Wu Zhifang, Wu Peili, Kudinova Maryna, Zhang Hailiang, Shum Perry Ping, Shao Xuguang, Humbert Georges, Auguste Jean-Louis, Dinh Xuan Quyen, Pu Jixiong
Fujian Key Laboratory of Light Propagation and Transformation, College of Information Science and Engineering, Huaqiao University, Xiamen 361021, China.
School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Sensors (Basel). 2020 Aug 24;20(17):4772. doi: 10.3390/s20174772.
Polarization-maintaining fibers (PMFs) have always received great attention in fiber optic communication systems and components which are sensitive to polarization. Moreover, they are widely applied for high-accuracy detection and sensing devices, such as fiber gyroscope, electric/magnetic sensors, multi-parameter sensors, and so on. Here, we demonstrated the combination of a fiber Bragg grating (FBG) and Sagnac interference in the same section of a new type of PANDA-structure PMF for the simultaneous measurement of axial strain and temperature. This specialty PMF features two stress-applied parts made of lanthanum-aluminum co-doped silicate (SiO-AlO-LaO, SAL) glass, which has a higher thermal expansion coefficient than borosilicate glass used commonly in commercial PMFs. Furthermore, the FBG inscribed in this SAL PMF not only aids the device in discriminating strain and temperature, but also calibrates the phase birefringence of the SAL PMF more precisely thanks to the much narrower bandwidth of grating peaks. By analyzing the variation of wavelength interval between two FBG peaks, the underlying mechanism of the phase birefringence responding to temperature and strain is revealed. It explains exactly the sensing behavior of the SAL PMF based Sagnac interference dip. A numerical simulation on the SAL PMF's internal stress and consequent modal effective refractive indices was performed to double confirm the calibration of fiber's phase birefringence.
保偏光纤（PMF）在对偏振敏感的光纤通信系统及组件中一直备受关注。此外，它们还广泛应用于高精度检测与传感设备，如光纤陀螺仪、电/磁传感器、多参数传感器等。在此，我们展示了在一种新型熊猫结构保偏光纤的同一部分中，将光纤布拉格光栅（FBG）与萨尼亚克干涉相结合，用于同时测量轴向应变和温度。这种特殊的保偏光纤具有两个由镧铝共掺杂硅酸盐（SiO-AlO-LaO，SAL）玻璃制成的施加应力部分，该玻璃的热膨胀系数高于商用保偏光纤中常用的硼硅酸盐玻璃。此外，刻写在这种SAL保偏光纤中的光纤布拉格光栅不仅有助于该装置区分应变和温度，而且由于光栅峰的带宽更窄，还能更精确地校准SAL保偏光纤的相位双折射。通过分析两个光纤布拉格光栅峰之间波长间隔的变化，揭示了相位双折射对应变和温度响应的潜在机制。它准确地解释了基于SAL保偏光纤萨尼亚克干涉凹陷的传感行为。对SAL保偏光纤的内部应力及由此产生的模式有效折射率进行了数值模拟，以进一步证实光纤相位双折射的校准。
