Interdisciplinary Program of Biomedical Mechanical & Electrical Engineering, Pukyong National University, Busan 48513, Korea.
School of Electrical Engineering, Pukyong National University, Busan 48513, Korea.
J Nanosci Nanotechnol. 2021 Mar 1;21(3):1883-1889. doi: 10.1166/jnn.2021.18908.
Here we report an optical fiber sensor capable of performing strain-insensitive simultaneous measurement of bending and temperature using a long-period fiber grating (LPFG) inscribed on doubleclad fiber (DCF) with a CO₂ laser at ˜10.6 μm. The LPFG inscribed on DCF, referred to as a DC-LPFG, was fabricated by scanning CO₂ laser pulses on an unjacketed DCF with a specific period. Due to co-directional mode coupling, the fabricated DC-LPFG has discrete attenuation bands widely distributed over hundreds of nanometers. Among these wavelength-dependent loss dips, adjacent two dips with different resonance wavelengths were selected as sensor indicators for the measurement of bending and temperature. For these two indicator dips designated as dips and , their bending and temperature responses were investigated in a curvature range of 4.90 to 21.91 m and a temperature range of 30 to 110 °C. With increasing bending applied to the DC-LPFG at room temperature, dips and showed different blue shifts. The bending sensitivities of dips and were measured to be approximately -0.77 and 0.51 nm/m, respectively. Unlike the bending response, they showed red shifts of different amounts with increasing ambient temperature, while the sensor head (i.e., the DC-LPFG) remained straight without any applied bending. The temperature sensitivities of dips and were measured to be ˜0.094 and ˜0.078 nm/°C, respectively. Owing to their linear and independent responses to bending and temperature, bending and temperature changes applied to the DC-LPFG could be simultaneously estimated from the measured wavelength shifts of the two indicator dips using their pre-determined bending and temperature sensitivities. Moreover, in a strain range of 0 to 2200 με (step: 200 με), strain-induced spectral variations of dips and were also measured, and the strain sensitivities of dips and were evaluated as approximately -0.028 and -0.013 pm/με, respectively. These strain-induced wavelength shifts were so small that they had little effect on the measurement results of bending and temperature. Thus, it is concluded that the fabricated DC-LPFG can be employed as a cost-effective sensor head for strain-insensitive separate measurement of bending and temperature.
在这里，我们报告了一种光纤传感器，该传感器使用 CO₂ 激光在双包层光纤（DCF）上刻写长周期光纤光栅（LPFG），可实现应变不敏感的弯曲和温度同时测量。在未加套的 DCF 上扫描 CO₂ 激光脉冲，制作了刻写在 DCF 上的 LPFG，称为 DC-LPFG。由于同向模式耦合，所制作的 DC-LPFG 具有离散的衰减带，分布在数百纳米范围内。在这些与波长相关的损耗陷波中，选择两个具有不同共振波长的相邻陷波作为传感器指标，用于测量弯曲和温度。对于这两个指定为陷波 和 的传感器指标，在曲率范围为 4.90 至 21.91 m 和温度范围为 30 至 110°C 的范围内，研究了它们的弯曲和温度响应。在室温下对 DC-LPFG 施加逐渐增加的弯曲时，陷波 和 表现出不同的蓝移。测量到陷波 和 的弯曲灵敏度分别约为-0.77 和 0.51 nm/m。与弯曲响应不同，随着环境温度的升高，它们表现出不同程度的红移，而传感器头（即 DC-LPFG）保持笔直，没有施加任何弯曲。测量到陷波 和 的温度灵敏度分别约为 0.094 和 0.078 nm/°C。由于它们对弯曲和温度的线性和独立响应，因此可以使用两个指标陷波的预定弯曲和温度灵敏度，从测量的两个指标陷波的波长位移中同时估算施加到 DC-LPFG 的弯曲和温度变化。此外，在应变范围为 0 至 2200 με（步长：200 με）下，还测量了陷波 和 的应变引起的光谱变化，并评估了陷波 和 的应变灵敏度分别约为-0.028 和-0.013 pm/με。这些应变引起的波长位移非常小，对弯曲和温度的测量结果影响不大。因此，可以得出结论，所制作的 DC-LPFG 可以用作具有成本效益的传感器头，用于应变不敏感的弯曲和温度的独立测量。
