Terahertz Optical Asymmetric Demultiplexer Research Articles

All-Optical 3:8 Decoder with the Help of Terahertz Optical Asymmetric Demultiplexer

An all-optical 3:8 decoder unit with the help of terahertz optical asymmetric demultiplexer (TOAD) is proposed. The all-optical 3:8 decoder unit with a set of all-optical full-adders and optical exclusive-ORs (XORs), can be used to perform a fast central processor unit using optical hardware components. We try to exploit the advantages of TOAD-based optical switch to design an integrated all-optical circuit which can perform decoding of signal. A theoretical model is presented and verified through numerical simulation. The new method promises both higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuit of enhanced functionality in which decoder is the basic building block. The operation of the proposed circuit is parallel in nature. The impact of the switching energy with small signal gain and variation of extinction ratio and contrast ration with control pulse energy of the switching outcome is explored and assessed by means of numerical simulations.

Design of 2-to-4 All-Optical Decoder with the Help of Terahertz Optical Asymmetric Demultiplexer

An all-optical 2-to-4 decoder unit with the assist of terahertz optical asymmetric demultiplexer (TOAD) is presented. The all-optical 2-to-4 decoder with a set of all-optical switches is designed which can be used to achieve a high-speed central processor unit using optical hardware. The unique output lines can be used for all-optical header processing. We attempt to develop an integrated all-optical circuit which can perform decoding of signal. This scheme is very simple and flexible for performing different logic operation and to design advanced complex logic. Simulated results are confirming the described methods.

All-optical repetition rate multiplication of pseudorandom bit sequences based on cascaded TOADs

A scheme for all-optical repetition rate multiplication of pseudorandom bit sequences (PRBS) is demonstrated with all-optical wavelength conversion and optical logic gate ‘OR’ based on cascaded Tera-Hertz Optical Asymmetric Demultiplexers (TOADs). Its feasibility is verified by multiplication experiments from 500Mb/s to 4Gb/s for 23−1 PRBS and from 1Gb/s to 4Gb/s for 27−1 PRBS. This scheme can be employed for rate multiplication for much longer cycle PRBS at much higher bit rate over 40Gb/s when the time-delay, the loss and the dispersion of the optical delay line are all precisely managed. The upper limit of bit rate will be restricted by the recovery time of semiconductor optical amplifier (SOA) finally.

Experimental Investigation of All-Optical NRZ-DPSK to RZ-DPSK Format Conversion Based on TOAD

We propose and experimentally demonstrate a novel all-optical non-return-to-zero differential-phase-shift-keying (NRZ-DPSK) to return-to-zero differential-phase-shift-keying (RZ-DPSK) format conversion scheme. This scheme is based on the terahertz optical asymmetric demultiplexer (TOAD). A 10 Gb/s converted RZ-DPSK signal is obtained with a wide duty cycle tuning range from 16% to 66%. For all converted RZ-DPSK signals, the receiver sensitivities at BER of 10−9 are 0.4 to 1.7 dB higher compared with the original NRZ-DPSK signal. The clear and open eye diagrams are presented to demonstrate the high quality format conversion performance. Moreover, the optical spectra show that this conversion is in a wavelength-preserving operation.

All-optical repetition rate multiplication of pseudorandom bit sequences by employing power coupler and equalizer

A scheme for all-optical repetition rate multiplication of pseudorandom bit sequences (PRBS) is demonstrated with a precision delay feedback loop cascaded with a terahertz optical asymmetric demultiplexer (TOAD)-based power equalizer. Its feasibility has been verified by experiments, which show a multiplication for PRBS at cycle 2 ^7 − 1 from 2.5 to 10 Gb/s . This scheme can be employed for the rate multiplication of a much longer cycle PRBS at a much higher bit rate over 40 Gb/s if the time-delay, the loss, and the dispersion of an optical delay line are all precisely managed.

