Polarization encoded all-optical quaternary successor with the help of SOA assisted Sagnac switch

The application of multi-valued (non-binary) signals can provide a considerable relief in transmission, storage and processing of large amount of information in digital signal processing. Optical multi-valued logical operation is an interesting challenge for future optical signal processing where we can expect much innovation. A novel all-optical quaternary successor (QSUC) circuit with the help of semiconductor optical amplifier (SOA)-assisted Sagnac switch is proposed and described. This circuit exploits the polarization properties of light. Different logical states are represented by different polarization state of light. Simulation result confirming described method is given in this paper. Proposed all-optical successor circuit can take an important and significant role in designing of all-optical quaternary universal inverter and modulo arithmetic unit (addition and multiplication).     

Polarization-encoded all-optical quaternary multiplexer and demultiplexer - A proposal

Multi-valued logic is positioned as a coming generation technology that can execute arithmetic functions faster and with less interconnect than binary logic. Furthermore, nonbinary data storage would require less physical space than binary data. The application of multi-valued digital signals can provide considerable relief of capacity constraints. In electronics many proposals have already been reported. But, here for the first time we propose an all-optical circuit for designing quaternary (four-valued) multiplexer and demultiplexer with the help of some polarization-encoded basic quaternary logic gates (quaternary min and quaternary delta literal). Nonlinear interferometer-based optical switch can take an important role here. The principles and possibilities of design of all-optical quaternary multi-valued multiplexer and demultiplexer circuits are proposed and described.     

All-optical pseudorandom binary sequence generator with TOAD-based D flip-flops

An all-optical pseudo random binary sequence (PRBS) generator is designed using serially interconnected discrete Terahertz Optical Asymmetric Demultiplexer (TOAD)-based D flip-flops in a configuration exactly like the standard electronic setup. The performance of the circuit is evaluated through numerical simulation, which confirms its feasibility in terms of the choice of the critical parameters. The proposed scheme has been theoretically demonstrated for a 3-bit and 7-bit degree PRBS but can be extended to higher order by means of additional TOAD-based D flip-flops. Thus it can constitute an efficient solution for implementing all-optically a PRBS in an affordable, controllable and realistic manner.     

Eliminating the additional input beam in all-optical XOR gate using Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometer: A theoretical analysis

All-Optical XOR Logic is a key technology for performing a set of operations in optical time division multiplexing (OTDM) multi-access network. In this paper an All-Optical Boolean XOR logic gate with Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch is designed and described. In this proposed XOR gate, no additional input light source is used. Numerical simulation is also presented, which verifies the theoretical results. Contrast ratio, extinction ratio, amplitude modulation, bit error rate and signal to noise ratio values have also been analyzed.     

Semiconductor optical amplifier (SOA)-assisted Sagnac switch for designing of all-optical tri-state logic gates

Tri-state logic plays a significant role in carry free arithmetical operation. Design of all-optical scheme of three basic tri-state logical operation (NOT, AND, OR) with the help of polarization encoded semiconductor optical amplifier (SOA)-assisted Sagnac interferometric switch has been studied and investigated in this present paper. Numerical simulation is also presented, which verifies the theoretical results. Insertion loss, contrast ratio, extinction ratio, amplitude modulation, bit error rate and signal to noise ratio values have also been analyzed.     

Demonstration and characterisation of a non-inverting all-optical read/write regenerative memory

An all-optical regenerative memory device using a single loop mirror and a semiconductor optical amplifier is experimentally demonstrated. This configuration has potential for a low power all-optical stable memory device with non-inverting characteristics where packets are stored by continuously injecting the regenerated data back into the loop.     

All-optical burst-mode clock extraction based on the thresholding operation of a modified terahertz optical asymmetric demultiplexer

To implement all-optical burst-mode clock extraction we adopt a modified terahertz optical asymmetric demultiplexer (MTOAD). The transmittance and reflectance of the MTOAD depend on the input intensity. For the MTOAD, two levels of pulse intensity can be chosen in such a way that while the pulses with similar intensity are reflected for both strong and weak pulses, only the strong pulse transmits. The device is useful, for example, for bit-level clock extraction from a packet, where strong and weak intensity pulses are assigned to ‘1' and ‘0', respectively. When the input optical signal power is fixed to −1.6 dBm and the intensity ratio between ‘1' and ‘0' is varied in the range of 0.2–0.5, the extinction ratio (ER) at the transmitted port is more than 10 dB and a clock amplitude jitter (CAJ) of the bit-level clock at the reflected port is less than 14%. Inversely, when the input power is varied in the range of −6–−1 dBm with fixed intensity ratio of 0.3, more than 11 dB of ER and less than 15% of CAJ are obtained.     

基于TOAD的10Gb/s全光或门

基于太赫兹光非对称解复用器（TOAD），提出了一种全光或门的实现方案.从TOAD原理出发，从理论上证实了该方案实现全光或运算的可行性.在此基础上进行了实验研究，成功实现了10 Gb/s的全光或运算.实验采用1100和0110编码的两路数据信号，完全验证了或运算真值表中各种可能的情况，并显示出该方案对实现任意编码或伪随机码数据或运算的潜力.对SOA增益恢复时间对结果的影响提出了改进办法.最后分析表明,该方案具有实现超高速高消光比或运算的潜力.     

