Optical Communications Research Research Articles

New Coupled Optical Solitons to Birefringent Fibers for Complex Ginzburg–Landau Equations with Hamiltonian Perturbations and Kerr Law Nonlinearity

In this study, we use an analytical method tailored for the in-depth exploration of coupled nonlinear partial differential equations (NLPDEs), with a primary focus on the dynamics of solitons. Traditional methods are quite effective for solving individual nonlinear partial differential equations (NLPDEs). However, their performance diminishes notably when addressing systems of coupled NLPDEs. This decline in effectiveness is mainly due to the complex interaction terms that arise in these coupled systems. Commonly, researchers have attempted to simplify coupled NLPDEs into single equations by imposing proportional relationships between various solutions. Unfortunately, this simplification often leads to a significant deviation from the true physical phenomena that these equations aim to describe. Our approach is distinctively advantageous in its straightforwardness and precision, offering a clearer and more insightful analytical perspective for examining coupled NLPDEs. It is capable of concurrently facilitating the propagation of different soliton types in two distinct systems through a single process. It also supports the spontaneous emergence of similar solitons in both systems with minimal restrictions. It has been extensively used to investigate a wide array of new coupled progressive solitons in birefringent fibers, specifically for complex Ginzburg–Landau Equations (CGLEs) involving Hamiltonian perturbations and Kerr law nonlinearity. The resulting solitons, with comprehensive 2D and 3D visualizations, showcase a variety of coupled soliton configurations, including several that are unprecedented in the field. This innovative approach not only addresses a significant gap in existing methodologies but also broadens the horizons for future research in optical communications and related disciplines.

Twists through turbidity: propagation of light carrying orbital angular momentum through a complex scattering medium

We explore the propagation of structured vortex laser beams-shaped light carrying orbital angular momentum (OAM)-through complex multiple scattering medium. These structured vortex beams consist of a spin component, determined by the polarization of electromagnetic fields, and an orbital component, arising from their spatial structure. Although both spin and orbital angular momenta are conserved when shaped light propagates through a homogeneous, low-scattering medium, we investigate the conservation of these angular momenta during the propagation of Laguerre–Gaussian (LG) beams with varying topological charges through a turbid multiple scattering environment. Our findings demonstrate that the OAM of the LG beam is preserved, exhibiting a distinct phase shift indicative of the ‘twist of light’ through the turbid medium. This preservation of OAM within such environments is confirmed by in-house developed Monte Carlo simulations, showing strong agreement with experimental studies. Our results suggest exciting prospects for leveraging OAM in sensing applications, opening avenues for groundbreaking fundamental research and practical applications in optical communications and remote sensing.

Continuous-wave degenerate cavity laser for optical imaging in scattering media.

Lasers play a significant role in optical communication, medical, and scientific research, owing to their high brightness and high coherence. However, the high spatial coherence will lead to specific challenges, such as speckle noise in imaging and wavefront distortion during propagation through scattering media. Here, a continuous-wave (cw) degenerate cavity laser (DCL) with low spatial coherence is demonstrated with efficient suppression of the thermal lensing effect from the gain crystal. Experimentally, a cw degenerate laser output with about 2000 transverse modes corresponding to a speckle contrast of about 0.0224 is achieved. This laser can be used for speckle reduction and is robust against atmospheric turbulence, which may find applications in the field of laser imaging technology and illumination.

Advancements in Optical Communication Research: A Review of India's Progress

Advancements in Optical Communication Research: A Review of India's Progress

Two-Stage Link Loss Optimization of Divergent Gaussian Beams for Narrow Field-of-View Receivers in Line-of-Sight Indoor Downlink Optical Wireless Communication (Invited)

