Volume 45, Issue 2

This study is to investigate the impact of thulium concentration on the performance of in-band pumped thulium-doped silica fiber amplifiers with considering ion–ion interactions. Due to the fluorescence quenching in silica glass, the fluorescence lifetimes are required to compute at every Tm concentration. The theoretical model of fluorescence decay curves at in-band pumped thulium-doped silica fiber is used to determine the fluorescence lifetimes of the 3 F 4 and 3 H 4 levels. The calculated lifetimes of the commercially available thulium-doped silica fiber are 650 µs for 3 F 4 level and 14 µs for 3 H 4 level and these results are consentient well with the experimental reported results. The theoretical evaluating of the amplifier performance shows that the gain amplifier reduces with concentration increase because of the impact of both fluorescence quenching and the reverse cross-relaxation process. Thus, in contrast to pumping wavelength at 790 nm, there are negative effects of the high doping concentration of Tm ions on the amplifier performance at the in-band pumping scheme.

Explosive increase in internet services put peer pressure on conventional band grid (1530–1570 nm) and therefore L-band wide wavelength grid is required to cater the ever-increasing demands. In this work, accentuation is given to enhance the gain flattening of ultradense (25 GHz) L-band WDM system using single stage EDFA amplifier when ultralow power is launched from 16 and 32 channels. High gain and gain flattening is achieved by incorporating three fiber Bragg gratings (FBGs) for amplified spontaneous noise reinjection. Maximum Amplified spontaneous emission (ASE) is emerged at 1565 nm for the 1575.69–1579 nm input wavelengths (16 channels) and 1572.58–1579 nm (32 channels) at −55 dBm ultra low carrier powers. To optimize different parameters of L-band EDFA, different physical parameters such as core radius, EDF link lengths, and launched powers are varied, and results are analyzed in terms of lateness. Maximum gain is found out to be 34.12 dB at optimal physical parameters of the EDF with gain flatness of ±0.45 dB in case of 16 channels and ±1.41 in case of 32 channels.

This paper presented the high performance signature of transceiver fiber system based on cascade uniform fiber Bragg grating devices. This model has a data rate of 20 Gb/s extended along optical fiber length of 10 km that amplified with an optical EDFA amplifiers at 5 m length. The presented study clarified max. Q of 20.33 compared to the previous models at the value of 8.66. The electrical visualizer measured the total power at the receiver that is 9.564 dBm at the previous model and 23.347 dBm at the presented model. Therefore the total power at the receiver increased by 2.44 times at the presented model and the max. Q also upgraded by 2.96 times at the presented model.

A new connected structure of an all-optical “OR” logic gate realized with photonic crystals is proposed in this study. The structure is based on coupling the input guides with two microcavities; the unit cell of the structure is designed to achieve a band gap around the communication wavelength (i.e., 1.55 µm). The performance of the structure results in transmission efficiency and low losses. This compact size logic gate is considered an important element in the integration of a nanoscale photonic device.

In this paper, an all-optical XOR-AND gate operation has been proposed using one-dimensional periodic nonlinear material model. This structure consists of alternating layers of different nonlinear materials. In this design, we can obtain XOR and AND logical operation simultaneously at the reflected and transmitted port of the periodic structure. Numerical simulation has also been done using the finite-difference-time-domain (FDTD) method. The response time of this switching operation is picoseconds (ps) range order. We find low insertion loss (−3.01 dB), high contrast ratio (14.13 dB) and high extension ratio (10.93 dB) of this device. This design will be useful in future all-optical computing.

Reversible gate has been one of the emerging research areas that ensure continual process of innovation trends that explore and utilizes the resources. Due to the increasing power consumption of electronic circuits, it has been observed that quantum computing is one of its latest applications. This technology can be utilized by reducing the energy consumption by preserving the bits of information that are still useful. A photon has zero rest mass, while an electron has a nonzero rest mass. These characteristics inspired the researchers to develop an all-optical Fredkin gate. The proposed gate design overcomes the shortcomings of conventional Fredkin gates and provides better performance.

