高速全光型时分解复用器

全光时分解复用器是光时分复用（ＯＴＤＭ）系统的关键器件。本文分析了基于光纤交叉相位调制、半导体激光放大器（ＳＬＡ）和四波混频（ＦＷＭ）等三种高速非线性光子开关的工作机理,讨论并比较了一般型、环境型和马赫－曾特干涉仪型三种单级全光解复用器的结构配置和工作特性。     

An Enhanced SOA-Based Double-Loop Optical Buffer for Storage of Variable-Length Packet

To extend the buffer depth of a fiber loop optical buffer, we have experimentally demonstrated an enhanced semiconductor optical amplifier (SOA)-based dual-loop optical buffer (DLOB) for storing variable-length optical packets. We have theoretically derived constraints governing the buffer depth of the DLOB, in which the SOA not only provides a nonlinear phase shift in the loop to implement the buffer function but also compensates for the fiber loop attenuation during long-time storage. It is found that the maximum allowable length of a stored packet to avoid the counter-propagation packet collision inside the SOA depends on the SOA bias position as well as the length of the fiber loop. To demonstrate the effectiveness of the proposed enhanced configuration, we have successfully demonstrated the storage of 2.5-Gbps variable-length packets even when the length of the input packet exceeds the corresponding length of the fiber loop. Another unique advantage of the proposed enhanced DLOB configuration is that it can also overcome the problem of power leakage of the stored packet due to a directional gain difference of single SOA and gain saturation. Index     

All-optical loadable and erasable storage buffer based on parametric nonlinearity in fiber

We present a loadable and erasable all-optical fiber storage buffer based on parametric gain and cross-phase modulation (XPM) loading. The gain is provided by a phase-sensitive amplifier (PSA), implemented as a Sagnac interferometer, and relies on the nonlinear interaction within standard dispersion-shifted fiber. PSAs inherently have the property of stabilizing ones and zeros and thus eliminate the need to use optical filters within the buffer, or the need for any other kind of intensity discriminator. The action of the PSA is then twofold. It provides the gain and also achieves bistability of the buffer, which gives it an advantage over a linear amplifier such as erbium-doped fiber amplifier for our experimental configuration. External data are written into the buffer using wavelength-induced XPM. This method is insensitive to the optical phase of the incoming data and thus does not require tracking of its phase. The buffer is erased by employing a nonlinear optical loop mirror as a switch. We demonstrate storage of picosecond pulse packets at bit rates of 1 Gb/s for periods of time up to 1 ms.     

Design Analysis of Optical Loop Memory

This paper describes the fiber optic loop buffer-based switch in which contention is resolved in the time and wavelength domain. In the loop buffer, tunable wavelength converters (TWCs) are placed in place of semiconductor optical amplifiers (SOAs) as in conventional loop buffer-based architectures. The placement of TWCs inside the buffer facilitate simultaneous read/write operation and dynamic re-allocation of wavelengths and improves the switch performance significantly. It is a well known fact that the re-circulating type buffer structure suffers from circulation limit (maximum revolutions that data can take in the buffer) due to the loss and noise accumulation in the switch. This paper presents a mathematical model to obtain a maximum number of allowed circulations of the data in loop buffer-based switch architecture. This model is derived for various configurations (transparent, noisy, and regenerative) of TWC. The detrimental effect of crosstalk and four wave mixing are shown, and the affect of dispersion on the maximum allowed bit rate is discussed. The minimum length of the loop is also evaluated. Finally, the bounded region is shown (bit rate versus number of wavelengths graph) where memory can work efficiently.     

基于光纤环的光缓存器

提出了一种基于光纤环的光缓存器的结构,对结合半导体光放大器作光开关的此结构的物理模型进行了详细描述,并根据此模型分析了其增益、噪声、信噪比等方面的特性.     

One million pulse circulations in a fiber ring using a SLALOM forpulse shaping and noise reduction

The distinctly nonlinear input-output characteristics of a nonlinear element consisting of a semiconductor laser amplifier (SLA) in a loop mirror configuration (SLALOM) that may be utilized for pulse shaping and noise reduction is described. As an example, it is shown that nearly unlimited circulations of optical pulses in a fiber ring are possible     

SLALOM: semiconductor laser amplifier in a loop mirror

The processing of optical signals in the optical domain is an important issue resulting from the desire to take advantage of the full bandwidth of the optical fiber. In this paper, we present detailed investigations on a device, which utilizes a semiconductor laser amplifier in a loop mirror configuration (SLALOM). Different modes of operation are reported like nonlinear single pulse switching and two-pulse switching at different operation speeds (1-100 Gb/s). Furthermore, a number of applications of the SLALOM in photonic systems, like pulse shaping, decoding, retiming and time-division demultiplexing, are presented. In addition, the SLALOM can be used for an estimate of the linewidth enhancement factor α and the carrier lifetime τ _e in an SLA     

