Optical Communication Systems Research Articles

Optimization of digital back-propagation for coherent optical fiber communication systems using fourth-order Runge-Kutta in the interaction picture method

The digital back-propagation (DBP) is an algorithm that can equalize the chromatic dispersion and nonlinearity in the coherent optical fiber communication system. However, the nonlinear equalization effect of traditional split-step Fourier method (SSFM)-based DBP is limited. This paper replaces the SSFM in DBP algorithm with the fourth-order Runge-Kutta in the interaction picture (RK4IP) method, and employs the Bayesian optimization algorithm (BOA) to optimize the coefficients in RK4IP-based DBP algorithm, then compares it with SSFM-based DBP algorithm, which is also optimized using BOA. The experimental results of 9×100 km standard single-mode fiber (SSMF) 20 Gbaud 16QAM transmission system demonstrate that the coefficient-optimized RK4IP (CO-RK4IP)-based DBP algorithm can achieve the maximum improvement of 0.89 dB in the Q-factor compared to the coefficient-optimized SSFM (CO-SSFM)-based DBP algorithm at equivalent complexity, proving that CO-RK4IP is an effective recursive method for DBP algorithm.

Nonpolar P-type Conjugated Small Molecules Enable High-Performance Organic Photodetectors for Potential Application in Optical Wireless Communication.

The high responsivity and broad spectral sensitivity of organic photodetectors (OPDs) present a bright future of commercialization. However, the relatively high dark current density still limits its development. Herein, two novel nonpolar p-type conjugated small molecules, NSN and NSSN, are synthesized as interface layers to enhance the performance of the OPDs, which not only can tune energy alignments and increase the reverse charge injection barrier but also can reduce the interfacial trap density. Moreover, benefiting from the smoother surface morphology and enhanced conductivity, the NSN exhibited superior charge transport and collection properties. Consequently, the OPD with NSN achieved a dark current density of 0.37 nA cm-2 and a high specific detectivity of 2.77 × 1013 Jones at -2 V. More importantly, the optimized OPDs can be successfully integrated into optical communication systems, demonstrating precise digital signal communication without obvious distortion, showing promising application potential in the wireless transmission system.

Analysis of PAPR reduction algorithms for optical OFDM 5G radio waveform system for visible light communication

Abstract The integration of Optical Orthogonal Frequency Division Multiplexing (OFDM) with the 5G radio waveforms has lately been attracting special attention toward its possible Visible Light Communication (VLC) systems. On the other hand, however, a key challenge in the Optical OFDM is the presence of very high PAPR, degrading the overall system performance by introducing nonlinear distortions in the optical transmitter. In the present paper, different kinds of PAPR reduction algorithms specifically developed for Optical OFDM in VLC systems are developed and investigated. Analyze techniques like clipping, selective mapping (SLM), partial transmit sequence (PTS), and companding for their PAPR reduction efficiency along with the preservation of spectral efficiency and signal integrity. Based on the above aspects, various performance metrics, such as BER, computational complexity, and SNR, have been considered in order to understand each technique’s trade-off. It can be clearly seen that the hybrid and adaptive approaches achieve greater PAPR reduction without much loss of performance and are thus appropriate for future generation optical communication systems. This analysis underlines the use of optimized PAPR reduction algorithms to achieve robust and efficient systems for 5G VLC applications.

Mode Division Multiplexing Free Space Optical Communication System Performance with Aperture Averaging in Atmospheric Turbulence and Various Weather Conditions

Due to the serious challenge for mobile operators as a result of spectrum congestion in radio frequency spectrum, free space optical (FSO) communication has been considered a timeous alternative especially for future generation high capacity wireless networks. Although FSO offers advantages such as huge data carrying capacity among others, it suffers from the drawback of atmospheric turbulence and adverse weather conditions. As a mitigation to this problem, mode division multiplexing (MDM) has been another research direction. This paper proposes the design and numerical simulation of a hybrid modified duobinary return to zero (MDRZ) MDM free space optical communication system, which to the best of the authors’ knowledge has not been a subject of investigation. The performance metrics used are the bit error rate, quality factor and received optical power. Two modes, HG00 and HG01 were investigated and compared. It has been observed that the BER, Q factor and received power degrades as we increase the beam divergence, FSO transmission distance and data rate. Moreover, the performance gap between clear and moderate weather conditions is more for HG00 than for HG01 for the same considered data rates. The aperture averaging has been shown to be a strong mitigation strategy especially in foggy conditions.

