提出一种基于七芯光纤和保偏光纤结构的光纤曲率传感器,该传感器先将一段七芯光纤和保偏光纤对芯熔接,然后在其两端熔接普通单模光纤分别作为输入和输出光纤。实验研究了七芯光纤长度分别为80,100,120 mm的三种传感器的曲率特性,结果表明:当曲率增大时,传感器的透射谱发生明显的红移现象,因此通过监测透射谱谐振波谷波长的漂移可实现曲率的测量。传感器的曲率灵敏度随着七芯光纤长度的增加而增大,在七芯光纤长度为120 mm时传感器获得最大的灵敏度,为17.31 nm/m -1。但温度特性实验表明该长度下的传感器对温度具有较高的灵敏度,故在实际应用中,为避免温度对测量结果的影响,可选择温度灵敏度最低、七芯光纤长度为100 mm的传感器进行曲率测量,该长度下的最大曲率灵敏度为16.79 nm/m -1。与其他光纤结构传感器相比,所提出的传感器具有制作简单、价格低廉、消光比高等优点,可用于土木工程等领域。

An optical fiber curvature sensor based on seven-core fiber (SCF) and polarization-maintaining fiber (PMF) structures is proposed. First, a section of SCF is fused with the PMF, and then a common single-mode optical fiber is fused at both ends as the input fiber and output fiber, respectively. Experiments have studied the curvature characteristics of three sensors with SCF lengths of 80, 100, and 120 mm, respectively. The results show that when the curvature increases, the transmission spectrum of the sensor has a significant red shift, and the curvature measurement can be realized by monitoring the shift of the resonant valley wavelength in the transmission spectrum. The curvature sensitivity of the sensor increases with the increasing SCF length. When the length of SCF is 120 mm, the maximum sensitivity is 17.31 nm/m ^-1. However, the temperature characteristic experiment shows that the sensor with this length has high sensitivity to temperature. Therefore, in order to avoid the influence of temperature on the measurement results, the sensor with the lowest temperature sensitivity and the SCF with a length of 100 mm can be selected for curvature measurement. The maximum curvature sensitivity under this length is 16.79 nm/m ^-1. Compared with other optical fiber structure sensors, the proposed sensor has the advantages of simple fabrication, low cost, and high extinction ratio, which can be used in civil engineering and other fields.