In the field of optical communication, laser and its modulation bandwidth and modulation rate are very important for optical wireless communication. There are two main modulation modes for semiconductor laser signal: internal modulation and external modulation. These two modulation technologies have their own characteristics and are suitable for different fields of optical fiber communication. Internal modulation laser, also known as direct modulation laser, has become a cost-effective light source for the Fifth Generation Mobile Communication Technology (5G) fronthaul and data center because of its high-speed transmission and low cost. There is no additional Chirp of light source in external modulation laser, so the Composite Second Beat (CSB) distortion caused by fiber dispersion can be effectively overcomed. On the basis of reviewing the development history of communication laser and its modulation technology, this paper introduces the work and main progress made by Xi’an University of Technology in this field. This paper discusses the internal and external factors of nonlinear distortion of semiconductor laser, simulates the effects of various parameters of response characteristics, linearization compensation method and power control system on the output light source of light emitting device, and analyzes the influence of temperature fluctuation on the output power of laser and modulation device. Based on the basic theory of refractive index ellipsoid and numerical analysis, the variation trend of emitted light intensity with temperature is discussed under the longitudinal and transverse modulation, respectively. The results show that the variation trend of outgoing light intensity with temperature under longitudinal modulation is only related to the refractive index of Lithium Niobate (LN) crystal. Under transverse modulation, the variation trend of outgoing light intensity with temperature is affected not only by the refractive index of the crystal, but also by the crystal size and its expansion coefficient. Therefore, the special size crystal can be used to improve the temperature stability of the electro-optic modulator.

【Objective】In this paper, the objective of the research is to improve the performance of Orthogonal Frequency Division Multiplexing (OFDM)-Wavelength Division Multiplexing (WDM) optical fiber communication system. a Quadrature Grouped Subcarrier Amplitude Shaping (QGSAS) dual-Phase Conjugate Twin Waves (dual-PCTW) scheme is proposed, which can suppress the nonlinear effect of the systems. In addition, the simulation systems under different conditions are built to explore the performance of the scheme. The specific experimental methods are as follows.【Methods】With the mixed programming of Optisystem and Matlab, a QGSAS dual-PCTW OFDM system is simulated based on 16-ary and 64-ary Quadrature Amplitude Modulation (QAM) formats. Two kinds of QGSAS (sinusoidal amplitude shaping, rectangular amplitude shaping) and three dimensions dual-PCTW (time domain, polarization domain, sub-carrier domain) are adopted for the system to form 12 different combinations.【Results】The simulation results show that the QGSAS dual-PCTW scheme can effectively suppress the nonlinear effects in the system. In several combination schemes discussed, the 16QAM dual-PCTW scheme in time domain has the best performance. When the QGSAS technology is used, the scheme of rectangular amplitude shaping is better than the sinusoidal amplitude shaping.【Conclusion】Therefore, it can be concluded that in the scheme studied in this paper, the rectangular amplitude shaping scheme combined with the time domain scheme dual-PCTW technology under 16QAM can effectively suppress the nonlinear effect of OFDM-WDM system.

