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Free Space Optics is a field of communication with atmosphere as the channel, imposing a number of challenges in transmission of information. This paper presents a novel analytical approach to analyze the performance of multi-branch EGC combiner operating over independent fading environments in Free Space Optical System by implementing two-point Pade approximants theory in a moment-based approach. The Log-normal, Nakagami-n (Rician), and Rayleigh fading channels, representing weak-to-strong turbulence regimes, are considered for investigation. By deriving the exact closed-form expressions of moments of the output signal-to-noise ratio and joint probability density function of the sum of N-independent fading random variables, the significant performance metrics, such as the amount of fading, average output signal-to-noise ratio, and spectral efficiency are evaluated. Moreover, the average symbol error rate, outage probability and channel capacity of the system are assessed by approximating moment generating function using two-point Pade Approximants theory. Various numerical results achieved from proposed theoretical approach are validated for accuracy using computer simulations.

For generating digital codes based on the frequency of input signal we need frequency shift keying demodulators. Optical demodulators are required for optical communication networks. In this paper we are going to design and propose a new structure for implementing all optical frequency shift keying demodulator. The proposed structure was designed using four resonant rings. Finite difference time domain method was used for simulating the propose structure. The simulation results show that when the frequency of input signal is 193.5 THz, 194 THz, 194.5 THz and 195 THz the proposed structure can generate 00, 01, 10 and 11 code at the output ports respectively. The maximum delay time of the proposed structure is 2 ps.

This paper builds exact optical solitons to the coupled of nonlinear equations which describes the pulse propagation in birefringent optical fibers with the effects of ellipticity angle and coupling coefficient. By adopting the new Sardar sub-ODE method, diverse optical solitons as W-shaped bright, dark optical solitons, trigonometric function and singular function solutions have been secured. To show out the warranty of the stability of the acquired results, we examine the effects of the ellipticity angle and coupling coefficient on modulation instability. It is noted beside of the linear and circular birefringence, for $$\theta =45^o$$ , it is exhibited unstable zone where MI growth rate. To enroll the effects of the coupling coefficient on MI growth rate, we fixed a value of the ellipticity angle $$\theta =45^o$$ . In Figs. 6 and 10, we acquired some new behavior of the MI gain compared to Houwe et al. (2021). These results show out stable/unstable zones compared to Ablowitz and Horikis (2017), Houwe et al. (2021). Moreover, these results will be helpful in nonlinear optical fibers to explain the communication over long distance and optical fibers design.

This paper presents the work on the efficient scheme of Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA). This is one of the promising solution to the emerging need of high data rates. The systems based on OCDMA suffer from Multiple User Interference (MAI) and Phase-Induced Intensity Noise (PIIN). The SAC-OCDMA systems are able to eliminate them by using better code structuring. This script presents the numerical analysis and detailed comparison of logical interference cancellation of used 1D codes which are Enhanced Double Weight (EDW) and Modified Double Weight (MDW) codes. The three-user system is simulated and designed for associating BER and other performance parameters with respect to the length of the optical cable. The receiver side is using Single Photo Diode Detection (SPD) technique. The results reveal that EDW performs better than the MDW codes moreover, the transmission length for standard error free transmission is 120 km with EDW codes and 102 km for MDW codes. For comparative study PIN as well as APD detectors are used for the same parameters where a significant increase up to 45 km is seen while using APD.

Optical Wireless Communications (OWCs) can play vital role in providing communication in healthcare infrastructure’s, where contagious patients are admitted or treated as well as other patients are coming without any side effects as of radio frequency communication. In this paper, we propose high-speed cost-efficient free space optical (FSO) system for transmission of information (20 Gbps) inside healthcare premises comprising of number of buildings by integrating mode division multiplexing (MDM) scheme. The MDM scheme uses Laguerre Gaussian (LG) 00 and 01 modes whereas a simple On off Key (OOK) encoding scheme is employed for the proposed MDM-FSO system. The reported results show the efficient transmission of 20 Gbps data over 27 km of FSO link under clear atmospheric condition. Moreover, the proposed MDM-FSO link is evaluated under the impact of different fog conditions—low, medium and heavy.

Free space optics (FSO) communication is a very recent mechanism. It is mainly needed when physical connection between the transmitter and the receiver is practically impossible and when high bandwidth data transmission is expected. This paper walks through the investigation of the performance of FSO communication adopting spectral amplitude coding optical code division multiple access (SAC-OCDMA) systems at different weather scenarios. The suggested system uses enhanced double weight codes as signature codes by 3 clients, simultaneously. To eliminate multiple access interference and phase induced intensity noise, two different detection schemes are used; single photodiode (SPD) and modified-AND subtraction detection schemes. Furthermore, a comparison between PIN and APD detectors is performed. The performance is evaluated through its propagation distance, received power, Q-factor and bit error rate (BER). The obtained numerical results reveal both Q-factor and BER are modified by 30%. Accordingly, the system performance is enhanced by 30%, when using SAC-OCDMA-FSO with SPD detection technique compared with modified-AND subtraction technique.

The paper explores the non-locality dynamics of two moving atoms in a hybrid nonlinear system, which describes a nondegenerate parametric amplifier cavity containing two moving atoms with Stark shift interactions. Based on the Bell function, uncertainty-induced non-locality and concurrence, the two moving atomic non-locality is calculated numerically, when the cavity is filled initially by pair coherent fields. The results showed that the hybrid nonlinear qubit-cavity interactions have a high ability to generating quantum correlations. The amount of the generated quantum correlation can be improved and accelerated significantly with the increase of the time-dependent qubit location parameter. The increase of the Stark shift ratio and the difference between the mean-number photons of the two cavity fields leads to a clear deterioration of the generated quantum correlation.