New Prospects of Optical Wireless Communication Systems Exploiting VCSEL-Based Transmitters

New Prospects of Optical Wireless Communication Systems Exploiting VCSEL-Based Transmitters

Robust Wide-angle Optical Wireless Communication System: From Design to Prototype

Robust Wide-angle Optical Wireless Communication System: From Design to Prototype

Chaos Synchronization in a Dual-Laser Chaotic Multiplexing System Based on Nanolasers

Nanolaser (NL), as an important optical source device, has a significant impact on photonic integrated circuits and has become a research hotspot in recent years. This study investigates the synchronization performance of a dual-channel laser chaotic multiplexing system based on NLs and employs an active-passive decomposition to enhance signal processing and multiplexing efficiency. By establishing a rate equation model, the synchronization characteristics of the system were analyzed, focusing on the effects of two key parameters—the Purcell factor (F) and the spontaneous emission coupling factor (β)—as well as system parameters, single-parameter mismatches, and multi-parameter mismatches. Numerical simulations show that, with proper parameter configurations, the two master NLs can maintain low correlation, ensuring the "pseudo-orthogonal" of chaotic signals while achieving high-quality chaotic synchronization with their paired slave NLs. The study found that both the Purcell factor (F) and the spontaneous emission coupling factor (β) significantly influence the synchronization performance of the system, and the optimal parameter ranges for achieving high-quality synchronization were identified. Additionally, the effects of feedback strength and frequency detuning were explored, revealing that frequency detuning plays a more critical role in the synchronization between the master NLs. The impact of parameter mismatches on system synchronization performance was also emphasized. The system exhibits robustness against single-parameter mismatches, with minimal impact on master-slave synchronization quality. However, multi-parameter mismatches introduce more complex effects. Compared to traditional semiconductor laser systems, this system can maintain "pseudo-orthogonal" over a wider parameter range, achieving higher security and lower channel interference. This research lays a theoretical foundation for chaos synchronization based on NLs and provides new insights for designing secure, stable, and efficient optical communication systems.

End-to-End Learning of Transmitter and Receiver Filters in Bandwidth Limited Fiber Optic Communication Systems

End-to-End Learning of Transmitter and Receiver Filters in Bandwidth Limited Fiber Optic Communication Systems

Dynamics and soliton solutions of the perturbed Schrödinger-Hirota equation with cubic-quintic-septic nonlinearity in dispersive media

<p>This study systematically investigates the dynamics of the perturbed Schrödinger-Hirota equation with cubic-quintic-septic nonlinearity under spatiotemporal dispersion, providing insights into soliton propagation in dispersive media. We begin by examining the system's phase portrait and chaotic behavior, followed by the derivation of exact traveling wave solutions, including optical solitons and periodic solutions, using an enhanced algebraic method. The findings are vividly illustrated through three-dimensional and two-dimensional graphical simulations, which analyze the impact of key parameters on the solutions. This study not only presents a variety of optical soliton solutions, but also clarifies the underlying dynamics, offering theoretical guidance for fiber optic communication systems and holding significant applied value for achieving more efficient and reliable optical communications.</p>

Performance Analysis of fso Communication system with Different Modulation Schemes

Free-space optical communication (FSO) is a technology which use optical signals to transmit data wirelessly, providing a viable alternative to conventional wired systems. The Free Space Optical (FSO) communication system has emerged as an attractive option due to its large license free bandwidth, high security and low cost It is one of the very promising technologies for wireless communication. However, the sensitivity to weather conditions is one of the major disadvantage of FSO systems. Weather factors, such as rain, fog, snow, and dust, can significantly attenuate the optical signals, which can lead to a reduction in signal strength and it can affect potentially data transmission reliability. Present work focusses on two key performance parameters Average Bit Error Rate (ABER) and Outage Probability (OP) which is of much importance due to the adverse impact of weather factors on FSO communication system. For the present study the OP and ABER performance are analysed over Gamma- Gamma (G-G) fading for FSO links in the presence weak and moderate atmospheric turbulence with four different modulation schemes. The CDF functions for the channel model has been derived and MATLAB codes are used to predict the OP and ABER performance for the FSO communication system.

