Quantitative monitoring of relative clock wander between signal and sampling sources in asynchronous optical under-sampling system

Optical performance monitoring using asynchronous optical or electrical sampling has gained considerable attention. Relative clock wander between data signal and sampling source is a typical occurrence in such systems. A method for the quantitative monitoring of the relative clock wander in asynchronous optical undersampling system is presented. With a series of simulations, the clock wanders recovered using this method are in good agreement with the preset clock wanders of different amounts and frequencies for both RZ and NRZ signals. Hence, the reliability and robustness of the method are proven.     

Reconfigurable optical differential phase-shift-keying pattern recognition based on incoherent photonic processing

We propose and experimentally demonstrate asynchronous optical differential phase-shift-keying (DPSK) pattern recognition using a fully reconfigurable technique. The proposed method uses optical phase-to-bipolar intensity conversion through all-optical differentiation in conjunction with an incoherent time-spectrum convolution system where the pattern to be recognized is implemented directly in the spectral domain through optical amplitude-only linear filtering. Full reconfigurability in terms of bit rate, pattern sequence, and pattern length is achieved using electronically programmable optical filters. We demonstrate dynamically switching recognition of different 64?bit patterns in a continuous 12?Gb/s DPSK pseudorandom optical bit stream with contrast ratio up to 3.8?dB.     

Ultrafast Photonic Asynchronous Transfer Mode Switch Based upon Parallel Signal Processing

An ultrafast photonic asynchronous transfer mode (ATM) switch is proposed that incorporates a holographic buffer memory and an optical parallel routing controller. Ultrafast serial-to-parallel conversion of the temporal profiles of optical cells into spatial patterns is used to process optical cells in space in a parallel manner. The spatial pattern of the data payload is holographically recorded as a page in the optical buffer memory. The routing control to establish the switching state consists of header recognition performed by optical matched filtering, followed by control signal generation via reference to a lookup table. The ultimate throughput of the switch is expected to be 103 Tb/s with line bit-rates of 17 Tb/s.     

Dual-wavelength operation of a figure-eight fiber laser

We study numerically an erbium-doped figure-eight fiber laser including a double-band-pass optical filter for dual-wavelength pulse generation. Simulations are performed for several values of the filter band-width and wavelength separation between the transmission windows. The results show that dual-wavelength mode-locking is obtained in most cases, with a balanced energy distribution between wavelengths. Due to cavity dispersion, the pulses at each wavelength are asynchronous for a large wavelength separation, whereas they are synchronous for closely spaced wavelengths, as in this case cross-phase modulation is able to compensate for the dispersion-induced walkoff. In the asynchronous case, dual-wavelength operation is favored by the filter loss, whereas in the synchronous case it is favored by the saturable absorber action of the nonlinear optical loop mirror. Simulations also show that, thanks to those stabilization mechanisms, dual-wave-length pulsed operation does not require precise cavity loss equalization between the two oscillating wave-lengths.     

Demonstration of an optical self-clocked time-division switch

A novel architecture for an optical time-division switch is investigated and demonstrated at a bit rate of 625 Mbit/s. The self-clocked configuration eliminates some of the limitations found in previous optical implementations of time-division switches: the switch operation is asynchronous, no read gate is required, and an optimal number of delay lines is used. Furthermore, this paper reports the first experimental demonstration of optical space-sorting demultiplexing.     

Demonstration of an optical self-clocked time-division switch

A novel architecture for an optical time-division switch is investigated and demonstrated at a bit rate of 625 Mbit/s. The self-clocked configuration eliminates some of the limitations found in previous optical implementations of time-division switches: the switch operation is asynchronous, no read gate is required, and an optimal number of delay lines is used. Furthermore, this paper reports the first experimental demonstration of optical space-sorting demultiplexing.     