This paper presents the analytic investigation of the effect of noise on the Fidelity of Photonic Qubit based deterministic CNOT gate (designed employing quantum dot (QD) spin within the double sided optical micro-cavity), considering vacuum noise and sideband leakage. It is found that the performance of the CNOT gate is significantly dependent on the interaction between the spin of QD and photon within the optical cavity. In strong $$(g/k=2.5$$ and $${k}_{s}/k=0.05)$$ and weak $$(g/k=0.4$$ and $${k}_{s}/k=1)$$ coupling conditions the calculated fidelity is 57.14% and 56.23% respectively. The analysis demonstrates that the CNOT gate works satisfactorily in both high and weak coupling regime under noisy condition. The computed maximum fidelity for CNOT gate and compact CNOT gate model is 58.17% at $$(g/k=4$$ and $$k_{s} /k = 0.01$$ and 77.19% at $$(g/k=0.1$$ and ks/k = 0.01 respectively under noisy conditions. The study can be used in the optimization of the performance of any quantum circuit, having a QD cavity system for photonic Qubits, under noisy conditions.

In this paper, we propose a novel hybrid strategy that combines mixed integer linear programming (MILP) formulation with different alternative routing approaches that is capable of solving, simultaneously, the routing, modulation format and spectrum assignment problem in the design of elastic optical networks. We extend our proposal to a path-link formulation that, although it is not guaranteed to find the optimal solution, it has shown reasonable solutions within inferior simulation time, allowing it to be used in not very short networks. We also compare our proposal with another MILP formulation and three adapted heuristics, all available in the literature. The results show the benefits of our proposal considering diverse simulation scenarios and different number of modulation formats over 19 realistic networks in terms of simulation run time and maximum number of used set of slots.

In this paper an all optical comparator was designed and simulated. The proposed structure works using nonlinear threshold switching that was implemented by application of nonlinear resonant cavities. The proposed structure works based on nonlinear threshold switching. X and Y are the input ports of the proposed structure using different combination of these input ports one can control that which bias port can be connected to its corresponding output port. The optical intensity required at input ports is about 0.1 W/µm2. The maximum rise and fall times for the proposed structure are 3 ps and 1 ps respectively. Therefore the bit rate is about 250 GS/s. Also the ON/OFF contrast ratio of the proposed optical comparator is 9.8 dB.

In this paper, we proposed an analytical model for a non-Hermitian orthogonal frequency division modulation system considering space time block coding (STBC) with polarization diversity in presence of strong atmospheric turbulence and compare the bit error rate (BER) performance with the same system considering space frequency block coding (SFBC). We developed this analytical model to calculate the impact of crosstalk and fading on system performance due to cross polarization and strong atmospheric turbulence respectively. The analytical expressions for signal to noise plus crosstalk ratio are derived for a certain amount of random misalignment angle. We consider two different independent probability density functions one is Maxwellian distribution and another is Gamma-Gamma distribution for angular misalignment and strong turbulence respectively. The average BER is found by averaging the conditional BER over this two probability density functions. It is noticed that, receiver sensitivity improvement due to STBC coding is almost 4.5 dB at a BER of 10–12 compare to 7.5 dB due to SFBC coding reported earlier by the authors. From the analytical results, we clearly found that SFBC coding performs better than STBC coding for the same system’s constraints. Finally, results of our proposed work are verified with others earlier published results and it is found that our result is almost 2 dB better than the published results.

To handle the massive high-speed internet traffic, free space optics (FSO) or single-mode fiber (SMF) based fiber optic communication is being used everywhere across the world. These technologies are capable of providing huge bandwidth and transmitting the data at very high speed with low energy consumption. FSO is a very convenient technology to quickly expand the legacy network in the adverse geographical areas. However, its link performance is highly dependent of inconsistent weather conditions. SMF based fiber optic link has a very low loss and its performance is almost independent on the weather conditions. Though, the installation and maintenance of fibers are quite complex and costly. Individually, FSO or SMF links have their limitations and have to be integrated to leverage their benefits. In this paper, we integrated FSO/SMF links and compared the performance of the proposed architecture which is capable of providing high-speed dual-rate data transmission. The proposed architecture transmits data over either FSO or SMF or both links simultaneously and has 100% more reliability against any one of the link failures. In case of operational link failure (FSO/SMF), data may be switched to the alternative working link (SMF/FSO), simply by tuning the transmitted signal by 50 GHz. The proposed architecture is also reliable against the optical line terminal transceiver (TRx) failure as each user located in the network can be served by two transceivers (1 Gbps and 10 Gbps). The proposed architecture also supports the wavelength division multiplexing overlay transmission for broadcasting the common signal to all the available users in the networks. The architecture reduces ~ 27% of the energy consumption by utilizing the appropriate link of hybrid architecture and TRx according to weather conditions and traffic load. The integrated architecture looks attractive for providing energy-efficient, high speed, and reliable internet coverage to the areas where there is a difficulty of laying fibers and has frequent fiber faults. The architecture is useful for strengthening and boosting rural and urban development.