The construction of an all-optical frequency-encoded Toffoli gate employing a reflecting semiconductor optical amplifier (RSOA) is proposed in this article. By establishing fields such as quantum computing, optical quantum computing, quantum-dot cellular automata, and superconducting flux logic family, quantum gates have been proved to perform reliably in the present day. A nonzero-mass electron, on the other hand, moves far slower than a quantum particle with zero rest mass, such as a photon. Photons can also be utilized to store data while being sent. These photon qualities have motivated researchers to create quantum gates in the all-optical domain based on them. The RSOA-based implementation of the Toffoli gate gives a significant improvement in the case of high speed, low power, and fast switching time. MATLAB Simulink (R2018a) software is used to simulate the devised design. The theoretical prediction is satisfied by the simulation results.

In optical processing systems, multiplexer is used to design optical devices such as arithmetic logic unit (ALU) and shift register (SR). Through this paper, we investigate the application of nonlinear photonic crystal ring resonator (PhCRR) based on nonlinear Kerr effect for realizing an all optical 2 × 1 multiplexer. The structure consists of two PhCRRs and five optical waveguides using hexagonal lattice silicon (Si) rods with a background of air. Performance of all optical 2 × 1 multiplexer is replicated with the help of finite difference time domain (FDTD) procedure at a wavelength of 1571 nm, and simulations presented an ultra-compact optical structure with ultra-fast switching speed.

The photonic crystal fiber (PCF) is a resourceful optical device that can be used in various applications. The dispersion is a major impediment for such optical waveguides. We propose a modified PCF that evaluates the negative dispersion coefficient−3126 ps/(nm–km) at 1.55 μm wavelength. The precise value calculation of the design parameters is helpful to improve the desired output. The machine learning approaches are now more in fashion to predicate such parameters. The dispersion parameters are obtained for three different PCF models as conventional PCF with fixed radius air holes and type 1 and type 2 models with dual radius air holes. Further, the negative dispersion of a type-I PCF is modeled using an extreme learning machine (ELM) as a regression task and its performance is tested against benchmark models such as support vector machine with linear and radial basis function kernel function, Gaussian process regression, and artificial neural network. Results indicate superior performance of ELM as a regressor both, in terms of prediction and computation time.

A new technique is presented for computing very useful propagation parameters like effective core area and effective index of refraction of mono-mode dispersion shifted and dispersion flattened fibers both in the presence and in the absence of Kerr nonlinearity. The technique involves application of accurate but simple expressions for modal fields developed by Chebyshev formalism. The study of the influence of Kerr nonlinearity on the aforementioned parameters, however, requires the application of the method of iteration. For the purpose of such investigation, in linear as well as nonlinear region, we take some typically used dispersion shifted and dispersion flattened fibers and we show that the results found by our simple formalism are in excellent agreement with those obtained by using complex finite element method. Further, the necessary evaluation by our simple method needs very less computations. Thus, our formalism generates ample opportunity for applications in many areas in the field of nonlinear optics.

Photonic crystal ring resonators (PCRR) as momentous candidates for future photonic crystal integrated circuits (PCICs) draw worldwide attention. In this paper, different configurations are proposed based on single, parallel, and serial PCRRs. To be precise, the different coupling lengths and alignments have been discussed in double and triple PCRRs in parallel and serial configurations to achieve the highest efficiency concerning the desired applications such as an add-drop filter (ADF) and a power splitter. Moreover, in the achieved optimum double and triple PCRRs, the effect of coupling radius change has been discussed.

In this work, a high-performance multioperation bit-manipulator is presented. The presented electro-optical design can perform several bit-manipulations such as bidirectional bit-shifting, bit-rotation, multiply-by-2 and divide-by-2, and sequence designing operation. The technique relies on the electrooptic principle in lithium niobate. Lithium niobate-based waveguides have been used to design Mach–Zehnder interferometer, which is the fundamental optical switching element of the whole model. Extinction ratio, contrast ratio, and insertion loss values computed for the simulated results are 29.16 dB, 29.48 dB, and 0.77 dB, respectively.