Low-Complexity TOAD-Based All-Optical Sampling Gate With Ultralow Switching Energy and High Linearity

We present experimentally a low-complexity ultralow switching energy and high-linearity all-optical sampling gate based on a terahertz optical asymmetric demultiplexer, constructed by placing a polarization-insensitive multiple-quantum-well semiconductor optical amplifier (PI-MQW-SOA) asymmetrically within a fiber loop mirror. Using a picosecond pulse train as the trigger clock, we analyze, in detail, the influence of the sampling pulse power and the offset of the PI-MQW-SOA from the loop midpoint on the shape, width, and amplitude of the sampling window, respectively. Furthermore, the switching energy and linearity of this sampling gate under different widths of sampling windows are specifically investigated. Results demonstrate that our sampling gate possesses a switching energy as low as 25 fJ and a high linearity above 0.99.

Experimental study on a low switching energy and high-linearity all-optical sampler based on terahertz optical asymmetric demultiplexer

We demonstrate experimentally a low switching energy and high-linearity all-optical sampler based on terahertz optical asymmetric demultiplexer (TOAD) composed of a nonlinear semiconductor optical amplifier (SOA) with a multiple quantum well structure. Effects of the sampling pulse power and asymmetric offset of SOA on the shape, width and amplitude of sampling windows are analyzed in detail respectively. It is found that the sampling pulse power has no effect on both the shape and the width of sampling windows, but has a significant effect on the window amplitude. Meanwhile there exists an optimal power which maximizes the sampled output and determines the switching energy of TOAD. The asymmetric offset of SOA from the center position in the loop determines the width of sampling windows and has great influences on both the shape and the amplitude of the sampling window. The sampling windows with different widths have approximately the same rise edge due to the fast response of SOA for the sampling pulse. However, the normalized amplitude of sampling windows firstly increases sharply with the increase of the asymmetry, then gradually flattens out, and tends to be stable in the end. In addition, the switching energy and linearity of TOAD are studied. The switching energy is as low as 25 fJ, and the linearity is as high as 0.99. Moreover, at different window widths, the switching energy of TOAD remains the same and the sampling windows have a very good linearity. However, the sensitivity of a TOAD sampler with different width is different: the wider the sampling window, the higher the sensitivity and the larger the corresponding dynamic range.

Optical Time Division Multiplexing Using Terahertz Optical Asymmetric Demultiplexer

AbstractIn this paper, optical time division multiplexing is demonstrated using TOAD (terahertz optical asymmetric demultiplexer), which employs semiconductor optical amplifier (SOA) as nonlinear switching element. The TOAD device in its original configuration is based on Sagnac interferometer (also referred to as nonlinear optical loop mirror – NOLM).

All-optical half-adder/half-subtractor using terahertz optical asymmetric demultiplexer.

Logic gates are the fundamental building blocks of digital systems. Using these logic gates, one can perform different logic and arithmetic operations. All-optical logic and arithmetic operations are very much expected in high-speed communication systems. In this paper, we present a model to perform addition/subtraction operations on two binary digits based on a terahertz optical asymmetric demultiplexer (TOAD). Using four TOAD-based switches, we have designed a half-adder and half-subtractor circuit. The approach to designing all-optical arithmetic circuits not only enhances the computational speed but is also capable of synthesizing light as inputs to produce the desired outputs. The main advantages of this circuit are that synchronization between inputs is eliminated and simultaneous addition and subtraction operations are realized at the outputs. This circuit is designed theoretically and verified through numerical simulations. The impact of the control pulse energy, gain recovery time, and the input data pulse width on the extinction ratio, contrast ratio, amplitude modulation, Q-factor, and relative opening of the pseudo-eye diagram of the switching outcome is explored and assessed by means of numerical simulations.