The predominant focus of research in high-speed optical wireless communication (OWC) lies in line-of-sight (LOS) links with narrow infrared beams. However, the implementation of precise tracking and steering necessitates delicate active devices, thereby presenting a formidable challenge in establishing a cost-effective wireless transmission. Other than using none-line-of-sight (NLOS) links with excessive link losses and multi-path distortions, the simplification of the tracking and steering process can be alternatively achieved through the utilization of divergent optical beams in LOS. This paper addresses the issue by relaxing the stringent link budget associated with divergent Gaussian-shaped optical beams and narrow field-of-view (FOV) receivers in LOS OWC through the independent optimization of geometrical path loss and fiber coupling loss. More importantly, the geometrical path loss is effectively mitigated by modifying the transverse intensity distribution of the optical beam using manipulations of multi-mode fibers (MMFs) in an all-fiber configuration. In addition, the sufficiently excited higher order modes (HOMs) of MMFs enable a homogenized distribution of received optical powers (ROPs) within the coverage area, which facilitates the mobility of end-users. Comparative analysis against back-to-back links without free-space transmission demonstrates the proposed scheme’s ability to achieve low power penalties. With the minimized link losses, experimental results demonstrate a 10 Gbps error-free (BER < 10−13) LOS OWC downlink transmission at 2.5 m over an angular range of 10° × 10° without using any optical pre-amplifications at a typical PIN receiver. The proposed scheme provides a simple and low-cost solution for high-speed and short-range indoor wireless applications.

Resonant electro-optic phase modulator and photodetector for stabilizing laser frequency and quantum optics

Photoelectric functional device with specific optical, electrical and photoelectric conversion effects is one of the most important resources of modern information science and technology. Electro-optic modulator and photodetector are very important photoelectric functional devices, which are key devices in the fields of frequency locking, feedback control, photoelectric information conversion, optical communication, photoelectric information modulation, etc., and play an irreplaceable role in frequency stabilization locking technology of PDH (Pound-Drever-Hall, simply referred to as PDH). The PDH technology is widely used in researches of large scientific devices, quantum optics, optical communication and other fields. Using electro-optical phase modulator to carry out laser phase modulation is the primary process to realize frequency stabilization locking of standard PDH. Photoelectric detection can implement the photoelectric conversion of the carried weak modulation signal and spectral peak signal into electrical signal, and then feedback control through proportional integral and differential circuits, so as to achieve stable locking and frequency stabilization. The resonant electro-optical phase modulation (RPM) with high modulation depth, low power consumption and low half-wave voltage and microwatt resonant photoelectric detection (RPD) functional device with high signal-to-noise (SNR) ratio are invented to meet the demand for extraction and detection of extremely weak signals. The resonant circuit is composed of the single-end wedge-angle lithium niobate crystal, low noise photodiode and low-loss and high-Q electronic components. Low power consumption, high modulation depth electro-optic modulation, and high gain photoelectric detection are realized by the principle of resonant enhancement. When the optimal modulation frequency point is 10 MHz, the bandwidth of RPM is 225 kHz with <i>Q</i> of 44.4, when the modulation depth is 1.435, the RPM requires RF drive voltage of RPM to be 4 V. When the optimal modulation frequency point is 20 MHz, the bandwidth of RPM is 460 kHz with <i>Q</i> of 43.5, the required RF drive voltage of RPM is 6.5 V when the modulation depth is 1.435. The optimal detection frequency point of the self-invent RPD is 20.00 MHz, with a bandwidth of 1 MHz, Q of 20, the gain of 80 dB at 100 μW. With the home-made RPM and RPD in the extraction loop for extremely weak signal, the SNR of error signal is as high as 5.088 at 10 μW, 34.933 at 50 μW and 58.7 at 100 μW. Such a loop improves the performance and stability of the entire feedback control loop by optimizing parameters of proportional integral differential, which provides key devices and technological approaches for preparing a highly stable quantum light source and ultra-stable laser.

Dynamic Behavior of Optical Soliton Interactions in Optical Communication Systems

In optical systems, it is necessary to investigate the propagation of optical solitons in optical fiber systems for fiber-optic communications. By means of the bilinear method, we obtain the two-soliton solution of the variable coefficient higher-order coupled nonlinear Schrödinger equation. According to the obtained two-soliton solution, a novel two-soliton interaction structure of the system is constructed, and their interactions are studied. Two optical solitons occur with elastic interaction under certain conditions, and their amplitudes, shapes and velocities remain unchanged before and after the action. In addition to the elastic interaction, splitting action and polymerization also occur. The present study on the dynamic behavior of interaction of optical solitons may be valuable for research and applications in optical communication and other fields.

The Application Research of Atmospheric Optical Communication in Joint Modulation Transmission System

The Application Research of Atmospheric Optical Communication in Joint Modulation Transmission System

Efficient continuous-wave eye-safe Nd:YVO4 self-Raman laser at 1.5 µm.

