Terahertz Optical Asymmetric Demultiplexer Research Articles

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.

All-optical XOR gate with optical feedback using highly Ge-doped nonlinear fiber and a terahertz optical asymmetric demultiplexer

We experimentally demonstrate an all-optical exclusive-OR (XOR) gate with optical feedback using a highly Ge-doped nonlinear fiber. The XOR is achieved based on cross-polarization rotation in nonlinear fiber, while the optical feedback employs a terahertz optical asymmetric demultiplexer (TOAD). The TOAD simultaneously cleans up the XOR output and converts the wavelength of the feedback signal to allow proper feedback operation. The performance of the all-optical XOR gate with optical feedback is studied through both experimental and simulation analysis. An open eye diagram of the XOR output in feedback mode is obtained experimentally, and a correct logic operation in feedback mode is proved through simulation.

All-Optical Binary-Coded Decimal Adder with a Terahertz Optical Asymmetric Demultiplexer

In electronic computing systems, the binary-coded decimal (BCD) method encodes decimal numbers with each digit represented by its own four-bit binary sequence. The method allows easy conversion to decimal digits for printing or display and also offers rapid decimal calculations. A proposed all-optical BCD adder uses a terahertz optical asymmetric demultiplexer (TOAD) to perform BCD addition in all-optical domain.

Interferometric switch based all optical scheme for conversion of binary number to its quaternary-signed digit form

Multi-valued logic (with radix>2) 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. In arithmetical operation signed digit number is very essential for carry free computation. To achieve the parallelism in computation, a suitable number system and an efficient encoding/decoding scheme for handling the data are very much essential. In radix-4 system negative number is represented by quaternary-signed digit (QSD). In this study a conversion from 3-bit binary number (2's complement representation) to its equivalent single-digit QSD is reported. The technique for conversion of QSD to its binary equivalent form is also presented. All-optical circuits are designed with non-linear material-based interferometric switches such as terahertz optical asymmetric demultiplexer in optical tree architecture, where the numbers are represented by different discrete polarised state of light. Device-based simulation of the proposed optical circuit is used to verify the operation of the optical converter.

All-optical prefix tree adder with the help of terahertz optical asymmetric demultiplexer

We propose and describe an all-optical prefix tree adder with the help of a terahertz optical asymmetric demultiplexer (TOAD) using a set of optical switches. The prefix tree adder is useful in compound adder implementation. It is preferred over the ripple carry adder and the carry lookahead adder. We also describe the principle and possibilities of the all-optical prefix tree adder. The theoretical model is presented and verified through numerical simulation. The new method promises higher processing speed and accuracy. The model can be extended for studying more complex all-optical circuits of enhanced functionality in which the prefix tree adder is the basic building block.

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.

Enhancement of Input Power Dynamic Range for Multiwavelength Amplification and Optical Signal Processing in a Semiconductor Optical Amplifier Using Holding Beam Effect

We demonstrate a considerable enhancement of input power dynamic range (IPDR) for multiwavelength amplification and optical signal processing in a semiconductor optical amplifier (SOA) by using holding beam effect. The effect is used in SOA gain region at power level well below 10 dBm, which is much smaller than the required power as the setting at transparency wavelength. The IPDR is extended not only to high power range due to the reduction of nonlinear crosstalks, but also to low power range due to the compression of amplified spontaneous emission (ASE) noise. The technique is first applied to the amplification of wavelength-division multiplexed (WDM) channels using a continuous wave (CW) holding beam. The holding beam is particularly useful for the amplification of large number of channels thanks to the suppression effect of interactions among WDM channels. It is then carried out for one of extensively-used optical processing schemes, terahertz optical asymmetric demultiplexer (TOAD), for multiwavelength data format conversion without the need of an external CW light. The IPDR of TOAD reaches over 20 dB as control clock behaves simultaneously as the holding beam. We also present that the patterning effect and the impact of ASE noise on the converted signal are strongly dependent on the TOAD's switching window, which is optimized at 40% duty ratio for the largest IPDR.

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.

All-optical quaternary Galois field sum of product (GFSOP) circuits

Quaternary Galois field (QGF) arithmetic has a great contribution in future computation in the field of multi-valued logic (MVL). Any multi-valued logical function having many input variables express Galois field sum of product (GFSOP) expression easily. In this paper, all-optical circuits of two Galois field arithmetical operations (addition and product) are proposed and described. All-optical basic reversible quaternary literal circuits using GFSOP expression is also proposed. In this present scheme the different quaternary logical states are represented by different polarized state of light. Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch takes an important role in this manuscript.

TERAHERTZ OPTICAL ASYMMETRIC DEMULTIPLEXER BASED ALL OPTICAL DATA COMPARATOR

An all-optical data comparator with the help of Terahertz Optical Asymmetric Demultiplexer (TOAD) is proposed. The paper describes the all-optical data comparator by using a set of all-optical full-adder and optical switch. Comparison between two binary data is required in many data processing systems. It is sometimes necessary to know whether a binary number is greater than, equal to, or less than another number. The all-optical data comparator can be used to perform a fast central processor unit using optical hardware components. In this present communication, we have tried to exploit the advantages of TOAD-based switch to design an integrated all-optical circuit which can perform data comparison operations.

Designing of an all-optical scheme for single input ternary logical operations

In this paper, for the first time to our knowledge, we propose and describe a novel design of single circuit capable of generating all the possible 27 logic functions for single input ternary (3-valued) logic system in all-optical domain. Here the different logical states have been represented by different polarized state of light. Terahertz optical asymmetric demultiplexer (TOAD) based interferometric switch plays a significant role as ultra-fast all-optical switching device. Proposed all-optical circuit is numerically investigated and simulated.

