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.     

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.     

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.     

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.     

Ternary Galois field arithmetic operations with optical nonlinear material (OPNLM) switch

Ternary Galois field (GF3) arithmetic can take an important and significant role in future information processing with multi-valued logic (MVL). An all optical circuit for two arithmetical operations (addition and multiplication) in ternary Galois field with OPNLM switch is proposed and discussed. The different states of polarization of light are taken as different logic states. An outline of Ternary Galois field sum of product (TGFSOP) is also discussed. Mathematical simulation has confirmed the result.     

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.     

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.     

A method of developing all-optical mono-stable multivibrator system exploiting the Kerr non-linearity of medium

Optics has already been established as a potential candidate for conduction of digital logic and arithmetic operation in communication and computation processes. Different proposals have been reported by different scientists to make optics meaningful signal for conduction of the above operations. As it is well known that the memory device is a basic building block of any computation and communication system hence developing systems such as digital memory, multivibrator, etc. are the obvious requirements for optical communication as well as computation systems also. As the role of switching devices is an essential part of any processing system, many proposals were seen where all-optical switches using the combination of linear and non-linear materials were used, to implement the logic elements.In this context, the authors propose a new scheme for implementation of an all-optical mono-stable multivibrator using the non-linear material based switches and high refractive index based material. This multivibrator can generate a time pulse of definite width.     

Design of SOA-MZI based all-optical programmable logic device (PLD)

Photon being the ultimate unit of information with unmatched speed and with data package in a signal of zero mass, the techniques of computing with light may provide a way out of the limitations of computational speed and complexity inherent in electronics computing. Information processing with photon as information carrying signal has shown a high level potentiality through the researches in last few decades. The driving force behind this evolution has been the utilization of interferometric configurations that employ a semiconductor optical amplifier (SOA) as the nonlinear element in combination with cross-phase modulation to achieve switching by means of light. Here, in this paper we present an all-optical circuit of programmable logic device (PLD) with the help of SOA-MZI (Mach-Zehnder interferometer) based optical tree-structured splitter. Numerical simulation result confirming described method is reported here. This paper also explains the applicability of this scheme to perform logical and arithmetic operations in all-optical domain.     

Design of ternary Multiplexer and De-multiplexer circuit with optical nonlinear material (OPNLM) based switch

Multiplexer and De-multiplexer operation play a very important role in all-optical computation, communication and control. Considerable number of multiplexing – de-multiplexing scheme in digital optical processing have already been reported. A design of all-optical ternary Multiplexer De-multiplexer circuit with optical nonlinear material (OPNLM) based switch is proposed and described in this paper. Different logic states have been represented by different polarization states of light. Logical simulation is also included here. This circuit will be useful in future all-optical multi-valued logic based computing and information processing system.     

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.     

Polarization phenomena in the optical properties of porous silicon

We examine the polarization memory effect for porous Si excited by linearly polarized light. The various observations for the red-luminescing, slow band are discussed in the general framework of particle shape asymmetry. We show that because of the intrinsically nonlinear luminescence response, measurement parameters influence the polarization response. The preparation of porous Si with photoassisted etching is found to control the polarization retention parameter ρ. Using linearly polarized light during etching produces in-plane asymmetries. We find a substantial ρ-anisotropy linked to crystal symmetry planes and axes as a consequence of anisotropic etching. The effects are discussed with reference to current models of the light emission mechanism.     

Study on the cascadability of a SOA-assisted Sagnac switch pair

The ability of the SOA-assisted Sagnac switch to be cascaded in a pair scheme where the output from the transmission port drives directly the subsequent control terminal is investigated and demonstrated. For this purpose an efficient model that simulates the behavior of the SOA employed in each one of these interferometric arrangements is suitably applied to describe their concatenated setup. By conducting an extensive theoretical treatment the impact of the involved critical operational parameters on the defined quality metrics is thoroughly analyzed and assessed enabling to provide useful design rules for their proper selection and the achievement of enhanced performance. The two switches in tandem are a replica of each other if the leading one is driven as well as serially triggers its trailing counterpart with the proper amount of energy so that both SOAs are biased around the same saturation point. In this manner the formed chain is practically realizable and its contrast ratio can be optimized by means of the second module it comprises of. The outcome of this work can facilitate the implementation of larger, multistage switch fabrics and combinatorial circuits of non-trivial logical functionality in which this kind of interconnected architecture is the basic building block.     

