Phase Modulation/Demodulation And Related Experimental Studies Of Reflective Coherent Optical Communication System

Compared with the use of electromagnetic waves to propagate information,optical fiber communication has natural confidentiality,but with the development of coherent optical communication,information eavesdropping problems such as intrusive beam splitting and non-intrusive bending coupling methods make the confidentiality of optical fiber communication systems has been reduced,and information security has been severely challenged.Therefore,it is of practical significance to actively study new optical fiber security information transmission technologies to reduce the problem of optical fiber eavesdropping.Secure communications include cryptographic secrets,communication secrets,and diffusion secrets.In this thesis,a novel reflective structure of quadrature phase shift keying(QPSK)modulation format lithium niobate traveling wave electrooptic modulator is designed.It is used in high-order modulation coherent optical communication systems.This system can avoid the leakage of transmission information in the optical fiber,reduce the complexity of the system damage compensation algorithm,and achieve better transmission performance without greatly increasing the cost.Thus this system can applied to secure communications.This thesis conducts detailed performance analysis of the system through theoretical derivation,simulation,and experimental testing to verify the feasibility of the system.First,this thesis designs a coherent optical communication system based on a reflective lithium niobate electro-optic modulator,and details the design principles of the reflective system,the reflective electro-optic modulator,the receiver and transmission link design.At the same time,the dispersion and noise existing in the reflective system are analyzed,and a compensation algorithm based on digital signal processing(DSP)is given.The theoretical derivation verifies the correctness of the new system.Secondly,this thesis simulates reflective systems and traditional coherent optical communication systems through OptiSystem and MATLAB to obtain data such as constellation diagrams,eye diagrams,Q factors,and bit error rate curves.The performance and compensation algorithm of the system are compared and analyzed.The transmission performance of the reflective system is slightly lower than that of the traditional transmission system,and it is more suitable for use in the metropolitan area network.The compensation algorithm for phase noise compensation is lower in complexity,and the overall compliance with the requirements of the communication system.The reflection system is verified at the simulation level feasibility.Finally,based on the reflection system structure and the test results of each port of the system,this thesis determines the performance values of each device and builds an experimental platform.The vector network analyzer is used to compare and analyze the performance of traditional coherent optical communication systems and reflective systems,so as to obtain the shortcomings of reflective systems,analyze them and give solutions,and propose the design of the second version of reflective systems idea.The system plan of the system was again built on the experimental platform,and the final test data achieved the expected results.The feasibility of the new system was verified at the experimental test level.