A Complete 8-GHz QPSK-MODEM Featuring Novel Subcarrier and Data Synchronization for Optical Communications

We describe the application of subcarrier multiplexing (SCM) to enable broadband transmission beyond the modal bandwidth of multimode fiber (MMF) optical links. The application of a quadrature phase-shift keying modem featuring novel carrier and symbol-timing recovery circuits, demonstrates significant enhancement in channel capacity. By using a 2.7-GHz pilot-tone-injected phase-locked loop (PLL) and referencing subscriber data to a prescaled version of the subcarrier, zero-latency carrier and data synchronization has been achieved exhibiting 675 Mb/s bit-oriented clock extraction in network terminal equipments. The novel scheme is scalable to higher aggregate rates and upgrades to existing installed-base 50 mum MMF infrastructure to provide low-cost, high-capacity interconnects for storage area and campus network applications     

10-Gb/s Wavelength Transparent Optically Controlled Buffer Using Photonic-Crystal-Fiber-Based Nonlinear Optical Loop Mirror

We have proposed and experimentally demonstrated a 10-Gb/s optically controlled buffer using a photonic-crystal-fiber (PCF)-based nonlinear optical loop mirror for all-optical packet-switched networks. The 10-Gb/s data can be stored in the buffer up to a period of 2.5 mus. By using the cross-phase modulation property between the control signal and the data signal inside the PCF, the total length of the fiber used in the buffer can be shortened to 30.9 m. The stored data packets are retrieved after they are stored in the memory for 2,4,..., and 12 round-trips. Independent bit-error-rate (BER) measurements have been carried out. The maximum power penalty is 3.3 dB at 1550 nm. The proposed buffer is wavelength transparent. For data packets stored in the C-band, the maximum power penalty after the data are stored in the memory for 12 round-trips is 3.5 dB at the BER of 10^-9     

自适应弹性环光缓存结构设计及其网络性能分析

最大缓存时间限制、时延粒度限制、光分组长度限制3大限制因素,对传统光缓存器的前馈型和反馈型两种结构进行了分析。分析表明,影响光缓存器性能的3大限制因素在两种结构中的相互制约关系限制了光缓存器性能的进一步提高。在此基础上提出的一种自适应弹性环光缓存器(E-FLOB)结合了两种传统结构的优势,并分离了3大限制因素间的相互制约关系。结构分析显示,E-FLOB在缓存级数为16时可减少反馈型光缓存器噪声积累约3个数量级。网络性能仿真表明,弹性环结构比前馈型结构使用更少的缓存级数,获得比两种传统结构更低的分组丢失率。     

新型波导多层光存储原理和实验

一种新型的波导多层存储器(WMM)由多层平面光波导叠合构成，利用波导缺陷记录数据，通过缺陷的光散射效应读出数据，并利用波导对光的空间约束作用实现层选址。制作了10层WMM模型器件，并给出了数据读出原理性实验结果。结果表明：WMM的层内信噪比大，层间信号串扰小，是一种很有潜力的三维光存储技术。     

7 Gbit/s optical JK flip flop design with two optical AND gates and NOR gates

This study presents a simple methodology for implementation of all optical JK flip flop for future optical high speed networks. The scheme utilizes electronic model of JK flip flop for implementation of all optical JK flip flop at the bit rate of 7 Gbit/s. Firstly, all-optical AND and NOR gates are implemented. Furthermore, with the combination of these basic gate structures, the optical model of JK flip flop is verified. This structure makes use of two optical AND gates and two optical NOR gates. This technique uses a semiconductor optical amplifier (SOA) as the nonlinear medium to produce considerable amount of cross gain and cross phase modulation to attain truth table conditions of optical JK flip flop. In this method, the number of gates is reduced as compared to earlier schemes. Rise time and fall time of 5.6 ps with contrast ratio more than 60 dB are achieved in this design.     

