for large networks to provide flexibility and granularity. A layered network architecture with a transparent optical layer and optical packet layers has been elaborated. Four switching concept options for large optical ATM switch fabrics in the public network and small access nodes are presented. The technology for the related key functions of space and wavelength switching was developed in the RACE ATMOS project and the feasibility of concepts and technologies was verified in four system demonstrators.     

基于光纤环形激光器和光放大的100 km光纤布拉格光栅传感系统

在基于掺铒光纤-拉曼混合放大的可调光纤环形激光器的光纤布拉格光栅(FBG)传感系统结构基础上,提出了延长传感距离的新方法。该方法以环形掺铒光纤激光器作为光源,采用双波长拉曼放大的方法对信号进行低噪声的双向放大,系统中间的两段掺铒光纤再利用剩余的抽运功率产生自发辐射光和放大传感信号,使得整个系统能够在超长的传感距离上获得很高的信噪比。实验表明使用一只40 mW的掺铒光纤放大(EDFA)抽运源、一只170 mW的拉曼抽运源和一只2 W的拉曼抽运源,可以使整个系统的传感距离达到100km,并且传感系统的光纤布拉格光栅反射信号均能获得超过57 dB的优良信噪比,从而实现在超长距离上的光纤布拉格光栅传感。     

Nature-Inspired Routing and Wavelength Assignment Algorithms for Optical Circuit-Switched Polymorphic Networks

Polymorphic optical networks simultaneously support several optical switching paradigms over a single physical network. In this way, they provide service differentiation at the optical layer by employing the most appropriate paradigm for each service. One type of such architecture is the optical circuit-switched polymorphic network (OCSPN), which combines optical circuit switching paradigms with different grades of dynamism. The performance of this network relies on the utilization of efficient routing and wavelength assignment (RWA) algorithms. In this article, we review the fundamentals of OCSPNs and present a set of efficient RWA algorithms based on ant colony optimization and genetic algorithms.     

Nature-Inspired Routing and Wavelength Assignment Algorithms for Optical Circuit-Switched Polymorphic Networks

Polymorphic optical networks simultaneously support several optical switching paradigms over a single physical network. In this way, they provide service differentiation at the optical layer by employing the most appropriate paradigm for each service. One type of such architecture is the optical circuit-switched polymorphic network (OCSPN), which combines optical circuit switching paradigms with different grades of dynamism. The performance of this network relies on the utilization of efficient routing and wavelength assignment (RWA) algorithms. In this article, we review the fundamentals of OCSPNs and present a set of efficient RWA algorithms based on ant colony optimization and genetic algorithms.     

Optical modulator using metal-oxide-semiconductor type Si ring resonator

Electric-field drive optical modulators using a Si ring resonator were fabricated on silicon-on-insulator (SOI) wafers. The fabricated resonators consisted of Si waveguides with width and thickness of 1.0 and 0.3 μm, respectively. In order to induce the linear electro-optic (EO) effect in the Si core layer, the strain was applied by covering the layer with Si₃N₄ film (0.26 μm thick) deposited by low pressure chemical vapor deposition (LPCVD) at 750 °C. The vertical electric-field was applied to the Si waveguide through the top and bottom cladding layers, and the optical output from the drop port at the resonance wavelength was measured. At a wavelength of 1501.6 nm, the optical modulation of 33% was obtained at 200V (electric-field at the silicon surface ∼3 × 10⁵ V/cm, nearly the breakdown field). The resonance wavelength was shifted toward the short wavelength side by applying both positive and negative voltages, this shift was explained by carrier concentration modulation. The linear EO effect in the Si core layer was not observed, presumably because the strain in the Si core layer was too small.     

Wavelength conversion in optical transport networks

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical amplifiers (SOAs) and on cross-phase modulation (XPM) obtained by two SOAs put in an interferometric configuration. An analysis of transmission performances of optical transport networks employing both types of wavelength conversion and both the node architectures is reported. The performances are evaluated by means of a system modeling that facilitates considering physical phenomena occurring during transmission and all the important transmission impairments. The analysis reveals that both the types of converters can be employed with different features and limitations, according to the considered network and switching architecture.     

基于半导体光放大器和整形滤波器的40 Gb/s的归零正码波长变换研究

理论上分析了通过整形滤波器方法实现正码波长变换的原理,并讨论了滤波器带宽及偏移方向对正码脉冲效果的影响,解释了目前实验报道中多采用蓝移滤波方案的技术根由。在实验上利用半导体光放大器(SOA)和通带滤波器完成了40Gb/s的归零码波长变换实验,验证了理论分析的结构,证明了整形滤波器加半导体光放大器的方案可以实现正码的波长变换。这对于简化网络的设计,提高信号传输质量都有重要的意义。     

All‐optical virtual private network in passive optical networks

We review recent progress on all‐optical virtual‐private‐network (VPN) schemes in passive optical networks (PONs). PON is a promising candidate in future access areas to provide broadband services with low cost. With all‐optical virtual private network (VPN) function, PON can support efficient internetworking among end users with dedicated optical channels, thus enabling guaranteed bandwidth and enhanced security at the physical layer. Here, we discuss and compare existing schemes of all‐optical VPNs in time‐division‐multiplexed (TDM) PONs, and also recently proposed schemes for deployment in wavelength‐division‐multiplexed (WDM) PONs and two‐stage TDM/WDM PONs.     

Investigation of wavelength division multiplexed hybrid ring-tree-star network topology to enhance the system capacity

In this paper, we have investigated wavelength division multiplexed (WDM) hybrid (ring-tree-star) topology. Eight optical add/drop multiplexers (OADMs) are used to make ring structure. The single mode fiber and dispersion compensating fiber and semiconductor optical amplifier (SOA) are employed between each OADM to achieve a maximum. To increase the number of users each OADM node of ring network is connected to star and tree network topology which can accommodate more than 2048 users. Various system parameters (for different channel spacing, different input power signal, different data rates and the fiber length) are varied to investigate the system performance in the term of BER and Q factor.     

WDM光网络安全生存机制研究

针对WDM光网络安全生存性问题的故障的发现、定位和恢复三个重要环节之中的恢复问题,提出了一种WDM光层中的安全保护与恢复方案。采用了恢复路由选择算法和恢复波长分配算法,提出了一种混合的多层恢复机制,从而构建了一种从故障的发现、定位到故障恢复的覆盖各环节的连续性光网络安全生存机制,并在理论上进行了性能比较。     

A Simple Configuration for Discontinuous Wavelength-tuning Optical Pulse Source

A simple configuration is proposed to perform wavelength switching in actively mode-locked fiber ring lasers, in which a sampled fiber Bragg grating and a tunable optical filter are cascaded in the ring cavity to exactly select the operating wavelength. The switching of four wavelengths with a spacing of 1.6 nm is obtained. The experimental results demonstrate that this technique is reliable and convenient.