Novel packet architecture for all-optical ultrafast packet-switching networks

Header recognition and packet detection in all-optical networks using on/off optical ultrafast signalling at a fixed wavelength can be implemented by means of recently demonstrated optical sampling AND gates. A novel packet structure in which the header is spread in a TDM fashion over the optical packet allows the number of such AND gates to be minimised in the routing and receiving blocks thereby best exploiting the required electronics.<>     

A 32-channel tunable receiver module for wavelength-division multiple-access networks

We report the realization of a 32-channel tunable optical receiver module for packet-switched multiwavelength computer networks. The tunable receiver consists of a planar array waveguide grating demultiplexer, photodetector array and followed by selectable receivers. The channel selection is based on sequential switching of the received optical signals in stages at the analogue level. Typical receiver sensitivity is -24 dBm at 10/sup -9/, using a 700-Mb/s nonreturn-to-zero (NRZ) pseudorandom binary sequence (PRBS). The channel switching time is /spl sim/40 ns.     

多域全光网络快速多链路故障定位机制

提出了一种运用于多域全光网络的多链路故障定位机制.该机制根据网络中的告警信息确定多链路故障发生域;通过边界节点收集的监测信息和告警信息定位域间多链路故障;对于域内多链路故障,在分离各单故障后基于LVM协议进行故障定位.仿真结果表明,该机制不仅能够陕速定位多域全光网络中的域间、域内多链路故障,而且具有较高的故障定位率.     

Efficient time gating in ultrafast optical TDM networks

Ultrafast optical communication is the backbone of high-speed global networking infrastructure. Optical time division multiplexing (OTDM) is a popular technique for embedding data from many simultaneous users on a single optical channel. This paper studies the optimal clock signal used in optical time gating to extract the data of the desired user in an OTDM network. We show that the pulse width of the clock signal can be optimized to achieve a minimum bit error rate (BER) in these networks. In this paper, we assume that the optical clock signal used for time gating has jitter, and there is therefore a delay variation between the clock and data signals. We model this delay as a zero mean Gaussian random variable. Using this model, an analytical BER expression is derived for systems with Gaussian pulses. In the numerical results, we find the optimal values of the clock pulse width by evaluating the BER versus the pulse width for different variances of the delay. Simulation results are also presented to evaluate the accuracy of the analytical expression.     

On fast algorithms for TDM switching assignments in terrestrial andsatellite networks

Bipartite graph and network circulation formulations of the TDM switching assignment problem are compared; a correct proof is given of the existence of a feasible circulation in the network model corresponding to a valid switching assignment. Dividing users into groups, an O(K⁴) algorithm for solving the assignment problem is described where K is the number of TDM lines, and a bound is derived on the number of switching configurations     

用于X波段相控阵天线的高速可调光纤延迟线

设计并制作了一种用于X波段相控阵天线的5bit光纤延迟线,采用高速磁光开关和单模光纤级联组成.测试结果显示,该光纤延迟线可实现时间延迟量在0～ 1096ps范围内步进为35.4ps的任意可调,延迟精度小于±2ps,开关切换时间小于30μs.     

Electronically tunable nondispersive magnetostatic wave delay line

An electronically tunable, nondispersive magnetostatic wave delay line consisting of cascaded magnetostatic backward volume waves and magnetostatic surface waves delay lines has been designed and realised. The distinguishing feature of the device is a wide continuously tunable time delay range of ±30% with the central value of 58 ns. An obtained bandwidth for constant time delay is ~300 MHz at a 3.15 GHz centre frequency. A deviation from constant delay is <±5%     

Novel scheme for ultrafast all-optical XOR operation

A novel scheme for all-optical exclusive-OR (XOR) operating at 160 Gb/s is proposed and analyzed by means of numerical simulations. It consists of a Mach-Zehnder interferometer (MZI) where a semiconductor optical amplifier (SOA) is placed in each of its arms. This SOA-MZI setup is coupled to a delay interferometer, which acts as a signal regenerator. It is shown that error-free operation can be achieved at a data rate of 160 Gb/s, indicating that the proposed scheme is not limited by the SOA recovery time.     

Electrically tunable delay line using an optical single-side-band modulator

The authors propose a tunable delay line using an optical single-side-band modulator, a fiber Bragg grating and an optical fiber loop. The number of times light circulates in the loop can be controlled by the electric signal fed to the modulator. Packets of any lengths can go through the proposed delay line without any collisions, even if the length of the packet is larger than that of the delay loop.     

A 6 × 320-MHz 1024-channel FFT cross-spectrum analyzer for radio astronomy

A wide-band FFT spectrum analyzer, which we call FX, has been in operation since 1983 at the Nobeyama Radio Observatory for spectroscopy of radio waves from interstellar molecules. It processes an input of six 320-MHz-bandwidth data streams to produce the output of fifteen cross-power spectra of 1024 frequency channels each. Its highly parallel pipeline architecture made it possible to achieve the above speed, 10¹⁰butterfly operations per second, which is 10⁵times that of usual mainframe computers. The FX incorporates about 4500 newly developed CMOS LSI chips. They are designed using CAD (computer-aided design) and have 3900 or 2000 gates/chip, operate at a clock rate of 10 MHz, and consume 100 mW/chip or less. For 80-MHz bandwidth signal at an optimum input level, the SNR (signal-power to noise-power ratio) of the FX is better than 10 dB, which is adequate for astronomical use.     

