Volume 46, Issue 4

MIMO-OTFS (multiple input multiple output in orthogonal time-frequency space) modulation is a key component of sophisticated optical radio systems, helping to increase their speed and range. The increased capacity of optical communication can be put to use in a number of applications. In order to minimize latency, we optimize the bit error rate (BER) and power spectral density (PSD) of the framework by applying the hybrid signal detection technique known as zero forcing equalizer and minimal mean square error (ZFE + MMSE) to the MIMO-optical OTFS system (16 × 16, 64 × 64, and 256 × 256) in this article. The suggested ZFE + MMSE works better than the traditional signal detection algorithms, according to the work’s experimental study. Furthermore, without using any detection techniques, the MIMO-OTFS outperforms the MIMO-OFDM by attaining an SNR gain of 1.2–2.3 dB.

Night vision significantly impacts our daily visual efficiency and has more impact in communications networks. This work primarily emphasises enhancing the safety and security of individuals through advancements in night vision systems. While research on night vision is crucial for addressing contemporary social challenges, there remains a scarcity of databases tailored for deep-learning investigations in this domain. To address these challenges, this study evaluates the performance of three distinct object detection models: Yolo v3 achieving a mean average precision (mAP) of 87.9 % at 45 frames per second (FPS), Yolo v5 with a mAP of 88.7 % at 20 FPS, and modified Yolo v5 with a remarkable mAP of 95.1 % at 79 FPS. From the results, it is proven that this algorithm successfully detects classes including humans, animals, and vehicles.

We report mathematical techniques for determining the coefficient of transmission at the splice, where anomalies like transverse and angular are present. The investigation involves the first mode of higher order (LP 11 ) in Kerr pattern nonlinear fiber. In this case, the LP 11 mode for the triangular index (TI) profile is calculated using a standard power series. Chebyshev formalism is the source of the aforementioned term. When there is third-order nonlinearity (TON), the iteration approach is utilized on the analytical mathematical terms to obtain the characteristics listed above. It has been demonstrated that our findings closely match the simulated exact outcomes obtained with the complex finite element method (FEM). Consequently, the suggested straightforward and precise technique offers enormous promise for investigating alternative propagation characteristics in dual-mode fibers.

This paper has demonstrated the performance signature of fiber to fiber connectors with minimum insertion loss and low distortion in optical fiber transceiver systems. Insertion loss is clarified against the lateral and longitudinal misalignment for single mode graded index fiber for various fiber core diameter. Insertion loss is clarified in relation to angular misalignment for joints in multimode step index silica doped optical fibers with numerical apertures variations. Total coupling signal loss efficiency is demonstrated versus the lateral and longitudinal misalignment for single mode graded index fiber for different fiber core diameter. As well as the coupling loss efficiency is studied versus angular misalignment for joints in multimode step index silica doped optical fibers with numerical apertures variations. Insertion loss is demonstrated versus numerical aperture variations for joints in multimode step index silica doped/germanium doped/plastic optical fibers with various degree angular misalignment variations.

Communication networks are forced to transition to optical access networks in order to boost the information rate of transmission due to huge utilization of internet. Passive optical networks (PONs) are a highly developed and promising technology that offers low cost design, high bandwidth, and information rate for both residential and commercial use. PON uses the passive components incorporating couplers, splitters, as well as combiners. Compared to modern access networks, PON features bidirectional capabilities, cost-effectiveness, high resource efficiency, transparency, privacy, flexibility, along with upgradeability. Due to these ever increasing demands for high bandwidth, high capacity, and long reach communication for next generation networks, next generation passive optical networks (NG-PONs) are optimum choice. It provides cost-effective, energy efficient network architecture and can be realized in integrated wired/wireless network scenarios for fronthaul/backhaul data transmissions. This paper reviews the standardization process of PON that led to the development of the NG-PON. The detail literature review of various technologies related to PON and NG-PON has been conducted. Potential drawbacks of NG-PON as well as the advantages and disadvantages of various strategies are also discussed besides the future scope. Meanwhile it offers long haul high bandwidth hybrid scenarios. The futuristic PON networks may be realized for high undersea, satellite, and beyond sixth generation (6G) networks.