Under investigation in this paper is a nonlinear conformable time-fractional Boussinesq equations as an important class of fractional differential equations in mathematical physics. The extended trial equation method, the $$\exp (-\Omega (\eta ))$$ -expansion method and the $$\tan (\phi (\eta )/2)$$ -expansion method are used in examining the analytical solution of the nonlinear fractional equations. The proposed methods are based on the integration method and a wave transformation. The fractional derivative in the sense of conformable time-fractional derivative is defined. Fractional complex transform is implemented to change fractional differential equations into ordinary differential equations in this paper. In addition, explicit new exact solutions are derived in different form such as dark solitons, bright solitons, solitary wave, periodic solitary wave, rational function, and elliptic function solutions of nonlinear conformable time-fractional Boussinesq equations.

The experimental ultra-wideband radio tomographic imagings inside and behind dielectric barriers with resolution near the diffraction limit are described. The problem is solved by the method of radio wave tomosynthesis using the theory of spatial spectra of the received signals. The ultra-wideband pulse sensing of the air—building structure medium, developed in Tomsk State University, are described. It has been shown that for the case of sensing with ultra-wideband pulses of 0.2 ns duration, the resolution is about 2 cm. The paper also shows the possibility of accelerating scanning of the investigated space through the use of the MIMO (timed or switched) antenna array technology. As in the timed mode the distance between the receiving and transmitting antennas varies from time step to time step, the algorithm of processing the data obtained from the array is to be modified. The modification itself is a nonlinear stretching of the received UWB signal in time. The signal transformation allows preparation of data for the above algorithm to receive three-dimensional images of the tested space. The paper presents the results of the processed experimental data which confirm the efficiency of the proposed method for MIMO arrays. The resulting image resolution is about 2 cm.

Optical networks pose real difficulty in finding the flexible optical routing path for high speed data transmission in optical communication network environment because of critical path, blocking performance, and security; processing delay, etc., to overcome this pitfall, a new algorithm fuzzy graph based ranking has been proposed. In this algorithm contain two schemes that are: fuzzy and graph theory, for this work we consider the distance and processing time, these two parameters are represented by fuzzy numbers and fuzzy triangular numbers, those values are used to find the shortest path from the different paths. In this paper observed that fuzzy graph based alternate routing scheme provided for better routing performance. In addition to that, the simulated results show that the network, performance can be improved when alternative routes are used in optical router architecture and also illustrate the numerical example of shortest path and fuzzy graph theory has been surveyed. The definite architecture for optical router and analytical approach is given in this paper, It helps that the researchers to improve the optical routing capabilities according to the fulfillment of present needs better analysis and simulation report shows that proposed method provides an optimized route in the optical network over the existing algorithms. The objectives of this paper, to minimize the processing delay of finding the shortest path (optimum path) and attain higher throughput.

This paper introduces basic concept of the detection range of a low-light-level (LLL) imaging system, and on the basis of previous derivation of visual distance detection equation for the LLL imaging system, the influence of noise factor on visual distance of LLL night vision system is discussed emphatically. Image intensifier is the most important part of LLL night vision device and SNR is one of the important parameters of micro-light image intensifier, whose value determines the detection distance and image sharpness of LLL imaging system in low-light conditions. In this paper, using system noise factor relation, by modifying the noise factor, a more practical and perfect horizon detecting equation is established, and the horizon estimation is carried out with the experiment, and the practicability of the corrected Horizon formula is verified. It has a certain guiding significance for improvement of the LLL imaging system and the development of night vision technology.

Glass frit encapsulation for laser-base sealing of the complex interiors results challenges for the electronics manufacturing process. The conventional frit packaging method relies on elevating thermal process by furnace where the package is heated to required temperature, hence limiting the use of temperature-sensitive materials and also creating problems in different packaging processes or multi-stage sealing products. In this paper, the benefits of combining novel laser-assist hermetical sealing and low temperature glass frit packaging are demonstrated and the technique offers a suitable and feasible solution. This frit of absorbent at specific laser wavelength is selected and applied as excellent contact with both large CTE range substrates. Glass frit composites consisting of a PbTiO3 ceramic and the rare earth Nd2O3 are evaluated for thermal properties and electrical characteristics. This developed glass frit hermetical sealing method achieves moisture durability, satisfying the enculturation of electronics-level. In this paper, we demonstrate successfully using laser to seal organic light emitting diode (OLED) via low melting temperature glass frit.

A novel algorithm based on a phase modulation and demodulation technique for multiple self-mixing interferometry was proposed in this paper. This algorithm can measure nanoscale vibration in real time and enhance the measurement resolution of a multiple self-mixing interferometer twofold compared with that of a self-mixing interferometer. In this paper, the principles of the method were described in detail, and a phase equation for multiple self-mixing interferometry was derived. Experiments were confirmed by conducting a series of experiments with different amplitudes, different signal-to-noise ratios, and different vibration waveforms. The experimental results showed that the algorithm can rapidly demodulate vibration in real time and indicated good agreement between theory and experiment.

The rapid development in areas such as fiber-optic communication, fiber lasers, and high power transmission has generated an increasing demand for photonic crystal fiber (PCF). However, there is no well-proven approach for PCF coupler fabrication because most approaches proposed introduce defects that are non-negligible in practice. Previously, we have made an attempt by applying side-adhering technique to PCF coupler fabrication. This paper presents our recent effort in establishing a model of side-polished PCF (SPPCF) coupler and tuning various fabrication parameters in search for its desirable characteristics. It is found that the optimal coupling effect is achieved when the residual radius is set 5.7 μm and the polishing angle is set 0°. The optimizations presented in this paper may serve as a foundation for further research and development of SPPCF coupler.

