Volume 45, Issue 4

As per the increasing demand of users, the wireless network fulfils significant challenges in terms of capacity, data rate, reduced environmental impact and better receiver performance. Radio over fiber (RoF) is the technique by which radio signal is modulated over the optical fiber link. The functioning of RoF is dependent on the optical modulator, optical fiber and photodetector. In this paper, dual parallel Mach–Zehnder modulator (DPMZM) is used, which gives good results against intermodulation distortion (IMD) errors. In order to investigate the receiver performance, positive-intrinsic-negative (PIN) and avalanche photodiode (APD) photodetectors are utilized at the receiver end. The analytical analysis of DPMZM based RoF system is analyzed, and the simulation model is implemented using OptSIM software, including PIN and APD photodetectors. The performance is scrutinized against various optical fiber lengths. The performance of the proposed model is analyzed and investigated by the presence of desired components and distorted (IMD) components for 1 and 5 km optical fiber distance between the control station and base station.

With the exponential growth in information related applications and the continuous increase in voice over IP (VoIP) applications, the carriers are expanding their networks to provide improved services to their end users. In such cases, the synchronous optical network/synchronous digital hierarchy model is not suitable. In this work, we are going to investigate the electro optic switch with the help of a VB script to simulate the device for various parameters. Further, we will then scan the central electrode voltages and take account of the overlap integral taking place at the output port with the help of waveguide mode. The best switching for switches at different voltages so as to have negligible coupling loss for different input signals is investigated. We aim to evaluate the MZI switches with the Li-Tn channel profile wave guiding structure and confirm their performance as compared to the existing MZI switches.

Photonic crystal fiber is a category of optical fibers, getting great attention by its promise to offer a range of optical characteristics that are not achievable in conventional optical fibers. Engineered dispersion and nonlinear characteristics of photonic crystal fiber (PCF) make it an attractive candidate for nonlinear optics and advanced optical networking in the all-optical domain. An optical network consists of different optical components such as laser sources, amplifiers, regenerators, and convertors for proper signal transmission over long distances. In recent years, the performance of the components has been improving by employing the appealing properties of PCF. The PCF’s application on such components is discussed, and the simulated results on gain amplification, regeneration, conversion, fiber laser are reviewed. These developments reveal that the enhanced performance provided by PCF makes it suitable for different optics applications.

In this paper, we have presented the far field pattern in presence and absence of Kerr type nonlinearity for the first higher order mode in Dispersion shifted and dispersion flattened type optical fibers. Our analytical results are based on simple power series expressions for the first higher order (LP 11 ) mode of aforesaid fibers, which have been formulated by Chebyshev formalism. Using the analytical expressions for the linear case, method of iteration is applied in order to predict the concerned propagation parameters in presence of Kerr type nonlinearity. We have taken some typical trapezoidal index, step W and Parabolic W fibers for our study. Our results for the far field pattern have been shown to be in excellent agreement with the exact numerical results computed by rigorous finite element technique. The simplicity and accuracy of our formalism will prove helpful to the designers for setting up of efficient low dispersion optical link.

This article presents the refractive index (RI) sensitivity study of cladding reduced uniform long-period fiber grating. The displacement of resonant wavelength with the change in ambient RI is observed to inspect the sensitivity. Here, the grating period is fixed at a value (550 μm) to analyze RI sensitivity of cladding modes (HE 13 -HE 14 ). However, it varies in earlier mathematical studies to adjust the resonant wavelength of all modes at a specific wavelength. The three-layer fiber geometry-based mathematical approach is employed to estimate the core and cladding modes. The obtained results support decline in quantity of cladding modes sustained by a single-mode fiber. The decrease in cladding radius has shown enhancement in RI sensitivity. For a reduction of 22 μm in cladding radius, the highest ordered HE 14 cladding mode has shown 5.8 times improvement in its sensitivity.

A PCF (photonic crystal fiber) with high birefringence and single-mode polarization retention over a wide wavelength range is designed and studied. The birefringence and polarization retention characteristics of the PCF base mode were studied using FVFEM (full vector finite element method) and APML (anisotropic perfect matching layer) as boundary conditions. The simulation results show that by rotating the elliptical air hole parallel to the horizontal axis by 45°, and then rotating the elliptical air hole parallel to the longitudinal axis by 45°, the birefringence of the PCF obtained is as high as 4.7 × 10 −2 , and it has good single model ability, which can be used for various optical devices.