【Objective】High-frequency microwave carriers (GHz) with tunable capability have a wide range of applications in 5th Generation Mobile Communication Technology (5G)/ 6th Generation Mobile Communication Technology (6G) wireless networks, radar systems, and satellite communications. Due to the relatively simple structure of the system, the large bandwidth and the low loss, the technical scheme of generating high-frequency tunable microwave carriers based on photonic technology has attracted extensive attention from domestic and international research teams. Current photogenerated microwave experiments are mostly conducted in C-band wavelengths because of the mature commercial devices. Meanwhile, the Wavelength Division Multiplexing (WDM)-Radio Over Fiber (ROF) technology integrates the WDM technology with the ROF technology so as to flexibly realize the combining/splitting of microwave bands with the help of the combining/splitting of WDM system in the optical frequency domain. The ROF part of the system employs photogenerated microwave technology to simplify the base station configuration. Constrained by the limited bandwidth resources in the C-band wavelengths(35 nm, 1 530~1 565 nm), there is a drive for the generation of microwave to expand to wider spectral ranges. The U-band wavelengths can also provide channel bandwidths as wide as 50 nm (1 625~1 675 nm) to alleviate the channel utilization pressure in the C-band wavelengths; In the U-band wavelengths, Standard Single Mode Fibers(SSMFs) have achieved optical power loss as low as 0.195 dB/km (@1 625 nm); In particular, thulium-doped fiber amplifiers have also demonstrated a large bandwidth gain of 18.7 dB (@1 655 nm). These advantages attract SSMFs-based WDM systems to expand into the U-band, which leads to the extension of WDM-ROF technology into long wavelengths, and in turn leads to the expansion of photogenerated microwave technology. Therefore, this paper studies the photogenerated microwave technology in the U-band.【Methods】From the mathematical model, the commonly used photogenerated microwave carriers technologies are transparent to the applied optical carrier bands, and can be used to generate microwave carriers at arbitrary bands by selecting photonics devices corresponding to the operating bands. In principle, C-band wavelengths photonics devices (such as polarization controllers, Phase Modulator (PM), Fiber Phase Shifter (FPS), etc.) can work in the U-band, and the process technology of these devices is mature. Therefore, in this paper, photonics devices such as C-band wavelengths PM, FPS and optocouplers are used to build a photogenerated microwave carrier system based on U-band optical carriers.【Results】Finally, tunable microwave carrier with a tuning range of 7.5~12.0 GHz and a spurious rejection ratio of 29.6~35.2 dB is ultimately generated based on this system.【Conclusion】Through formula principle analysis and experimental verification, this paper extends the working band wavelengths of the photogenerated microwave carrier to the U-band wavelengths.

【Objective】In order to improve the confidentiality and performance of the mixed Radio Frequency (RF)/Free Space Optical (FSO) communication systems, it is necessary to study the security performance of the Reconfigurable Intelligent Surface (RIS)-assisted mixed RF/FSO system to obtain the relationship between system security performance and parameters such as RIS deployment location and the degree of correlation between different antennas branches.【Methods】In the article, a single eavesdropper is considered to eavesdrop against RF links and FSO links respectively, with RF links obeying an arbitrarily correlated Nakagami-m distribution and FSO links obeying a Gamma-Gamma distribution. Closed expressions for the Security Outage Probability (SOP) and Strictly Positive Security Capacity (SPSC) probability of the communication system for the two eavesdropping scenarios are derived using the decode-and-forward protocol, and the SOP is analyzed asymptotically. Simulation experiments are also conducted using the Matlab software to verify the accuracy of the derived formulas through Monte Carlo simulation.【Results】Simulation results show that deploying the RIS close to the receiver reduces the security outage probability of the system. It is also shown that an increase in the degree of antenna correlation increases the SOP of the system when the channel quality of the RF main channel is better compared to the eavesdropping channel.【Conclusion】The RIS-assisted FSO link has better security compared to the RF link. Although the multi-antenna diversity technique can effectively improve the security performance of the system, antenna correlation, similar to the fading caused by pointing error and atmospheric turbulence, can also damage the security performance of the system. It is also shown that the security of the system can be effectively improved by reducing the degree of antenna correlation.

【Objective】Power Line Carrier(PLC)communication adopts the frame burst transmission mode. Due to the carrier frequency offset between transceivers, various noise and time-varying characteristics of PLC channel and the system has no dedicated reference signal. The traditional channel estimation has no tracking and prediction ability for the channel, which leads to the deterioration of the PLC system performance.【Methods】Aiming at the existing problems, this paper proposes a Denoising Long Short Term Memory (DnLSTM) neural network based on Long Short Term Memory (LSTM) neural network and Denoising Convolutional Neural Network (DnCNN), which is used for PLC channel estimation. First, offline training is performed on DnLSTM and the parameters are saved after training. Then the trained parameters are deployed in PLC system. After loading parameters, online prediction is performed to obtain the predicted PLC system channel estimation. In the simulation of PLC system, this paper uses Least Squares (LS) algorithm, Minimum Mean Square Error (MMSE) algorithm and DnLSTM to estimate the channel response, and gives the simulation results under the conditions of Additive White Gaussian Noise (AWGN), combined noise, impulsive noise and colored noise. Meanwhile, simulations for different number of preamble symbols for channel estimation are performed.【Results】The results show that there is a relationship between the accuracy of DnLSTM channel estimation and the number of preamble symbols. Using four preamble symbols for channel estimation, its estimation accuracy is better than LS and close to MMSE algorithm. DnLSTM has a good ability to resist carrier frequency offset and channel time-varying. When the number of preamble symbols for channel estimation increases, PLC system performance with low Singnal to Noise Ratio (SNR) gets better and PLC system performance is similar with high SNR.【Conclusion】According to simulation results above, it can be concluded that DnLSTM, which is based on DnCNN and LSTM, can predict PLC system channel response with frequency offset very well and it can track the varying PLC system channel response in real time.