针对WWW业务的光缓存优化设计

研究了异步光分组网中的输出光缓存问题，与以往不同的是在处理光分组到达时间间隔时采用Weibull分布，以便更有效地描述互联网中的WWW业务流量类型．通过建立基于Weibull分布的排队模型，得到了排队模型中的丢包率的解析式，并根据数值解得出了光缓存系统的丢包率、系统实际利用率、服务窗口利用率以及平均排队时间随光纤延时线单位缓存时间变化的关系曲线．研究结果表明：在不同的业务强度和缓存深度下选取恰当的单位缓存时间，可以优化光缓存系统的性能．     

Upstream Channel Utilization of CSMA/CD-Based Ethernet over Passive Optical Networks

We demonstrate that an asynchronous CSMA/CD protocol with an optical loop-back star coupler can achieve high upstream channel utilization in an Ethernet PON, readily supporting a large installed base of Ethernet 10BaseT and 100BaseT interfaces.     

光分组交换矩阵的实验研究

对光交换矩阵的基本机理进行了研究,介绍了所研制成功的光分组交换矩阵的基本结构、功能、性能和相关的实现技术,重点分析了质子交换型铌酸锂（APE：LiNbO3)光波导开关与相应的系统技术,给出了2．5Gbit/s异步转移模式（ATM）光信元交换实验研究结果。     

Enhanced performance analysis of optical CDMA communication system

Optical CDMA technique is required to meet the increased demand for high speed, large capacity communications in optical networks. OCDMA assures data access security and supports asynchronous burst data transmission. In this paper, improvement in optical CDMA has been done by implementing forward error correction technique and a distance of 100 km was achieved BER 10⁻¹⁹ at bit rate 3.75 Gbps with forward error correction in optical CDMA.     

10-Gbit/s Serial Optical Interconnection for an ATM Switch

Serial optical interconnection is proposed for connections in a Torus asynchronous transfer mode switch. A cross-point switch was developed that operates at a bit rate of 20 Gbit/s. The switching operation was successfully performed using cascaded cross-point switches through an optical interconnection configuration consisting of commercial optoelectronics devices. The measured switching rate was 10 Gbit/s, and it was limited by the responses of the optoelectronics devices.     

无人机异步图像数据采集系统设计

针对无人机遥感要求高空间分辨率、高光谱分辨率和高时间分辨率且体积小、重量轻,采用离轴三反消像散光学系统满足其大视场轻量化设计要求.提出各相机异步工作,采用单片现场可编程门阵列(FPGA)实现各异步相机数据整合并以同一参考时钟同步实时输出.介绍了整个异步图像数据采集系统的结构,采用FPGA内部的异步先进先出(first in first out, FIFO)实现两路不同时钟域数据按接收端时钟同步输出,在Xilinx ISE7.1环境下用Modelsim6.1进行了时序仿真,并进行了实际测试.实验结果表明:系统稳定可靠,整个成像系统焦距f=70 mm,相对孔径D/f=1/6,视场角2w=65°.采用两组线阵CCD相机工作,总重量仅6 kg.     

OMNI: An optoelectronic multichannel network interface based on hybrid CMOS-SEED technology

This paper presents a hybrid CMOS-SEED multiprocessor network interface smart pixel design that implements a reservation-based channel control protocol for collisionless concurrent access to multiple optical interprocessor communication channels. An asynchronous optical token is used as the arbitration mechanism for reservation control instead of slotted access. This work demonstrates that complex network protocol functions can be implemented using optoelectronic smart pixel technology.     

基于异步延迟采样的光通信性能监测方法

基于异步延迟采样和人工神经网络统计学习提出了一种光通信性能监测方法。通过对高速光信号进行异步延迟采样,获得信号二维幅度直方图,然后提取其中特征参数并对人工神经网络进行训练,最后以人工神经网络的预测输出实现对光信号损伤的监测。构建10 Gb/s非归零码开关键控,40 Gb/s光学双二进制码和归零码差分移相键控光通信仿真系统,并对光信噪比、色散和偏振模色散损伤进行监测。仿真结果表明,所提方法对被监测光信号的速率、码型调制格式透明,可同时准确监测多种并存的传输损伤,损伤参数监测误差小于5%。该方法具有电域处理带宽要求低、采样机制简单的特点,适用于分布式在线光性能监测。     

