Research On OPA Phase Control System With Adaptive Control

Optical phased arrays use the electro-optical or thermo-optical effects of materials to modulate the phase of the optical field and to achieve control of the pointing of the synthetic beam of the array.With its inertia-free beam scanning and flexible beam pointing,it has important research significance and application value in wireless optical communication and LIDAR applications.However,the phased array devices suffer from phase noise mainly generated by processing technology and external operating environment(e.g.temperature and platform vibration),which causes a serious impact on the quality of the synthesis beam.Therefore,it is essential to study phase noise compensation of the array beam in practical applications.Since the environmental vibration on the fiber changes quickly and randomly,the phase noise generated by the optical fiber array has high requirements for its real-time phase noise compensation.There are problems such as the large interference of background light and the weak light signal of optimization target in the optimum process of silicon-based optical waveguide phased array beam.The solution to the above problems requires not only effective and fast optimization algorithms,but also the hardware support of a high-speed,high-precision phase controller.Aiming at realizing adaptive phase control of optical fiber and silicon-based optical waveguide phased arrays,this work presents the design,development,and testing of a multi-channel phased array phase control system.The main contents are as follows.1.In order to compensate for the phase noise caused by the external environment and system structure errors,a high-speed adaptive phase controller is developed based on the FPGA.Specifically,the modular hardware circuit of the controller is designed,and the schemes of performance evaluation function acquisition module,SPGD algorithm data processing module,digital-to-analog conversion and amplification module and data interaction module are given,including ADC/DAC and algorithm chip selection and the design of each module circuit and auxiliary circuit.At the same time,the thesis completes the logic control of each module implementation according to control timing requirements of the chip and the principle of SPGD algorithm.The phase control accuracy of the system can reach λ/76,and the control bandwidth can reach above 195 Hz for 64 array phased array system.2.A two-dimensional 8×8 array optical fiber phased array experiment system is built by using a selfdeveloped phase controller,and phase modulation experiments are carried out by using a high-speed lithium niobate phase modulator under the controller’s open-loop and closed-loop conditions.The experimental results show that the array beam can be optimized and compensated effectively,and the main and sub-flap rejection ratio of the optimized light field is 23.7d B,which is close to the theoretical value.The optimization time of the array light field is about 6.9ms,and the control bandwidth of the system is 150Hz;The angle error of the scanning control system is less than 5% measured by the control voltage loading experiment.This shows that the method achieves high-quality beam output and highprecision beam scanning.3.A phase noise compensation system based on 64 array optical phased array chip is built by using selfdeveloped phase controller,The results show that the beam optimization time of single angle beam takes0.21 s,which can effectively solve the problem of optical field optimization under weak light signals.The controller can achieve precise scanning control of the optical waveguide-based phased array,by measuring the control voltage loading experiment.The experimental results show that the phase controller designed in this work has the advantages of high phase control accuracy,fast operation speed,easy debugging and good channel expandability,which can meet the phase noise compensation and scanning control requirements of different types and scales of phased arrays.It provides hardware conditions for high-speed phase control of array beams in large-scale optical phased arrays.And there are technical references for the development of different application directions of optical phased arrays.