Wavelength selective optical logic and interconnects

A wavelength selective optical logic (WSOL) element that uses monolithically integrated wavelength selective optical input and output elements is described. Input optical signals are detected by photothyristors situated in an optical cavity which provides a highly selective response of a wavelength determined by the fabrication process. Output signals are generated by vertical cavity surface emitting lasers, whose lasing wavelengths can also be specified during the fabrication process. A vertical integration of these input and output elements that is suitable for wavelength selective optical logic and wavelength selective optical interconnect applications is proposed. The proposed circuitry is easily cascadable so that arbitrarily complex optical logic functions can be performed by WSOL devices in series. Several of the possible logic functions are described, including OR and AND gates, an adder, and a flip-flop     

利用光纤参量放大器构成全光与门

利用光纤参量放大器(FOPA)中的波长转换特性完成全光与逻辑运算。以波长转换的原理为基础, 从两路输入光波的四种码字组合的相位匹配关系入手, 证明了FOPA的闲散光输出与两路输入光波的逻辑关系符合与门的逻辑。通过龙格-库塔方法数值求解非线性耦合方程组, 仿真证实了FOPA的输出与输入光波满足全光与门的逻辑, 研究了此全光与逻辑门闲散光波的输出功率随光纤长度、输入光波的功率比值以及输入光波波长位置的变化关系, 为实际中优化设计全光与门提供了参考。并对100 Gb/s的全光与逻辑运算中所应选择的输入光波脉冲宽度的问题进行了讨论。     

基于半导体光放大器的光单稳态触发器

为实现全光缓存中的光读写控制和光逻辑判断,提出并实验验证了一种基于半导体光放大器(SOA)双环结构的全光单稳态触发器。此触发器的稳态与非稳态激射不同的光波长,状态间静态消光比超过40 dB,切换时间仅仅为1-2个环腔周期,控制信号光波长范围大。通过减小环腔长度可进一步减小两状态之间切换时间,并可作为光缓存的控制单元。     

新型电光逻辑门的设计及计算机图形光谱

光逻辑门是未来全光网络中光信息处理的核心元件,它可以实现高速光包交换,全光地址识别,数据编码,奇偶校验,信号再生等功能。采用微环谐振器设计了一种新型的电光逻辑门,结构通过三个非对称微环组成,分析耦合区的传输矩阵方程得出加载电压信号的变化能够实现微环折射率的变化,利用光强的逻辑开关特性可以实现光门逻辑。计算机仿真验证了工作波长1 600 nm时,实现的高电平50.7 V定义为逻辑1,低电平0 V定义为逻辑0,通过光强变化得出了6位逻辑运算;整个系统的响应时间理论上得到了1.8 ps,运算速率可达近200 Gbit/s。逻辑的双稳态分析中得出:微环发生最大谐振值时对应的控制波长等于微环未发生形变前的谐振波长和偏移量之和;调制可以通过微环谐振波长实现控制。这一研究对于未来全光通信的实现具有一定的意义。     

All-optical signal processing based on semiconductor optical amplifiers

In this paper,we review the recent progress in the optical signal processing based on the nonlinearity of semiconductor optical amplifiers (SOAs).The four important optical signal processing functional blocks in optical switching are presented,i.e.,optical wavelength conversion,optical regeneration,optical logic,and optical format conversion.We present a brief overview of optical wavelength conversion,and focus on various schemes to suppress the slow gain recovery of the SOA and improve the operating speed of the SOA-based optical switches.Optical regeneration including re-amplification,re-shaping and re-timing is also presented.Optical clock recovery that is essential for optical regeneration is reviewed.We also report the recent advances in optical logic and optical format conversion,respectively.After reviewing the four important optical signal processing functional blocks,the review concludes with the future research directions and photonic integration.     

Optoelectronic logic operations by cleaved-coupled-cavity semiconductor lasers

We propose and demonstrate the operation of a new opto-electronic scheme of performing the set of logic operations including AND, OR, EXCLUSIVE OR, and INVERTER. The present scheme is not based on optical bistability, but rather utilizes the unique characteristics of the newly developed cleaved-coupled-cavity (C³) semiconductor laser. The C³laser always operates in a single longitudinal mode and the lasing wavelength can be tuned by varying the current levels (pulsed or dc) injected into the two optically coupled stripe-geometry laser diodes. Unlike the case of optical bistable devices (based on FP semiconductor diodes), which operate on optical inputs and produce optical outputs, the present device operates on electrical inputs and produces optical outputs. In addition to performing the logic operations, this can also serve as an electrical-optical interface. Further, the present scheme is also capable of producing multiple different logic outputs simultaneously for the same two inputs. Results from time-resolved spectral measurements using InGaAsP buried crescent lasers (lambda = 1.3 mum) showed that the switching time was in the subnanosecond region. This indicates that extremely high bit rate information processing in the Gbit/s range can be achieved by using the present C³semiconductor lasers as the logic gates. The present C³lasers are very compact (sim300 times sim200 mum) and rigid, and the scheme can be applied to semiconductor lasers with other types of stripe geometries and wavelengths.     

