Visible Light Three-Dimensional Positioning System Based on Light-Emitting Diode and Image Sensor
Yongze Xu, and Zhe Chen
With the rapid development of the Internet of Things, smart devices require high-precision, real-time location services. However, only two-dimensional positioning can be achieved in existing visible light positioning technologies; furthermore, the system is complex and has a low positioning accuracy and extended positioning time. To address these issues, this study proposes a visible light three-dimensional positioning system based on two light-emitting diodes (LEDs) and image sensors. First, a simulation model is established by combining the pinhole imaging model and the distortion model. Next, a stripe search algorithm based on bisection and a double pointer is proposed to rapidly determine the position of the LED on the image. Finally, the geometric features of the LEDs on the image are used to achieve three-dimensional positioning. After calculations, in a 100 cm×100 cm×300 cm space, the average positioning error of the simulation experiment is 0.79 cm, and the average positioning error of the physical experiment is 5.61 cm. The average positioning time is 64.13 ms. In addition, the time performance of the proposed stripe search algorithm is improved by 70.06% compared with that of the linear stripe search algorithm. Therefore, the proposed system can provide a good three-dimensional positioning service.
  • Oct. 10, 2023
  • Laser & Optoelectronics Progress
  • Vol. 60, Issue 19, 1906004 (2023)
  • DOI:10.3788/LOP221643
Characteristics of Soil Vibration Propagation Based on Phase Sensitive Optical Time Domain Reflectometers
Ming Wang, Hao Feng, Zhou Sha, and Lipu Du
Phase sensitive optical time domain reflectometers (φ-OTDRs) have been widely employed in pipeline safety early warning systems, optical cable break-point searches, mechanical pipeline pig (PIG) positing and tracking, and other fields. The sensing optical cables of φ-OTDRs are mostly buried underground so that the soil characteristics, transmission distances, and optical cable structures all have considerable effects on the signal characteristics. This study considered the propagation characteristics of vibration signals in soils and explored the effects of non-event factors such as optical cable structures, soil moisture, and transmission distances on the signal characteristics of systems. In addition, in terms of energy change trends in characteristic frequency bands, the difference between real shock vibration and non-event signal fluctuations was investigated. A proposed method to judge external shock vibration is derived from the results.
  • Oct. 10, 2023
  • Laser & Optoelectronics Progress
  • Vol. 60, Issue 19, 1906003 (2023)
  • DOI:10.3788/LOP221585
Probabiliy Shaping Orthogonal Frequency Division Multiplexing Optical Signal Transmission System Based on Wavelength Conversion
Xia Hu, Li Zhao, and Jianjun Yu
This study theoretically analyzed the reasons why, in the copolarized dual-pump scheme, wavelength conversion does not change the probability distribution of the probability shaping (PS) signal and the order of orthogonal frequency division multiplexing (OFDM) signal subcarriers can remain unchanged. Then, after all-optical wavelength conversion, the transmission of the PS-64QAM-OFDM signal through a highly nonlinear optical fiber in a homodyne coherent detection system was experimentally verified. Finally, the experimental results indicate that when the baud rate is 20 Gbaud and the bit error rate is 1×10-2, the optical signal-to-noise ratio (OSNR) loss of an ordinary 64QAM signal is 1 dB, and the OSNR loss for PS-64QAM signal is improved by 0.5 dB.