The paper explores the possibilities to extend the direct modulation bandwidth in dual-longitudinal-mode distributed feedback lasers by exploiting the photon–photon resonance induced by the interaction of the two modes in the laser cavity. The effects on the direct amplitude modulation and on the direct modulation of the difference frequency between the two modes are analyzed using simulation and experimental results. When the photon–photon resonance, which occurs at the difference frequency between the two modes, is properly placed at a higher frequency than the carrier-photon resonance, the small-signal amplitude modulation (AM) bandwidth of the laser can be significantly increased. However, both simulations and experiments point out that a high small-signal AM bandwidth does not lead to a high large-signal AM bandwidth if the small-signal modulation response has significant variations across the modulation bandwidth. The paper shows that a high large-signal AM bandwidth is obtained when the two modes are significantly unbalanced, whereas a high-bandwidth difference frequency modulation can be best detected when the two modes are balanced and the DC bias is properly chosen. acceptedVersion

The Mach–Zehnder interferometer (MZI) structures working on the principle electro-optical effect shows the powerful ability to switch the optical signal from one output port to the another output port. Hence, it is possible to construct some complex optical combinational digital circuits using the electro-optic effect based MZI structure as a basic building block. The implementation of electrical binary to optical gray code converters and even parity checkers can improve the performance of the digital logic circuits. The paper provides the elementary theory about the electro-optic effects and describes efficient techniques to implement the electrical binary to optical gray code converters and even parity checkers using appropriate configuration of electro-optic based MZIs as basic building blocks. The paper includes the detailed mathematical derivation and corresponding MATLAB simulation result related to the optical switching phenomena of MZI structure. The paper describes the efficient techniques to implement the electrical binary to optical gray code converters and even parity checkers with the suitable mathematical expression and relevant MATLAB results. The proposed devices are verified with the appropriate optiBPM software. Finally, the paper shows the detailed analysis to check the appropriate device parameters such as Ti-thickness, switching voltages in order to obtain the optimum performance parameters such as cross-talk, extinction ratio and losses through the linear and curved waveguide section.

A hybrid algorithm, which couples rigorous time-domain electromagnetic analysis with rate equations representing a multi-level atomic system, is presented in this paper. It is explicitly shown that the rate equations can be decoupled from Maxwell curl equations, provided that the evolution of both systems is ongoing on different time scales. Consequently, the proposed algorithm allows substantially speeding up electromagnetic analysis of absorbing and lasing materials with no deteriorating impact on accuracy. Several computational examples, pointing out major properties of the proposed hybrid FDTD algorithms, are presented in this paper.

This paper presents long reach wavelength division multiplexing passive optical network (WDM-PON) system capable of delivering downstream 20 Gbit/s data and upstream 10 Gbit/s data on a single wavelength. The optical source for downstream data and upstream data is mode locked laser at central office and reflective semiconductor optical amplifier (RSOA) at each optical network unit. We use two RSOAs at each optical network unit for the 10-Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free-spectral range of the cyclic arrayed waveguide gratings used at the central office and remote node (RN) for (de)multiplexing the WDM channels. We extend the maximum reach of this WDM PON to be 45 km by using Erbium-doped fiber amplifiers at the RN.The hybrid amplifier is designed to enhance the signal power and compensated the fiber dispersion over a wide wavelength range. Optical Equalization technique is used before the receiver to improve modulation bandwidth of an RSOA based colorless optical network unit. Optical Equalization technique helps to improve downlink and uplink performance. Author also investigates analysis of backscattered optical signal for upstream data and downstream data simultaneously. Bit error rate, backscattered optical signal power were measured to demonstrate the proposed scheme. In this paper Long reach and large data service aspects of a WDM-PON is presented.

The purpose of this paper is to construct an identification model that can discriminate different transgenic cotton seeds with similar characteristics based on terahertz (THz) spectroscopy. An improved support vector machine (SVM) which using genetic algorithm (GA) to optimize parameters is proposed in this paper. Principal Component Analysis is applied to extract relevant features from original spectrum information and eliminate the anomalous samples. Instead of original spectral information, the feature spectrum is selected to be fed into the model of GA-SVM, where an improved SVM method to identify those samples. The results demonstrate that the GA-SVM method can effectively identify the distinct transgenic cottons, and THz spectroscopy can provide a nondestructive, rapid and reliable method to distinguish different transgenic cottons.

Asymmetrically clipped DC-biased optical frequency division multiplexing (ADO-OFDM) technology is developed in visible light communication (VLC) systems. Peak to average power ratio is the major problem in the optical OFDM signal, which reduces the performance of VLC due to the light-emitting diode non-linearity. This paper illustrates the uses of the signal clipping method, and different companding approaches for PAPR reduction, such as the μ-law, logarithmic, and novel proposed scheme. The proposed model is a non-linear companding technique which is a modified version of the μ-law and logarithmic models placed at the front end of the VLC transmitter. De-companding is placed before the ADO-OFDM modulator, which reconstructs the OFDM signal. Simulation results denote that the proposed model in companding and de-companding is a better choice. The advantage of this technique is a tradeoff between the bit error rate and PAPR. It reaches over 70% reduction of the original PAPR signal and can boost the BER from 0.03 up to 4.9 × 10–6 when signal-to-noise = 26 dB. So, according to these results, the proposed system is considered a performance enhancement model for the ADO-OFDM based on VLC.