Photonic switching technology: component characteristics versusnetwork requirements

Components for switching in the optical domain offer substantially different characteristics than electronic switches. However, except in special cases these characteristics do not immediately map well onto the network requirements as currently perceived so that there remains great challenge in establishing a viable technology. A variety of photonic switching technologies are discussed in this context. They are: passive pathway switches with electrical control active-path optical switches with electrical control; optically controlled electronic logic; optically controlled optical logic; and wavelength routing technologies. Optimum component and technology choices are discussed     

Optical logic functions using a tunable wavelength conversion laserdiode

The authors demonstrate optical logic functions of an inverter (NOT) and an exclusive-OR (XOR) using a tunable wavelength conversion (TWC) laser diode developed as a component in optical wavelength division multiplexing (WDM). The TWC laser's optical functions are easily changed by varying bias current settings in gain sections. At just above the turn-on threshold, the TWC laser acts as an optical inverter. At just below the turn-off threshold, it acts as an optical XOR element. The mechanism of both NOT and XOR operations is based on gain quenching accelerated through a saturable absorber, a major feature of the TWC laser. Single longitudinal-mode lasing and the tunability of the lasing wavelength, other features of the TWC laser, are effective in distinguishing lasing light signals from input light signals     

Nonlinear gain in vertical-cavity semiconductor optical amplifiers

We report on the wavelength-dependent nonlinear-gain properties of a vertical-cavity semiconductor optical amplifier. A step-like output versus input transfer curve and bistability are found on the long wavelength side of the resonant peak. The characteristics are caused by a dispersive nonlinearity arising from gain saturation in the device. The nonlinear transfer of the amplifier could be used for logic regeneration and all-optical logic operations, while the optical injection power required to switch the device is an order of magnitude lower than previously reported with edge-emitting devices.     

Wavelength-discriminating photodetector for lightwave systems

We demonstrate that a dual-wavelength photodetector can be used to determine simultaneously the wavelength and the power level of a lightwave signal. The signal wavelength is determined by monitoring the ratio of the two outputs from this photodetector at the crossover of its responsivity curves; the signal level is determined from the sum of the two outputs. Possible applications for this type of photodetector include mode-control of single-frequency injection lasers, direct demodulation for lightwave systems utilising frequency-shift-keyed transmission, wavelength-division multiplexing and optical logic.     

Efficient reversible NOR gates and their mapping in optical computing domain

Reversible logic is a computing paradigm in which there is a one to one mapping between the input and the output vectors. Reversible logic gates are implemented in an optical domain as it provides high speed and low energy computations. In the existing literature there are two types of optical mapping of reversible logic gates: (i) based on a semiconductor optical amplifier (SOA) using a Mach–Zehnder interferometer (MZI) switch; (ii) based on linear optical quantum computation (LOQC) using linear optical quantum logic gates. In reversible computing, the NAND logic based reversible gates and design methodologies based on them are widely popular. The NOR logic based reversible gates and design methodologies based on them are still unexplored. In this work, we propose two NOR logic based n-input and n-output reversible gates one of which can be efficiently mapped in optical computing using the Mach–Zehnder interferometer (MZI) while the other one can be mapped efficiently in optical computing using the linear optical quantum gates. The proposed reversible NOR gates work as a corresponding NOR counterpart of NAND logic based Toffoli gates. The proposed optical reversible NOR logic gates can implement the reversible boolean logic functions with a reduced number of linear optical quantum logic gates or reduced optical cost and propagation delay compared to their implementation using existing optical reversible NAND gates. It is illustrated that an optical reversible gate library having both optical Toffoli gate and the proposed optical reversible NOR gate is superior compared to the library containing only the optical Toffoli gate: (i) in terms of number of linear optical quantum gates when implemented using linear optical quantum computing (LOQC), (ii) in terms of optical cost and delay when implemented using the Mach–Zehnder interferometer.     

光通信网络中的信号导向逻辑器件设计

基于"导向逻辑"设计了一种应用于光通信网络的新型光信息流导向器件。采用微环谐振器作为光波导元件,应用折射率调制机理,实现了基于聚合物基的多功能电光逻辑门。通过改变不同端口的逻辑输入分别实现了"与/非"、"或/或非"和"同或/异或"等多种状态的光开关逻辑运算。静态仿真确定了微环谐振器的工作波长,验证了器件具有高速率逻辑运算功能。该器件可用于大规模光学集成电路中,实现高速光信号的调制输出。     

Nonlinear operations of 1.55-μm wavelength multielectrodedistributed-feedback laser diodes and their applications for opticalsignal processing

The nonlinear behavior of inhomogeneously excited 1.55-μm wavelength multielectrode distributed-feedback laser diodes, such as self pulsation and multistability for both injection current and for injection light, is described. Wavelength bistability is also described. Optical signal processing applications are experimentally demonstrated; they include optical logic circuits, optical memories, an optical demultiplexer, an optical timing extractor, and optical regenerative repeaters     

Quality of service aware fuzzy dynamic routing and wavelength assignment technique in all optical networks

In this paper, a novel fuzzy dynamic routing and wavelength assignment technique is proposed for a wavelength division multiplexing optical network to achieve the best quality of network transmission. This paper proposes a novel quality of service aware fuzzy logic controlled dynamic routing and wavelength assignment algorithm (QoS-FDRWA), where the optimum path is chosen by a fuzzy rule-based inference system. The proposed fuzzy routing technique incorporates optical network transmission attributes such as latency, physical length of the link, data packet loss, number of hops, and wavelength availability status in the path.     