  • Oct. 10, 2023
  • Laser & Optoelectronics Progress
  • Vol. 60, Issue 19, 1906001 (2023)
  • DOI:10.3788/LOP221106
Single-ended characterization of the coherent transfer matrix of coupled multimode transmission channels
Alireza Fardoost, Fatemeh Ghaedi Vanani, Sethumadhavan Chandrasekhar, and Guifang Li
Light propagation in random media is a subject of interest to the optics community at large, with applications ranging from imaging to communication and sensing. However, real-time characterization of wavefront distortion in random media remains a major challenge. Compounding the difficulties, for many applications such as imaging (e.g., endoscopy) and focusing through random media, we only have single-ended access. In this work, we propose to represent wavefronts as superpositions of spatial modes. Within this framework, random media can be represented as a coupled multimode transmission channel. Once the distributed coherent transfer matrix of the channel is characterized, wavefront distortions along the path can be obtained. Fortunately, backreflections almost always accompany mode coupling and wavefront distortions. Therefore, we further propose to utilize backreflections to perform single-ended characterization of the coherent transfer matrix. We first develop the general framework for single-ended characterization of the coherent transfer matrix of coupled multimode transmission channels. Then, we apply this framework to the case of a two-mode channel, a single-mode fiber, which supports two randomly coupled polarization modes, to provide a proof-of-concept demonstration. Furthermore, as one of the main applications of coherent channel estimation, a polarization imaging system through single-mode fibers is implemented. We envision that the proposed method can be applied to both guided and free-space channels with a multitude of applications.
  • Sep. 21, 2023
  • Photonics Research
  • Vol. 11, Issue 10, 1627 (2023)
  • DOI:10.1364/PRJ.491967
Effect of Marine Bubbles on the Performance of Underwater Quantum Communication Channel
Xiuzai Zhang, Yujie Ge, Mengsi Zhai, and Lijuan Zhou
ObjectiveIn recent years, quantum communication has become a research hotspot in China and abroad for its better data transmission security. As the core of the quantum information theory, quantum communication can be more secure and reliable for information transmission and is an important direction of inquiry. With the development of underwater wireless communication, it is important to research underwater quantum communication for marine and military fields. Bubbles are ubiquitous in the ocean, and the scattering and refraction effects of bubbles on light can cause certain losses in optical quantum transmission, which exerts a certain impact on the performance of underwater optical quantum communication. However, the research on the effect of bubbles on the channel performance of underwater quantum communication has not been conducted. By building the particle size distribution and scattering coefficient models of marine bubbles, the paper analyzes the effects of different condition parameters on link attenuation, entanglement, channel capacity, and channel bit error rate (BER) in the marine bubble environment to investigate the influence of these bubbles on the channel performance of underwater quantum communication. This is of great significance to improve the efficiency of underwater quantum communication.MethodsMarine bubbles are mainly generated by wind-driven wave breaking. With an aim to study the influence of marine bubbles on the channel performance of underwater quantum communication, the particle size distribution function of the bubbles is firstly derived and established. The scattering characteristics and extinction coefficient of the bubbles are studied according to the particle size distribution model of marine bubbles. Additionally, according to the extinction characteristics, the relationship between marine bubble parameters and link attenuation is firstly established, and then the effects of different depths and bubble radii on channel entanglement are analyzed. Then, the effects of different bubble concentrations and transmission distances on three channel capacities of amplitude damped channel, depolarized channel, and bit-flip channel are analyzed respectively. Finally, the effects of different bubble concentrations and transmission distances on channel BER are studied and analyzed. At the same time, the effects of different bubble concentrations and transmission distances on the channel BER are studied and simulated. The theoretical analysis and simulation results can provide a reference for the design of underwater quantum communication in the marine bubble environment.Results and DiscussionsThe simulation results show that the density of bubbles decreases with the increasing depth from the sea level, whereas increases with the rising wind speed. The scattering coefficient of bubbles has the same trend as the bubble density number under the same parameter conditions. Under short