摘要
对主从开环结构下,混沌激光偏振度对混沌同步质量的影响进行实验研究。在背靠背和200 km传输条件下,分析混沌激光偏振度以及同步质量的演变规律,发现随着距离和时间的增加,混沌激光偏振度逐渐减小,导致激光器的有效注入强度降低,进而削弱了注入锁定效应,恶化了主从混沌同步质量。增大注入强度可以提高同步质量对偏振度变化的容忍度,有助于实现稳定的长距离混沌激光同步。
Objective Secure communication based on chaotic laser has received much attention in recent years because of its high speed,long distance,and compatibility with existing fiber-optic networks.Much effort has been devoted to improving the rate of chaotic secure communication by increasing chaos bandwidth or using higher-order modulation.Unfortunately,there still exists a rate gap between the chaotic secure communication and the current fiber-optic communication.Polarization division multiplexing of chaotic laser is a potential alternative to reduce the rate gap.The key to implementing the polarization division multiplexing-based chaotic secure communication is establishing high-quality chaos synchronization.However,the influences of polarization of chaotic laser,i.e.,the degree of polarization(DOP),on the chaos synchronization are not ascertained clearly.In this paper,the effects of DOP of chaotic laser on the synchronization quality are investigated experimentally,and the optimization methods and conditions are achieved for yielding high-quality and stable chaos synchronization.This work underlies the high-speed chaotic secure communication using polarization division multiplexing.Methods Firstly,we generate a chaotic laser from the master laser subject to mirror optical feedback and use the polarization controller and polarization beam splitter to make the chaotic laser characterized with a single polarization.Then,we inject it unidirectionally into the slave laser over the fiber link to achieve the single-polarization master-slave open-loop chaos synchronization.The polarization controller can adjust the state of polarization of the chaotic laser,and the DOP can be analyzed quantitatively by detecting the power from the output ports of the polarization beam splitter.Based on this experimental system,we examine the evolution of DOP and analyze its effect on the synchronization quality over time for fiber links with different transmission distances,when the threshold point(0.90)and the critical saturation point of high-quality synchronization are selected as the initial states.By changing the DOP of the chaotic laser in an experiment,we ascertain the effects of DOP on the effective injection strength and the quality of master-slave chaos synchronization firstly;then we analyze the evolution trend of DOP and its effect on the effective injection intensity and the quality of chaos synchronization within 60 minutes.Finally,the trend of DOP of the chaotic laser as a function of distance and time,as well as its effect on the quality of master-slave chaos synchronization are studied.Results and Discussions We experimentally achieve master-slave chaos synchronization by injecting single-polarization chaotic laser from the master laser into the slave laser through a polarization beam splitter,and chaos synchronization with synchronization coefficients of 0.986 and 0.962 is achieved under back-to-back and 200 km scenarios,respectively(Figs.2 and 3).By comparing the back-to-back and 200 km transmission scenarios,we find that the quality of master-slave synchronization degrades under 200 km transmission with the same injection strength(Fig.4),which is due to the distortion of chaotic laser caused by chromatic dispersion and enhancement of nonlinear effects.It is also found that the DOP of chaotic laser changes with time after a long-distance transmission,which reduces the injection efficiency of the master laser to the slave laser(Figs.5-7).As a result,the effective injection strength is decreased,and the quality of master-slave chaos synchronization is degraded.In addition,we select the threshold point and the critical saturation point of high-quality synchronization as the initial states and observe the evolution of DOP and synchronization quality over time after transmission with different distances.It is found that under a similar variation of DOP and the same transmission distance,the chaos synchronization degrades less and is more stable for the initial state under the critical saturation point,compared with the initial state of the threshold point.It is noted that the deterioration of DOP originates mostly from the shape defect of fiber,as well as the vibration and temperature variation in the environment.Optimizing the fabrication technology of fiber,reducing vibration,and stabilizing temperature will all help to mitigate the deterioration of DOP.In addition,a polarization tracker can also be used to optimize the DOP in real time.Conclusions In this paper,the evolution of DOP of chaotic laser and its effect on the chaos synchronization quality,as well as the corresponding optimization methods are explored experimentally in the master-slave open-loop configuration.Results show that the DOP of chaotic laser deteriorates gradually with the increase in transmission distance and time:the DOP is separately reduced by 0.253,0.332,and 0.473 within 60 minutes when the chaotic laser is transmitted over 100 km,200 km,and 280 km fiber links,respectively.The deterioration of DOP reduces the effective injection strength of the master laser to the slave laser and thus degrades the chaos synchronization quality.The enhancement of injection strength will increase the system tolerance to the variation of DOP and improve the robustness of chaos synchronization,affording a high-quality long-distance chaos synchronization.It is believed that this work paves the way for high-speed longdistance chaotic secure communication based on the polarization division multiplexing.
作者
申嘉皓
狄呈震
黄辉宇
师天一
王龙生
王安帮
杨毅彪
王云才
Shen Jiahao;Di Chengzhen;Huang Huiyu;Shi Tianyi;Wang Longsheng;Wang Anbang;Yang Yibiao;Wang Yuncai(Key Laboratory of Advanced Transducers and Intelligent Control System,Ministry of Education and Shanxi Province,College of Physics and Optoelectronics,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;State Key Laboratory of Applied Optics,Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,Changchun 130033,Jilin,China;Guangdong Provincial Key Laboratory of Information Photonics Technology,College of Information Engineering,Guangdong University of Technology,Guangzhou 510006,Guangdong,China;College of Optoelectronic Engineering and Instrumentation Science,Dalian University of Technology,Dalian 116024,Liaoning,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2023年第21期186-194,共9页
Acta Optica Sinica
基金
国家自然科学基金(62035009,62105233)
山西省“1331工程”重点创新团队
山西省重点研发计划国际合作项目(201903D421012)
中央引导地方科技发展基金(YDZJSX2021A009)
应用光学国家重点实验室开放基金(SKLAO2022001A09)
中物院创新发展基金(C-2023-CX20230030)。
关键词
激光器
光偏振度
混沌激光
混沌同步
混沌保密通信
lasers
degree of light polarization
chaotic laser
chaos synchronization
chaotic secure communication
作者简介
通信作者:王龙生,wanglongsheng@tyut.edu.cn。