Novel insights into high-order dispersion and soliton dynamics in optical fibers via the perturbed Schrödinger–Hirota equation

This study offers a comprehensive analysis of the Perturbed Schrödinger -Hirota Equation (PSHE), crucial for understanding soliton dynamics in modern optical communication systems. We extended the traditional Nonlinear Schrödinger Equation (NLSE) to include higher-order nonlinearities and spatiotemporal dispersion, capturing the complexities of light pulse propagation. Employing the modified auxiliary equation method and Adomian Decomposition Method (ADM), we derived a spectrum of exact traveling wave solutions, encompassing exponential, rational, trigonometric, and hyperbolic functions. These solutions provide insights into soliton behaviors across diverse parameters, essential for optimizing fiber optic systems. The precision of our analytical solutions was validated through numerical solutions, and we explored modulation instability, revealing conditions for soliton formation and evolution. The findings have significant implications for the design and optimization of next-generation optical communication technologies.

Tunable Beam Steering Metasurface Based on a PMN-PT Crystal with a High Electro-Optic Coefficient

Existing tunable optical metasurfaces based on the electro-optic effect are either complex in structure or have a limited phase modulation range. In this paper, a simple rectangular metasurface structure based on a Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystal with high electro-optic coefficient of 120 pm/V was designed to demonstrate its electrically tunable performance in the optical communication band through simulations. By optimizing the structure parameters, a tunable metasurface was generated that can induce a complete 2π phase shift for beam deflection while maintaining relatively uniform transmittance. Simulations further demonstrated the electrical tunability of the beam deflection direction and operating wavelength of the metasurface. This tunable optical metasurface, with its simple and easily fabricated structure, can promote the development and application of multifunctional and controllable metasurfaces. Its adjustable beam deflection direction and operating wavelength may find applications in fields such as optical communication systems and imaging.

Underwater wireless optical communication system incorporating WMZCC and DPS codes under pure sea, clear ocean and coastal sea

Abstract The ability of the optical code division multiplexing approach to allow secure information transfer has sparked a great deal of interest in underwater wireless optical communication (UWOC). A weight managed zero cross correlation (WMZCC) code based UWOC system is presented delivering 5 users × 10 Gbps capacity under different ocean/sea conditions such as pure sea, clear ocean and coastal sea. The WMZCC code has least user interferences, mapping free code construction, weight managed, controlled code length, and less complexity. The performance comparisons between WMZCC codes and diagonal permutation shift (DPS) are established by considering Q factor as evaluation parameter and results revealed that performance of WMZCC is better than DPS due to ZCC code. Q factor values under pure sea at 13 m for WMZCC codes and DPS codes are 13.24 and 9.86 respectively. For 7.2 m UWOC link distance, Q factor values obtained are 13.1 and 10.2 in case of WMZCC and DPS respectively under coastal sea. On contrary, DPS has variable cross correlation and therefore experience more multiple access interference (MAI). The presented system successfully offered >20 % performance improvement in Q factor as compared to DPS codes in UWOC.

OPTIMIZATION OF THE SCATTERING MATRIX OF FREQUENCY -DETUNED ADD/DROP FILTERS FOR MULTIPLEXERS BUILT ON SYSTEMS OF OPTICAL DIELECTRIC RESONATORS WITH WHISPERING GALLERY MODES

