Optical Network System Research Articles

Space optical communication system for space optical networks and deep space exploration

The acquisition time of tens to hundreds of seconds in the optical link between satellites makes it difficult to meet the needs of constructing spatial optical networks. In addition, as a basic requirement for deep space explorers, autonomous attitude determination and autonomous navigation demand the installation of separate, expensive, and complex inertial devices, and the communication data rate is too low to meet the timely transmission of large amounts of data. In this paper, we proposed and developed a multifunctional fusion space optical communication system for space optical networks and deep space exploration, which has the functions of autonomous attitude determination, autonomous navigation, and high-speed optical communication. The sub-second acquisition time can meet the requirements of space optical network construction, and the ability of autonomous attitude determination and autonomous navigation significantly reduce the amount of R&D expenses of the explorer; decrease the volume, weight, and power consumption of the explorer; and improve the reliability and autonomous survival ability of the explorer. The paper provides the structure, working principle, and main algorithm models and conducts a feasibility analysis and field experiments. The experimental results showed that the average open-loop pointing accuracy of the optical terminal is 95.8 µrad (attitude determination accuracy), which can be improved to 39.1 µrad after filtering, and the acquisition time is less than 1 s. For deep space exploration, the navigation accuracy is less than 67.6 km in the cruise phase and 10 km in the acquisition phase, and field experiments have also proven its feasibility. The significance of our research work lies in proposing what we believe to be a new system operation scheme and design method for optical communication systems, and its results can be widely applied in all fields of space optical communication.

IQ-channel multiplexed DP-4ASK signal using power loading for downlink coherent PON system with access-span length difference

This study explores the integration of dual-polarized (DP) four-level amplitude shift keying (4ASK) signals within an intensity and quadrature division multiplexing framework, mainly focusing on coherent passive optical network (PON) systems. The primary objective is to address the challenges associated with distance disparities in downstream transmissions, which are prevalent in coherent PON architectures. We introduce a novel approach that significantly reduces the power consumption of digital-to-analog converters by implementing power loading strategies tailored explicitly for IQ channel division multiplexing (IQDM)-DP-4ASK signals. Our simulations confirm that ASK standard frequency offset compensation is adaptable to these signals, providing a robust method for managing frequency offsets in a dynamic network environment. Moreover, we propose and empirically validate an energy-efficient adaptive downlink solution capable of supporting 128 Gb/s per optical network unit (ONU), utilizing IQ-imbalanced DP-4ASK signals. This solution is particularly advantageous for systems where the transmission conditions include a 10 km variance in access span lengths between ONUs. Results from our experimental setup demonstrate that reducing the digital-to-analog converter output current for the Q channel by 137 mA is feasible without compromising signal integrity or system performance. Additionally, the research verifies the effectiveness of the automatic bias controller on the transmitter side, ensuring stable operation across varying conditions. Equally, the receiver-side digital signal processing effectively handles polarization separation, illustrating the system's capability to maintain high data integrity and reliability under diverse operational scenarios. These findings highlight the technical feasibility and operational benefits of using IQDM-DP-4ASK signals in coherent PON systems and underscore the potential for significant power savings and enhanced system efficiency in optical networks. The study paves the way for future research into scalable, energy-efficient solutions suitable for high-capacity optical access networks striving for increased sustainability and reduced operational costs.

Performance and energy efficiency enhancement of existing optical communication systems by incorporating resource allocation on demand technique in FiWi networks

