超低温下FBG温度传感器封装设计与性能分析

Encapsulation Design and Performance Analysis of FBG Temperature Sensors under Ultra-Low Temperature

摘要: 随着航空航天、超导技术及大型低温工程等领域的快速发展，超低温环境下的精确温度测量需求愈发迫切。传统电学式温度传感器易受电磁干扰、难以实现多点分布式测量，应用受限。光纤布拉格光栅(FBG)传感器具有本质抗电磁干扰、体积小、耐腐蚀等优势，是极端环境测量的理想选择，但在低于100 K的超低温条件下，其温度灵敏度显著衰减，制约了实际应用。本研究针对上述核心挑战，提出6063型毛细铝管与E-200耐低温环氧树脂协同封装方案，设计1.5 × 0.2 mm、1.5 × 0.25 mm两种规格对比实验；采用2 × 2熔锥型3 dB光纤耦合器实现低成本、稳定的反射式FBG传感。在−190℃至0℃温区，借助多孔真空硅控温与热电偶标定开展三次升温循环实验。结果表明：两种封装FBG线性拟合度均达0.97以上，温度灵敏度分别为裸FBG的2.5倍、3倍以上，其中1.5 × 0.25 mm规格因更强的热膨胀驱动力与更均匀的应力分布，灵敏度更优。本研究显著提升了FBG传感器在超低温环境下的综合传感性能，为其在超低温工程中的实际部署提供了理论与技术支持。

Abstract: With the rapid development of aerospace, superconducting technology and large-scale cryogenic engineering, the demand for precise temperature measurement in ultra-low temperature environments has become increasingly urgent. Traditional electrical temperature sensors are susceptible to electromagnetic interference and difficult to achieve multi-point distributed measurement, which limits their applications. Fiber Bragg Grating (FBG) sensors feature inherent anti-electromagnetic interference, small size and corrosion resistance, making them ideal for extreme environment measurements. However, their temperature sensitivity decreases significantly at ultra-low temperatures below 100 K, restricting practical applications. To address these core challenges, this study proposes a collaborative encapsulation scheme using 6063-type capillary aluminum tubes and E-200 cryogenic-resistant epoxy resin, and designs comparative experiments with two specifications (1.5 × 0.2 mm and 1.5 × 0.25 mm). A 2 × 2 fused-taper 3 dB fiber coupler is adopted to realize low-cost and stable reflective FBG sensing. Three heating cycle experiments are conducted in the temperature range of −190˚C to 0˚C, with porous vacuum silicon for temperature control and thermocouples for calibration. The results show that both encapsulated FBGs exhibit a linear fitting degree above 0.97, with temperature sensitivities 2.5 times and 3 times higher than that of the bare FBG, respectively. The 1.5 × 0.25 mm specification delivers superior sensitivity due to stronger thermal expansion driving force and more uniform stress distribution. This study significantly improves the comprehensive sensing performance of FBG sensors in ultra-low temperature environments, providing theoretical and technical support for their practical deployment in cryogenic engineering.