transmission distance and small bubble concentration, the link attenuation caused by marine bubbles is also small. With the increase in the transmission distance of optical quantum signals and the bubble concentration, the link attenuation grows rapidly. The channel entanglement increases with the rising depth from the sea level and the decreasing bubble radius. For the amplitude damping channel, depolarization channel, and bit-flip channel, the channel capacity decreases to different degrees with the increasing transmission distance and bubble concentration. The capacity of the depolarization channel and the bit-flip channel is more affected by the transmission distance, and the transmission distance exerts less effect on the channel capacity. The BER in the marine bubble environment is also affected by the transmission distance and bubble concentration. When the bubble concentration is small with a short transmission distance, the system BER changes slowly. When the bubble concentration is large with a long transmission distance, the optical quantum signal attenuates seriously and the BER value rises rapidly.ConclusionsTo investigate the effect of marine bubbles on the channel performance of underwater quantum communication, this paper studies the scattering characteristics of the bubbles according to the particle size distribution model of marine bubbles. In addition, the effects of different condition parameters on link attenuation, entanglement, channel capacity, and channel BER are analyzed according to the extinction coefficient of bubbles, and simulation experiments are conducted. The results show that the increase in bubble concentration and transmission distance increases the link attenuation and BER, and the channel capacity decreases for amplitude damping channel, depolarization channel, and bit-flip channel. The channel entanglement decreases with the increasing bubble radius and decreasing depth, and the impact of marine bubbles on communication performance cannot be ignored. Meanwhile, parameters related to underwater quantum communication should be adjusted appropriately according to the concentration of marine bubbles to reduce the impact of the marine bubble environment on the communication system and improve the reliability of the communication system in practical application.
  • Sep. 25, 2023
  • Acta Optica Sinica
  • Vol. 43, Issue 18, 1806001 (2023)
  • DOI:10.3788/AOS221816
Temperature Control Method for Multichannel PPLN Waveguides
Kunpeng Yi, Quan Yao, Jichao Lin, Jingli Fan, Daiying Wei, Yang Gao, and Mingyang Zheng
Conversion efficiency is the primary performance metric of a periodically poled lithium niobate (PPLN) waveguide and strongly correlates with temperature. Multichannel waveguides are limited by process issues; accordingly, ensuring consistency between each waveguide channel is difficult. This paper proposes an automatic temperature control method for multichannel waveguides. In this method, number of photons detected using multiple single photon detectors corresponding to the multichannel waveguide is obtained by field-programmable gate array (FPGA) chips. Thereafter, the photon number data of each channel is processed using equalization algorithms to determine the optimal temperature working point of the multichannel waveguide and achieve automatic adjustment of the waveguide temperature. FPGA chips are used in this study to achieve TEC driving control, construct a single photon detector with active quenching and fast recovery functions, and achieve automatic control of multichannel waveguide temperature using an equalization algorithm. Additionally, we develop a multichannel up-conversion single photon array detector with more uniform detection efficiency, greatly reducing initial manpower investment and avoiding errors caused by human factors.
  • Sep. 10, 2023
  • Laser & Optoelectronics Progress
  • Vol. 60, Issue 17, 1706006 (2023)
  • DOI:10.3788/LOP231469
Long-Range Optical Chaos Synchronization Based on Optical Domain Compensation
Yukun Zhang, Zhaoyun Li, Zhiyong Tao, and Yaxian Fan
Because of dispersion and nonlinear effects in optical fibers, chaotic signals are difficult to obtain long-range synchronization. Meanwhile, due to the characteristics of pure optical domain signal processing used for optical injection chaos synchronization, it cannot be fused with existing communication systems' electric domain nonlinear compensation. As a result, this paper proposes a technical solution for realizing laser chaotic long-distance synchronization by combining dispersion management with optical domain-based nonlinear management based on the NLS equation. The synchronization and transmission characteristics at various transmission distances and different injection intensities are studied in detail. The findings demonstrate that the system is capable of achieving secure communication at a 1 Gb/s information rate, 1000 km of transmission distance, and 0.5 mW of injection intensity. The synchronous carrier correlation coefficient can exceed 0.97.