Background. A significant increase in the speed of information transmission in fiber-optic communication networks is determined by the strict requirements imposed on the elemental base of receiving and transmitting devices. One of the important components of such devices is diplexers built on different notch and bandpass filters, which are often performed on dielectric resonators (DR) with whispering gallery mode (WGM) oscillations. Calculation and optimization of the parameters of multilink filters and diplexers built on DR is impossible without further development of the theory of their design. The development of the theory of diplexers today is often based on electrodynamic modelling, which is built on preliminary calculations of filter scattering parameters in various transmission lines with a complex topology of connections. Objective. The aim of this study is to construct electrodynamics' models of wave scattering on complex multi-connected DR structures with degenerate types of WGM natural oscillations, which contain several frequency-detuned bandpass or notch filters located in one or several transmission lines. To solve the scattering problem, we proposed a system of equations derived from perturbation theory for Maxwell's equations [24], modified to describe the DR fields with whispering gallery oscillations in transmission lines. The construction of such solutions is complicated by the fact that each of the partial optical resonators of the filters, in the case of excitation of azimuthally inhomogeneous WGM in it, has, as a rule, two degenerate types of natural oscillations. Moreover, each such type of oscillation is characterized by different complex values of the coupling coefficients with the line, open space, and also with other resonators. The latter circumstance leads to the fact that the systems of equations for the amplitudes of natural and forced oscillations of resonators are doubled. The signs of the coefficients of mutual coupling are usually different, this leads to the fact that the behaviour of DRs in the system becomes more difficult to predict, therefore the second objective of this work is to study the patterns of the scattering characteristics of line waves on systems of frequency-detuned DRs with degenerate types of oscillations with the possibility of constructing multiplexers for modern optical communication systems. Methods. The methods of technical electrodynamics are used for calculating and analysing scattering matrices. The end result is obtaining new analytical equations and formulas for new complex structures of coupled dielectric resonators with whispering gallery oscillations in the different transmission lines. Results. Frequency dependences of scattering matrices on complex structures of frequency-detuned filters built on coupled optical DR with whispering gallery oscillations located in one or more transmission lines are considered. Electromagnetic models of bandstop and add/drop filters are built, consisting of various optical resonators with degenerate types of natural oscillations. General analytical expressions of vector coefficients and matrices for building systems of equations describing coupled oscillations, as well as forced oscillations of resonators in cases of their use in optical filters with serial and parallel arrangement, are given. General solutions for the scattering field on frequency-detuned resonators located in different optical transmission lines have been found. Examples of calculating frequency dependences of the scattering matrix for the most interesting structures consisting of two different frequency-detuned filters are given. The frequency scattering characteristics of several types of devices are calculated, which consist of two notch filters with different blocking bands, made on detuned DRs in one transmission line. The possibilities of the earlier proposed method are demonstrated in the example of calculating the scattering characteristics of known types of diplexers built on the basis of the use of two add/drop filters with different frequency bandwidths. The frequency dependences of the scattering matrices of the two most common types of devices, located in parallel between two or four regular transmission lines of add/drop filters with different numbers of resonators; laterally coupled add/drop filters; parallel-coupled add/drop filters; twisted double-channel side-coupled integrated space sequence of resonators (SCISSORs), were studied. New scattering models of diplexers consisting of optical resonators of different connection topologies were built: serial, parallel with the use of laterally coupled add/drop filters; parallel-coupled add/drop filters; twisted double-channel SCISSORs. The frequency dependences scattering matrix of the diplexers were also calculated. The characteristics of the designed diplexers obtained from the examined filters of different types were compared. Conclusions. The theory of diplexer construction, which takes place on the simultaneous optimization of the scattering matrix of several filters built on complex systems of dielectric resonators with degenerate types of whispering gallery oscillations is expanded. A calculation method was developed and new analytical relations were found for the scattering matrix coefficients of optical diplexers of various types.

WS2/Graphene/MoS2 Sandwich van der Waals Heterojunction for Fast-Response Photodetectors.

Fast-response photodetectors have attracted considerable attention in the application of high-speed communication, real-time monitoring, and optical imaging systems. However, most reported photodetectors suffer from limitations of the inherent properties of materials, low carrier transport efficiency, and unmatched interfaces, which lead to a low response speed. Here, we report a WS2/graphene/MoS2 vertical van der Waals heterojunction fabricated by mechanical exfoliation and dry transfer methods for fast response. To improve the response speed of the previously reported WS2/MoS2 heterojunction with excellent photoelectric performances, the embedded graphene is employed to optimize the interface defects and improve the carrier transport efficiency due to its high mobility and smooth and flat surface. Under the illuminations of a 405 nm laser and a bias voltage of 0.5 V, our device can realize rise and fall times of 44 and 52 μs, respectively. For a bias voltage of 2.5 V, moreover, the device can also show outstanding performances including a high responsivity of 220 A/W, a considerable detectivity of 1.2 × 1013 Jones, a large external quantum efficiency of 6.7 × 104 %, and a low dark current of 1.05 × 10-13 A. Additionally, the device enables high-speed transmission with a low bit error rate in a closed-loop optical communication system. Therefore, the proposed scheme can provide an idea for the design of photodetectors with fast response and high performance.