We presented a concept of converged coexistence (CC) access network and generate, and test model is demonstrated for optimization of channel launch power PT ODN in the distribution network which subsequently confirm power budget class of NG-PON2 in this paper. Multiplexing of wavelength and time (TWDM) technology is incorporated for multichannel NG-PON2 configurations for 5G, internet-of-things (IoT) applications, and fiber-to-the-x (FTTX) services. CC NG-PON2 symmetric configuration supporting 2.5 and 10 Gbps channels are analyzed and compared in the sight of channel nonlinear impairments includes Kerr-effect ( γ ) spanning from self phase modulation (SPM) and cross-phase modulation (CPM), chromatic dispersion (CD), and four wave mixing (FWM) in worst-case scenario. Intensity modulation (IM) technique incorporated before multiplexing the D/S channels by coexisting element (CEx) and coupled to wavelength routed (WR) optical distribution network (ODN). U/S channels are routed using wavelength select (WS) ODN. ODN is implemented using G.652 non zero dispersion shift (NZ-DSF) single-mode (SM) fiber. Multi-channel spectrum envelope propagating in either direction is optimized to PT ODN  = 3/5/7/9 dBm and 4 dBm, respectively. The theoretical modeling and simulative results confirms the proposed network configuration supports incremental receiver sensitivity (Rxs) as −42.19/−42/−39.75/−37.97 dBm and −35.45/−35.38/−33.45/0.38/−42 dBm for λ1 2.5 Gbps and λ8 10 Gbps TWDM and PtP WDM channels, respectively, for all-class networks supporting splitter configuration ratio of 640 at 50 km mitigating effect of channel nonlinearities like CD, SPM, cross-phase modulation (XPM), and FWM for λ8 10 Gbps channel.

This paper focused on the novel design of receiver side of wavelength division multiplexing passive optical network (WDM-PON). It serves the need for a dramatic change in demand for high data rate beyond 10 gigabits per second (Gbps) at the last mile for a larger coverage area or distance. This increase in demand for higher bandwidth is due to the emerging future technologies like Internet of things (IoT), silicon on chip (SoC), cloud computing, machine learning (ML), and artificial intelligence (AI). Simulation results demonstrated for the different coverage areas which compare the bit error rate (BER), quality (Q)-Factor, and eye height as per the guidelines of ITU-T. It has been predicted that the proposed WDM-PON design supports up to a distance of 60 km. Results have been verified for 40 km, 50 km, 60 km, and 70 km, respectively, at 100 GHz frequency spacing with acceptable BER and better quality (Q)-factor as defined by ITU.

This paper demonstrated the efficient employment of vertical cavity surface emitting laser (VCSEL) light sources in high speed dispersion compensation systems. VCSEL are compared with CW laser and distributed feedback laser in the modulated light output power, signal quality factor and minimum data error rates through the fiber system. Light signal base band modulated power is clarified with spectral frequencies after LiNb MZ modulators. Light signal base band modulated amplitude is simulated against base band time frequencies after LiNb MZ modulators. The total light signal index base band modulated power/amplitude value is estimated after LiNb MZ modulators for various light sources. The light signal base band modulated power is demonstrated with both spectral frequencies and time interval after fiber loop control length with compensation system. Total light signal index base band modulated power/amplitude value is estimated numerically after fiber loop control length with compensation system. The modulated electronic signal base band modulated power is indicated with spectral frequencies after PIN receiver. The light signal base band modulated amplitude is studied clearly against base band time frequencies after PIN receiver. The signal quality factor, BER, and modulated lighted output power are clarified and sketched against fiber system lengths for various light sources.