全光网中基于跳数的波长分配算法

在有波长连续性限制的情况下,减少波长预留冲突需要在波长预留时尽量使用不同的波长,这使全网的空闲波长数减少,容易导致大跳数光路的连接请求失败。解决波长预留冲突问题的大多数算法都把解决问题的目标设为降低网络阻塞率,无法兼顾网络中大跳数光路的情况。本文提出了用于全光网中基于跳数的波长分配算法,该算法通过建立跳数与波长之间的相互对应关系,对未来可能发生预留冲突的光路及其要预留的波长进行预测,根据预测尽量使用相同波长,增加全网的空闲波长数。在解决波长预留冲突问题的同时,实现支持大跳数光路连接请求的目标。     

A fast time slot assignment algorithm for TDM hierarchicalswitching systems

A fast (polynomial time) network-flow-based algorithm is presented for time slot assignment in time-division-multiplexing (TDM) hierarchical switching systems. For a nonblocking time-multiplexed central switch the algorithm produces a conflict-free time slot assignment for a given frame (whenever this is possible) on O(M ⁵) time, where M is the system size     

Lightpath concentrators for all-optical networks

In some deployments of all-optical networks, it is necessary to concentrate the lightpaths from some fibers to fewer fibers. An N/spl times/M lightpath concentrator is an optical component for this purpose, and it concentrates the lightpaths from N incoming fibers to M outgoing fibers. In this paper, three designs of N/spl times/M lightpath concentrators are proposed. The first design is a generalization of optical crossconnects, and it requires M/spl times/M optical switches. The second design incorporates the concept of partial concentration so that it requires only m/spl times/m optical switches (where m相似文献   

Topologies for wavelength-routing all-optical networks

Three regular meshed topologies are compared in light of their possible use for the implementation of large all-optical wavelength-routing communication networks (or interconnection systems). These systems provide all source-destination pairs with end-to-end transparent channels that are identified through a wavelength and a physical path. The considered topologies are the K-dimensional bidirectional square lattice, the twin shuffle, and the de Bruijn graph. The comparison is based on the maximum and average distance between source and destination (number of traversed nodes), on the degree of connectivity for each node (number of input and output fibers), and on the minimum number of wavelengths in the WDM comb necessary to discriminate all source-destination pairs     

Fast tunable wavelength conversion for all-optical packet switching

We demonstrate a simple scheme to achieve fast tunable wavelength conversion over a wide spectral range. The wavelength conversion is obtained by four-wave mixing in a semiconductor optical amplifier using a double-pump scheme, 2048-bit sequences at 2.5 Gb/s, incoming at a given wavelength, are alternatively converted toward two different wavelengths for a total conversion interval of 20 nm. With this method, the time needed to change the destination wavelength is much shorter than the bit duration. This feature makes any guard-time spacing between packets unnecessary. Bit-error-rate measurements show that the process occurs with negligible penalties (less than 0.3 dB).     

基于全光波长变换和色散介质的可调谐光延迟线

对基于四波混频全光波长变换与色散介质组合的可调谐光延迟线进行了实验研究。将420m长的高非线性光纤(HNLF)分别与普通单模光纤(SMF)和色散补偿光纤(DCF)组合,依次实现了1ns和3ns的可调谐光延迟,实验结果与理论结果非常一致。     

一种新的用于全光网的光交换技术

介绍了一种新的没有运动部件的光交换技术的原理、结构、性能、长期可靠性及其在未来全光网中的应用。     

A novel signaling nested reservation protocol for all-optical networks

This work proposes a new reservation protocol for enhancing the performance of wavelength-routed networks. To be more robust and reliable, the proposed approach employs distributed control mechanisms. The new method particularly focuses on wavelength-division multiplexed (WDM) core networks with distant end-nodes. It takes into account the considerable amount of data that can be transferred by high-speed WDM networks within limited reservation periods. To increase the throughput, the protocol consumes the unoccupied bandwidth of reservation phases by transferring nonreal-time data packets during these intervals. This scheme is implemented by applying a modified form of backward reservation protocol. To initiate a multihop reservation call, this protocol labels a path as reserved instead of locking it. Meanwhile, labeled nodes with single-hop requests will receive permission signals to send predetermined packet sizes. The length of packets transmitted is defined by the round-trip propagation delay between the current and the upcoming nodes along the path. In case a reservation fails, already labeled nodes will be notified by receiving a prevention signal, which will block them from transferring data packets.     

Physical topology design for all-optical networks

When designing an all-optical network, the designers face a choice of laying down more fibers or increasing the number of wavelengths. Although either choice could be used to support new connections, one increases the link cost and the other increases the node (wavelength equipments) cost. The tradeoffs between link and node cost are not well understood. Using the efficient physical topology design algorithm that we propose, we study this tradeoff. We use the asymptotic growth rate of the provisioned capacity as a metric to compare various design alternatives. A higher asymptotic growth rate translates directly into a higher deployment cost for large networks. Our study shows that taking fiber length into consideration can lead to lower capacity requirement. We also find that a sufficiently large fiber-to-node ratio is necessary in order to minimize the asymptotic growth in the provisioned capacity, increase capacity utilization and minimize the need for wavelength conversion. We study a real network and find that its fiber-to-node ratio is too low. As a result, large provisioned capacity is required and less than 55% of the capacity is usable. By increasing the ratio, we can reduce the provisioned capacity and achieve close to 80% utilization.