基于SPGD硬件控制平台的光纤激光相干合成系统性能优化研究

发布时间：2018-06-03 00:57

本文选题：光纤激光 + 相干合成　；参考：《中国科学院研究生院（光电技术研究所）》2015年硕士论文

【摘要】：基于随机并行梯度下降算法(SPGD算法)的光纤激光相干合成方案是获得高亮度、高质量的相干合成光束的有效途径。实现光纤激光相干合成的关键是校正各组束间的相位误差。相位控制精度和控制带宽是评价系统校正能力的两个主要指标,它依赖于算法特性、算法实现平台和相位控制器件特性。本文主要研究基于SPGD算法的光纤激光相干合成系统的性能优化问题,主要包括基于现场可编程逻辑门阵列(FPGA)的硬件控制平台实现和自适应光纤准直器(AFOC)的谐振性能优化两个方面。首先,基于实际应用的光纤激光相干合成系统,开发了一个基于FPGA的硬件控制平台,该平台最多可以完成21单元光束的相干合成控制。然后结合平台的硬件特性,从相位控制精度和系统控制带宽两个评价指标的角度分析了硬件控制平台的性能。理论分析得知,该平台的锁相和倾斜控制的理论带宽分别为1.37 k Hz和9 Hz。然后,首次将双二阶数字滤波器用于优化AFOC的谐振特性,完成了该滤波器相关的理论推导和仿真分析。结果表明,该方法可以有效地抑制AFOC的谐振峰,提高AFOC的有效控制带宽。另外基于现有AFOC器件的谐振特性,结合阶梯减振结构和双二阶数字滤波器两种方法设计了一套减振方案,将AFOC的有效带宽从1k Hz提高到2.5k Hz。再者,结合自主开发的硬件平台和双二阶数字滤波器技术,基于实际应用的相干合成系统完成了各控制模块的分析、设计、编程和调试。控制模块主要包括数据采集、伪随机数生成、SPGD控制迭代、电压同步输出、双二阶数字滤波器、参数配置、信息显示和数据交换,通过各模块的组合可以实现该平台的锁相控制和倾斜控制功能。最后,搭建了一个基于硬件控制平台的七路光纤激光相干合成系统,在室内弱湍流情况下,分别完成了基于硬件控制平台的锁相和倾斜控制实验,并从桶中功率(PIB)、相位控制精度和系统控制带宽三个方面分析了系统性能。锁相实验结果表明,PIB值从锁相前的0.32提高到锁相后的1.20,系统实际相位控制精度为1/19?,锁相控制带宽约为1k Hz;倾斜控制实验结果表明,PIB值从开环时的0.45提高到闭环后的0.68,倾斜控制带宽约为6Hz。全文为后续基于SPGD算法的光纤激光相干合成系统的实际应用和性能提高提供了有效的硬件支撑和技术基础。
[Abstract]:The optical fiber laser coherent combination scheme based on the stochastic parallel gradient descent algorithm (SPGD) is an effective way to obtain high brightness and high quality coherent composite beams. The key to realize coherent combination of optical fiber laser is to correct the phase error between each group of beams. Phase control precision and control bandwidth are two main indexes to evaluate the system correction capability. They depend on the algorithm characteristics, the algorithm implementation platform and the phase controller characteristics. In this paper, the performance optimization of optical fiber laser coherent combination system based on SPGD algorithm is studied. The hardware control platform based on FPGA (Field Programmable Logic Gate Array) and the resonant performance optimization of adaptive optical fiber collimator (AFOC) are discussed in this paper. Firstly, a hardware control platform based on FPGA is developed based on the practical application of optical fiber laser coherent synthesis system. The platform can control the coherent combination of 21 units of beams at most. Then the performance of the hardware control platform is analyzed from the angle of the phase control precision and the system control bandwidth combined with the hardware characteristics of the platform. Theoretical analysis shows that the theoretical bandwidth of phase-locked and tilt control is 1.37 kHz and 9 Hz respectively. Then, the bisecond-order digital filter is used to optimize the resonant characteristics of AFOC for the first time, and the theoretical derivation and simulation analysis of the filter are completed. The results show that this method can effectively suppress the resonance peak of AFOC and increase the effective control bandwidth of AFOC. In addition, based on the resonance characteristics of the existing AFOC devices, a damping scheme is designed by combining the step damping structure and the two-order digital filter. The effective bandwidth of the AFOC is increased from 1kHz to 2.5kHz. Furthermore, based on the self-developed hardware platform and double-second-order digital filter technology, the coherent synthesis system based on practical application has completed the analysis, design, programming and debugging of each control module. The control module mainly includes data acquisition, pseudo random number generation SPGD control iteration, voltage synchronous output, double second order digital filter, parameter configuration, information display and data exchange. The phase lock control and tilt control function of the platform can be realized by the combination of each module. Finally, a seven-channel optical fiber laser coherent combination system based on hardware control platform is built, and the phase locking and tilt control experiments based on hardware control platform are completed in the case of weak turbulence in the room. The performance of the system is analyzed from three aspects: the power in the bucket, the precision of phase control and the control bandwidth of the system. The results of phase-locked experiment show that the PIB value increases from 0.32 before phase-locking to 1.20 after phase-locked. The actual phase control precision of the system is 1 / 19, and the control bandwidth of phase-locked is about 1kHz. The results of tilt control experiment show that the PIB value increases from 0.45 in open loop to 0.45 in closed loop. The tilt control bandwidth is about 6 Hz. This paper provides an effective hardware support and technical foundation for the practical application and performance improvement of the optical fiber laser coherent combination system based on SPGD algorithm.
【学位授予单位】：中国科学院研究生院（光电技术研究所）
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN24;TN253

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