Mode division multiplexing (MDM) is an emerging multiplexing technique that simultaneously transmits independent channels through a spatial light modulator (SLM). Further, Spectral amplitude coding optical code division multiple access (SAC-OCDMA) is an encouraging invention because it gives an appealing answer for burst and asynchronous environment. In addition, free space optics (FSO) provides a cost-effective, secure, high data rate for last mile access compared to other systems. In this paper, a hybrid 100 GB/s SACOCDMA-FSO-MDM system is proposed, and its performance is estimated by using four SAC-OCDMA codes that are Zero Cross Correlation (ZCC), Random Diagonal (RD), Multi Diagonal (MD), and Enhanced double weight (EDW) under atmospheric turbulences such as haze, rain, and clear weather. Laguerre Gaussian (LG) modes (used for MDM) and direct detection (DD) method are used for the construction of the system using 10 channels; each carries 10 Gb/s data. Results specify that the ZCC code is more suitable under all the atmospheric conditions as it possesses no cross-correlation, lesser noise that diminishes the hardware's complexity. For clear weather, the ZCC code gives a BER of 10–29 at a maximum distance of 22 km.

In the present day, optical communication technology is proving to be one of the potential replacements to the current electronic-based systems due to its much higher data transmission rate with low loss and electromagnetic interference. This paper designed and simulated our proposed circuit of a digital photonic even parity bit error detection system that is widely employed for the long-range digital signal transmission. Silicon photonic micro-ring resonators are used as their core component. Each of the rings is configured to operate as a digital logic XOR mode by taking advantage of the silicon waveguide's resonance shifting properties. Dynamic response characterization was carried out by simulating the proposed circuits at the data rate of 1-Gbps, with the data sampling rate of 1.6-THz. A clear timing waveform was generated to confirm that the proposed circuit operates as the parity bit error detection system.

This paper reveals a complete spectrum of soliton solutions that emerges from the governing model studied with anti-cubic law of nonlinear refractive index. Jacobi’s elliptic function scheme shall be implemented followed by a limiting approach for the corresponding modulus of ellipticity. The existence criteria for such solitons are also enumerated.

This paper aims to improve the traffic system through an imaging receiver. Different modulation schemes for visible light communication (VLC) are investigated, including On–Off Keying (OOK), L-Pulse Position Modulation (L-PPM), and Inverse L-Pulse Position Modulation (I-L-PPM) schemes. Considering a road with three lanes, the received information changes according to many factors such as the communication distance and the number of pixels for the imaging receiver. A simple traffic model has been proposed and analyzed for optimizing several remarkable characteristics, including signal to noise ratio (SNR), required average power, bit error rate (BER), and modulation scheme. The simulation results show that, an imaging receiver with 64 × 64 pixels is a good choice for a communication distance in the range 10–50 m between vehicle and traffic light. Also, in the three lanes, the received information increases with the number of pixels. The replacement of a photodiode with an imaging receiver enhances the SNR and reduces both required transmitter power and BER. It is found that 10 dB less power is required in 16-PPM scheme requires than that required by the 16-I-PPM, but in the expense of bandwidth used.

In this paper, stochastic Fornberg–Whitham and a stochastic Camassa–Holm (CH) type equations are studied. A Galilean transformation which previously used for a stochastic KdV equation is employed to transform the equations into their deterministic counterparts. Then $$(1/G')$$ -expansion method is used to obtain analytical solutions. 2D, 3D, and contour graphs representing the peakon solutions have been plotted by assigning special values to the constants in the solutions via computer software. In addition, by giving different random values to the external noise, the effect of the noise on the wave-forms has been exhibited. The obtained results have been discussed in detail.

In this paper, an artificial nanoscale optoelectronic synapse is designed and simulated. The device is based on an InAs nanowire phototransistor covered with a native oxide layer, which captures the photo-generated hot electrons before the thermalization back to the conduction band. Due to the large surface-to-volume ratio and high electron mobility of InAs nanowire, the device exhibits a high responsivity of 104 A/W under 633 nm excitation at 300 K. At low illumination power density range of 10–5 ~ 3 W/cm2, the device shows synaptic behaviors including short-term potentiation, long-term potentiation and paired-pulse facilitation. The influence of different factors, including illumination intensity, gate voltage and the depth and concentration of traps on the synaptic behaviors, is studied in detail. By adjusting the gate voltage, a transition from short-term potentiation to long term potentiation is realized. The synaptic behaviors are explained by energy band diagram and distribution of current density and trapped charges. This work may pave the way for the development of low-consumption high-speed large-bandwidth synaptic devices.

During the course of a typical deep space mission like Mars Earth mission, there exist a wide range of operating points due to the different changes in geometry that consequently cause different Link Budgets in terms of received signal and noise power. These changes include: Distance Range, Sun-Earth-Planet Angle, Zenith Angle and Atmospheric conditions. The different operating points with different losses (background noise, pointing losses and atmospheric losses) lead to different capacities and data rates over the course of a typical Deep Space mission. Consequently, different engineering parameters are adjusted and optimized to combat some of these varying losses in order to get an acceptable data rate and bit error probabilities. This provides a good basis to undertake analysis and simulations of the various operating conditions that occur with the varying spatial orbital time periods on the resulting received signal power level, noise power level, capacity, data rates and bit error probabilities. This paper details results of simulations done in a typical Deep Space Optical Communication link operation.