Abstract Fiber-wireless (FiWi) networks have begun to be fully integrated into contemporary optical access network systems as a result of utilizing the combined advantages of wired and wireless techniques. Passive optical networks (PON) are heavy energy consumers and one of the main contributors to greenhouse gas emissions (GHG) that are a result of climate change. These systems also present economic challenges. In this work, three different FiWi systems are presented such as (i) even/odd active transmitters with only free space optical (FSO) based optical network units (ONUs)/with dual channel option such as distribution fiber (DF)/FSO supported ONUs, (ii) a novel resource allocation on demand (RAoD) incorporated bidirectional FiWi system supporting DF/FSO based ONUs and four wave mixing (FWM) generated upstream wavelengths and (iii) transmitter diversity enabled 5G supported FiWi system supporting bidirectional communication. It is observed that the energy efficiency of 26.04 % is obtained in even/odd active transmitter and only FSO supported ONUs and under the harsh weather conditions, by adopting DF channel instead of FSO, 30 % energy efficiency further added. However, in novel RAoD technique, energy efficiencies for optical distribution networks (ODN1), ODN2, ODN3, and ODN4 are 48.52 %, 46.4 %, 36.96 %, and 44.31 %. Further, DF option in channel selection improve 30 % more energy saving. In performance enhanced transmitter diversity employed system, at 60 km reduction in bit error rate (BER) are 25 % for ODN1, 5.88 % for ODN2, 20 % for ODN3, and 12.5 % for ODN3.

Programmable Optoelectronic Synaptic Transistors Based on MoS2/Ta2NiS5 Heterojunction for Energy-Efficient Neuromorphic Optical Operation.

The optoelectronic synaptic transistors with various functions, broad spectral perception, and low power consumption are an urgent need for the development of advanced optical neural network systems. However, it remains a great challenge to realize the functional diversification of the systems on a single device. 2D van der Waals (vdW) materials can combine unique properties by stacking with each other to form heterojunctions, which may provide a strategy for solving this problem. Herein, an all-2D vdW heterojunction-based programmable optoelectronic synaptic transistor based on MoS2/Ta2NiS5 heterojunctions is demonstrated. The device implements reconfigurable, multilevel non-volatile memory (NVM) states through sequential modulation of multiple optical and electrical stimuli to achieve broadband (532-808nm), energy-efficient (17.2 fJ), hetero-synaptic functionality in a bionic manner. The intrinsic working mechanisms of the photogating effect caused by band alignment and the interfacial trapping defect modulation induced by gate voltage are revealed by Kelvin-probe force microscopy (KPFM) measurements and carrier transport analysis. Overall, the (opto)electronic synaptic weight controllability for combined in-sensor and in-memory logic processors is realized by the heterojunction properties. The proposed findings facilitate the technical realization of generic all 2D hetero-synapses for future artificial vision systems, opto-logical systems, and Internet of Things (IoT) entities.

Line-of-sight Initial Pointing Model of Space Dynamic Optical Network and Its Verification

In dynamic space networks, achieving high precision and fast initial pointing of the optical line of sight (LOS) is the key goal in developing this technology. It is the premise and basis of realizing optical LOS capture. Based on the composition and working principle of space optical networking systems, and the effect of real-time position and attitude changes on LOS initial pointing between networks, the matrix transformation and transfer principle is used to establish a multi-link LOS initial pointing model and analyze the factors affecting the size of the field of uncertainty (FOU). In a dynamic space optical networking experiment, the “one-to-two” simultaneous LOS pointing test is carried out, which shows that the model can realize the function of multi-link LOS initial pointing. The sizes of the FOU of the test terminal are 8.67 mrad and 8.34 mrad, respectively, with an average capture time of 18.3 s.

Towards constructing a DOE-based practical optical neural system for ship recognition in remote sensing images

The optical neural network system based on the 4f system (4f-ONN) is a feasible solution for on-orbit real-time target detection and recognition on remote sensing images, as it can directly modulate and encode the two-dimensional image information. However, traditional 4f systems based on spatial light modulators (SLMs) often encounter misalignment errors during assembly due to the reflective optical path used in SLMs. Additionally, implementing electronic SLM in space-based applications introduces problems such as particle number reversal, significantly reducing the reliability of the system. To address these issues, this paper proposes the adoption of diffractive optical elements (DOEs) to construct the 4f-ONN system. The DOE-based design offers a more compact structure, enhanced reliability, and reduced energy consumption, making it highly suitable for on-orbit image processing applications. Due to the expensive and time-consuming nature of the DOE manufacturing process, a design approach for a 4f system based on DOE was pursued through software simulation in this paper. The simulation phase involved the utilization of electronic neural networks to acquire the physical parameters of the DOE mask, while incorporating the array theorem and Fraunhofer diffraction theorem to accurately calculate the physical dimensions of the DOE. The effectiveness of the adopted DOE-based 4f system was initially validated through experiments on a simple pattern dataset. Subsequently, simulation experiments were conducted on three public datasets, namely Mnist, Fashion-mnist, and QuickDraw16, to confirm the efficacy of the DOE-based 4f system in classification tasks. Lastly, target recognition experiments were performed on the GF-2 dataset, and a corresponding hardware system was developed to demonstrate the potential of the DOE-based 4f system in on-orbit image processing.