【Objective】Deformable Mirror(DM) is a key device in adaptive optics system for wavefront correction, and its performance directly determines the wavefront correction capability of the system. By studying DM and their control algorithm, the wavefront correction capability of adaptive optics system can be continuously improved. On one hand, the accuracy and response speed of DM can be enhanced to better correct various complex wavefront distortions. On the other hand, the control algorithm can be improved to increase the efficiency and accuracy of the correction. These studies will directly affect the imaging quality and performance of adaptive optics system. Therefore, investigating the DM and their control algorithm is of great significance for improving the wavefront correction capability, expanding application fields, and enhancing imaging quality and performance of adaptive optics system.【Methods】The article aims to summarize the research progress on DM and their control algorithm both domestically and internationally, as well as analyze the correction accuracy of different control algorithm for wavefront distortion, establishing the groundwork for the advancement of adaptive optics. Firstly, several typical DMs are used as examples to model the DM and provide detailed introductions to the structures and working principles of separate actuator DM, splicer DM, thin film DM, dual piezoelectric DM, Micro Electromechanical System (MEMS) DM and voice coil DM. Then, several control algorithms such as the Prandtl-Ishlinskii (PI) hysteresis model-based control algorithm, decoupled control algorithm, and sparse sampling control algorithm are analyzed.【Results】Summarized the work done by Xi'an Technological University in this field, and finally pointed out the future technological breakthroughs and improvement directions in this field.【Conclusion】The research progress on DM and their control algorithm lays the foundation for the development of adaptive optics, enabling its application in more fields and further improving the performance of adaptive optics system. This will help improve imaging quality and drive the development of adaptive optics technology.

【Objective】Natural disasters such as earthquakes have the characteristics of persistence and wide range. During the occurrence of disasters, the link resources of the optical network will be continuously damaged, resulting in the constant change of the link risk. In the face of constantly changing link risks, improper service recovery planning may cause service failures. From a service perspective, repeated faults will interrupt data transmission many times, and the subsequent link status damage may be aggravated after a disaster occurs. From the perspective of network management and control, repeated recovery wastes route calculation resources and occupies the recovery resources of other services. At the same time, different services have different requirements for transmission reliability because of the importance of the data to be transmitted. When a fault occurs, the high-importance services should be recovered first. Therefore, in the scenario of a large-scale persistent disaster, it is a problem worth studying to comprehensively consider the sustained impact of the disaster on link risk and the difference in path reliability requirements of different services for service recovery. To solve this problem, this paper proposes a link risk-aware service recovery algorithm-Dynamic Link Risk Reroute Algorithm (DLRRA) under persistent disasters.【Methods】Firstly, according to the service importance and link risk, we establish the service importance evaluation model and link risk evaluation model. Then we propose the optimization target route reliability. The DLRRA, combined with the optimization objective, fully considers the change of link risk degree caused by the impact of disasters on the continuity of links. By preferentially allocating low-risk recovery resources to the fault services of high importance, the risk of secondary failure of the same high-importance services is avoided during the continuous occurrence of disasters.【Results】The simulation results show that the second failure probability of DLRRA recovery is reduced by 11% compared with the traditional algorithm, and the average importance of DLRRA recovery under the high load is increased by 10%.【Conclusion】Therefore, the algorithm effectively avoids the loss caused by multiple service interruptions caused, and ensures the continuous and stable operation of important services in the disaster environment.