Subscriber single-mode optical fiber ribbon cable technologiessuitable for midspan access

The loop network configuration and high-fiber-count, single-mode optical fiber ribbon cable and jointing technologies which enable a quick response to service demand and offer high reliability in the subscriber network are described. Fiber parameters were chosen for 1.3/1.55-μm wavelength division multiplexing (WDM) transmission, and a 1000-fiber cable composed of 8-fiber ribbons was developed. A mass-fusion splicing technique and a multifiber connector were developed for the fiber ribbon. These techniques were evaluated by constructing an experimental line. It was found that they are highly suitable for midspan access, which is indispensable for the high-fiber-count loop network     

半导体光放大器的光-光互作用及在全光信号处理中的应用(Ⅱ)

半导体光放大器(SOA)中非线性系数约为普通光纤的109倍,为光子晶体光纤的107倍.有4种光-光互作用,即交叉增益调制、交叉相位调制、交叉偏振调制和四波混频,可以灵活地组成各种光信号处理器件,如波长变换器、全光触发器、全光逻辑、全光时钟恢复、全光缓存器,正成为整个光信号处理的基础.介绍了这些技术的同时,分析当前应用的制约因素,指出半导体光放大器集成是下一步发展的必然趋势.     

高性能光纤参量放大器的设计与应用

近年来,光纤参量放大的发展非常迅猛。分析了提高光纤参量放大增益、扩展带宽、降低偏振灵敏度的几种重要方法,并就光纤参量在分立式集中放大、透明的波长转换、归零脉码生成、OTDM开关、全光抽样、可擦除全光缓存、3R再生等方面的典型应用进行了全面综述。光纤OPA在DWDM系统、全光网等领域将有非常广泛而重要的运用。     

三种基于EDFA的全光逻辑门及其应用

利用掺铒光纤放大器的增益缓变吸收和放大光脉冲信号的特性,结合光纤耦合器和萨格纳克干涉仪,提出了三种的不同结构的全光逻辑门,并分析了此三种全光逻辑门的优缺点和各自的用途。     

High-speed buffer management for 40 gb/s-based photonic packet switches

We develop a method of high-speed buffer management for output-buffered photonic packet switches. The use of optical fiber delay lines is a promising solution to constructing optical buffers. The buffer manager determines packet delays in the fiber delay line buffer before the packets arrive at the buffer. We propose a buffer management method based on a parallel and pipeline processing architecture consisting of (log/sub 2/N+1) pipeline stages, where N is the number of ports of the packet switch. This is an expansion of a simple sequential scheduling used to determine the delays of arriving packets. Since the time complexity of each processor in the pipeline stages is O(1), the throughput of this buffer management is N times larger than that of the sequential scheduling method. This method can be used for buffer management of asynchronously arriving variable-length packets. We show the feasibility of a buffer manager supporting 128 /spl times/ 40 Gb/s photonic packet switches, which provide at least eight times as much throughput as the latest electronic IP routers. The proposed method for asynchronous packets overestimates the buffer occupancy to enable parallel processing. We show through simulation experiments that the degradation in the performance of the method resulting from this overestimation is quite acceptable.     

Self-Clocked All-Optical Add/Drop Multiplexer for Asynchronous CDMA Ring Networks

In this paper, we demonstrate a novel self-clocked code-drop unit for incoherent optical code-division multiple-access (CDMA) networks. The unit is based on an all-optical thresholder with internal wavelength conversion that creates a control signal for the drop gate from the incoming data stream. This architecture does not require an external clock signal for drop operation and can be used in asynchronous ring networks. The proposed unit is experimentally demonstrated for two-dimensional time-wavelength optical CDMA codes at a bit rate of 2.5 Gbit/s with two different types of drop gates: terahertz optical asymmetric multiplexer and nonlinear fiber-based loop mirror. Error-free operation is achieved in both configurations. The development of a self-clocked add/drop multiplexer demonstrates a novel concept of asynchronous node operation in multiple access networks.      

New unipolar codes allowing electrooptical correlation utilizing a semiconductor laser amplifier

This letter reports on the development of a new code allowing the use of a semiconductor laser amplifier (SLA) to execute correlation in the optical domain. Semiconductor laser amplifiers act as AND gates and can only correlate codes in the unipolar domain and therefore have been limited by the lack of unipolar codes with good autocorrelation properties. The authors propose a new unipolar code derived from bipolar Golay codes which has a high probe duty cycle (50%) and is ideal for use with an SLA based correlator. Computer modeling of an SLA correlator used to interrogate a sensor network is described, indicating crosstalk levels of less than 0.7%.     

半导体光放大器的光-光互作用及在全光信号处理中的应用(Ⅰ)

半导体光放大器(SOA)中非线性系数约为普通光纤的109倍,为光子晶体光纤的107倍.有4种光-光互作用,即交叉增益调制、交叉相位调制、交叉偏振调制和四波混频,可以灵活地组成各种光信号处理器件,如波长变换器、全光触发器、全光逻辑、全光时钟恢复、全光缓存器,正成为整个光信号处理的基础.介绍了这些技术的同时,分析当前应用的制约因素,指出半导体光放大器集成是下一步发展的必然趋势.