Research On The Driving Technology Of Electro-optic Modulator In DPSK Optical Modulation System

Modern technology is becoming more and more powerful,people's demand for high speed,high quality and large capacity information transmission is increasing day by day.Due to the characteristics of large bandwidth,high speed,high sensitivity,long transmission distance and good confidentiality,optical communication has attracted more and more scholars' attention.In signal modulation,compared with amplitude and frequency modulation,phase modulation produces less nonlinear damage and higher optical signal-to-noise ratio,while DPSK in phase modulation has high sensitivity and can avoid phase inversion,which is widely used in the field of communication and transmission.How to modulate high quality DPSK signal is the key to improve transmission performance.Electro-optic phase modulator is an indispensable part of optical modulation.In this paper,the driving technology of electro-optic modulator is studied according to DPSK modulation characteristics.Firstly,the current status and research significance of optical communication technology and DPSK modulation are introduced,and the research status of electro-optical modulator and the development of modulator driving technology are discussed.The working principle of electro-optic modulator,DPSK signal generation principle and characteristics are analyzed,and the DPSK optical modulation system is designed with a modulation rate of 2.5Gbps.The DPSK optical modulation system was divided into modules,and the differential coding module was studied and designed.This paper analyzes the theory of automatic gain control and the basic theory of RF power amplifier and use ADS software to design the RF driver with controllable gain which meets the requirements of various parameters of phase modulator.The FPGA-based adaptive gain control module and the eye map intersection control system are designed to ensure that the output voltage of the amplifier works at the set value and the fluctuation range is small.At the same time,the eye map intersection is guaranteed at 50% and the modulation signal phase is stable,which solves the problem of phase shift in DPSK optical modulation system.Finally,the DPSK optical modulation system is built and tested to verify the feasibility and effectiveness of the system design.The adaptive gain control and eye map intersection control system designed by FPGA improves the problem that the amplifiers in the traditional DPSK optical communication transmitting system need to control the gain manually and the internal control parameters of the system cannot be adjusted in real time.The experimental results show that the DPSK optical modulation system designed in this paper has a rate of 2.5Gbps,and the adaptive gain control technology proposed in this paper can effectively stabilize the driving voltage at the half wave voltage of the modulator(7.2V),and the floating voltage is less than 0.1V,and the eye map intersection point is stable at 50%,effectively improving the communication performance.