Han Chunyang, Zhao Chenyu, Ding Hui, Chen Chen
Opt Lett. 2022 Jun 1;47(11):2714-2717. doi: 10.1364/OL.456245.
Vibration measurement is a frequent measurement requirement in a number of areas. Optical vibration sensors have many advantages over electrical counterparts. A common approach is to optically detect the vibration induced mechanical movement of a cantilever. Nevertheless, their practical applications are hindered by the cross-sensitivity of temperature and dynamic instability of the mechanical structure, which lead to unreliable vibration measurements. Here, we demonstrate a temperature insensitive vibration sensor that involves an enclosed suspended cantilever integrated with a readout fiber, providing in-line measurement of vibration. The cantilever is fabricated from a highly birefringent photonic crystal fiber by chemical etching and fused to a single-polarization fiber. Mechanical vibration induced periodic bending of the cantilever can significantly modify the state of polarization of the light that propagates along the photonic crystal fiber. The single-polarization fiber finally converts the state of polarization fluctuation into the change of output optical power. Therefore, the vibration could be demodulated by monitoring the output power of the proposed structure. Due to the special design of the structure, the polarization fluctuation induced by a variation of the ambient temperature can be significantly suppressed. The sensor has a linear response over the frequency range of 5 Hz to 5 kHz with a maximum signal-to-noise ratio of 60 dB and is nearly temperature independent.
振动测量是许多领域中常见的测量需求。与电子振动传感器相比，光学振动传感器具有许多优势。一种常见的方法是通过光学方式检测悬臂梁因振动引起的机械运动。然而，它们的实际应用受到温度交叉敏感性和机械结构动态不稳定性的阻碍，这会导致振动测量结果不可靠。在此，我们展示了一种对温度不敏感的振动传感器，它包括一个与读出光纤集成的封闭悬浮悬臂梁，可提供在线振动测量。该悬臂梁由高双折射光子晶体光纤通过化学蚀刻制成，并与单偏振光纤熔接。机械振动引起的悬臂梁周期性弯曲会显著改变沿光子晶体光纤传播的光的偏振状态。单偏振光纤最终将偏振波动状态转换为输出光功率的变化。因此，可以通过监测所提出结构的输出功率来解调振动。由于该结构的特殊设计，环境温度变化引起的偏振波动可得到显著抑制。该传感器在5 Hz至5 kHz的频率范围内具有线性响应，最大信噪比为60 dB，且几乎与温度无关。