Optical wireless communication systems employing free-space optical (FSO) links utilize modulated lasers to transmit information. FSO–fiber optic (FO) link provides an alternative possible way in scenarios where infrastructures employing optical fibers are widely destroyed due to disasters or when difficulties are faced during the installation of FO links. Furthermore, the link is integrated with decision-making ability. To encounter the distortions in the received signal carrier-suppressed return-to-zero modulation format has been used. FSO–FO hybrid link has been compared with simple FSO channel. The terrestrial links depend strongly on weather conditions as optical beams propagate through the atmosphere. Atmospheric attenuation could affect the FSO channel and has been considered to analyze the performance of the designed system.

In today’s scenario, wireless communication is turning into a decisive and leading backbone to access the worldwide network. Therefore, the usage of mobile phones and broadband is rising staggeringly. To satisfy their expulsive needs, it demands increment in data rates while providing higher bandwidth and utilizing optical fiber in wireless communication, and this becomes a worldwide analysis area. Radio over fiber (RoF) system is taken into account as best solution to fulfill these needs. In RoF system, the radio frequency signal operated at millimeter wave (30–300 GHz) is centralized and processed at control station (CS) and also, the CS upconverts this electrical signal to optical domain. By employing optical fiber link, this signal reaches to base station (BS). Then, the received optical signal converts back to electrical domain at the respective BS. Now BS radiates the electrical signal to corresponding mobile station (MS) in commission with the millimeter wave frequency bands. This RoF system is providing massive bandwidth, facilitating large mobility for RF frequency signals, small loss, fast and cost effective setup, wonderful security, and unlicensed spectrum etc. The RoF system introduces microcells structure for BS cells to boost the frequency reuse and needed capacity. It has benefits in terms of ability to fulfill increasing bandwidth demands to cut back the power consumption and the dimensions of the handset devices. This paper firstly explains the overview of existing wireless mobile communication and broadband systems and then, targets the review of RoF system which will become energy efficient system for next generation mobile communication and future broadband systems. This paper also includes the performance degradation and evaluation parameters. Finally, this paper presents the various research opportunities for its implementation zone.

In the discretely amplified transmission systems with erbium-doped fiber amplifiers, the system performance of nonlinearity-compensated optical transmission based on pre-dispersed spectral inversion (PSI) is investigated numerically. We find that PSI offers more significant performance improvement in dispersion-managed (DM) links than that in non-dispersion-managed (noDM) links. On the other hand, the DM link is more sensitive to the span offset from the center of the transmission link than noDM link. The performance difference between DM and noDM links is 1 dB if the span offset equals four spans in 20 × 90 km nonlinear transmission. Furthermore, we show that for the dispersion-managed transmission, in order to obtain the best system performance, the amount of pre-dispersion of the PSI, should be optimized over different dispersion maps.

Hybrid wavelength-division-multiplexing (WDM) and free space optical (FSO) access networks are getting great attention due to numerous advantages. In this work, hybrid WDM-FSO system is demonstrated for 55 km at capacity of 5 × 10 Gbit/s using compressed spectrum return to zero (CSRZ) WDM-FSO in downstream and nonreturn to zero (NRZ) in upstream for demonstrating transmitter diversity which inturn decrease the interchannel interference. For the suppression of Rayleigh backscattering (RB) interferometric beat noise, bidirectional cyclic multiplexer is employed. Cyclic multiplexer provide λ 1 to λ 5 wavelengths for optical line terminal (OLT) to ONU transmission and λ 2 to λ 6 for ONU to OLT transmission. Insertion losses of each component are considered and in the end, power budget is also calculated. Results revealed that FSO length of 780–1050 m are obtained using various WDM-FSO downstream signals and their power budget, redundant budget, maximum distance, and insertion losses also calculated.

