提出了一种基于LP₀₁和LP₁₁模式干涉的少模光纤温度传感器,利用单模光纤(SMF)和少模光纤(FMF)在入射端偏芯熔接、出射端对准熔接制作而成。利用标量法对FMF建立理论模型,通过光场的电磁边界连续条件推导出了FMF的特征方程,并通过对特征方程数值求解详细分析了FMF中的传输模式;通过有限元分析软件对上述理论模型仿真计算,验证了理论计算结果的正确性;利用制作的传感器进行温度传感实验,并对不同温度下的传输光谱进行傅里叶变换,对参与干涉的两种模式进行了分析。根据光纤的热光效应,建立温度传感模型,分析计算该传感器的温度灵敏度,实验结果与理论计算一致。利用上述特性制作的传感器进行温度测量,当温度发生变化时,干涉峰发生漂移,在25.3~77.3 ℃范围内,传感器长度为16 mm时,温度灵敏度为158.06 pm/℃。该传感器能广泛应用于工业生产、生物医学等领域的温度测量。

A few-mode fiber (FMF) temperature sensor based on the interference between LP01 and LP11 modes is proposed. The sensor is fabricated with an FMF, of which one end is spliced to a lead-in single-mode fiber (SMF) with small lateral core-offsets and the other is spliced to a lead-out SMF with alignment. Firstly, the theoretical model of FMF is established with the scalar method and the characteristic equation of FMF is derived by the light field of continuous electromagnetic boundary condition. Through the numerical solution of the characteristic equation, the transmission mode of FMF is analyzed in detail. Then, the theoretical results are verified through the finite element analysis. Finally, the sensor is used for temperature sensing experiments. Through the Fourier transform of the transmission spectra at different temperatures, the two modes of interference are analyzed. According to the thermo optic effect, the temperature sensing model is established. The temperature sensitivity of the sensor is analyzed and calculated, which is consistent with the experimental results. The temperature measurement experiment is carried out with the proposed sensor, and the results show that when the temperature changes, the interference peak drifts, and the temperature sensitivity of a 16-mm-long sensor is 158.06 pm/℃ at 25.3-77.3 ℃. The temperature sensor can be widely used in industrial production, biomedical and other fields.