【Objective】With the development of domestic optical network construction, the management of fiber optic cable routing resources increasingly attract the attention of operators, especially the problem of low efficiency in fiber optic cable survey. There is an urgent need for a feasible fiber optic cable survey method and plan to solve the current problems. The effectiveness and practicality of fiber optic cable routing survey methods are also important indicators that determine the improvement of network construction and maintenance indicators in the region.【Methods】The article investigates and analyzes the existing survey methods and laws of a large number of complex environmental optical cable routes. It also compares and analyzes the detection principles, application scenarios, and existing problems from multiple dimensions. The article focuses on evaluating efficiency improvement, operability, and cost. Combining with actual case situations, it analyzes the actual survey effects of different schemes in a targeted manner.【Results】The article innovatively proposes the research concept of a new fiber optic cable survey method and its application in multiple types of scenarios. The focus is on the practical application of cable identification instruments and cable knocking survey instruments that can be used for full process identification. They have advantages in efficiency and cost, and can solve the pain points of pipeline resource management for operators, providing ideas for the informational development and innovation of pipeline resources for domestic operators.【Conclusion】The method of fiber optic cable routing survey are important breakthroughs in effectively solving practical problems such as cable laying, cable inspection, and cable repair, which are important links in the construction of high-quality optical networks.

【Objective】In response to the needs of Ultra High Voltage (UHV) site infrastructure control and intelligent transportation and inspection, 5th Generation Mobile Communication Technology (5G) is applied to the construction phase of UHV converter station for the first time in China.【Methods】On the basis of realizing 5G full coverage of Henan southern converter station, 5G virtual private network of converter station is built and the Mobile Edge Computing (MEC) cloud platform is deployed. Fully considering the needs of early infrastructure and late operation, the intelligent infrastructure site is connected with the intelligent converter station in the later stage. Relying on the advantages of 5G and integrating Artificial Intelligence (AI) and other technologies, various types of data on the construction site of UHV infrastructure can be collected in real-time and unified, providing multi-functional 5G solutions for remote video monitoring of UHV infrastructure, engineering monitoring and early warning, panoramic presentation of infrastructure site, identification of safety hazards, and expert remote assistance guidance. 5G applications such as smart construction site, intelligent inspection and intelligent control are organized and 5G network adaptation test is carried out.【Results】Providing a flexible, large-bandwidth and high-speed communication methods of 5G for the business application of Henan southern converter station. It effectively enables various business requirements in the UHV converter station, verifying the carrying capacity of 5G for UHV construction and inspection services. It also improves the management efficiency, and reduces the operation and maintenance cost.【Conclusion】The successful application of 5G in the Henan southern UHV converter substation provides a typical UHV substation solution of 5G+ energy Internet, which verifies the feasibility of 5G in the power industry and also promotes the application of 5G in power scenarios.

Liquid Crystal-Spatial Light Modulators (LC-SLM) control the optical path by modulating the refractive index of liquid crystal, and play an important role in adaptive optics. This paper sorts out the development status of LC-SLM at home and abroad, and introduces the working principle and phase calibration principle of LC-SLM in detail. Aiming at the application of LC-SLM in adaptive optics, the research status of key technologies of LC-SLM at home and abroad is discussed. The experimental research in this field of Xi'an University of Technology is analyzed and summarized. Finally, the application status of LC-SLM is prospected.

With the development of the social informatization, the demand for optical fiber communication system capacity continues to grow. Channel impairment has always been the key factor limiting the capacity in optical fiber communication system. As the basic function and key technology in optical fiber communication system, channel impairment compensation is constantly improved. Applying deep learning technology in channel impairment compensation of optical fiber communication has attracted the attention of many researchers. This paper introduces the common deep learning models used and the development of deep learning technology for impairments compensation of optical fiber communication systems in recent years.

