基于掺铒光纤中动态粒子数光栅的振动检测

Mechanical Vibration Detection Based on Dynamic Population Gratings Recorded in Er-Doped Optical Fiber

根据动态粒子数光栅形成机理,设计了一种线性双波混频结构的光纤系统。系统中,1490nm波长分布式反馈(DFB)激光器光源发出的连续激光,通过环形器进入一根3m长掺铒光纤作为注入光,被与掺铒光纤另一端光学耦合的压电振动镜反射后形成反射光。掺铒光纤中注入光与后向传播的反射光干涉形成驻波场,通过空间烧孔效应沿光纤纵向形成动态粒子数光栅。压电振动镜对反射光波进行相位调制时,环形器反射端口输出的双波混频(TWM)信号可视作输出光波的强度调制。实验中通过此双波混频系统对压电换能器产生的机械振动进行检测,结果表明:光纤双波混频检测系统具有良好的动态响应特性,能够测量50Hz^10kHz的振动信号,采集到的输出信号频率与压电驱动信号频率很好地吻合。

According to the dynamic population grating formation mechanism,a fiber-optic system with linear double-wave mixing structure is designed.In the system,light from a semiconductor distributed feedback（DFB）continuous wave（cw）laser operating at 1490 nm,as the incident light,is launched to a 3-m Er-doped optical fiber through a fiber optic circulator.The incident light is reflected from the vibrating mirror mounted on a piezoelectric actuator as reflected light.The dynamic population gratings are recorded along the longitudinal direction of the Erdoped optical fiber by spatial hole burning in standing-wave cavity formed by the two counter-propagating mutually coherent recording waves.The two-wave mixing（TWM）signal is observed as an intensity modulation wave in the output of the circulator when the reflected wave from vibrating mirror is phase modulated.Mechanical vibration induced by piezoelectric vibrating mirror can be detected through the designed two-wave mixing system.The results demonstrate that the two-wave mixing detection system displays a good dynamic response,with a frequency range of50 Hz^10 kHz,and the frequencies of acquired vibration signals exactly agree with the driving signals from piezoelectric actuator.