Uddin Nezam, Liu Guigen, Sheng Qiwen, Han Ming
Opt Lett. 2019 May 15;44(10):2578-2581. doi: 10.1364/OL.44.002578.
We demonstrate the constant temperature (CT) operation of a fiber-optic anemometer based on a laser-heated silicon Fabry-Perot interferometer (FPI), where the temperature of the FPI is kept constant by adjusting the heating laser power through a feedback control loop and the output signal is the heating laser power. We show that the CT operation can dramatically improve the frequency response over the commonly used constant power (CP) operation, where the laser heating power is kept constant and the output signal is the temperature of the FPI. For demonstration, we used a 100-μm-diameter, 200-μm-thick silicon FPI attached to the tip of a single-mode fiber as the anemometer. The FPI was heated by a 980-nm diode laser, and the temperature was measured using a 1550-nm diode laser. The effect of flow changes was simulated by exposing the silicon FPI to radiation from an external intensity-modulated laser beam. We show that the 10%-90% rise time of the step response in air was reduced from 625 ms for CP operation to 1.8 ms for CT operation, and the 3-dB bandwidth was increased from 0.5 Hz for CP operation to 2 kHz for CT operation. The response of the anemometer also shows good linearity to the radiation power.
我们展示了一种基于激光加热硅法布里-珀罗干涉仪（FPI）的光纤风速仪的恒温（CT）操作，其中通过反馈控制回路调节加热激光功率来保持FPI的温度恒定，输出信号为加热激光功率。我们表明，与常用的恒功率（CP）操作相比，CT操作可以显著提高频率响应，在CP操作中激光加热功率保持恒定，输出信号为FPI的温度。为了进行演示，我们使用了一个直径为100μm、厚度为200μm的硅FPI，它附着在单模光纤的尖端作为风速仪。FPI由一个980nm的二极管激光器加热，温度使用一个1550nm的二极管激光器进行测量。通过将硅FPI暴露于外部强度调制激光束的辐射来模拟气流变化的影响。我们表明，在空气中阶跃响应的10%-90%上升时间从CP操作的625ms减少到CT操作的1.8ms，3dB带宽从CP操作的0.5Hz增加到CT操作的2kHz。风速仪的响应也显示出对辐射功率具有良好的线性关系。
