激光干涉测速中信号光纤色散测量

Dispersion measurement of signal optical fibers in VISAR

为对激光干涉测速系统(VISAR)中信号光纤的色散特性进行快速测量,搭建了一种基于时域法的多模光纤色散测量装置。该装置由532 nm的皮秒激光器、快响应光电探测器以及宽带数字示波器组成,通过对输入光纤前后的光脉冲时间宽度进行测量,来获得光纤的脉冲响应3 dB脉宽(即色散时间)。利用该装置分别对一根长度为123 m的国产梯度折射率光纤以及一根10 m长的阶跃折射率光纤在532 nm波长附近的色散特性进行了测量。测得的梯度折射率光纤色散时间为(683±16)ps,对应3dB频响带宽为646 MHz;阶跃折射率光纤色散时间为(1631±14)ps,对应频响带宽为271 MHz。对实验结果进行了测量不确定度分析,并与理论计算值进行了比较,获得了较好的一致性。研究表明,利用该实验装置,可对激光干涉测速应用中信号光纤的色散特性进行迅速、准确的测量,从而为实验中信号光纤类型、长度等的合理选用提供参考。

To measure the dispersion of the signal optical fibers in VISAR,a setup was built based on the time domain method.The setup is made up of a picosecond laser,a fast-response photodetector and a broadband digital oscilloscope,which can afford the 3dB duration of the impulse response function by measuring the optical pulse durations in and out the measured fiber.This setup was used to characterize the dispersion properties of a 123-m-length gradient index fiber and a 10-m-length step index fiber at about 532 nm,respectively.The obtained dispersion time of the gradient index fiber is（683±16） ps and the corresponding frequency response 3dB bandwidth is about 646 MHz.These of the step index fiber are（1631±14） ps and 271 MHz,respectively.Uncertainty analysis of the measured results was performed,and the measured results were compared with the theoretical calculations.It displays that the measured results are consistent with the theoretical calculations.The built setup can afford a simple and dependable dispersion time measurement for the signal optical fibers in VISAR applications,thereby it can provide reference for reasonably choosing the type and length of the signal optical fibers in experiments.