Opt Express. 2023 Feb 27;31(5):8844-8854. doi: 10.1364/OE.483885.
We propose a high-performance vector torsion sensor based on an in-fiber Mach-Zehnder interferometer (MZI), which consists of a straight waveguide inscribed in the core-cladding boundary of the SMF by a femtosecond laser in only one step. The length of the in-fiber MZI is 5 mm, and the whole fabrication time does not exceed 1 min. The asymmetric structure makes the device have high polarization dependence, and the transmission spectrum shows a strong polarization-dependent dip. Since the polarization state of the input light entering the in-fiber MZI varies with the twist of the fiber, torsion sensing can be achieved by monitoring the polarization-dependent dip. Torsion can be demodulated by both the wavelength and intensity of the dip, and vector torsion sensing can be achieved by setting the appropriate polarization state of the incident light. The torsion sensitivity based on intensity modulation can reach 5763.96 dB/(rad/mm). The response of dip intensity to strain and temperature is weak. Furthermore, the in-fiber MZI retains the fiber coating, so it maintains the robustness of the complete fiber structure.
我们提出了一种基于光纤马赫-曾德尔干涉仪（MZI）的高性能矢量扭转传感器，它由飞秒激光在单模光纤芯层-包层边界上刻写的直波导组成，仅需一步即可完成。光纤 MZI 的长度为 5mm，整个制作时间不超过 1 分钟。非对称结构使器件具有较高的偏振依赖性，其传输谱显示出强烈的偏振相关陷波。由于进入光纤 MZI 的输入光的偏振态随光纤的扭转而变化，因此可以通过监测偏振相关陷波来实现扭转传感。通过调节陷波的波长和强度可以解调扭转，通过设置适当的入射光偏振态可以实现矢量扭转传感。基于强度调制的扭转灵敏度可达 5763.96dB/（rad/mm）。陷波强度对应变和温度的响应较弱。此外，光纤 MZI 保留了光纤涂层，因此保留了完整光纤结构的鲁棒性。