All-optical polarization-encoded negabinary signed-digit adder designs using terahertz-optical-asymmetric-demultiplexer switches

Incontrast to intensity-encoded negabinary modified signed-digit number representation, a polarization-encoding scheme is proposed to design all-optical adders. The utilization of the proposed polarization-encoding produces more efficient circuits in terms of gates numbers and circuit delays. Three all-optical adder circuits are designed using Terahertz-Optical-Asymmetric-Demultiplexer (TOAD) switches,polarization beam splitters, polarization converters, and beam combiners. Itwill be shown that the proposed circuits utilize 51.7%, 45.5%, and 21% less gates and they are faster by 44.4%, 42.9%, and 40%, respectively, than thecorresponding intensity-encoded circuits.

Investigation of inter-channel crosstalk mitigation by assist light in a TOAD switch by using electrical equivalent circuit model of SOA

The paper investigates in depth analysis of inter-channel crosstalk in a terahertz optical asymmetric de-multiplexer (TOAD) switch. Large signal multi-wavelength circuit model of semiconductor optical amplifier (SOA) has been developed for crosstalk analysis of the TOAD. The circuit model is particularly suitable for numerical simulation of an integrated TOAD switch in presence of chip and package parasitics. Mitigation of inter-channel crosstalk by continuous wave (cw) assist light is studied experimentally and good prediction accuracy with the numerical result is obtained. It is found that the range of input probe power can be increased by 10 dB when assist light is injected and no error floor is observed. Best performance of crosstalk mitigation is obtained when assist light wavelength is set to the edge of 3 dB bandwidth of the SOA.

Ultra-fast all-optical polarization-encoded modified signed-digit addition using terahertz-optical-asymmetric-demultiplexer (TOAD) switches

In this paper, enhanced designs for ultra-fast all-optical circuits based on the terahertz-optical-asymmetric-demultiplexer (TOAD) adders are proposed. The high speed is achieved due to the use of the nonlinear optical materials and the nonbinary modified signed-digit (MSD) number representation. The proposed all-optical circuits use polarized light to present the trinary digits of the MSD numbers. It will be shown that the polarization-encoded MSD adder uses much less TOADs switches (37.5% less) and it is faster by 33.33% compared to the intensity-encoded ones.

Design of polarization encoded all-optical 4-valued MAX logic gate and its applications

Quaternary maximum (QMAX) gate is one type of multi-valued logic gate. An all-optical scheme of polarization encoded quaternary (4-valued) MAX logic gate with the help of Terahertz Optical Asymmetric Demultiplexer (TOAD) based fiber interferometric switch is proposed and described. For the quaternary information processing in optics, the quaternary number (0, 1, 2, 3) can be represented by four discrete polarized states of light. Numerical simulation result confirming the described methods is given in this paper. Some applications of MAX gate in logical operation and memory device are also given.

基于太赫兹光解复用器-四波混频效应的全光异或门方案

In order to solve the three problems of terahertz optical asymmetric demultiplexer-cross phase modulation effect based all-optical exclusive-OR gate,which are that the strict demand of synchronization;cannot be applied in the situation of not return to zero signal input;the speed of exclusive-OR operation is limited by carrier recovery speed of semiconductor optical amplifier.An all-optical exclusive-OR gate was proposed which utilizes the structure of terahertz optical asymmetric demultiplexer and is based on four wave mixing effect,because of based on four wave mixing,this exclusive-OR gate can radically solve the mentioned three problems of terahertz optical asymmetric demultiplexer-cross phase modulation based exclusive-OR gate.This paper illustrates the principle of this exclusive-OR gate through theoretic analyse,and realizes the exclusive-OR operation for the input of 40Gbps,return to zero signal;80Gbps,return to zero signal;10 Gbps,not return to zero signal.The Qfactor and bit error rate of exclusive-OR operation for above three kinds of input are 11.7,2.4×10-18;8,1.1×10-10;22,1.3×10-40.And then,we analyse the influence on the quality of exclusive-OR output signal which is generated by change of parameter of main elements of terahertz optical asymmetric demultiplexer and temperature and dispersion effect.The feasibility and effectiveness of this exclusive-OR gate for solving the three problems of terahertz optical asymmetric demultiplexer-cross phase modulation based all-optical exclusive-OR gate are verified by theoretic analyse and simulation.