In this paper, the design and simulation of an ultra-fast 4 × 2 encoder have been optimized in a new and unique way using the wave interference technique based on two-dimensional photonic crystal structures. To create the given structure, nano-resonators (NR) were used in combination with curved 2-branch waveguides to take advantage of wave interference as well as reduce losses and light scattering in the structure to achieve the desired results. Due to its special design, the proposed structure has been symmetrical with a structural size of about 149 µm2. This symmetry caused the same results to be obtained in different states of the used encoder. The results from the structure simulation indicated a contrast ratio of 7.88 dB, a delay time of 0.21 ps, and a bit rate of 4.761 Tbit/s. All simulations were performed with a central wavelength of 1550 nm and an input power intensity of about 1 mW/µm2. To optimize the structure and evaluate the results obtained from it, the changes were made in the structural parameters such as the size of the radius of dielectric rods, the size of NRs, and the value of lattice constant, and the effects of wavelength, operating frequency, and input power intensity on the simulation results were investigated. The analysis of the results of simulations and optimizations indicated the design of a completely principled and logical structure with very suitable results in comparison with other structures proposed in this field so that it can be used appropriately in integrated optical circuits and can be considered as the basic structure for other designs. In the present research, the plane-wave expansion method was used to extract and analyze the photonic bandgap and the finite-difference time-domain method to obtain the results of the output spectrum of the proposed structure.

In this paper, an optical modulator design based on a silicon-on-calcium fluoride platform with a layer of Vanadium dioxide (VO2) is proposed. The VO2 as a phase changing material is used to control the modulation process, making use of the phase transition of the VO2 material between dielectric and metallic states. The modal properties of the proposed optical modulator are studied and analyzed using the well-known full vectorial finite element method. Whereas, the light propagation is studied using the 3D finite difference time domain method. The suggested device offers a number of advantages such as low insertion loss of 0.431 dB/µm and high extinction ratio of 14.99 dB/µm at a wavelength of 3.95 µm and device length LD of 2 µm. To the best of the authors’ knowledge, this is the first time to present an infrared optical modulator based on silicon-on-calcium fluoride platform.

In this paper, we considered the nonlinear Schrodinger equation modeling cubic optical solitons in a polarization-preserving fiber with Kerr law. Using the improved $$tan(\varphi /2)$$ -expansion method, a powerful and effective method, we constructed exact solutions including the hyperbolic function solution, the trigonometric function solution, the exponential solution and the rational solution with free parameters. The geometrical shapes for some of the obtained results are depicted for various choices of the free parameters that appear in the results. The obtained solutions are entirely new and can be considered as generalization of the existing results in the ordinary derivative case.

In this paper, perturbed Chen–Lee–Liu equation is considered to describe pulse propagation in optical fibers. Chen–Lee–Liu equation is a derivative form of the nonlinear Schrodinger equation. Two renowned analytical techniques namely, $$\exp (-\varphi (\eta ))$$ -expansion method and the generalized Kudryashov method are applied to analyze this model. The algorithm of these methods is also presented. Different structures of soliton solutions are successfully investigated for perturbed this model. Additionally, constraint conditions on coefficients of perturbation terms are also defined to assure the existence of such solitons. The graphical representation of these solutions is shown to demonstrate the dynamics of pulse propagation governed by Chen–Lee–Liu equation in optical fibers.

In this paper, the optical solitons with M-truncated derivative and other solutions to the coupled nonlinear Schrodinger equation (NLSE) are obtained. The coupled NLSE describes the pulse propagation through a two-mode optical fiber. Complex amplitude ansatz and polynomial expansion methods are employed to construct such novel solutions. We successfully construct dark, mixed dark-bright, singular optical solitons and other solutions to the considered nonlinear model. Dark soliton describes the solitary waves with lowerintensity than the background, bright soliton describes the solitary waves whose peak intensity is larger thanthe background and the singular soliton solutions is a solitary wave with discontinuous derivatives; examples ofsuch solitary waves include compactions, which have finite (compact) support, and peakons, whose peaks have adiscontinuous first derivative. Numerical simulations of the solutions are used to analyze some of the propagation properties of pulses and their collision dynamics. Fusion along quasi-periodic waves is found to be exhibited. Under nonlinear refractive elements, the graded or phase index waveguide is seen to change the strength of the soliton. In addition, the properties are shown with figures for these solutions. These findings have been usefully extended to the transmission of long-wave and high-power telecommunication systems. In addition, through the figures presented, the effect of the fractional order $$\alpha$$ is reflected.

In this paper, we have studied different combinations of nanoparticles in the Fibonacci and the periodic array to simulate a transparent color display. We examined the effects of scattering and absorption cross-section of various combinations of three and six nanoparticles on the periodic and the Fibonacci arrays. For this purpose, we use spherical coated Si/SiO2 nanoparticles with specific sizes for core and shell at blue, green, and red wavelengths to obtain maximum scattering to absorption ratio. By examining different combinations of nanoparticles, we found that some combinations show a sharp and narrow scattering cross-section for specific wavelengths. With these characteristics, the amount of contrast and transparency in transparent color screens can be improved. We use the FDTD solution of Lumerical software and MATLAB software for the simulation of introduced structures.

Quantum-dot cellular automata (QCA) technology is believed to be a good alternative to CMOS technology. This nanoscale technology can provide a platform for design and implementation of high performance and power efficient logic circuits. However, the fabrication of QCA circuits is susceptible to faults appearing in this form of missing cells, additional cells, rotated cells and displaced cells. Over the years, several solutions have been proposed to address these problems. This paper presents a new solution for improving the fault tolerance of three input majority gate. The proposed majority gate is then used to design 2-1 multiplexer and 4-1 multiplexer. The proposed designs are implemented in QCA Designer. Simulation results demonstrate significant improvements in terms of fault tolerance and area requirement. The proposed gate consists of 11 cells and requires an area of 0.0096 μm2. The proposed design has 100% tolerance to the fault of a single missing cell and 71.43% tolerance to the rotation of one cell. The proposed 2-1 multiplexer consists of 41 cells and requires an area of 0.066 μm2. This multiplexer has 95.24% tolerance to the fault of a single missing cell.