Fabrication of high-quality colloidal photonic crystals with sharp band edges for ultrafast all-optical switching

Application of the pressure controlled isothermal heating vertical deposition method to the fabrication of colloidal photonic crystals is systematically investigated in this paper. The fabricated samples are characterized by scanning electron microscope and transmission spectrum. High-quality samples with large transmissions in the pass bands and the sharp band edges are obtained and the optimum growth condition is determined. For the best sample, the transmission in the pass bands approaches 0.9 while that in the band gap reaches 0.1. More importantly, the maximum differential transmission as high as 0.1/nm is achieved. In addition, it is found that the number of stacking layers does not increase linearly with concentration of PS spheres in a solution, and a gradual saturation occurs when the concentration of PS spheres exceeds 1.5 wt.%. The uniformity of the fabricated samples is examined by transmission measurements on areas with different sizes. Finally, the tolerance of the fabricated samples to baking was studied.     

Reducing polarization sensitivity for all-optical wavelength conversion of the optical packets based on FWM in the HNL-DSF using co-polarized pump scheme

Polarization insensitivity is a fundamental requirement for wavelength conversion technique in the future all-optical networks. Our experimental results show that a co-polarization pump configuration based on four-wave mixing in high-nonlinear fiber can reduce largely the polarization sensitivity. We have theoretically investigated those experimental phenomena, and the theoretical analyses are in good agreement with experimental results.     

Theoretical analysis and performance investigation of ultrafast all-optical Boolean XOR gate with semiconductor optical amplifier-assisted Sagnac interferometer

A comprehensive theoretical model of an ultrafast all-optical Boolean XOR gate implemented with a semiconductor optical amplifier (SOA)-assisted Sagnac interferometer is presented. The model accounts for the SOA small signal gain, linewidth enhancement factor and carrier lifetime, the switching pulses energy and width and the Sagnac loop asymmetry. By undertaking a detailed numerical simulation, the influence of these key parameters on the metrics that determine the quality of switching is thoroughly investigated and simple design rules are extracted for their proper selection so as to ensure optimum operation. The obtained results are in good agreement with the published experimental measurements and confirm the feasibility of realizing the gate at 10 Gb/s with fairly high performance. The model can be extended for studying more complex all-optical circuits of enhanced functionality in which the XOR gate is the basic building block.     

Polarization properties of nematic liquid crystal cell with tapered optical fiber

In the paper, an extended analysis of the polarization properties of a liquid crystal cell with a biconically tapered single-mode telecommunication optical fiber was presented. These properties are a result of a sample geometry and used LC materials. They were analyzed by using two theoretical models based on the matrix decomposition methods, i.e., polar and singular-value one. By measuring Mueller matrices, information about losses, depolarization, dichroism and birefringence was obtained. In the experiment two types of tested samples filled with well-known 6CHBT and E7 liquid crystals were prepared and all optical parameters were shown as the voltage dependence. The tested samples have dichroic properties and for both models calculated PDL is similar and it increases from 2.6 to 6.6 dB for E7 and from 0.4 to 2.7 dB for 6CHBT with voltage changes within the range of 40 – 190 V. Optical losses simultaneously decrease from 30 dB to 27 dB and from 36 dB to 28 dB, respectively. The birefringence properties cannot be directly comparable due to differences between both applied models but voltage fluctuations of these parameters are not significant. These results confirm expected dichroic properties of designed device and complete knowledge about its working principles. Moreover, presented analysis validates usefulness of the singular-value decomposition model applied to dichroic optical fiber elements.     

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.