All-optical parallel data and address recovery scheme

In this paper, we have presented a parallel system model to recover data and address based on terahertz optical asymmetric demultiplexer (TOAD)/semiconductor optical amplifier (SOA)-assisted Sagnac gate. The architecture is based on a system which has its input information containing data and address. Here, we first convert the original data into a coded form with the help of input address. Then the coded information is transmitted through the optical routing channel. At the receiver end, the model simultaneously extracts data and address at any point of the routing channel. The operations of the circuits are studied theoretically and analyzed through numerical simulations. The variation of contrast ratio, amplitude modulation, extinction ratio and bit error rate with control pulse energy and switching crosstalk with gain ratio has been thoroughly investigated.

All-optical ordinary quaternary inverter (QNOT) using binary NOT gate

Multi-valued logic (MVL) can be viewed as an alternative approach to solve many problems in transmission, storage and processing of large amount of information in digital signal processing. For the first time to our knowledge, the principle and possibilities of design of an all-optical ordinary quaternary inverter circuit has been proposed and described using binary NOT gate. Here, the different quaternary (4-valued) logical states are represented by different polarized state of light. Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch can take an important role in this regard. Computer simulation result confirming described methods and conclusion are given in this paper.

Terahertz optical asymmetric demultiplexer (TOAD) based half-adder and using it to design all-optical flip-flop

All-optical half-adder using Terahertz optical asymmetric demultiplexer (TOAD) switch is proposed and described in this manuscript. Here incoming and control signals are of same wavelength and their state of polarization is orthogonal to each other. Numerical simulation is also presented, which verifies the theoretical results. Also all-optical flip-flops (clocked S–R and J–K) with this help of half-adder unit are proposed in this literature. This work is actually the extension of my previous published paper (Chattopadhyay, 2011 [1]), where XOR gate using TOAD based switch was proposed.

Designing of Polarization Encoded All-Optical Ternary Multiplexer and Demultiplexer

The advantages of Multi-valued logic (MVL) systems and circuits have drawn a significant interest as a coming generation technology that can be viewed as an alternative approach to solve many problems in transmission, storage and processing of large amount of information in digital signal processing. The paper presents an all-optical circuit for designing ternary (three-valued) multiplexer & demultiplexer with the help of polarization encoded basic ternary logic gates (ternary min and ternary delta literal). It focuses on recent patents / publications in relevant field and future scope of works in the fascinating field of optical multi-valued logic. Keywords: Optical logic, nonlinear optics, optical multi-valued logic, polarization, ternary multiplexer/demultiplexer, Multiplexer, Demultiplexer, Quantum Electronics, Solid-State circuits, optical processors, spatial light modulator, Terahertz Optical Asymmetric Demultiplexer, broadband communications, digital signals, digital communication system

All-optical cross-bar network architecture using TOAD based interferometric switch and designing of reconfigurable logic unit

The design of all-optical 2 × 2 Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch is proposed and described in this manuscript. Numerical simulation has been done to achieve the performance of the switch. Using this 2 × 2 TOAD based switch, cross-bar network architecture is designed. A reconfigurable logic unit is also proposed in this manuscript, which can perform 16-Boolean logical operations.

All-optical carry lookahead adder with the help of terahertz optical asymmetric demultiplexer

An all-optical model of carry lookahead adder (CLA) implemented with a semiconductor optical amplifier (SOA)-assisted Sagnac interferometer (TOAD) is presented. The model accounts for the SOA small signal gain, linewidth enhancement factor, the switching pulses energy and width and the Sagnac loop asymmetry. Adder is a very basic component in a central processing unit. The CLA is the highest speed adder nowadays. Theoritical model is presented and verified through numerical simulation. The method promises both higher processing speed and accuracy. The model can be enhanced the functionality in which carry lookahead adder is the basic building block.