Visible Light Communication (VLC) can be utilized for Indoor Positioning Systems (IPSs). Most of VLC IPSs work when LED lights are ON. This causes energy less when lighting system is off, at least when sleeping. We face a fundamental challenge in VLC systems that require the light ON all time. Then how to communicate when the lights appears “OFF”? In this paper, we propose a positioning system of receiver that is used in dark light VLC based on the Received Signal Strength (RSS) positioning technique, showing its possibility to use in dark environment. Because of its simplicity, the RSS technique is used in indoor positioning. This proposition can ensure the IP even when light is “OFF”, which can be actualized in VLC systems to save energy and give precise illumination control. The obtained results reveal that the average error in positioning with LED power of dark VLC is lower than that in the normal mode. The obtained simulation results reveal that the average positioning error is improved by 25% of traditional method when Dark VLC is used with 1.4 mW LED power without background noise. This ensures that the proposed system shows superiority when compared with other VLC IPS systems, in energy saving and high positioning accuracy.

In this paper, we study the power absorbance enhancement in thin film silicon solar cells with the help of plasmonic sphere-cube hetero-dimer structures. Ag sphere-cube hetero-dimer structures are integrated on top of thin film crystalline silicon solar cells. The heterodimer structure highly localizes the light and redirects it inside the solar cell. Engineering the geometrical parameters and the gap between the sphere and the cube is a key parameter that determines the power absorbance enhancement in the solar cell. The simulation results show a broadband power absorbance enhancement compared to the plain cell and enhanced the photogenerated current. We compare different structures and materials of plasmonic nano single particle systems, symmetric sphere-sphere and cube-cube dimers, and sphere-cube hetero-dimers. The plasmonic sphere-cube heterodimer structure enhanced the absorbance of the solar cell compared to a plain cell.

In this paper, the simultaneous impact of interference and aggregated hardware impairments on the performance of mixed radio frequency/free space optical (RF/FSO) relaying systems is studied. The relay node is assumed to operate in decode-and-forward (DF) mode and the statistics of RF fading along with co-channel interferers have been modeled using the Nakagami-m distribution. The FSO link is affected by turbulence and pointing error fading which has been modeled using the Malaga distribution. For the considered system model, the closed-form analytical expressions have been derived for outage probability and ergodic capacity. The exact results have been further simplified using the high signal-to-noise ratio approximations to derive the asymptotic representations for the same. Finally, numerical and simulation results have been demonstrated to showcase the important findings of the research work to illustrate the impact of hardware impairment and interference on the mixed RF/FSO DF relaying system.

Light confinement technologies are especially effective in improving the power conversion efficiency of thin-film perovskite solar cells. For this purpose in this paper, designing an angular filter for these photovoltaic cells using nano-rough structures and index-near-zero materials is proposed. Since perovskites’ energy bandgap can be easily tuned by their chemical composition, an optimal structure with typical compounds was proposed that produced the highest power conversion efficiency limit. Besides improving light confinement in the thin, perovskite active layer, the proposed structure improved the solar cell performance by enhancement of short-circuit current and open-circuit voltage through controlling radiative and non-radiative recombination. With these arrangements, an optimal power conversion efficiency limit of 40.01% has been calculated using the detailed-balance method, which indicates a 15.27% improvement compared to the original structure. The Finite-Difference Time-Domain (FDTD) method was used to demonstrate the expansion of the absorption spectrum and calculate the absorption efficiency for presenting an optimal structure design with nano-roughness for different perovskite compounds.

Wireless communication refers to data transfer in an unguided propagation medium through wireless carriers such as visible light (VL) and radio frequency (RF). The rapidly growing demand for high data rates overloads conventional RF wireless communication. Therefore, technologies such as cognitive radios and millimeter waves (mmWaves) have been utilized to overcome capacity limitation and spectrum scarcity of RF systems. In parallel, optical wireless communication (OWC) is a promising alternative solution to its radio frequency (RF) compeer. OWC has been revolutionized to support fifth generation (5G) wireless communication and Internet-of-Things (IoT) terminals. In addition, OWC has no health hazard, low power consumption, unlicensed spectrum and shows immunity to interferences from electromagnetic sources. As RF and OWC are compatible, so a joint application scenario is referred as an excellent solution to support 5G and beyond systems. Hybrid optical/optical and RF/optical system is a promising approach to remove the limitations of each system as well as to enable supporting features of each technology. An optical/optical hybrid system is based on two or more OWC technologies while RF/optical hybrid system contains both RF and OWC technologies. The hybrid systems can enhance system performance in terms of energy efficiency, reliability and throughput of each system. Thus, hybrid RF/optical systems are envisioned as a key enabler to enhance user mobility and data rate on the one hand and to optimize power consumption, network load, interference and network capacity on the other hand. This survey seeks to provide the state-of-the-art and future research directions regarding optical wireless hybrid networks. This paper represents a technological overview of existing optical wireless hybrid networks. We have discussed optical-based free-space optics (FSO), optical camera communication (OCC), light fidelity (LiFi) which extends the concept of visible light communication (VLC) to attain bi-directional and fully networked wireless communication, as well as RF-based Bluetooth, wireless fidelity (WiFi), small cell, macrocell, mmWave and microwave. In addition, we have also considered underwater acoustic communication for acoustic/optical and acoustic/RF hybrid networks. An extensive range of applications such as indoor, vehicular communication, eHealth, backhaul connectivity solution and underwater communication is considered. We have addressed potential challenges and open research issues for design and successful deployment of hybrid wireless networks.

