全光纤速度干涉仪设计及应用

Design and Application of All-fiber Velocity Interferometer

针对冲击波物理与爆轰物理等研究领域中对高速运动物体进行连续速度测量的需求,设计了一种全光纤速度干涉仪.该干涉仪采用单模光纤作为光传输和延迟元件,对t和t-τ两个时刻由于速度变化而引起的多普勒差拍信号进行检测.由于两个时刻的两束光信号对应的待测物体速度变化不大,因而两者几乎有相等的频移量,从而大大降低了差拍信号频率.并且,通过光纤长度的改变,灵活调节条纹常量(τ值),使差拍信号频率不超过记录系统的带宽,从原理上解决记录系统响应带宽受限问题,拓展测速的上限.单模光纤的采用,对漫反射光起到了较好的选模作用,使干涉仪实现了对漫反射靶的测量.实验设计了1.5m.s-1和150m.s-1两种条纹常量,对低速过程的霍普金森杆实验和高速过程的激光驱动实验分别进行了测试,取得较好结果,证明了该干涉测试技术的有效性.

In order to develop the laser interferometer velocimetry in the experimental research of shock wave physics and explosion physics,an all-fiber velocity interferometer is presented.The single-mode fiber is adopted as optical transmission and delay components for this interferometer,which detects Doppler beat signals caused by velocity change to two moments of t and t-τ.Because of little velocity change of objects to be tested corresponding to two-beam optical signals of two moments,which almost have equivalent frequency shift,and the beat frequency is also significantly lowered.Meanwhile,the fringe constant（value τ）can be flexibly adjusted in accordance with velocity change rate of objects to be tested,thereby making the beat signal frequency caused by velocity change less than the system bandwidth within the time scale of τ,so as to solve the problem of recording system corresponding to bandwidth limitation and extend upper limit of velocity measurement.As result of the adoption of single-mode fiber,only one space pattern in the fiber participates in interference,even the light returned from diffuse-reflection surface can preferably participate in interference after the mode selection of single-mode fiber,thereby realizing the measurement to diffuse-reflection target.Two fringe constants of 1.5 m·s^-1 and 150 m·s^-1 are adopted to conduct the Hopkinson bar experiment at low-velocity process and laser-driven experiment at high-velocity process.The experimental result proves the feasibility of this interference technique.