【Objective】For the problem of limited sensing distance of distributed optical fiber sensing system, a Phase-Sensitive Optical Time Domain Reflectometry (φOTDR)distributed optical fiber sensing system based on Remote Optically Pumped Amplifier (ROPA) technology was proposed.【Methods】Adopting polarization diversity reception technology to obtain orthogonal polarization signals to solve the problem of polarization mismatch, Frequency division band processing suppresses coherent fading and polarization fading. Applying high-order Raman pumping technology and cascaded ROPA technology, three remote gain units are selected with appropriate gain medium lengths. Introduced at the appropriate positions in the transmission link, the pump light and signal light are coupled and sent by the remote pumping unit to excite erbium ionst for unrepeatered amplification, realizing ultra long single span vibration signal sensing and solving the problem of insufficient single-span sensing distance of existing φOTDR.【Results】The experimental results show that In-phase and Quadrate (IQ) demodulation algorithm can be used to achieve linear recovery of Piezoelectric Transducer (PZT) disturbed 100 Hz signal.【Conclusion】The results show that this system can achieve vibration signal sensing of 176.6 km ultra long single span, breaking the existing φOTDR single span sensing distance recording. The vibration curve of the first 176 km is stable and the amplitude is below 0.4 rad. The undisturbed position in the three-Dimensional (3D) map is relatively stable, and the disturbance signal added by PZT at the end of the link can be accurately perceived. After Fast Fourier Transform (FFT) transformation processing, the signal-to-noise ratio of the 100 Hz disturbance signal is 8.9 dB. The experimental results are crucial for building ultra long single-span φOTDR sensing system and provides a certain reference value for the development of unrepeatered ultra long-distance sensing in OTDR systems.

【Objective】This paper studies numerical characteristics and characteristic matrix of attenuation spectrum of G.652.D single-mode optical fibres, and considers the attenuation factor to optimize the mathematical expression of optical fibre attenuation spectrum model. The study aims to improve the digital modeling ability of optical fibre attenuation spectrum for research and manufacturing of optical fibre and development of optical system.【Methods】ITU-T G.650.1(2020) provides an example matrix for use in the "spectral attenuation modelling" method to calculate attenuation spectrum of G.652.D single-mode optical fibres. This paper analyzes and demonstrates that the spectral attenuation model method could approximately obtain optical fibre attenuation spectrum with low error by characteristic matrix corresponds to four wavelengths. An optimized attenuation spectrum characteristic matrix is given by considering sources of attenuation, and the effect of the new matrix is verified with attenuation spectrum test data of 1000 fibre samples.【Results】Main research results of this paper include: (1) When there is a good correspondence between the wavelengths corresponding to the fibre attenuation spectrum characteristic matrix and main attenuation sources of G.652.D fibre, the spectral attenuation model method is able to approximate the fibre attenuation spectrum with small errors; (2) An attenuation spectrum characteristic matrix of G.652.D single mode fibre is calculated based on attenuation sources of the fibre, and this matrix is able to reflect mechanism of fibre attenuation better, compared to the characteristic matrix calculated solely from data; (3) Verification with test data of optical fibre samples shows that the new matrix could calculate the attenuation spectrum of optical fibre samples with comparable small errors.【Conclusion】This paper studies and concludes that the reason why the spectral attenuation model method is able to approximate the optical fibre attenuation spectrum is that the corresponding wavelengths of the characteristic matrix has a good correspondence with main attenuation sources of the optical fibre. Combining with the attenuation sources, optimized characteristic matrix can be calculated. The new matrix could reflect the mechanism of the optical fibre attenuation and also effectively calculate the attenuation spectrum of the optical fibre samples with small errors.

