Interdisciplinary Program of Biomedical Mechanical & Electrical Engineering, Pukyong National University, 45 Yongso-ro, Nam-gu, Busan 48513, Korea.
School of Electrical Engineering, Pukyong National University, 45 Yongso-ro, Nam-gu, Busan 48513, Korea.
J Nanosci Nanotechnol. 2021 Mar 1;21(3):2024-2031. doi: 10.1166/jnn.2021.18915.
Here we propose an optical fiber sensor capable of simultaneous measurement of liquid level and temperature by utilizing cascaded long-period fiber gratings (LPFGs) inscribed on high-birefringence fiber (HBF) and a Faraday rotator mirror (FRM). Due to the in-fiber Mach-Zehnder interference and birefringence of the HBF, these cascaded LPFGs have polarization-dependent discrete interference spectra, each of which is created within one of the two different attenuation bands obtained in the two orthogonal input polarization states, e.g., linear horizontal polarization (LHP) and linear vertical polarization (LVP). The minimum transmittance dip was selected as a sensor indicator for each interference spectrum obtained for LHP or LVP input signal. To monitor these indicator dips associated with LHP and LVP, referred to as the IDH and IDV, respectively, with one spectral scanning, an FRM was connected to the end of the cascaded LPFGs. Both the IDH and IDV spectrally shifted according to liquid-level or temperature changes and showed very linear responses to them with adjusted ₂ values greater than 0.997. The liquid-level sensitivities of the IDH and IDV were measured as approximately -37.29 and -121.08 pm/mm in a liquid-level range of 0 to 55 mm, respectively. The temperature sensitivities of the IDH and IDV were measured as ˜28.79 and ˜218.21 pm/°C in a temperature range of 30 to 60 °C, respectively. Owing to their linear and independent responses to liquid level and temperature, our sensor can perform temperature-independent liquid-level measurement using their pre-determined liquid-level and temperature sensitivities, even if both liquid level and temperature change simultaneously.
我们提出了一种光纤传感器，它利用在高双折射光纤（HBF）上刻写的级联长周期光纤光栅（LPFG）和法拉第旋转镜（FRM）实现了液位和温度的同时测量。由于光纤中的马赫-曾德尔干涉和 HBF 的双折射，这些级联 LPFG 具有偏振相关的离散干涉光谱，每个光谱都是在两个正交输入偏振态之一获得的两个不同衰减带之一中产生的，例如线性水平偏振（LHP）和线性垂直偏振（LVP）。选择最小透射谷作为 LHP 或 LVP 输入信号获得的每个干涉光谱的传感器指示符。为了监测与 LHP 和 LVP 相关的这些指示谷，分别称为 IDH 和 IDV，使用一个光谱扫描，将 FRM 连接到级联 LPFG 的末端。随着液位或温度的变化，IDH 和 IDV 的光谱都发生了偏移，并且与它们的响应非常线性，调整后的 ₂值大于 0.997。在 0 至 55 毫米的液位范围内，IDH 和 IDV 的液位灵敏度分别约为-37.29 和-121.08 pm/mm。在 30 至 60°C 的温度范围内，IDH 和 IDV 的温度灵敏度分别约为 28.79 和 218.21 pm/°C。由于它们对液位和温度的线性和独立响应，我们的传感器可以使用其预定的液位和温度灵敏度进行与温度无关的液位测量，即使液位和温度同时发生变化。