This paper has clarified long wavelength fluoride optical glass fibers performance signature in high speed local area data networks. The signal attenuation and the total fiber pulse broadening are studied versus network length for various fluoride optical glass fibers and AS 2 Se 3 glass fiber at various spectral wavelengths. The total signal delay time is demonstrated with fiber numerical aperture with 15 km network length for various fluoride optical glass fibers and AS 2 Se 3 glass fiber at 2.5 μm optimum spectral wavelength. Total fiber signal bandwidth, total Shannon channel bit rate, and NRZ/RZ channel data rate transmission are clarified with 15 km network length for various fluoride optical glass fibers and AS 2 Se 3 glass fiber at 2.5 μm optimum spectral wavelength.

The evaluation of the next-generation XGPON network involves assessing parameters like bandwidth utilization, packet loss, and queuing delays, all of which impact on efficient upstream bandwidth allocation. In a condition of heavy traffic load, one ONU trying to monopolizing bandwidth utilization for itself, and lead to disadvantaging others. This issue is exacerbated by long distances in extended-reach XGPON networks, causing redundant bandwidth requests, lead to higher queuing delays at others ONUs. To address this, a proposed game-theoretic model is introduce, to ensure fair bandwidth distribution while maintaining Quality of Service parameters, load fairness, delay fairness. The performance of the proposed DBA, tested alongside the XGIANT DBA using the NS3 simulator, and demonstrates improved fairness that validates the proposed DBA’s effectiveness.

This paper addresses the reduction of peak-to-average power ratio (PAPR) in optical filter bank multicarrier (FBMC) with offset quadrature amplitude modulation (OQAM) using a fast Hadamard transform (FHT) centered partial transmit sequence (PTS) algorithm. High PAPR in FBMC-OQAM systems can cause non-linear distortions in optical transmitters, such as LEDs, leading to signal degradation. The proposed FHT-PTS algorithm effectively mitigates this issue by dividing the data symbols into disjoint subsets, applying phase rotations, and performing inverse FHT to generate multiple candidate sequences. The sequence with the lowest PAPR is selected for transmission. This technique ensures significant PAPR reduction while maintaining acceptable bit error rate (BER) performance. Simulation results demonstrate that the FHT-PTS algorithm achieves substantial PAPR reduction gain of 3 dB–6 dB compared to conventional PTS and other existing methods. The power spectrum density (PSD) analysis shows that the spectral efficiency of the FBMC-OQAM system is preserved, with minimal out-of-band emissions. The FHT operations significantly reduce the complexity compared to traditional Fourier transform-based methods, making the algorithm more feasible for real-time applications.

Using modified phase-conjugate twin wave (M-PCTW) scheme, in which additional information bits are modulated one of the conjugated wave, is helpful to increase the spectral efficiency (SE) of the conventional PCTW scheme. In this paper, we show that the phase modulated formats, but not the conventional square QAM formats are more suitable to M-PCTW scheme. Results of 1600 km nonlinear transmission show that for polarization multiplexed (PM) 8-PSK format, performance improvement from M-PCTW is about 3.3 dB, while it is about 2.2 dB for PM 8-QAM formats. For PM 16-PSK (QAM) modulation, performance improvement from M-PCTW is about 3.4 dB and 1.6 dB, respectively.

The ever-increasing demand for bandwidth in optical networks necessitates efficient spectrum utilization. To address this challenge, this paper proposes a novel hybrid spectrum sensing algorithm tailored explicitly for 256-QAM (Quadrature Amplitude Modulation) optical communication waveforms. The proposed algorithm combines the strengths of energy detection and cyclostationary feature detection to overcome the limitations of individual methods. Energy detection (ED) provides fast and low-complexity sensing, while cyclostationary feature detection offers higher accuracy and sensitivity. First, ED is employed for rapid initial spectrum assessment. Subsequently, matched filter (MF) detection is selectively applied only to frequency bands identified as potentially occupied by primary users based on the energy detection results. This selective approach significantly reduces computational complexity while maintaining high detection accuracy. The results demonstrate significant improvements in detection accuracy, sensitivity, and computational efficiency compared to existing methods. In particular, the hybrid algorithm performs better in scenarios where weak 256-QAM signals coexist with strong primary users, showcasing its effectiveness in dynamic spectrum-sharing applications. This work contributes significantly to optical spectrum sensing by offering an efficient and accurate solution for advanced radio systems. The proposed hybrid algorithm paves the way for improved spectrum utilization and facilitates the development of high-performance, next-generation optical networks. The projected method obtained a gain of −200 as compared with the existing methods.