Investigation of 16 × 10 Gbps mode division multiplexed enabled integrated NGPON–FSO architecture under wired-wireless link losses

Abstract To enhance the transmission capacity for energy consumption and low cost system, mode division multiplexing (MDM) using mode 0 and mode 1 is proposed and investigated. A pair of eight downlink and uplink wavelengths is transmitted by using each MDM mode in an integrated bidirectional next generation passive optical network and free space optics (NGPON–FSO) system at 10 Gbps per channel transmission rate under the impact of FSO–fiber links impairments. Simulation results indicate that received power of −21.2 dBm with 0.2 dB power penalty can be obtained over 1 km FSO and 100 m multimode fiber under unfavourable turbulent effects. The system provides extended FSO link range, and fiber range of 150 km and 600 m respectively at threshold limit of 10−3. Besides, the mathematical analysis depicts the receiver sensitivity and splitter power budget of 42 dBm and 18 dB, respectively, for the proposed system. The system offers finest performance than other pre-existing systems.

Robust optical mode converter based on topological waveguide arrays

Abstract Optical mode converters are essential for enhancing the capacity of optical communication systems. However, fabrication errors restrict the further improvement of conventional mode converters. To address this challenge, we have designed an on-chip TE0–TE1 mode converter based on topologically protected waveguide arrays. The simulation results demonstrate that the converter exhibits a mode coupling efficiency of 93.5% near 1550 nm and can tolerate a relative fabrication error of 30%. Our design approach can be extended to enhance the robustness for other integrated photonic devices, beneficial for future development of optical network systems.

Client scheduling and bandwidth slicing for multiple federated learning tasks over multiple passive optical networks

Federated Learning (FL) has attracted extensive attention in facilitating emerging edge intelligence applications for its inherent advantages of ensuring data security and privacy. Especially in the edge computing networks connected by Passive Optical Network (PON) system, FL is introduced to enable applications like autonomous driving, intelligent manufacturing, and precision medicine. However, in this system, the FL deployment over PON inevitably faces challenges induced by the conflict between a large volume of model data with the restrict latency limitation and the confined bandwidth resource of PON, especially for the multiple FL tasks. To address these issues, a novel scheme is proposed for tackling the client distribution and bandwidth allocation problems under the scenario of multiple simultaneous FL tasks supported by the multiple interconnected PON systems, which is consisted of the client scheduling and bandwidth slicing processes. To be specific, an easy-to-implement heuristic algorithm is first performed to assign the client numbers to PONs based on iterative method, with which certain operations are repetitively executed to achieve optimal solutions. And then, the serial bandwidth slicing which adapts the traditional policy, i.e., one-task-per-cycle, to the situation with multiple FL tasks, and parallel slicing with the multi-task-per-cycle, are designed for the investigated system. Furthermore, the simulation system is constructed to verify our method. The corresponding results exhibit that, the largest 43.2 % round time reduction is achieved by client scheduling compared to benchmark without the scheduling. Compared to the benchmark with serial slicing, our scheme can achieve a maximum 50.11 % of the round time decrease. It's also validated that, our proposed client scheduling and parallel bandwidth slicing method can improve the learning efficiency by reducing communication delay, especially for the situation with less client number and smaller FL threshold.

