激光干涉测速中信号光纤的模式色散对速度测量的影响

The influence of the modal dispersion of signal fiber on velocity measurement in VISAR applications

详细分析了测量任意反射面的激光干涉测速系统(VISAR)中信号光纤的模式色散对速度测量的影响,建立了数学分析模型,数值模拟了色散对比度因子与测速系统所使用的条纹常数和被测速度增量之间的关系。研究结果表明:(1)测速时使用的条纹常数越大,信号光纤模式色散的影响越小;(2)被测速度越大,信号光纤模式色散的影响越大;(3)阶跃折射率光纤的色散影响比剃度折射率光纤大得多。通过本项研究,给出了减小信号光纤模式色散的有效措施,对提高VISAR的干涉图对比度及测试精确度具有重要作用。

The influence of the modal dispersion of a signal fiber on velocity measurement in VISAR is theoretically analyzed and discussed in detail. A mathematical analysis model about the interfering contrast decreased by model dispersion is set up. The dispersion contrast factor varied with fringe constants and velocity increment is calculated. The results show： （1） the larger the fringe constants, the smaller the influence of the modal dispersion of a signal fiber; （2） the larger the measured velocity , the larger the influence of the modal dispersion~ （3） the influence of the modal dispersion of a multimode step-index fiber is larger than one of a multimode graded-index fiber. After this research, the efficient methods that decrease the influence of the modal dispersion of a signal fiber is put forward. This play an important role in improving interfering contrast and measuring precision in VISAR.