Due to a high Raman threshold and serious thermal effect, a challenge is to achieve efficient continuous-wave (CW) operation of a crystalline Raman laser at 1.5 µm. Based on effective thermal management and the self-Raman effect, we demonstrate, to our knowledge, the first efficient CW operation of a Nd:YVO4 Raman laser at 1.5 µm. We achieve 685 mW of CW eye-safe emission at 1524.5 nm by the use of a 20-mm-long composite Nd:YVO4 and 300-µm pump beam radius, with a diode-to-Stokes conversion efficiency of 4.8%. Lasers operating at ∼1.5µm have found many important applications in various areas such as optical communication, laser radar, laser ranging, remote sensing, and spectral research.

Preface

It was a great pleasure to welcome all the participants from different countries to the 2021 International Conference on Electronic Materials and Information Engineering (EMIE 2021), which was successfully held during April 09-11, 2021 in Xi´an, China. EMIE 2021 provides an enabling platform for Electronic Materials and Information Engineering experts to exchange new ideas and present research results. This conference also promotes the establishing of business or research relations among global partners for future collaboration. We hope that this conference could make significant contribution to the update of knowledge about these latest scientific field.The conference model was divided into two sessions, including oral presentations and keynote speeches. In the first part, some scholars, whose submissions were selected as the excellent papers, were given 15 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches. In this conference, we were greatly honored to have invited Professor Alex Lugovskoy from Department of Chemical Engineering, Ariel University as our Conference Chair. There were over 70 experts and scholars in the area of Electronic Materials and Information Engineering representing different famous universities and institutes around the globe to attend the conference.During the conference, we were pleased to invite four distinguished experts to present their insightful speeches. Prof. Fanian Shi, our first keynote speaker, from Shenyang University of Technology. His research interests: Crystal Structure Design and Elucidation; Electromagnetic wave absorbing material; Composite. Prof.Jing Guo, from School of Materials Science and Engineering, Xi’an Jiaotong University. He devoted to electronic ceramics, low temperature sintering, microwave dielectric materials and other related research area. Prof.Yang Yue, from Nankai University. He had outstanding research in intelligent photonics, optical communications and networking, optical interconnect, detection, imaging and display technology, integrated photonics, free-space and fiber optics and other related area. Prof. Xiaoming Zhang, our finale keynote speaker, from Hebei University of Technology. His research area: Topological theory; Electronic materials; 2D materials.The participants of the conference were from most part of the world, with background of either academia or industry, even well-known enterprise. The success and prosperity of the conference is reflected high level of the papers received. The proceedings are a compilation of the accepted papers and represent an interesting outcome of the conference. EMIE 2021 for exchange of research findings, analysis, information, and knowledge in areas which include but are not limited to: Electronic Materials, Information Engineering and other related topics.We would like to acknowledge all of those who supported EMIE 2021. Each individual and institutional help are very important for the success of this conference. Especially we would like to thank the organizing committee for their valuable advices in the organization and helpful peer review of the papers. We sincerely hope that EMIE 2021 will be a forum for excellent discussions that will put forward new ideas and promote collaborative researches. We are sure that the proceedings will serve as an important research source of references and the knowledge, which will lead to not only scientific and engineering progress but also other new products and processes.The Organizing Committee of EMIE 2021List of Committee member are available in this pdf.

Review of underwater optical communication system

From deep oceans to coastal waterways, UOWC offers a wide range of possible uses. However, the most significant obstacle to underwater wireless communication is the fundamental properties of ocean or sea water; overcoming these obstacles necessitates a deep understanding of complicated physio-chemical biological systems. The major goal of this article is to determine the feasibility and dependability of high data rate underwater optical connections in light of different propagation phenomena that affect the system's performance. This article gives a comprehensive review of current UOWC developments. UOWC-specific noise sources, channel characterization, modulation methods, coding approaches, and different noise sources are all covered. This article intends to give not only comprehensive research in underwater optical communication, but also the creation of new concepts that will aid in the future expansion of underwater communication. All of this has spurred the rise of underwater optical wireless communication (UOWC), which provides faster data rates and lower power consumption than traditional acoustic communication systems, as well as lesser computing complexity for short-range wireless communications. UOWC has a wide range of applications, from deep seas to coastal rivers. The basic characteristics of ocean or sea water, on the other hand, are the most important impediment to underwater wireless communication; overcoming these difficulties requires a thorough understanding of complex physio-chemical biological systems.