  • Sep. 10, 2023
  • Laser & Optoelectronics Progress
  • Vol. 60, Issue 17, 1706004 (2023)
  • DOI:10.3788/LOP222405
Research on Placement Algorithm of Flexible Virtual Machine in Elastic Optical Data Center
Zhongjun Ma, Fengqing Liu, and Yuxing Chen
To absorb the traffic uncertainty and map the service network to the physical network of the data center flexibly and efficiently, this paper studies the dynamic virtual data center mapping problem in an elastic optical data center network, where the service model is a hose model. First, the mapping model of a flexible virtual machine is established in an elastic optical data center network, and then the virtual machine placement algorithm based on virtual topology (VT-VMPA) is proposed. The VT-VMPA first converts the hose model into the pipe model before looking for the core virtual machine using the maximization of traffic volume as a guideline. Then, in descending order of service volume, the virtual machines that adhere to the resource constraints and are linked to the core virtual machines are combined into clusters. The communication bandwidth requirement is reduced after the cluster is mapped to the server. Finally, the cluster sets are mapped to the servers and virtual links between clusters are mapped to optical paths of the elastic optical data center network according to hop distance adaptive and shortest path principles. In comparison to previous methods, the proposed algorithm has decreased blocking rate by 27%, increased average time revenue by 117%, and decreased average bandwidth usage by 21%. It demonstrates that this method may increase network mapping speed while consuming fewer network traffic.
  • Sep. 10, 2023
  • Laser & Optoelectronics Progress
  • Vol. 60, Issue 17, 1706003 (2023)
  • DOI:10.3788/LOP222310
Accurate mode purity measurement of ring core fibers with large mode numbers from the intensity distribution only
Zekun Shi, Baiwei Mao, Zhi Wang, and Yan-ge Liu
Mode purity measurement is crucial for various applications utilizing few-mode fibers and related devices. In this paper, we propose a simple and accurate method for measuring the mode purity of the output optical field in few-mode ring-core fibers (RCFs). Mode purity can be calculated solely from the outgoing intensity distribution with high precision. This method is theoretically capable of measuring the mode purity of RCFs that support orbital angular momentum modes with an infinite number of azimuthal orders and has strong applicability to various RCF types and image qualities simultaneously. We demonstrate our approach numerically and verify it experimentally in a few-mode RCF supporting four (five) mode groups at 1550 (1310) nm. A polarization test method is proposed to verify its accuracy. We believe that this straightforward and cost-effective characterization method for RCFs and RCF-based devices can promote the development of mode-division multiplexing technology and its applications.
  • Aug. 31, 2023
  • Photonics Research
  • Vol. 11, Issue 9, 1592 (2023)
  • DOI:10.1364/PRJ.494864
Implantable Fiber Bragg Grating Temperature Sensor Inside Lithium-Ion Battery
Yan Mao, Xinglin Tong, Shigang Lu, and Weida Chu
In the operation of lithium-ion batteries, particularly at the high discharge rate, the temperature of the battery significantly increases owing to heat generation. The most accurate and reliable sensor data for the battery management system (BMS) cannot be obtained by relying solely on temperature monitoring of the surface of individual cells. In-situ monitoring of lithium-ion batteries is one of the most effective methods to prevent the thermal runaway of lithium-ion batteries. A sensor is implanted in the heat source core of the lithium-ion battery, and the temperature change can be sensed immediately. A fiber optic composite temperature sensor is embedded in the inner center of the 18650 cylindrical lithium-ion battery, and the cross sensitivity of temperature and stress inherent in the Bragg grating sensing mechanism is eliminated using the Fabry-Perot (F-P) air cavity on the same fiber. The experimental results show that the internal temperature change of the battery can be monitored in real time in the charge and discharge stages, and the optical fiber sensor is compatible with the internal cell of the battery. This can facilitate the long-term health monitoring of large-scale lithium-ion battery-integrated components.
  • Sep. 10, 2023
  • Laser & Optoelectronics Progress
  • Vol. 60, Issue 17, 1706005 (2023)
  • DOI:10.3788/LOP221764