The CO-OFDM system plays a critical role in managing the effects of polarization mode dispersion (PMD) in optical communications, providing opportunities to optimize performance, durability and polarization state capability. DSP digital compensation is crucial to maintain signal quality, reducing error vector magnitude (EVM) and binary error rate (BER). DSP optimizes transmission, adapts to changing conditions, compensates for chromatic dispersion (CD) and PMD without physical intervention, reducing costs and extending network reach. Using modulations such as 16-QAM and 4-QPSK at 100 Gbps, it is advantageous for data centers and inter-satellite communications. A Python-based DSP model has been proposed to mitigate these effects, significantly improving signal integrity and system performance with a binary error rate (BER)∼10 −4 .

Filter bank multicarrier (FBMC) has become a favorable option compared to other advanced waveforms because it can reduce interference between symbols and carriers. This is especially advantageous in Rician optical channels prone to frequency-selective fading. The article proposed novel PAPR algorithms based on combining partial transmission sequence (PTS) and complementing methods to lower the peak-to-average power ratio (PAPR) of the optical FBMC. High PAPR results in power amplifier performance degradation, which severely affects the optical FBMC framework’s performance and throughput. Compared to the original signal, the proposed PTS + Companding makes the PAPR much lower while keeping the bit error rate (BER) and power spectral density (PSD). This leads to enhanced efficiency and fewer nonlinear distortions in the transmission system. Simulation studies assess the efficacy of those approaches in terms of PAPR, spectral efficiency, and throughput. The results help improve the use of FBMC in optical communication systems by showing practical ways to boost performance metrics necessary for advanced radio systems to handle the needs of fast data transmission.

The Gulf of Mannar Marine National Park is famous for shallow water and an affluent diversity of aquatic plants and animals. It preserves the endangered mammals and marine life for global significance. Routine monitoring and surveillance of the fish and aquatic species is necessary without any type of disturbance to the natural environment as a protected area of the marine national park. An aquatic bio-optical communication system is a feasible method for transferring the data from the benthic of the park to the sea surface and terrestrial area using the natural resources and sediments. The physical and geographical conditions near the Ram-Setu bridge and the surrounding area of marine national park have shallow water, low water pressure, low salinity, availability of light at benthic, sediments of limestone, and presence of pumice stones that make it more reliable. The model is based on natural resources like optical light source, deployment of buoys for transceivers, and canals in the stone and will be used for providing messages and warning instructions to the fisherman, pilgrimage tourists, merchant ships, and in patrolling security forces.

The design and simulation of indoor visible light communication (VLC) system with preemphasis is proposed for 5 m transmission of signal at the data rate of 10 Gbps for receiving only applications like smart TV, smart speaker, and smart home appliance control. The preemphasis driver circuit is designed to reduce the intersymbol interference by pulse shaping the signal and transimpedance amplifier is used to amplify the signal for longer distance transmission. Intensity modulation at the sender side and direct detection at the receiver-side are adopted in this work for the improvement of the system’s overall performance and to decrease its implementation cost. The system performance is analyzed in terms of BER, data-rate, Q-factor, and eye diagrams. The setup is developed, which includes a nonreturn-to-zero (NRZ) generator, preemphasis driver, light-emitting-diode, VLC channel, and receiver with an avalanche photodiode and Gaussian LPF. At 10 Gbps data rate, the maximum transmission distance that can be obtained is 5 m with a BER of less than 10 −31 .

Unidirectional transmission of optical waveguides in optical communication bands has been a difficult problem in the field of optical communication. In this paper, the valley Hall effect is utilized to enhance the transmission efficiency of optical wave in optical communication system. Valley photonic crystal is selected as the main material of optical waveguide in optical communication band. Valley photonic crystal is composed of air columns periodically arranged according to the honeycomb lattice in the dielectric material, which shows the valley Hall topological effect in transverse electric wave mode. By introducing the energy valley degree of freedom into the photonic crystal, the light wave is transmitted locally on the dielectric material at the interface, and the control of the dielectric material realizes the regulation of light transmission. The Chern number of optical waveguide topology in the optical communication band, the exchange phenomenon occurs at the same energy band position and realizes efficient unidirectional transmission of optical waveguides in optical communication bands. The experimental results show that the optical communication band optical waveguide based on the valley Hall effect has unique unidirectional transmission characteristics and robustness to cornering and is capable of realizing unidirectional optical transmission in optical communication systems.