Design of ATP control system for space optical communication

This article first introduces the significance of studying space optical communication and the current research status at home and abroad, and gives a general discussion on the application prospects and development trends of space optical communication, and elaborates the necessity and importance of conducting optical communication research. Then, the working principle of ATP in space optical communication system is studied, the mathematical model of ATP control system is established according to the actual needs, and the ATP control system design of space optical communication is designed. By selecting appropriate motors and gyroscopes as the actuators and detection elements of the system, substituting the actual parameters for simulation analysis, and correcting and verifying the results, some useful results are obtained. The simulation results show the rationality and effectiveness of the ATP design scheme.

Experimentally Derived Feasibility of Optical Camera Communications under Turbulence and Fog Conditions.

Optical camera communications (OCC) research field has grown recently, aided by ubiquitous digital cameras; however, atmospheric conditions can restrict their feasibility in outdoor scenarios. In this work, we studied an experimental OCC system under environmental phenomena emulated in a laboratory chamber. We found that the heat-induced turbulence does not affect our system significantly, while the attenuation caused by fog does decrease the signal quality. For this reason, a novel strategy is proposed, using the camera’s built-in amplifier to overcome the optical power loss and to decrease the quantization noise induced by the analog-digital converter of the camera. The signal quality has been evaluated using the Pearson’s correlation coefficient with respect to a reference template signal, along with the signal-to-noise ratio that has been empirically evaluated. The amplification mechanism introduced allows our system to receive the OCC signal under heavy fog by gradually increasing the camera gain up to 16 dB, for meteorological visibility values down to 10 m, with a correlation coefficient of 0.9 with respect to clear conditions.

Effect of moving microalgae on underwater wireless optical links.

Underwater wireless optical communications is a promising technique for addressing short-range data networks, as it provides cost, performance, and complexity improvements as compared with other alternatives, such as acoustic communications or radio frequency links. It is a part of the optical wireless communications research area, since for these applications, broad optical sources such as visible LED lamps can be used. Unless those links are designed for short distances (about 1 m, as in data-muling services on internet-of-things submerged systems), they are still severely affected by channel perturbations, such as scattering due to the presence of particles. This effect is particularly important when considering sensing applications for algae or aquaculture farming, which are becoming a crucial economic resource in many maritime areas. In this work, the effects of moving microalgae on underwater short-range optical links are studied so as to estimate a model for this scattering under dynamic conditions. The statistical parameters over experimentally measured received signal level and signal-to-noise ratio (SNR) are calculated, and the experimental setup is described. Results show that in clear water (no-algae scenario), the water-pump-induced movement effect over the mean and variance of the received optical power can be neglected, while when microalgae are present, the average optical power value decreases and the variance increases with all measured wavelengths. Finally, the SNR penalty due to the movement of microalgae is statistically evaluated.

Transmission of M-type combined solitary wave in the birefringent fiber with comprehensive management

In this paper, we reveal the transmission properties of the M-type combined solitary wave in birefringent fiber with third-order dispersion, self-frequency shift, self-steepening, fifth-order nonlinearity and the gain (loss) effects. The numerical simulations show that the M-type solitary wave can be stably transmitted through 300 dispersion lengths via balancing the variety of effects. And it can even be stably transmitted under the condition of limited interference under a small perturbation of noise, amplitude and phase position. The results can provide certain references for the research of optical soliton communication and optical devices.

Spaceborne, low-noise, single-photon detection for satellite-based quantum communications.