Design proposal of a photonic multicast Bloom filter node

This paper presents the design of a hardware accelerated forwarding architecture for processing packets that are labelled with a Bloom Filter (BF)-based header. The architecture consists of a conventional broadcast-and-select all-optical switching fabric, composed of Semiconductor Optical Amplifiers (SOAs), and a hardware-based Serial Processing Unit (SPU) that uses an on-the-fly processing mechanism to forward optical packets. The proposed SPU avoids the use of memory units and uses a small number of logic gates that facilitate a straightforward all-optical implementation using photonic logic gates. The SPU also supports flexible wavelength multicasting by allowing each incoming wavelength to be forwarded to any number of output ports. Contention resolution is provided by the introduction of an Optical Delay Line (ODL) that provides a single-packet optical buffer if the output channel is occupied.     

Synchronization of passively mode-locked erbium-doped fiber lasersand its application to optical communication networks

We synchronized two passively mode-locked erbium-doped fiber lasers using a phase lock loop with a large dynamic range and bandwidth, which is realized by using a novel acoustooptic-modulator-grating scheme. Cross-correlation of the two lasers shows the interlaser jitter is under 2 ps (same as the laser pulse width) for period as long as hours. To prove the quality of phase locking, we apply synchronized lasers in two all-optical network applications, one of which requires the lasers to have the same wavelength and the second requires the lasers to be at different wavelengths. In the single wavelength application, the synchronized lasers drive a cascade of two low-birefringence, polarization maintaining, optical logic gates with switching timing window of 4 and 5 ps, respectively. We obtain nonlinear transmission of ~50% at a switching energy of 8 pJ and contrast ratio of 16 dB, which are comparable performance as that obtained using a single laser. In the different wavelength application, we use 0.8 ps pulses to switch 2 ps pulses in a two-wavelength nonlinear optical loop mirror demultiplexer with timing window of 5.5 ps. Stable switching is reached at a efficiency as high as 90% at switching energy of 0.8 pJ, and a contrast ratio of 20 dB. Excellent agreement is found between the experimental data and the simulated results, which exclude the timing jitter     

All-optical network subsystems using integrated SOA-based optical gates and flip-flops for label-swapped networks

In this letter, we demonstrate that all-optical network subsystems, offering intelligence in the optical layer, can be constructed by functional integration of integrated all-optical logic gates and flip-flops. In this context, we show 10-Gb/s all-optical 2-bit label address recognition by interconnecting two optical gates that perform xor operation on incoming optical labels. We also demonstrate 40-Gb/s all-optical wavelength-switching through an optically controlled wavelength converter, consisting of an integrated flip-flop prototype device driven by an integrated optical gate. The system-level advantages of these all-optical subsystems combined with their realization with compact integrated devices, suggest that they are strong candidates for future packet/label switched optical networks.     

WDM packet routing for high-capacity data networks

We present experimental and numerical studies of a novel packet-switch architecture, the data vortex, designed for large-scale photonic interconnections. The selfrouting multihop packet switch efficiently scales to large port counts (>10 k) while maintaining low latencies, a narrow latency distribution, and high throughput. To facilitate optical implementation, the data-vortex architecture employs a novel hierarchical topology, traffic control, and synchronous timing that act to reduce the necessary routing logic operations and buffering. As a result of this architecture, all routing decisions for the data packets are based on a single logic operation at each node. The routing is further simplified by the employment of wavelength division multiplexing (WDM)-encoded header bits, which enable packet-header processing by simple wavelength filtering. The packet payload remains in the optical domain as it propagates through the data-vortex switch fabric, exploiting the transparency and high bandwidths achievable in fiber optic transmission. In this paper, we discuss numerical simulations of the data-vortex performance and report results from an experimental investigation of multihop WDM packet routing in a recirculating test bed     

All-optical logic NOR gate using two-cascaded semiconductor optical amplifiers

The authors present a novel all-optical logic NOR gate using two-cascaded semiconductor optical. amplifiers (SOAs) in a counterpropagating feedback configuration. This configuration accentuates the gain nonlinearity due to the mutual gain modulation of the two SOAs. The all-optical NOR gate feasibility has been demonstrated delivering an extinction ratio higher than 12 dB over a wide range of wavelength.     

一种基于反射式SOA的FBG传感解调方法

提出一种基于反射式半导体光放大器（R-SOA）的光纤Bragg光栅（FBG）传感解调方法。周期性调谐R-SOA与可调谐FBG构成的窄带可调谐激光器,当其输出波长与FBG传感器反射波长一致时,由光电探测器输出光电流最大判断2个FBG周期的匹配并完成对传感FBG周期的测量。测量结果表明,FBG传感器中心波长在1 551.9...