Enhanced PON and AMCC Joint Transmission with GMM-Based Probability Shaping Techniques

In ITU-T standards, auxiliary management and control channels (AMCCs), as defined, facilitate the rapid deployment and efficient management of wavelength division multiplexing passive optical network (WDM-PON) systems. The super-imposition of an AMCC introduces additional interference to a PON signal, resulting in the degradation of the performance of the overall transmission. In prior research, we proposed employing a Gaussian mixture model (GMM) to fit a baseband-modulated AMCC signal. Following the analysis of the interference model and the distribution characteristics of received signal errors, we propose a combined optimization method for a transmitter and receiver in this paper. This method, grounded in probabilistic shaping (PS) techniques, optimizes the probability distribution of the transmitted signal based on the AMCC interference model, with the objective of reducing the error rate in PON signal transmission. We have validated this approach within a 50G-PON experimental system by utilizing PAM4 modulation. The experimental results demonstrate the effectiveness of this method for mitigating the impact of baseband-modulated AMCC, thereby reducing the error rate in PON signal transmission. The approach presented in this paper can further minimize the performance degradation introduced by baseband-modulated AMCC in WDM-PON systems, enhancing the efficiency of WDM-PON deployment.

Liner multimode fibers with high distributed optical amplification system based high efficient quadrature modulation system for reliable high capacity local area network

Abstract This paper clarified the liner multimode fibers with high optical amplification system based high efficient quadrature modulation system for high capacity local area optical networks. The clarified the lighted QPSK transmitter system based linear multimode fiber profile is clarified under modal bandwidth effects. The optimum power variations are studied with spectral base band wavelength variations for various modal bandwidths based linear multimode fiber. Optimum power is clarified with time variations for various modal bandwidths based linear multimode fiber. Total power for 1500 and 1700 MHz km modal bandwidth is demonstrated based linear multimode fiber. The Max-Min signal base band amplitude based QAM pulse generator is clarified after photo-detector by using electrical constellation visualizer. The optimum Q Factor form with Min BER is demonstrated after photo-detector for 1300, 1500, and 1700 MHz km modal bandwidth based linear multimode fiber. The base band lighted SNR is clarified and simulated with the modal bandwidth variations based linear multimode fiber. Optimum Q form factor through photo-detector is demonstrated with the modal bandwidth variations based linear multimode fiber. The electrical SNR through photo-detector is studied and simulated with the modal bandwidth variations based linear multimode fiber.

Design and Anti-Interference Analysis of Fault Monitoring System Based on Multi-Wavelength Grouping for Passive Optical Network System

Design and Anti-Interference Analysis of Fault Monitoring System Based on Multi-Wavelength Grouping for Passive Optical Network System

Auxiliary Management and Control Channel Transmission and Performance of High-Speed Coherent Frequency Division Multiplexing Passive Optical Network System

Auxiliary Management and Control Channel Transmission and Performance of High-Speed Coherent Frequency Division Multiplexing Passive Optical Network System

Flexible open network operating system architecture for implementing higher scalability using disaggregated software‐defined optical networking

AbstractThe enhanced capacity of optical networks is a significant advantage within the global telecommunications industry. Optical networks provides transmission of information over large distances with reduced latency. However, the growing intricacy of network topologies poses a significant challenge to network adaptability, network resilience, device compatibility, and service quality in the contemporary era of technology and 5G networks. In light of these challenges, recent studies leverages on disaggregation in the context of Software Defined Network (SDN) and network service orchestrators as a viable remedy. Disaggregated optical systems offer SDON (Software‐Defined Optical Networking) enhanced control options and third‐party dynamism streamlining upgrades and diminishing single vendor dependency. Although, the advancement of disaggregation improves network flexibility and vendor neutrality of Software Defined Optical Networking (SDON), this improvement comes at the cost of reduced scalability and network controllability performance. The current research paper posits two potential resolutions to the aforementioned challenge. The authors present recommendations and an enhanced architecture that leverages Open Network Operating System (ONOS) containers and Kubernetes orchestration to improve scalability inside the Software‐Defined Optical Networking (SDON) architecture. The suggested architectural design has underlining novel flow charts and algorithms that enhances scalability performance by 33% while also preserving flexibility and controllability in comparison to pre‐existing SDON architectures. This architecture also makes use of the Mininet‐Optical physical‐layer architecture to simulate a real‐time scenario, as well as yang models from the Open Disaggregated Transport Network (ODTN) working group, the pioneers of SDONs. A detailed analysis of the rules and procedural processes involved in the implementation of the proposed architecture. In order to demonstrate the practical application of this architectural framework to a real‐world Software‐Defined Optical Network (SDON) system, the pre‐existing SDON ONOS architecture within the Optical Transport Domain Networking (OTDN) working group was adjusted and refined. This adaptation aimed to illustrate the use of ONOS in conjunction with established optical network systems, highlighting the advantages it offers.