Single-photon detectors (SPDs) play important roles in highly sensitive detection applications, such as fluorescence spectroscopy, remote sensing and ranging, deep space optical communications, elementary particle detection, and quantum communications. However, the adverse conditions in space, such as the increased radiation flux and thermal vacuum, severely limit their noise performances, reliability, and lifetime. Herein, we present the example of spaceborne, low-noise, high reliability SPDs, based on commercial off-the-shelf (COTS) silicon avalanche photodiodes (APD). Based on the high noise-radiation sensitivity of silicon APD, we have developed special shielding structures, multistage cooling technologies, and configurable driver electronics that significantly improved the COTS APD reliability and mitigated the SPD noise-radiation sensitivity. This led to a reduction of the expected in-orbit radiation-induced dark count rate (DCR) increment rate from ∼219 counts per second (cps) per day to ∼0.76 cps/day. During a continuous period of continuous operations in orbit which spanned of 1029 days, the SPD DCR was maintained below 1000 cps, i.e., the actual in-orbit radiation-induced DCR increment rate was ∼0.54 cps/day, i.e., two orders of magnitude lower than those evoked by previous technologies, while its photon detection efficiency was > 45%. Our spaceborne, low-noise SPDs established a feasible satellite-based up-link quantum communication that was validated on the quantum experiment science satellite platform. Moreover, our SPDs open new windows of opportunities for space research and applications in deep-space optical communications, single-photon laser ranging, as well as for testing the fundamental principles of physics in space.

Optical vortex fiber laser based on modulation of transverse modes in two mode fiber

Optical vortices, characterized by helical phase fronts, are usually generated outside the laser cavity using passive modulation methods. Here, we demonstrate an all-fiber laser to directly deliver mode-locked and continuous-wave vortex beams based on modulation of transverse modes in the two mode fiber. The mode couplers and reflectors for three schemes are long period fiber grating (LPFG) and fiber mirror, fiber taper and fiber Bragg grating, and LPFG and fiber Bragg grating, respectively. The laser is switchable between ±1 order vortex operations by tuning the intracavity polarization controller, and the optical vortex can directly work as an optical tweezer to manipulate rhenium diselenide nanosheets. The pulse duration at the mode-locked state is tunable from subpicoseconds to several picoseconds by spectral filters, and the maximum output power at the continuous-wave state exceeds 35 mW. The cost-effective all-fiber vortex laser is quite attractive for research of micromanipulation, spatiotemporal soliton, and optical communication.

An Optical Communication's Perspective on Machine Learning and Its Applications

Machine learning (ML) has disrupted a wide range of science and engineering disciplines in recent years. ML applications in optical communications and networking are also gaining more attention, particularly in the areas of nonlinear transmission systems, optical performance monitoring, and cross-layer network optimizations for software-defined networks. However, the extent to which ML techniques can benefit optical communications and networking is not clear and this is partly due to an insufficient understanding of the nature of ML concepts. This paper aims to describe the mathematical foundations of basic ML techniques from communication theory and signal processing perspectives, which in turn will shed light on the types of problems in optical communications and networking that naturally warrant ML use. This will be followed by an overview of ongoing ML research in optical communications and networking with a focus on physical layer issues.

Hybrid LD and LED-based underwater optical communication: state-of-the-art, opportunities, challenges, and trends [Invited

In this paper, the current research of an underwater optical wireless communication (UWOC) network is reviewed first. A hybrid laser diode (LD) and light-emitting diode (LED)-based UWOC system is then proposed and investigated, in which hybrid cluster-based networking with mobility restricted nodes is utilized to improve both the life cycle and throughput of the UWOC network. Moreover, the LEDs are utilized for the coarse alignment, while the LDs are used for high-precision positioning to reduce the difficulty of optical alignment. Finally, challenges and trends for UWOC are pointed out to provide some insight for potential future work of researchers.

Performance Estimation of Advanced Intensity Modulation Formats Using Hybrid SAC-OCDMA through IsOWC Channel

Abstract Spectral amplitude coding optical code division multiple access (SAC-OCDMA) is one of the most important multiplexing schemes of OCDMA that has turned out to be a stimulating investigating area in optical communication due to its increased privacy, network capacity and its flexibility in allocating the channels and asynchronous environment. On the other hand, Inter-satellite optical wireless communication (IsOWC) which is a favorable area of research in optical communication is useful for bursty transmissions and long-distance communications. In this paper, we have designed a hybrid SAC-OCDMA system through IsOWC channel using ZCC code for advanced intensity modulation formats (CSRZ, Db, and AMI). The investigation is done for four users at a bit rate of 40(4×10) Gb/s using a direct detection technique. Further, on comparing the proposed system using advanced intensity modulation formats, the result shows that system using CSRZ format is better in terms of BER, Q-factor, SNR and the eye diagram with respect to AMI and Db.