Radio-over-fiber (RoF) is a technology in which radio frequency (RF) signals are distributed from central station to remote antenna units using fiber. Wavelength division multiplexing (WDM) is a technique in which different data streams are allowed to be sent parallely over a single fiber at different frequencies for increasing bandwidth. Hence, RoF combined with WDM technology is a prominent solution for many applications. In this article, we have designed an 8-channel 40 Gbps WDM-RoF system for future generation networks. The performance of the system has been evaluated using a simulator and then compared with a 4-channel existing system. A dispersion compensating fiber with a dispersion value at −85 ps/nm/km is used for combating nonlinearity. The simulated 8-channel WDM-RoF system has been analyzed by varying bit rate, input power, number of loops (transmission span), and channel spacing using performance parameters such as Q-factor and BER. It has been observed that the performance of the network improved as the channel spacing increased from 50 to 200 GHz. Moreover, the system performance is reliable up to 200 km.

Optical communications and their security have been got a great attention. In this work, a simple, low cost and secure optical system integrating orthogonal frequency division multiplexing-based passive optical network (OFDM-PON) and chaotic theory is proposed. In the proposed system, a novel scheme of quadrature amplitude modulation (QAM) encryption method is adopted. For privacy of image and video encryption, the process of encryption consists of two processes and a 3D chaotic system is employed. The chaotic system is used to generate the encryption sequences. In the first stage, the first generated chaotic sequence is XORed with the incoming data. While in the second stage, the QAM symbol is remapped using the other two generated chaotic sequences. Generally, the proposed system is designed to provide secure data, videos, and images transmission. The proposed system is simulated and evaluated with a transmission of a 10 Gb/s along 50 km single-mode fiber (SMF). The performance of the proposed system showed that there is a performance enhancement in terms of Peak to average power ratio (PAPR) and bit error rate (BER). The BER of unauthorized user is around 0.6147, while the PAPR is reduced to approximately half. The proposed system is simple and doesn’t require complex computations. It requires simple analog multiplexers for its implementation.

In this paper, the system consists of 80 Gbps next-generation passive optical network stage 2 (NG-PON2) co-existing with gigabit passive optical network (GPON) and 10 Gbps gigabit passive optical network (XG-PON) has been presented. The performance of the system has been evaluated for minimum bit error rate (BER) for varied distances (40 km to 100 km). It has been observed that due to the inadequate performance of XG-PON for upstream for higher lengths; the proposed system is limited to 40 km fiber length. To overcome this problem the proposed system is further simulated by increasing upstream transmission power of GPON and XG-PON. With the optimum parameters, the system maximum distance of 60 km has been reached for all GPON, XG-PON, and NG-PON2 without any inline amplification.

In recent years, wireless communication systems have exploded in popularity. Optical wireless technology is an excellent alternative to RF wireless, but it has high capacity, data speed, frequency, and license-free spectrum, and it is simple to implement. Optical wireless communication sends data through air using optical beams. Atmospheric turbulence degrades the functioning of free-breathing space photosensitive interaction methods by causing interruptions due to weather conditions like fog, smoke, and different pollutants. In this paper, free-space optical communications using snow and fog attenuations and Numerical Weather Prediction (NWP) method is used to determine the turbulence due to the atmosphere. This method improves the data transmission during unfavorable weather conditions by changing the various parameters like receiver aperture size, the wavelength of the transmitter, etc. Furthermore it shows that decrease in air quality and instability are the double significant causes, that can degrade general usage routine, especially when it’s foggy or raining heavily. The result shows that the aperture size and wavelength should be changed as per the weather condition.

Radio over fiber (ROF) is a very attractive technology for the increasing demand for flexibility and transmission capacity and due to its high bandwidth and low attenuation, it offers an economic advantage. The wavelength division multiplexing (WDM) is used to multiplex the different wavelengths signals within a single optical fiber. In this paper, WDM-ROF system is analysed with different filters using an optisystem. Results were compared using max Q factor, min BER, and eye height parameters.