Real-time radiation monitoring of high energy 1.2-GeV synchrotron accelerator using experimental physics and industrial control system

The high energy 1.2-GeV electron accelerator facility’s radiation detection and monitoring system (RDMS) has greatly evolved to be the effective backbone of real-time radiation monitoring for the new light source 3-GeV synchrotron facility. Experimental Physics and Industrial Control System (EPICS), ethernet hardware connections (Optic fibers), and Web-based software interfaces make up the new RDMS framework, built on well-liked network technology. The problems of monitoring i.e., a lot of manpower, poor monitoring accuracy, and inability to monitor continuously in the high radiation dose are eliminated. EPICS, composed of an Input/Output Controller (IOC) and Client Workstations which can communicate with a Local Area Network (LAN), were applied for remote control and radiation measurement. EPICS has been able to transport and store massive amounts of data for large-scale systems with a wide range and high accuracy. The monitoring data were sent to the server through the optic fibers network system, which is more advantages such as no distance restrictions, low attenuation of the signal, faster responding times, and particularly electromagnetic resistance. The data can be accessed anywhere from client monitors with graphical user interfaces. This system is successfully developed and tested for the high energy 1.2-GeV electron accelerator. The RDMS is useful for radiation safety to monitor the radiation dose level during machine operation to protect occupational workers and the public from radiation hazards.

Comparative experimental study on gain clamping performance of O-band BDFA with different pump schemes at different input powers

Gain clamping can overcome the effects of power transients caused by unstable factors when fiber amplifiers are used in optical networks. In recent years, bismuth-doped fiber amplifiers (BDFA) operating in the O-band have been developed rapidly, while there are fewer studies on its gain-clamping aspects. In this work, we experimentally investigate the gain-clamping performance of O-band BDFA with different pumping schemes in the ultra-wide input range. Variable optical attenuator (VOA), 3-dB coupler, and a Fiber Bragg Grating (FBG) are utilized to form a ring cavity to generate the oscillating light. The experimental results demonstrate that the BDFA achieves a gain stabilization range under all three pumping schemes compared to the unclamped one, with the best effect under bidirectional pumping. Under the condition that the pump power is 500 mW and the VOA loss is 0 dB, the maximum gain fluctuation (MGF) of the signal in the input range from −15 dBm to 6 dBm is less than 0.5 dB and the average output gain is 6.3 dB, while when the VOA loss is 5 dB, the MGF of the signal below 0 dBm is less than 0.36 dB and the average output gain is 10.3 dB. This work provides a positive reference value for the application of O-band BDFA in optical network systems.

Optical Networks Automation Overview: A Survey

The increasing demand for data has driven the advancement of optical networks from traditional architectures to more flexible, dynamic and efficient solutions. This includes technologies like flexgrid reconfigurable optical add-drop multiplexers (ROADMs), variable bandwidth transponders (VBTs) providing different modulation, coding schemes and baud rates. These advancements have brought about new challenges that concerns to the routing and spectrum allocation (RSA), fragmented spectrum, need for rapid and efficient channel restoration, and operation and maintenance management of optical networks. To address these challenges, a dynamic and flexible network requires a highly advanced network operational system (OS) capable of efficiently managing and allocating network resources. It relies on network abstraction, sensors, actuators, and software-defined networking (SDN) to enable algorithms, management, control, and decision-making. Improving the sensing capabilities of the network is crucial. Modern hardware and sensor technology can help forecast fiber breaks, equipment failures, and other potential issues in advance, allowing for proactive actions to be taken. Machine learning (ML) methods have been proposed in the literature to enhance the accuracy of quality of transmission (QoT) estimation, mitigate nonlinearities and provide decisions. This reduces the need for conservative design margins, maximizes the capacity of optical network systems and reduces the investment in infrastructure. Failure management is a critical aspect of optical networks. Providing early-warning and proactive protection is essential. This includes detecting failures, localizing them, identifying the root causes, and estimating their magnitude. Quick response to failures is vital to maintaining network reliability

Model and experimental verification of SOP transient in OPGW based on direct strike lightning.