All-optical reconfigurable logic operations with the help of terahertz optical asymmetric demultiplexer

An all-optical reconfigurable logic operation essentially constitutes a key technology for avoiding complex and speed limited optoelectronics conversions and performing various processing tasks. All-optical reconfigurable logic operations with the help of terahertz optical asymmetric demultiplexer (TOAD) is proposed and described. The paper describes the all-optical reconfigurable logic operations using a set of all-optical multiplexer and optical switches. We have tried to exploit the advantages of TOAD-based switch to design an integrated all-optical circuit which can perform the different logic operations AND, XOR, NOR and NOT. Numerical simulation confirming described methods is given in this paper.     

High repetition rate optical switch using an electroabsorption modulator in TOAD configuration

A novel optical switch featured with high repetition rate, short switching window width, and high contrast ratio is proposed and demonstrated for the first time by placing an electroabsorption modulator (EAM) in a terahertz optical asymmetric demultiplexer (TOAD) configuration. The feasibility and main characteristics of the switch are investigated by numerical simulations and experiments. With this EAM-based TOAD, an error-free return-to-zero signal wavelength conversion with 0.62 dB power penalty at 20 Gbit/s is demonstrated.     

A novel realization of all-optical dibit represented frequency encoded Boolean and quaternary inverters without switching device

All-optical frequency encoded dibit representation technique conduct real-time operations with ultra high switching speed rather than all conventional optoelectronic, optical and all-optical switches. So, a high degree of parallelism can be exploited from these proposed systems.     

Implementation of an all-optical binary comparator based on material nonlinearity and polarization encoded light signal

Bitwise comparison and classification of binary data is an essential requirement in digital signal and image processing applications. Here in this paper a new method of a one bit all-optical binary comparison scheme is proposed. This scheme is developed by the proper use of optical nonlinear material and also polarization encoding technique. Very high speed performance can be adopted easily in this mechanism. The scheme can be used to compare any two bits such as 0 and 0, 0 and 1, 1 and 0, 1 and 1.     

控制光和信号光频差对太赫兹光非对称解复用器性能的影响

讨论了半导体光放大器中的带间效应，及载流子热效应、谱烧孔效应、双光子吸收以及超快非线性折射等带内效应对半导体光放大器的动态特性的影响，讨论了两种情况：1)保持控制光波长不变而改变信号光频率，2)保持控制光和信号光频率相同而同时改变它们的频率下半导体光放大器的增益、相位动态特性以及太赫兹光非对称解复用器的开关窗口特性。数值结果表明，为了得到较为平坦而窄的开关窗口，控制光波长应与信号光波长相同，且其与半导体光放大器增益谱中心波长的差值应该大一些。     

Static and dynamic analysis of an all-optical inverter based on a Vertical Cavity Semiconductor Optical Amplifier (VCSOA)

We report the static and dynamic properties of an all-optical inverter based on an 850 nm Vertical Cavity Semiconductor Optical Amplifier (VCSOA). The inverter exhibits low switching power requirements (~ 15 μW), large on/off contrast ratio (> 11 dB), and high speed operation (~ 1.4 GHz). Large and small signal measurements show that the speed of operation and the on/off contrast ratio improve with increased bias current. This holds important prospects for the development of VCSOA-inverters for high-speed, low-power optical logic applications. Finally, a theoretical model of the VCSOA-inverter has been employed giving good agreement with experiments.     

Periodicity Characteristic of TOAD's Switching Window

The periodicity characteristic of switching window of a terahertz optical asymmetric demultiplexer (TOAD) using numerical simulation was investigated. The results show that the switching window width of TOAD changes periodically with the time asymmetry of TOAD and the period is one half of the period of control pulses. The theoretical results agree with the experimental results very well.     

Effect of amplified spontaneous emission on semiconductor optical amplifier based all-optical logic

The performances of all-optical logic gates XOR, AND, OR, NOR and NAND based on semiconductor optical amplifier (SOA) have been simulated including the effects of amplified spontaneous emission (ASE). For the parameters used, all-optical logic gates using SOA are capable of operating at speed of 80 Gb/s.     

Designing an all-optical packet filtering module for WDM broadcast-and-select star networks

An all-optical packet filtering module for WDM broadcast-and-select star networks is introduced. At each time instant, only one packet per wavelength is allowed to pass to the star coupler. Therefore, collisions are avoided and the network performance is improved. The proposed module is based on the use of optical logic circuits for controlling the passing of the transmitted packets to the star coupler, without the need of optical to electronic translation or electronic processing of the network feedback information. In this way, the processing time is drastically reduced, while the need for slowly tunable optical filters is eliminated. Furthermore, due to the all-optical nature of the network hub, the reliability of the system is improved.     

Periodicity Characteristic of TOAD's Switching Window

1 IntroductionThere are a variety of all-optical demultiplexing schemes for OPtical time divisionmultiplexing (OvuM) system, such as nonlinear optical loop horror (NOLM)[IJ,terahertz optical asyrnxnetric demultiplexer (TOAD)[2], four wave ndking (aaM) offiber or semiconductor optical amplifier (~)[3'4), etc. Axnong them, the terahertzoptical asymmetric demultiplexer (TOAD) has advantages of requirement for shorterlength of fiber and lOWer energy of control pulse, no dispersion and walk…