This paper demonstrates underwater communication using a green laser with On-Off Keying (OOK) modulation. The study focuses on communication performance between an underwater platform and an air-based platform under varying conditions, including different weather, saline, and clear water environments. A photovoltaic (PV) cell is used as a receiver to detect signals. The experiment analyzes data transmission from air to underwater across various conditions, including with and without sunlight. The results indicate that green lasers are optimal for underwater communication, with improved performance as the water depth increases, making them particularly suitable for underwater communication systems.

Free space optical (FSO) communications has garnered significant attention as a potential substitute for radio frequency (RF) wireless communication in short and long range transmissions. Free-space optical (FSO) communication is a method where an optical beam is sent across an unguided channel, gaining favour in high-speed wireless networks due to its large optical bandwidth, fast data transmission, lack of licencing requirements, secure nature, and easy setup. Despite several inherent advantages that FSO has over existing radio frequency (RF) communication technologies, its link performance is severely hampered by atmospheric fog and turbulence, which not only reduce optical irradiance but also cause the modulated optical beam to deviate from its intended path, impacting the quality of the received signal. This review paper discusses FSO technology, channel impairments under varied atmospheric attenuation conditions, advantages, and applications. Various channel models in terms of probability density functions are described, which characterise the statistical nature of the irradiance fluctuations of optical transmission through scattering and atmospheric turbulence. Key objectives that need to be addressed in the near future, particularly in fifth-generation (5G) and beyond, includes enhancing capacity, boosting data rates, minimising latency, and enhancing service quality. Last but not the least, several uses of FSO that facilitates 5G and future technologies have also been covered in this study.

DWDM technology is gaining popularity in fiber-optic communication due to high-speed transmission channel capacity demands. The adoption of this system has been driven by this demand. Researchers focus on optimizing data transmission parameters within channel characteristics for maximum performance. The signal’s form typically influences the optical channel capacity, the guiding medium’s dispersive and non-linear characteristics, and interference from multiple sources. This study investigates how efficient modulated systems control linear and non-linear impairments in optical channel capacity due to high data rates transmitted over optical communication networks, aiming to circumvent current issues. The selection of pulse shape and modulation format is crucial for an effective DWDM optical communication system due to the rigorous specifications of the optical channel. Modulation formats like intensity and phase have become viable network design technologies, allowing for network creation that operates to the designer’s satisfaction. This academic study examines the theoretical properties of various models used to analyze and recreate high-speed optical communication links, aiming to understand the impact of system components and modulation techniques.

In recent years, the evolution of optical wireless communication (OWC) system has emerged as a viable alternative to radio frequency communication. These technologies provide an effective solution for addressing the need for point-to-point communication, offering benefits such as higher bandwidth, faster data rates, no licensing requirements, low power usage, quick and simple installation, enhanced security, and resistance to electromagnetic interference. In this article, we analyze two wireless optical communication systems: one using an FSO channel and the other using an OWC channel. The analysis focuses on range and quality factor as performance metrics. We examine the performance of one-to-many Tx/Rx FSO/OWC channel under three different atmospheric conditions: clear weather, haze, and fog, using eye diagrams. The system analysis includes mathematical models for the received optical power and the pointing error. Additionally, we investigate the impact of spatial diversity on the performance of FSO/OWC channel with configurations of 1 × 1, 2 × 2, 4 × 4, and 8 × 8. Our findings indicate that the 8 × 8 FSO/OWC configurations yield better results compared to other configurations and the OWC channel performs well over long distances up to 110 km, while the FSO channel is more suitable for short range communication up to 37 km.

Wireless communication signals experienced fluctuations in intensity due to atmospheric turbulence. The presented work uses a multi-input-multi-output (MIMO) system to study the performance free-space optical (FSO) communication over a diverse atmospheric turbulence condition channel. The findings produced demonstrate how various channel models perform in FSO system at varying levels of channel turbulence. From 7.9 for the Weak turbulence to 45.3 for the strong turbulence, the turbulence attenuation rises linearly. The data could be transmitted via a link length of up to 1 km with strong turbulence. Strong turbulence could have higher Q-factor, yet is constrained by short distance (1 km) in comparison with weak turbulence, which has greater distance (3.8 km), therefore communication quality is lower. For moderate and weak turbulence, the maximum link is around 1.5 km and 3.8 km, respectively. This study is useful for designing a stable FSO system for regional environments suffer from frequent fluctuated weather turbulence such as the Middle East and South Asia.