In recent times, nonorthogonal multiple access (NOMA) has appeared as an encouraging system for satisfying the requirements of 5G communications in alleviating the spectrum insufficiency problems. The purpose of NOMA in heterogeneous networks (HetNets) is to increase the spectrum exploitation with the cost of proficient allotment of resources. Therefore, to achieve effective resource assignments for NOMA HetNets, this study develops the best user pairing and efficient power allocation approach. Here, the newly devised optimization method, Feedback Sea Lion Optimization (FSLnO), is employed for achieving a less-difficult optimal solution when user pairing. In addition, the designed FSLnO is also accomplished for performing the energy-efficient power allocation process by enhancing the lesser energy effectiveness of the femtocell users. The Feedback Artificial Tree (FAT) and Sea Lion Optimization (SLnO) are combined to create the developed FSLnO algorithm. Additionally, according to evaluation metrics like achievable rate, energy efficiency, sum rate, and throughput, the developed approach performed better, with maximum values of 2.384 Mbits/s, 0.028 Mbits/Joules, 13.27 5 Mbits/s, and 0.154 Mbps, respectively.

In order to serve the explosive demands of triple play services or multimedia services with high quality of data transmission in Fifth Generation (5G) communication systems which has availability of large spectrum unlike Fourth Generation (4G), low latency, improved transmission, and increased reliability, an access networks with optical fiber distribution network and wireless enabled technology is urgently needed and therefore, a prominent technology known as Radio over Fiber (RoF) is suggested by researcher/Scientists due to a perfect blend of flexible fiber technology and wireless mobility. RoF technology is helping the data transmission systems from last thirty years with great success and has numerous advantages such as scalability, transparency, antenna site complexity reduction, low installation cost, accessibility of radio carrier by diverse antenna sites dynamically. Millimeter waves (Mm waves) integration in 5G wireless RoF systems comes out to be an encouraging candidate to cater the bandwidth hungry current as well as future generation internet application such as high definition TV (HDTV), online games, video conferencing, and voice over IP (VoIP) etc. For the prolonged reach, economical installations, and improved performance, optimal Mm wave generation methods should be incorporated in 5G such as employing multi carrier generation technique (MCG). Deployment of single mode fiber (SMF) in 5G offers high speed, large capacity, improved security, etc., but also has a prominent limitation of nonlinear effects and it is unwanted phenomenon which degrade the system performance by introducing intermodulation distortion, distortion of signal phase, harmonic distortion, and interference in the neighbouring channels. Minimum modifications of architecture and minimum cost should be spent on the compensation of nonlinear effects or Kerr’s effects in RoF systems and recently mode division multiplexing has emerged as an ultimate solution. In this review article, detailed discussion of an evolutionary technology, i.e., RoF is presented with a literature review, present evaluations, and future challenges. Our utmost goal is to enrich the young researchers with precious aspects for RoF technology on single platform and also encourage them to conduct the technology advancement research works in various fields such as nonlinear compensation, Mm wave generation, dispersion compensation, cost reduction, complexity reduction, and security enhancements for 5G RoF systems.

A dense wavelength division multiplexing (DWDM) system improves the capacity of an optical communication system. On the other hand, nonlinear effects are critical issues that limit the performance of the DWDM system. The nonlinear effects of self-phase modulation, cross-phase modulation, and four-wave mixing affect optical communication’s capacity. This paper focuses on mitigating the nonlinear effect of cross-phase modulation in the DWDM system with a suitable technique.

In this paper, the proficiency of nonlinearity compensation studied on the polarization division multiplexing 0.3 return-to-zero quadrature phase-shift keying (PDM-0.3RZ-QAM) coherent optical system. The considerable nonlinear effect is the self-phase modulation (SPM) in the presence of chromatic dispersion. The nonlinearity mitigation technique based on the digital backpropagation (DBP) algorithm is implemented on the receiver side. The performance of the system was investigated in different terms as the optical signal-noise ratio, bit error rate, and the maximum transmission distance. The results demonstrated that the penalties were decreased by 3 dB. The maximum achievable distance was extended to 2000 km.