Low-loss weakly coupled four-mode hollow-core antiresonant fiber based on centrosymmetric nested structure

Abstract This paper designs a novel centrosymmetric double-layer nested antiresonant fiber (CDNAF) with few-mode transmission characteristics. The cladding structure of the CDNAF incorporates glass plates and multilayer capillaries, effectively mitigating the coupling between various core modes and cladding modes. Simulation results show that the CDNAF can support four modes of low-loss transmission from LP01 to LP02 at 1550 nm. The confinement loss (CL) of the four modes is less than 0.008 dB/km, 0.07 dB/km, 0.42 dB/km, and 4.8 dB/km, respectively, and the CDNAF has a sizeable differential group delay (DGD) and weak bending sensitivity. The loss of high-order modes is much greater than that of the other four transmission modes, ensuring high-purity transmission of the four modes. In the wavelength range of 1200–1700 nm, the CDNAF ensures few-mode characteristics with at least two low-loss transmission modes. Furthermore, the effective refractive index difference (Δneff) between adjacent modes is much greater than 10^(-4), eliminating or significantly reducing the need for multiple-input multiple-output digital signal processing (MIMO-DSP) techniques in optical communication systems. Additionally, the results demonstrate that CDNAF can transmit three modes at an ultimate bending radius of 5 cm and can transmit four modes like a straight fiber at a bending radius of 18 cm, which demonstrates that CDNAF has excellent bending performance. These excellent characteristics give the CDNAF great potential for application in large-capacity optical communication systems.

Simulation and investigation of optical artificial neuron by optical injection in semiconductor laser

Abstract This research investigates the experimental implementation of a feed-forward (FF) optical neural network using optical injection (OI). Two follower laser diodes (FLD1, FLD2) are subjected to chaotic modulation, with their respective signal weights adjusted via optical filtration. The study analyzes the behavior of these FLDs during FF operation, focusing on frequency spectra derived from time series data. The research examines the impact of both signal weights and control parameters, including the bias voltage of the influencer laser diodes (ILD1, ILD2), on the FLDs. A maximum FWHM of 1.7 GHz is observed for FLD2 when both the bias voltage is set to 4V, and the modulated signal is attenuated to -20 dB. To assess the synchronization state, the correlation between the ILDs and FLDs is calculated. Results show fluctuations between positive and negative values, with a maximum correlation of 0.42 observed for FLD1 when influenced by FLD2's voltage. These findings demonstrate an anti-synchronized relationship between the ILDs and FLDs, a crucial requirement for ensuring privacy in a chaotic optical communication system, simulating an optical neural network. (ILD1,ILD2) bias voltage in additional tow FLDs. Maximum FLD2 measured FWHM 1.7

Revolutionizing Free-Space Optics: A Survey of Enabling Technologies, Challenges, Trends, and Prospects of Beyond 5G Free-Space Optical (FSO) Communication Systems.

As the demand for high-speed, low-latency communication continues to grow, free-space optical (FSO) communication has gained prominence as a promising solution for supporting the next generation of wireless networks, especially in the context of the 5G and beyond era. It offers high-speed, low-latency data transmission over long distances without the need for a physical infrastructure. However, the deployment of FSO systems faces significant challenges, such as atmospheric turbulence, weather-induced signal degradation, and alignment issues, all of which can impair performance. This paper offers a comprehensive survey of the enabling technologies, challenges, trends, and future prospects for FSO communication in next-generation networks, while also providing insights into the current mitigation strategies. The survey explores the critical enabling technologies such as adaptive optics, modulation schemes, and error correction codes that are revolutionizing FSO communication and addressing the unique challenges of FSO links. Also, the integration of FSO with radio frequency, millimeter-wave, and Terahertz technologies is explored, emphasizing hybrid solutions that enhance reliability and coverage. Additionally, the paper highlights emerging trends, such as the integration of FSO with artificial intelligence-driven optimization techniques and the growing role of machine learning in enhancing FSO system performance for dynamic environments. By analyzing the current trends and identifying key challenges, this paper emphasizes the prospects of FSO communication in the evolving landscape of 5G and future networks. In this regard, it assesses the potential of FSO to meet the demands for high-speed, low-latency communication and offers insights into its scalability, reliability, and deployment strategies for 5G and beyond. The paper concludes by identifying the open challenges and future research directions critical to realizing the full potential of FSO in next-generation communication systems.

Guided-Mode Resonance Enhanced Ge-on-Si Self-Powered Surface Illuminated Photodetector for Ultrahigh-Speed Optical Communication Systems

Guided-Mode Resonance Enhanced Ge-on-Si Self-Powered Surface Illuminated Photodetector for Ultrahigh-Speed Optical Communication Systems

Security Performance Enhancement Chaotic Optical Communication System Based on Reservoir Computing for Physical-Layer Security

Security Performance Enhancement Chaotic Optical Communication System Based on Reservoir Computing for Physical-Layer Security