We introduce inductive lightning and direct lightning that affect the state of polarization (SOP) of signal light in optical ground wire (OPGW) of power transmission line, deduce the helical component of direct lightning on OPGW, and establish the transient model of signal SOP in OPGW based on direct lightning. We also monitored actual optical transport network (OTN) systems deployed on OPGW in thunderstorm-prone areas for three months, recorded error codes and SOP transients of more than 1.5 Mrad/s using a bit error rate tester and a polarimeter accordingly. The highest SOP transient rate was up to 43 Mrad/s. Finally, we verify the accuracy of the model through simulation and experiment comparison.

Covert fault detection with imbalanced data using an improved autoencoder for optical networks

Covert faults are characterized by the performance parameters falling within the normal range, without any observable abnormalities. These types of faults pose a significant risk as they present no apparent warning signs of potential danger. Therefore, it is crucial to establish an efficient covert fault detection method to ensure the reliable and stable operation of optical networks. Data-driven technology, which reveals the internal relations and data patterns between the historical data by mining and analyzing the historical data, offers a new perspective for covert fault detection. However, equipment failures are extremely rare in real optical network systems, and the data imbalance of covert fault samples poses a challenge for standard machine learning classifiers in learning precise decision boundaries. To address this challenge, we propose a fault detection scheme based on an improved autoencoder for covert fault detection under data imbalance. The designed covert fault detection model exclusively utilizes normal samples during training and remains unaffected by data imbalance. Specifically, the model is specifically designed according to a number of encoder and decoder components to learn the normal sample data patterns in the latent space and detect covert faults based on the reconstruction errors in that space. To validate the proposed scheme, we conducted experiments using actual backbone data. According to the results, the detection accuracy and F1 score of the designed model on the test set were 0.9811 and 0.9527, and the false negative and false positive rates were 0.0026 and 0.0227, respectively. Furthermore, the visualization of the latent space reconstruction error principle for detecting covert faults was implemented using the principal component analysis dimension reduction and scatter plots.

Development of a cost-effective optical network based on free space optical (FSO) and optical fiber links for enabling smart city infrastructure: A hybrid approach

Due to the gigantic rise in the use of high data rate-based applications and the ongoing transformation of Indian cities into smart cities, there is a need for a high-speed communication framework to handle the enormous data traffic. The radio frequency (RF) and microwave links seem to be incapable of offering sufficient bandwidth required by the data-hungry applications and consequently, the need for a more effective solution for tackling the issue of scarcity of bandwidth resources has become the necessity of current network infrastructure in India. In this study, a hybrid optical fiber-free space optical (OF-FSO) system for offering high-speed data services has been proposed to assist the implementation of smart city infrastructure in India. This study aims to inspect the system performance of the proposed model under the climatic conditions of mountainous, desert, flatland, and seaside regions of India. The proposed hybrid OF-FSO system comprises a fixed single-mode fiber (SMF) of 20 km and an FSO link (having a varied transmission range between 0–2 km). The proposed hybrid model can support an FSO link of 1.72 km for a fixed SMF of 20 km, corresponding to a bit error rate of the order of 10−4 for atmospheric conditions of the seaside location of Chennai and the range of FSO link varies from 1.32 km to 1.57 km for other locations of India, for the same length of SMF and bit error rate. Furthermore, the proposed hybrid OF-FSO has demonstrated a reduction of 30.8% in Capital Expenditure (CAPEX) cost in contrast to the conventional passive optical network (PON) system.