We report the designing of a free-space-optics (FSO) transmission system capable of transmitting high rate information by utilising novel mode division multiplexing (MDM) transmission technique. In the work reported, 2-channels transmitting 10 Gbps data, using either non-return-to-zero (NRZ) encoding scheme or return-to-zero (RZ) encoding scheme are modulated by using different Hermite–Gaussian (HG) modal beams of the single laser beam to realize of 20 Gbps transmission system. The system proposed is simulative analysed under the effect of different weather states. Also, we have compared the bit error rate (BER) and Quality factor (Q Factor) performance for RZ and NRZ encoding schemes in the system for varying weather states. The results reported show that NRZ encoding exhibits a superior performance. Also, we have analysed the system performance by taking into consideration atmospheric scintillation effect and the reported results show notable signal degradation in the presence of scintillation.

In this paper, we have designed and presented a simulation analysis of 96 × 40 Gbps CSRZ based DWDM long-haul transmission system under the influence of Kerr non-linearities using hybrid dispersion compensation technique. The proposed system performance is measured at 50 GHz channel spacing in terms of BER, Q-factor and eye-diagram for the varied launched power ranging from −4 dB m to 12 dB m of CW laser array and various transmission distances. We have implemented pre-filtering before multiplexing the modulated data of all the channels and post-filtering after de-multiplexing for avoiding co-channel interference and to suppress the cross-talk. By optimizing the system parameters, the transmission distance of 16,500 km is achieved for BER value of 1.48,875E-14 with corresponding Q-factor value of 7.55,989 at 6 dB m input power. The CSRZ modulated system has shown much robustness against the occurred linear and non-linear degradation factors due to its narrow spectrum.

Free space optical (FSO) communication has shown promising advantages among other wireless schemes. It provides a very high data rate, freedom from licensing, low cost of deployment and requires low power. FSO is a technology that has undergone rapid development over the last several years. These communication systems are a line-of-sight technology in which information is transmitted through the atmosphere on modulated laser beams or light-emitting diode (LED) beams. When FSO technology was first introduced, it was seen as an attractive option to bridge the “last mile bottleneck” that is present in many of today’s optical fiber-based networks. As compared to existing radio frequency (RF) based wireless systems, this technology possesses multiple advantages, such as high bandwidth, license-free band use, long operational range, spatial reusability, security and immunity to electromagnetic interference. The narrow and directional characteristics of a laser beam employed in FSO enable spatial reuse and make it hard to eavesdrop, thus raising the level of security. The use of light as carrier in this technology provides immunity to electromagnetic interference. Despite its many advantages, this technology is susceptible to some weather conditions, such as fog, rain, sleet and snow, and to misalignment of transmitter–receiver terminals. Atmospheric conditions will impair the propagation of an optical signal because the propagation of light may undergo absorption and scattering. Pointing error caused by misalignment of the transceivers is another major challenge in FSO communication system. The pointing error may result in degradation or even total loss of the received signal. This error may arise because of transceiver sway, platform vibration, the motion of mobile stations, errors or uncertainties in the tracking system. Another type of pointing error is beam wandering caused by the in-homogeneity of large-scale eddies in the atmosphere (i.e., atmospheric turbulence), where the transmitted beam may deviate from its intended path. This survey paper focuses on the systems involved in the alignment of the transmitter and the receiver so that the maximum amount of power is collected by the receiver and the analysis of beam profile in various atmospheric conditions and their mitigation methods.

Security postulates of visible light communication (VLC) is a paramount area of consideration due to its deployment in military, businesses, and residential establishments. Optical code division multiplexing (OCDMA) is prominent multiples access technique to serve multiple users and offer better security as compared to other available techniques such as wavelength and time division multiplexing (TDM). Wavelength conversion, multicode keying, optical logic gates, and quantum key distribution are some of the widely used security enhancement techniques but come at high cost and greater complexity. Zero cross correlation codes (ZCC) with integration of time dimension is an ultimate solution to the complex security improvement techniques but conventional two dimensional (2D) ZCC codes has an utmost issue of adjacent weights (W) and time (t) in the code which can be easily decoded by eavesdropper. Therefore, in this work, a novel weight managed ZCC (WMZCC) OCDMA code is presented with the non-adjacent W and t in the code matrix for making authentic information decoding difficult. Proposed 2D-WMZCC codes are investigated for 5 users at 100 Gbps over VLC link length of 5 m using polarization division multiplexed (PDM) quadrature phase shift keying (QPSK) and digital signal processing in terms of log symbol error rate (log SER), Q factor and bit error rate (BER). Further, a detailed comparison of 2D-WMZCC codes is performed with existing 2D diagonal identity matrix (DIM) codes and results revealed that former one exhibits better security than later OCDMA code.

