光纤模式散斑对天文光纤光谱测量精度影响及其抑制方法  

Influence of Optical Fiber Mode Speckle on the Measurement Accuracy of Astronomical Optical Fiber Spectrum and Its Suppression Method

作　　者：王安之 金玲玉 王佳斌 甘兆虚 岳罡 杨浩杰 胡冬生 陈传奇 闫奇[1,2] 严云翔 汪盛佳 耿涛 孙伟民 WANG An-zhi;JIN Ling-yu;WANG Jia-bin;GAN Zhao-xu;YUE Gang;YANG Hao-jie;HU Dong-sheng;CHEN Chuan-qi;YAN Qi;YAN Yun-xiang;WANG Sheng-jia;GENG Tao;SUN Wei-min(Key Laboratory of In-Fiber Integrated Optics of Ministry of Education,College of Physics and Optoelectronic Engineering of Harbin Engineering University,Harbin 150001,China;Yantai Research Institute of Harbin Engineering University,Yantai 264000,China;Qingdao Innovation and Development Center of Harbin Engineering University,Qingdao 266000,China)

机构地区：[1]哈尔滨工程大学物理与光电工程学院,纤维集成光学教育部重点实验室,黑龙江哈尔滨150001 [2]哈尔滨工程大学烟台研究院,山东烟台264000 [3]哈尔滨工程大学青岛创新发展中心,山东青岛266000

出　　处：《光谱学与光谱分析》2024年第12期3422-3428,共7页Spectroscopy and Spectral Analysis

基　　金：天文联合基金项目(U1931206,U1831115,U2031130);国家自然科学基金项目(12103015)资助。

摘　　要：在利用多模光纤进行太阳表面磁场、视向速度测量等高分辨率天文光谱探测时,获得的光谱图像存在明显的能量分布不均匀的现象,出现了散斑。分析其原因可知,光纤光谱成像时,成像系统收到的是光纤出射端不同波长的像沿色散方向的展开。而光谱仪的高色散率使成像系统的每个像元所对应的光谱范围都非常窄,具有非常好的相干性。多模光纤内存在多种传输模式,每个波长的各个模式之间干涉形成的散斑图样的能量中心会偏离光纤几何中心,降低了光谱测量准确度。为了解决这一问题,设计了一种抑制散斑影响的多维机械扰模系统,用来提高光纤光谱测量精度。多维机械扰动装置由三个不同方向、不同频率运动的机械结构组成。通过调节三个机械装置以不同的频率振动,使光纤中的传导模式产生接近随机的相位漂移,从而使光纤出射端的散斑图样发生随机改变,经过长时间曝光(对应多幅散斑图样叠加平均)可以消除散斑的影响。为了检验系统的扰模效果,使用芯径为35μm的光纤研究了650 nm激光的出射散斑场能量分布,并提出以能量中心偏移位置的标准偏差作为光纤模式散斑能量分布离散度以及对天文光纤光谱测量精度影响的评价函数。首先,对比分析了不扰模、手动扰模、一维扰模和多维扰模下的各1000张散斑图叠加平均效果,结果显示手动扰模和多维机械扰模效果较好,散斑平均叠加图能量分布较为均匀。然后,又比较了散斑图叠加数量(等效于不同曝光时间)的多维扰模效果。实验结果表明,经过多维机械扰模的100张散斑图叠加平均后,标准偏差仅为单张散斑图的1/13。最后,对扰模装置频率和振幅对扰模效果的影响进行了测试。结果表明较高的频率和振幅都有益于散斑抑制。对于本次实验中光纤而言,频率选为1.2 Hz、振幅选为6 cm最为合适。在此条件�In high-resolution astronomical spectral detection using multi-mode optical fibers for solar surface magnetic field and visual velocity measurement,there is a significant phenomenon of uneven energy distribution and speckle in the obtained spectral images.Analyzing the reasons,it can be concluded that during fiber optic spectroscopic imaging,the imaging system receives the image of the output fiber end at different wavelengths and spreads along the dispersion direction.The high dispersion rate of the spectrometer results in a very narrow spectral range,which has excellent coherence,corresponding to each pixel in the imaging system.There are multiple transmission modes in multimode optical fibers,and the energy center of the speckle pattern formed by interference between different modes at each wavelength will deviate from the fiber's geometric center,reducing the accuracy of spectral measurement.To address this issue,this paper proposes a multi-dimensional mechanical perturbation system to suppress speckle effects and improve the accuracy of fiber optic spectral measurements.The multi-dimensional mechanical disturbance device consists of three mechanical structures with reciprocating motion in different directions and frequencies.By adjusting three mechanical devices at different frequencies,the conduction mode in the optical fiber undergoes a nearly random phase drift,resulting in a random change in the speckle pattern at the output end of the optical fiber.After long-term exposure(corresponding to superimposing and averaging multiple speckle patterns),the influence of speckles can be eliminated.To test the mode disturbance effect of the system,the energy distribution of the outgoing speckle field of a 650 nm laser was studied using a fiber with a core diameter of 35μm.The standard deviation of the energy center position was proposed as the evaluation function for the dispersion of the fiber mode speckle energy and its impact on the accuracy of astronomical fiber spectral measurement.Firstly,a comparative analy

关 键 词：光纤光谱 模式散斑 机械扰模 测量精度 标准偏差 

分 类 号：P182.2[天文地球—天文学]