All optical analog to digital converters will play crucial roles in the future generation of all optical data processing. Cascading optical limiters is a suitable method for designing all optical analog to digital converters. In this paper an optical limiter was proposed using two nonlinear photonic crystal ring resonator, then by cascading 4 optical limiters an structure was proposed for realizing a 5-bit all optical converter. With the help of two examples the correct operation of the proposed structure was confirmed. The total foot print of the proposed structure is about 1796 mm2.

In this paper, four different configurations of sensitive metamaterial absorbers based on graphene-plasmonic combinations are designed and proposed. The nanostructures are made of graphene, SiO2, aluminum and gold layers on a silicon substrate. Graphene-ring shaped structures with diagonal strips in vertical and horizontal directions are considered in the structures which greatly affect the absorption characteristics (absorption peak value and wavelength). Aluminum layer is used in the structure to prevent the transmission of light throughout some layers and improve the absorption factor. To promote the functionality of the structures, effects of the structural parameters (R1 and R2) and chemical potentials (Ef1, Ef2, Ef3 and Ef4) on the absorption peak are also studied. The four individual configurations with different layers and strip directions demonstrate distinct and different wavelength ranges; structure-1: 45–60 µm, structure-2: 50–70 µm, structure-3: 70–85 µm, and structure-4: 80–100 µm. Thus, they can be utilized for wide categories of applications. Sensitivities of 1500 nm/RIU, 2250/RIU, 3750 nm/RIU and 4850 nm/RIU are obtained for four types, respectively. The proposed structures can be categorized as refractive index biosensors, which indicate acceptable sensitivities and can be used for detection of different elements like hemoglobin and glucose in blood samples.

This paper reports the numerical investigation of the Talbot effect for biomaterial detection at optical frequencies. Cytop polymer grating Plasmonics structure with periodicity comparable to the incident wavelength are applied to evaluate of the plasmonics Talbot biosensor. Significant sensitivity from the proposed Talbot biosensor is obtained. For this purpose, the effect of the different biomaterials including Ether, Ethyleneglycol, Chlorobenzene and Quinoline on plasmonics Talbot effects at wavelength range of 550-650 nm are then inspected to improve the structural parameters of the biosensor. Also, the sensitivity and figure-of-merit are calculated. Our numerical results show that the proposed biosensor are able to operate as a high sensitivity with maximum FOM of 20.99, and sensitivity of 324 nm/refractive index unit for small change of $$\Delta n$$ = 0.4, in the refractive index of biomaterials. We believe that the proposed biosensor can be applied as a label free on-chip biosensor.

In this paper, the efects of external electric, magnetic and non-resonant intense laser felds on the nonlinear optical rectifcation (NOR), second-harmonic (SH), and third harmonic (TH) generation in a GaAs quantum well with asymmetrical Gaussian potential are theoretically investigated. Firstly, the energy eigenvalues and eigenfunctions of a single electron confned in the structure are obtained by using the diagonalization method within the framework of the efective-mass and parabolic band approaches. Then, using these energy eigenvalues and eigenfunctions, expressions derived within the compact density matrix approximation have been employed to calculate the coefcients of the nonlinear optical response in the structure. The obtained simulation results show that the infuence of the external felds leads to signifcant changes in the coefcients of nonlinear optical rectifcation, second and third harmonic generation in the system. As a result, it has been seen that the amplitude and position of the peaks of nonlinear optical rectifcation, second and third harmonic coefcients can be controlled by changing the applied external felds.

This paper offers to analyze the performance and mitigation strategy for multi-user interference (MUI) based line-of-sight (LOS) infrared (IR) communication system in free space optics (FSO). The model is predicated upon the modulation scheme of code shift keying (CSK) in comparison with the conventional on off keying technique (OOK) for the outdoor environment. To interpret the analytical study, in addition to CSK, 20 μm is guaranteed as an operating wavelength for far infrared (FIR) communication purpose. With a power allocation of 1–10 mW, a maximum data rate of greater than $$10^6$$ bps is achieved and the results are obtained in 1000 m distance. The results indicate that the device output is very responsive to the channel model preference. During the case of atmospheric instability, the comparatively unused FIR spectrum has been found to be ideal for external optical communications. The outcomes are illustrated with the consequences on the system due to intrusions and disruption with the FSO waveforms with increasing numbers of users and the performances of signal to noise ratio as well as bit error rate are improved in the turbulence FSO environment.

Kudryashov–Sinelshchikov equation arises in the study of pressure waves in the mixture of liquid and gas bubbles. In this paper, the exact wave solutions of the Kudryashov–Sinelshchikov equation are obtained using the improved tan $$\left( \frac{\phi (\eta )}{2}\right)$$ -expansion technique. Four types of solutions namely, trigonometric function solution, hyperbolic function solution, exponential function solution and rational solution are constructed. Exact travelling wave solutions including kink, periodic, bright and dark solitons are obtained. The wave solutions are graphically illustrated by 3D-surface plots and the corresponding 2D-contour plots. The comparison of the results obtained by the improved tan $$\left( \frac{\phi (\eta )}{2}\right)$$ method with results obtained by other methods reveals that the improved tan $$\left( \frac{\phi (\eta )}{2}\right)$$ method is more effective and powerful.