In this work, an optical angular momentum (OAM) multiplexing enabled 400 Gbps free space optical communication (FSOC) system has been proposed using polarization division multiplexed (PDM) quadrature phase shift keying (QPSK) and digital signal processer (DSP) in the receiver. Different weather conditions such as clear weather, rain and fog are explored in proposed system and their deteriorating effects are observed in terms of log BER. Laguerre Gaussian (LG) beams (LG0,0, LG0,13, LG0,40, and LG0,80) are employed to realize four channel FSOC system and OAM multiplexing. Results revealed that integration of DSP in the PDM-QPSK receiver cause significant improvement in symbols placements in constellation and moreover proposed system successfully covered 3500 m, 3000 and 1200 m in FSO under clear weather, rain and fog, respectively.

Satellite communication, in over half a century have attained remarkable breakthrough in high speed transmission. These innovations, on the other hand, have come in tandem with significant performance improvements in other IT and telecommunications systems. As a result, these significant benefits are not as visible to the broader public as they would be as if this burst of performance had occurred in isolation. In nutshell, space satellite communication using optical technology provide powerful alternative to radio frequency (RF) and make communication reliable and cost effective. Satellite communications systems allow a whole new race of civilian and defence operations in surveillance, telecommunications, object tracking and space exploration. Since independent satellites are restricted by volume, space and strength, small satellites production in bulk clusters may be effective for a range of wildfire monitoring, science missions, mapping in gravity and water management exploration, among others. The development of communications satellites would provide for a more comprehensive understanding of the near-earth environment as well as a more efficient and cost-effective way of reaching space, thanks to the utilisation of multi-satellite systems. As a result, when satellites are designing, IsOWC is an utmost point to be considered. The numerous researches being performed in the satellite communications for introducing multi communications based on different orbits are described in this study. IsOWC systems over radio frequency based communication are preferred due to large bandwidth, high speed, absence of electromagnetic interference (EMI), lower transmission losses and improved security. We also present a detailed listing of challenges in Is-OWC such as Doppler shift, point ahead angle, satellite vibration and tracking, acquisition tracking and pointing (ATP) and background noise sources.

Underwater wireless optical communication (UOWC) systems have lately garnered a significant amount of attention for both academic purposes and trial applications. Although the idea is not new, the fact that seawater has a smaller window of absorption for blue-green light has reawakened interest in it, and it has grown an essential attraction because of its high bandwidth, it can cover a wide variety of underwater activities as compared to radio frequency and acoustic technologies. To monitor pollution, maintain oil pipelines, monitor climate change, conduct offshore investigations, and conduct oceanography research, the wireless transmission of information underwater technology is of importance to the military, industrial, and scientific organizations all around the world. The use of wavelengths of visible light to transmit secure data across point-to-point connections in underwater optical wireless communication (UOWC) compares well with the usage of free-space optical (FSO) communications. However, UWOC systems also have a huge amount of absorption and scattering introduced by the aquatic channels. Different from standard terrestrial free-space optical communication, many unique system design strategies have been investigated in recent years to solve these technological issues. This article presents a vision as well as various obstacles in the domain of underwater optical wireless communication, a detailed overview, and comparison of underwater communications techniques (UOWC) links, basic modulation technique techniques, and c pursuits on UWOC.