【Objective】In order to realize intelligent cloud-light integration and to solve the problem of slow deploying optical transport network, the article provides a fast deployment method for end-to-end business of cross-domain and cross-vendor.【Methods】By analyzing current status of cross-domain and cross-vendor service deployment on the live network, we find and solve the problems of intelligent optical business integration of Software Defined Network (SDN) control system of the device manufacturer with Abstraction and Control of Traffic Engineered Networks (ACTN) and Software Defined Optical Transport Network (SDOTN) standards. The paper also proposes the methods and directions to improve the SDN management and control system of device manufacturers.【Results】Verified by testing, by optimizing and improving the Synchronous Digital Hierarchy (SDH) management and control system of device manufacturers, the efficiency of enabling end-to-end services within a domain can be improved. The intelligent one-click deployment of cross-domain end-to-end services can be implemented.【Conclusion】Proved by the test results, Optimizing and improving the SDN management and control system of equipment manufacturers is conducive to the service opening of intelligent cloud-light integration.

【Objective】To meet the diverse application demands for high-performance Optical Frequency Comb (OFC), especially in terms of independently adjustable parameters like bandwidth, flatness, central wavelength, and spectral line spacing, a method based on secondary coupled Radio Frequency (RF) signals to drive a single Dual Drive Mach-Zehnder Modulator (DDMZM) for OFC generation is proposed.【Methods】Utilizing a single multiplier to generate the secondary RF coupled signals not only increases the number of comb lines produced by the OFC but also offers the advantages of a simple structure and low cost. Additionally, to further enhance the optimization efficiency and performance of the OFC, a deep learning-based inverse design and analysis approach is adopted.【Results】The study shows that the inverse design based on the constructed cascaded network can identify the corresponding parameters for the target OFC in less than one second. This rapid parameter determination method enables programmability of the number of comb lines, OFC power, and line spacing. It can also generate a 13-line OFC with a flatness of 1.769 dB. This efficient design method provides robust support for the rapid preparation and application of OFCs.【Conclusion】The proposed solution in this study demonstrates significant advantages in OFC generation technology, particularly in performance, flexibility, and optimization efficiency. The method of generating OFC through DDMZM driven by secondary coupled RF signals not only simplifies the system structure and reduces costs but also significantly improves design efficiency through the reverse design approach of deep learning. These characteristics make this solution suitable for a wide range of applications, especially in scenarios requiring quick, efficient, and flexible adjustment of OFC parameters.

Ultraviolet technology has a wide range of applications in military and civilian fields, such as space detection, ultraviolet light guidance, ultraviolet interference, corona discharge detection and military communications. Starting from the single and multiple scattering of ultraviolet light, this paper first introduces the progress of ultraviolet optical communication at home and abroad. Then it analyzes the different links in ultraviolet optical communication. Next, it discusses the pulse broadening effect and atmospheric turbulence of ultraviolet communication in non-direct link ultraviolet communication. Finally, the paper summarizes the ultraviolet Ad Hoc network, and shows the trend of the development of ultraviolet optical communication.

【Objective】Coherent optical communication is a high-speed, high-quality, and highly secure communication method, and coherent detection plays an extremely important role in coherent optical communication. High sensitivity coherent detection systems can significantly increase the distance of coherent optical communication. By studying the factors that affect the sensitivity of coherent detection, targeted corrections can be made to improve the detection sensitivity.【Methods】This paper first briefly describes the principle of the coherence detection, and summarizes the research progress in this field at home and abroad. Then the paper analyzes the influence of thermal noise, shot noise, wavefront distortion, polarization loss, spot size deviation, optical axis deflection, coupling efficiency, detector performance, preamplifier and other aspects on coherence detection sensitivity of wireless optical coherence detection system.【Results】The results show that the influence of the thermal noise and shot noise of the system on the detection sensitivity can be minimized by controlling the local oscillator power. The wavefront distortion of signal light can be suppressed by adding an adaptive correction system. The polarization control compensation device can be used to compensate the polarization mismatch between signal light and local oscillator light. The deviation of spot size and optical axis deviation requires improving the processing level of hardware to reduce this error. The use of new detectors can improve the performance of detectors to a certain extent. The pre-amplifier can amplify weak signal light, which is crucial for improving detection sensitivity.【Conclusion】This article analyzes the factors that affect the sensitivity of wireless optical coherent detection, and summarizes the methods used by domestic and foreign scholars to improve detection sensitivity in recent years. It provides theoretical reference for improving the sensitivity of detection systems in practice, which has important significance for improving the performance of coherent optical communication systems.