In this article, we investigate the performance of convolutional coding against the fading associated due to atmospheric turbulence as well as the polarization-induced crosstalk in free-space optical (FSO) communication system. The performance of FSO system strongly depends on atmospheric turbulence. Orthogonal frequency division modulation (OFDM) is one kind of solution for frequency selective fading channel. The OFDM modulated output signal is complex, which is not possible to transmit through FSO channel. To overcome this constraint, we consider non-Hermitian approach by adding polarization diversity. However, polarization add crosstalk to the system, which deteriorates the system bit error rate (BER) performance. All the analytical simulation results are presents graphically by using MATLAB software. All the provided results are in terms of system’s BER by varying the number of OFDM subcarrier, local oscillator power, link distance, and mean misalignment angle. Our earlier published article where we used space frequency block code (SFBC) and reported that almost 7.5 dB coding gain possible. In this proposed system model, we considered convolutional code instead of SFBC and found a significant amount almost 10 dB coding gain at a BER of 10 −12 when all the system’s parameter remains unchanged. Finally, we developed the closed-form expression of system’s average BER.

Free space optical communication is promising wireless technology which saves cost, saves time, has high security and acts as backend, backhaul system. Optical code division multiplexing based on spectral amplitude coding is a potential method to support many users with high data speeds. Optical code division multiplexing reliant spectral amplitude coded zero cross-correlation free space optical communication is proposed in this work incorporating shift zero cross-correlation codes. Mode Division Multiplexing is used to lower the cost of the system and to minimize the interferences. With the realization of the proposed system, the capacity of 100 Gbps is accomplished supporting 10 different users. Different atmospheric turbulences are also analyzed over FSO to investigate their effects on BER.

This paper introduces a novel method for solving the Schrödinger equation through the use of deep neural networks (DNNs), presenting a significant departure from traditional techniques. Conventional approaches to solving the Schrödinger equation, such as analytical methods and numerical algorithms, often face challenges when dealing with complex quantum systems due to their inherent limitations. These traditional methods can become cumbersome or even infeasible as the complexity of the systems increases. In contrast, our approach harnesses the capabilities of deep neural networks to approximate both the wavefunction and the energy eigenvalues of quantum systems. By leveraging the flexible and powerful nature of DNNs, we provide a new pathway to solving the Schrödinger equation that can potentially overcome the constraints of classical methods. To validate the effectiveness of our approach, we apply it to the particle in a box problem – a fundamental quantum mechanics model with well-established analytical solutions. This benchmark problem serves as a useful test case, allowing us to demonstrate that DNNs can not only replicate the known results accurately but also offer insights into how these networks can handle more intricate quantum systems. Our results reveal that DNNs are capable of accurately reproducing the analytical solutions for the particle in a box, illustrating their potential as a versatile tool for quantum mechanics.

Free space optical (FSO) communication system is a promising candidate for day-to-day progressing networks because of its potential advantages such as, large bandwidth, line-of-sight communication, non-licensed spectrum, high data rates and many more. Relay-assisted communication provides an additional hike to the system’s performance by expanding its coverage range, enhancing data rates, capacity and mitigating the effect of turbulence. In this manuscript, FSO-radio frequency (RF) dual hop system is considered using decode and forward (DF) relaying protocol. Furthermore, chaotic signals are incorporated in the proposed system to enhance their confidentiality using differential chaos shift keying (DCSK). This is demonstrated by performing secrecy analysis of the proposed system. Here, it is assumed that FSO link experiences Gamma-Gamma turbulence along with pointing errors while RF link experiences Nakagami-m fading. The probability of error of the proposed system is analyzed, and the results indicated huge gain in the SNR requirements in FSO-RF-DCSK system. Also, secrecy analysis is performed using secrecy outage probability (SOP) as a metric for the proposed system. The findings are noteworthy as FSO-RF-DCSK system presents superior performance in terms of secrecy.

This paper presents a new combination of channel estimation (CE) methods and peak-to-average power ratio (PAPR) reduction techniques for orthogonal frequency division multiplexing (OFDM)-based visible light communication (VLC) systems. We first propose iterative clipping and filtering to minimize the PAPR of optical OFDM signals. Then, we introduce a computationally efficient, high-performance channel estimation approach using block-type pilots with modified clipped signals. The proposed method integrates clipping with three distinct CE techniques, resulting in both significant PAPR reduction and enhanced bit error rate (BER) performance. Among the CE methods evaluated, the expectation-maximization (EM) technique provides better BER results compared to other approaches. Simulation results confirm that the combined use of clipping and advanced CE methods leads to notable improvements in PAPR reduction and BER performance for OFDM-based VLC systems.