Simple novel all-optical half-adder

On the basis of Sagnac interferometric structure, a simple novel ultrafast scheme of all-optical half-adder is proposed. The structure comprises two of the same balanced terahertz optical asymmetric demultiplexers (TOADs). One TOAD is utilized to achieve an all-optical XOR gate, which is logic SUM. The other is utilized to obtain an all-optical AND gate, which is logic CARRY. Logical SUM and CARRY are simultaneously realized at 80 Gbit/s. Through numerical analysis, the operating characteristics of the scheme are illustrated at 80 Gbit/s. Furthermore, the carrier recovery time of the semiconductor optical amplifier is no longer a crucial parameter to restrict the operation speed of this scheme.

All-optical symmetric ternary logic gate

Symmetric ternary number (radix=3) has three logical states (1¯, 0, 1). It is very much useful in carry free arithmetical operation. Beside this, the logical operation using this type of number system is also effective in high speed computation and communication in multi-valued logic. In this literature all-optical circuits for three basic symmetrical ternary logical operations (inversion, MIN and MAX) are proposed and described. Numerical simulation verifies the theoretical model. In this present scheme the different ternary logical states are represented by different polarized state of light. Terahertz optical asymmetric demultiplexer (TOAD) based interferometric switch has been used categorically in this manuscript.

All-optical binary flip-flop with the help of Terahertz Optical Asymmetric Demultiplexer

The memory device is very important as they store various values either temporary or permanently. Optical flip-flop memories form a fundamental building block for all-optical packet switches in the next generation communication networks. All-optical flip-flop memory with the help of Terahertz Optical Asymmetric Demultiplexer (TOAD) is proposed and described. Principles and possibilities of all-optical circuits for TOAD based S---R, J---K, D and T flip-flop are reported. Numerical simulation confirming described method is also given in this paper.

ALL-OPTICAL TERAHERTZ OPTICAL ASYMMETRIC DEMULTIPLEXER (TOAD) BASED BINARY COMPARATOR: A PROPOSAL

Comparator determines whether a number is greater than, equals to or less than another number. It plays a significant role in fast central processing unit in all-optical scheme. In all-optical scheme here 1-bit binary comparator is proposed and described by Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch. Simulation result by Mathcad-7 is also given. Cascading technique of building up the n-bit binary comparator with this 1-bit comparator block is also proposed here.

Polarization encoded TOAD based all-optical quaternary literals

Multi-valued logic can be viewed as an alternative approach to solving many problems in transmission, storage and processing of large amount of information in digital signal processing. For the first time to our knowledge, the principal of possibilities of design of all-optical quaternary multi-valued literals circuit (truncated sum, truncated difference and down literals) are proposed and described. Here the different quaternary logical states are represented by different polarized state of light. Terahertz optical asymmetric demultiplexer (TOAD) based interferometric switch can take an important role here. Computer simulation result (by Mathcad-7.0) confirming described methods and conclusion are given in this paper.

Polarization encoded all-optical quaternary R–S flip-flop using binary latch

The developments of different multi-valued logic (MVL) systems have received considerable interests in recent years all over the world. In electronics, efforts have already been made to incorporate multi-valued system in logic and arithmetic data processing. But, very little efforts have been given in realization of MVL with optics. In this paper we present novel designs of certain all-optical circuits that can be used for realizing multi-valued logic functions. Polarization encoded all-optical quaternary (4-valued) R–S flip-flop is proposed and described. Two key circuits (all-optical encoder/decoder and a binary latch) are designed first. They are used to realize quaternary flip-flop in all-optical domain. Here the different quaternary logical states are represented by different polarized state of light. Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch can take an important role. Computer simulation result confirming described methods and conclusion are given in this paper.

基于太赫非对称光解复用器（TOAD）的全光加法/减法器

An all-optical adder/subtractor (A/S) unit with the help of terahertz optical asymmetric demultiplexer (TOAD) is proposed. The all-optical A/S 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 binary addition and subtraction. With computer simulation results confirming the described methods, conclusions are given.

Demonstration of an All-Optical OCDMA Encryption and Decryption System With Variable Two-Code Keying

We demonstrate the first all-optical optical code-division multiple-access (OCDMA) encryption and decryption system with variable two-code keying. The nonlinear optical loop mirror (NOLM)-based exclusive or (xor) employed in encryption utilizes the shortest length silica-based nonlinear fiber element to date, enabling a compact architecture. Fiber Bragg grating arrays create wavelength-hopping time-spreading OCDMA codes from broadband pulses at output ports of the xor resulting in variable two-code keying, a code-switching modulation format characterized by a random alternation in bit representation and immunity to differential analysis unlike fixed two-code keying. The terahertz optical asymmetric demultiplexer employed in decryption shows mutual compatibility of nonlinear fiber-based and semiconductor optical amplifier-based NOLM configurations. Our architecture can potentially perform one-time pad encryption and decryption for unconditional security.

Reconfigurable optical logic unit with a terahertz optical asymmetric demultiplexer and electro-optic switches

A reconfigurable optical logic unit that can execute any binary logic and arithmetic operation on the same hardware with different configurations is proposed. The design, based on cascaded terahertz optical asymmetric demultiplexer switches, introduces reconfigurability with the help of electro-optic switches. The model is simple and practicable.