This article has indicated optical coherent differential polarization (DP) 16 quadrature amplitude modulation (QAM) transceiver systems with free-space optical (FSO) channel in the presence of differential coding scheme. The optical coherent DP 16-QAM receiver executes the reverse process conversion of the optical signal into an electrical one that is detected to the users. The proposed optical coherent DP-16 QAM transceiver systems based FSO channel model with differential coding has been presented and compared with the previous model. However, the simulation results have confidence realization about the superiority of the proposed simulation model. Hence the proposed optical coherent DP-16 QAM transceiver systems simulation model with differential coding is verified and validated the enhancement performance based on simulation performance parameters.

In this work, a free-space optical (FSO) communication system with the integration of mode division multiplexing and circular polarization shift keying (CpolSK) is proposed at 2 × 40 Gbps using LG00 and LG01 modes. Effects of diverse weather conditions such as clear weather, light rain, moderate rain, heavy rain, thin fog, thick fog, and heavy fog are studied on system performance. Further, a detailed comparison of CpolSK and polarization shift keying (PolSK) is performed at different FSO lengths in terms of log bit error rate. For implementation, analysis, and comparison, Optiwave Optisystem software is used and results show that CpolSK covers 100 km link distance and PolSK limits to 90 km only. Also, LG00 mode performs better than LG01 mode under all weather instabilities in the proposed system.

Future wireless networks are researching how to fulfill the growing demand for wireless optical communication. The increased usage of mobile devices and sensors in the real world has resulted in this increasing demand. The fifth-generation (5G) wireless network is the most promising wireless network in the future, with the potential to improve various performance metrics such as spectrum and energy efficiency, high capacity, and low latency. Orthogonal frequency division multiplexing (OFDM) can be produced using cyclic prefix and Fast Fourier Transforms to fight extreme multipath fading. Filtered OFDM, such as Filter-Bank Multi-Carrier (FBMC), can be used to circumvent this limitation. The usage of FBMC to improve the performance of 5G networks is discussed in this paper, along with several hot issues like visible light communication, cognitive radio, and multiple-input multiple-output that FBMC may be utilized with to improve communication.

In the present work, orthogonal frequency division multiplexing (OFDM) is combined with wavelength division multiplexing-passive optical networks (WDMPONs) to obtain the combined benefits of both technologies for overall system improvement. performance of five OFDM signals using WDM is analyzed. An optical system is designed using the OFDM signal, and its performance is analyzed using various matrices like bit error rate (BER) and Q-factor under the effect of varying laser power. Mapping of OFDM signals is done using 16-QAM modulation. The system shows an enhancement in the performance by increasing the laser power but up to some limit, and efficient results are obtained in the 70–130 mW laser power range.

In this article, a free-space-optics (FSO) model for a metro city based on real-time visibility data under different weather conditions is presented. Here, the relation between atmospheric attenuation and visibility value and its impact on the FSO performance is carried out. Also, the hybrid-SIM modulation technique is applied for the bit error rate (BER) improvement of the system. Here, Bhubaneswar (the capital of Odisha, India) is considered for the above analysis. The total attenuation, BER, and link margin are calculated for the FSO performance evaluation of Bhubaneswar city and these are simulated using Matlab. The simulation results show that the proposed hybrid-SIM modulation technique achieves about 2.9 dB of SNR improvement than the existing BPSK-SIM technique. Also, from the link margin analysis, it is observed that the sunny day is the most suitable for FSO link transmission. These results can be helpful to decide the FSO parameters and the FSO setup can be designed for any city.