Orthogonal frequency division multiplexing (OFDM) is a famous multi-carrier modulation technique as it has a vast range of features like robustness against multi-path fading, higher bandwidth efficiency, and higher data rates. Though, OFDM has its own challenges. Among them, high peak power to average power ratio (PAPR) of the transmitted signal is the major problem in OFDM. In recent years, deep learning has drastically enhanced the performance of PAPR. In addition, the excessive training data and high computational complexity lead to a considerable issue in OFDM system. Thus, this paper implements a new PAPR reduction scheme in OFDM Systems through hybrid deep learning algorithms. A new optimized hybrid deep learning termed O-DNN + RNN is implemented by integrating the deep neural networks (DNN) and recurrent neural networks (RNN), where the parameters of both DNN and RNN are optimized using Hybrid Reptile Dragonfly Search Algorithm (HR-DSA). The new deep learning model is adopted for determining the constellation mapping and demapping of symbols on each subcarrier. This new optimized hybrid deep learning helps in reducing the PAPR and maximizes the performance.

FSO is the best communication medium for data transmission because of its high bandwidth, effective deployability and maximum transmission data rates with very high security. In this research paper an optical network model has been designed in the optisystem for different modulation schemes with WDM to enhance the capacity of the system. Attenuations for different weather conditions in Dehradun have been calculated and the performance has been evaluated accordingly. The performance is analysed in terms of BER (Bit Error Rate), maximum Q-factor, and eye height for each of the modulation schemes at different transmission distances and different weather attenuations. Analysis comprehends that the polarization shift keying is the best modulation technique for the WDM-FSO communication network among all. Thus, we suggest a model for an optical communication network using WDM and PolSK modulation scheme for Dehradun (Uttarakhand), where internet service is not very easy due to its extreme weather variations and got the excellent performance.

Orthogonal frequency division multiplexing (OFDM) – a new wireless multicarrier modulation which uses number of subcarriers that will be orthogonal to each and every other to send signals. An OFDM signal contains tightly spaced modulated providers that every have low bit info on each with the subcarriers. The major objective of our specific model is to apply MATLAB modelling to model OFDM modulation approach among 6, 12 and 15 MHz bandwidths inside the great consistency (HF) radio group (3–30 MHz). Typically, the motive of the pattern is to be able to make HF very long haul transmission more quickly and further trusted in order to each element worldwide, including typically the bulk remote elements, undergo use of rapid speed, very long haul hands-free connection. The designed unit enables us all to alter typically the bandwidth, carrier consistency, type of modulation, sign to noise rate (SNR), and photo dimensions to identify the particular blend regarding criterion provides trusted OFDM details gears in the HF radio band. Desire use four modulation techniques such while 32-QAM, 16-PSK, QPSK and BPSK. 32-QAM always transmitted typically the data the speediest despite the photo size, number regarding subcarriers and company frequency. 16-PSK seemed to be the second speediest type of modulation followed by QPSK and finally BPSK. To look with regard to the success associated with our model, all of us will figure out information rate and the particular bit to error ratio (BER) right next information transfer. Preferably, we wish to possess a bit error rate associated with 10e −5 for a good SNR that will be symbol of the particular noise intensity skilled within the ionosphere.

Optical code division multiple access (OCDMA) is one of the promising technologies to be implemented using all-optical networks. The OCDMA system performance is substantially determined by the particular encoding codes. Due to the different transmitter and receiver design considerations, selecting the right code family and code dimension is critical. In this research, 2D codes based on permutation vectors’ (PV) codes are presented to overcome the Multiple Access Interference (MAI) problem and system complexity. Consequently, the research work focused on two-dimensional unipolar codes to mitigate the probability error and cardinality of the optical CDMA system. A fast wavelength-hopping/time-spreading (FWHTS) is introduced as an encoding technique. The FWHTS is used for code construction design, and it achieves cardinality in upper bound theory without sacrificing good auto-and-cross correlation properties. Accordingly, hybrid codes with serial elimination interference receivers are presented to estimate the error probability of 2D optical codes. The proposed method is simulated using Python software. The performance metrics are flexibility, bit rate, minimum temporal length, computational complexity, cardinality and wavelength. The proposed method is compared with the existing 2D balanced incomplete block design (BIBD) technique and multidiagonal (MD) codes. The performance of the proposed method is approximately 4% higher than these existing methods. Subsequently, in the future work, a SAC-OCDMA code construction design shall be presented and the decoding techniques can be introduced, which can reduce the receiver noise and other phase intensity induced noise, respectively.