研制了一种多纵模光纤激光器,提出了光纤多纵模直腔激光谐振腔结构,并完成纵模动态观测及其传感实验测试.在泵浦光源的泵浦下,光纤激光器产生多个激光纵模,相互干涉生成拍频信号,通过光电探测器转换成电子拍频信号,然后通过频谱仪实时观察光纤多纵模激光器的拍频频率特性.同时,阐述了多纵模激光器的传感监测原理,并依据传感监测原理将激光器应用于应力实验,通过对多纵模的频率动态变化监测实现对应力变化感知.通过实验现象可以让学生形象地理解激光器腔长和多纵模频率间隔的关系,加深学生对激光器多纵模的物理概念的理解.该实验装置不仅对激光原理实验教学具有一定的参考价值,还提供了一个激光器性能测试、温度、应力、加速度等多种物理量测量的实验平台.%In this paper,a longitudinal mode dynamic observation and sensing experiment base on multi-longitudinal mode fiber laser was proposed.The fiber laser cavity was formed by two fiber Bragg gratings and a piece of erbium fiber.When 980nm pump laser was high enough,there appeared many laser modes with a periodic frequency spacing related to the cavity length.Many beat signals would be produced by beating any two longitudinal modes,and then electrical beat signals would be generated on the photodetector.The frequency characteristic of multi-longitudinal modes fiber laser could be observed by a radio-frequency spectrum analyzer.Meanwhile,the strain was applied on the multi-longitudinal fiber laser in order to observe the dynamic longitudinal modes change.The principle of the fiber laser sensor for monitoring strain was discussed.The strain experiment study makes students better understand the change between the fiber cavity length and the frequency interval among the laser modes.The experiment of multi-modes fiber laser sensor not only are of great significance for the experimental course in laser principles,but also provide an experiment design platform for the performance testing of the laser,temperature sensing,strain sensing and acceleration monitoring and so on,which helps students to conduct innovative experiments.
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