Underwater video regulation is an insightful research field that can help engineers with bettering investigation on the lowered condition. Submerged video preparing has been utilized in a many fields, such as submerged infinitesimal location, landscape examining, mine identification, media transmission connections, and self-proficient lowered vehicles. Be that as it may, submerged video experiences solid assimilation, dissipating, shading contortion, and clamor from the manufactured light sources, causing video obscure, cloudiness, and a somewhat blue or greenish tone. In this way, the improvement can be separated into two techniques, submerged video de-preliminaries and underexposed video concealing remaking. Relentless in remote correspondence structures, for instance 3G, 4G, and so on, a coming crisis is endless deftly of the nonattendance of consistently Radio Frequency (RF) resources; this deterrent in moving speed cannot strengthen the improvement notable for high information speed. So the new innovation of Light-Fidelity (Li-Fi) came into picture. This innovation can be contrasted to that of Wi-Fi and offers points of interest like expanded available spectrum efficiency, effectiveness, security, low idleness and a lot higher speed. Communication is accomplished by exchanging light-emitting diode (LED) lights on and off at a speed higher than what is detectable to the human eye. This paper presents the explanation behind underexposed picture corruption and surveys the cutting-edge knowledge calculations like video reduce hazing algorithm. In this calculation, it uses two different de-hazing methods, simple Dark Channel Prior (DCP) and Approximate Dark Channel Prior (ADCP), to reduce haze in a video.

Like OFDM, OCDM signal also suffers from high PAPR. SLM is an attractive PAPR reduction method but it needs to transmit the information regarding phase sequence i.e. SI to the receiver, which results in reduction in SE and data rate. Various SLM based SI free and SI embedding schemes are available in the literature. In this paper, different possible quaternary to 8-QAM mapping schemes for SI free SLM based PAPR reduction in OCDM system are discussed. Moreover, a new mapping scheme to eliminate the SI requirement has also been presented in this manuscript for SLM based PAPR reduction in OCDM system. Proposed Circular (6, 2) mapping scheme doesn’t require SI at the receiving end which results in increase in SE and data rate as compared to standard SLM technique. Random sequence with phase factors {1, −1} is used to generate the phase sequences for the proposed mapping scheme. Also, the analytical expression for SER of Circular (6, 2) mapping scheme over AWGN channel is derived. We have also evaluated the mathematical expression for SER of other possible quaternary to 8-QAM mapping schemes. Computer simulation using MATLAB are also carried out to investigate the performance of all these mapping schemes in terms of PAPR reduction performance as well as SER performance over AWGN and multipath Rayleigh fading channel. Proposed scheme achieves the same PAPR reduction and improved SER performance w.r.t. other six schemes taken into consideration.

Optical communication has emerged as the best solution to high-speed transmission systems due to its higher bandwidth and higher data rates. The higher data rates with simple transmitter and receiver modeling are one of the best solutions to design the spectrally efficient high-speed optical transmission system using different modulation techniques. In the recent past, optical communication networks have been specifically designed and optimized to support different communication standards increasing the capabilities of optic fiber, integrated waveguides, and related optical fiber hardware, and signal conditioning circuits. So, this research paper presents a study, modeling, simulation, and analysis of optical performance under different transmission systems which are considered in a practical high-speed design using orthogonal frequency division multiplexing (OFDM). This can be done by using both coherent detection OFDM and direct detection OFDM to minimize dispersion effects in optical communication because OFDM is basic for modern technology to increase the data rate and increase the requirement of bandwidth in broadband services. Many optical fiber problems, such as chromatic dispersion (CD) and polarization mode dispersion (PMD) are solved using OFDM. The performance analyses made in this work by using different parameters such as bit error rate (BER), optical signal-to-noise ratio (OSNR), quality (Q) factor at different distance transmission by using different quadrature modulation such as 4-QAM, 16-QAM, 32-QAM, and 64-QAM to maintain the OSNR value, spectral efficiency, and the required data rates. The simulated results have shown that the coherent detection OFDM and direct detection OFDM with considered QAM provides the best value of BER and quality of the signal at a specific distance.

A technique for the estimation of an optical signal-to-noise ratio (OSNR) using machine learning algorithms has been proposed. The algorithms are trained with parameters derived from eye-diagram via simulation in 10 Gb/s On-Off Keying (OOK) nonreturn-to-zero (NRZ) data signal. The performance of different machine learning (ML) techniques namely, multiple linear regression, random forest, and K-nearest neighbor (K-NN) for OSNR estimation in terms of mean square error and R -squared value has been compared. The proposed methods may be useful for intelligent signal analysis in a test instrument and to monitor optical performance.