光突发交换的交换控制策略和光缓存配置

光突发交换是面向下一代互联网的光交换模式.讨论了异步光突发交换系统的交换控制策略以及相应光缓存的优化配置策略.除了传统预约模式的交换策略,还研究了非预约和改进型预约模式,它们的性能评估由计算机仿真给出.结果表明:在条件相当情况下,改进型预约模式具有最低的丢包率.同时光缓存的配置对上述几类交换控制策略的性能都有很大影响,仿真结果指出:光缓存的粒度对系统性能具有重要影响,所讨论的几类交换模式都存在最佳时延粒度,研究结果对光交换矩阵的设计有指导意义.     

Comparison of the performance of optical systems in fiber links 4000 km long

This article reports a numerical investigation of the performance of single-channel and WDM optical systems, assuming a fiber link 4000 km long in the presence of the Kerr effect, chromatic dispersion, and the amplifier spontaneous emission noise of the optical amplifiers. Both solitons and NRZ signals are considered, and IM-DD and coherent asynchronous ASK detections are used. Results on the technique of the midpoint spectral inversion are also reported.     

适用于同步光码分多址通信系统的同步光码及其全光可调编/解码器

异步光码分多址通信系统,要求用户地址码具有好的循环自相关和互相关特性,因此,系统中的用户数受到很大的限制;而对同步光码分多址通信系统,只要求光地址码是非循环相关意义下的准正交,从而可实现较大的用户数,因此具有广阔的应用前景.实现同步光码分多址的关键之一是同步光码的设计和可调光编/解码器的实现.本文介绍了同步光码的构造方法,给出了同步光码的构造过程,分析了码的容量,提出了全光可调同步光码编/解码器的实现方法.     

Ultrafast All-Optical Serial-to-Parallel Conversion and Its Application to Optical Label Processing

A novel scheme for all-optical serial-to-parallel conversion (SPC) is proposed for label recognition of ultrafast asynchronous burst optical packets. Compact SP converter modules were developed using a fiber array or a surfaceemitting planar lightwave circuit, and 1-Tbit/s and 40-Gbit/s SPC for 16-bit optical packets is demonstrated using the modules. The key device in the converter is a spin-polarized surface-reflection all-optical switch (LOTOS) with an ultrafast switching time (250 fs) and an extremely high on/off ratio (>30 dB). Label recognition of 40-Gbit/s 16-bit burst-mode optical packets is experimentally confirmed using an optical clock-pulse generator and a complementary metal-oxide-semiconductor (CMOS) electronics circuit as well as the all-optical SP converter. 1 x 4 self-routing is also demonstrated using 2-channel control signals generated from the CMOS circuit according to a routing table.     

Asynchronous cross-correlation for weak ultrafast deep ultraviolet laser pulses

We have developed a technique for the temporal characterisation of weak deep-ultraviolet (DUV) ultrashort laser pulses by combining asynchronous optical sampling with difference-frequency mixing. The intensity profile of picosecond DUV pulses, with peak powers as low as 2.5 W, have been measured accurately with a resolution of 50 fs. The method can be extended to complete amplitude and phase characterisation of few femtosecond laser pulses at DUV wavelengths.     

Emerging Trends in Fiber Optic Networks

We propose a novel scheme for interconnection of multiple high-speed (2.5 10 Gbit s) asynchronous transfer mode (ATM) streams through an optical wavelength division multiplexing (WDM) network with a total network capacity of up to 4 Tbit/s. The proposed architecture is based on placing the optical WDM portion of the network in a physically small area, i.e., one central office or in a single rack. This helps to avoid technological obstacles such as power budget, dispersion, and synchronization limitations as well as optical output buffering. The interconnection is an ATM packet switched network and provides optical contention resolution. We show that the implementation of such a network is possible using currently available optoelectronic technology. An optional extension of the network is proposed by a combination of WDM and space division multiplexing (SDM) technology. Simulation results are presented, indicating network throughput of up to 100 %.