In this paper, high-order LP modes based Sagnac interference for temperature sensing are proposed and investigated theoretically. Based on the specific high-order LP modes excited through the mode selective couplers (MSCs), we design a stress-induced Panda-type few-mode fiber (FMF) supporting 4 LP modes and construct a Sagnac interferometer to achieve a highly sensitive temperature sensor. The performances of different LP modes (LP₀₁, LP₁₁, LP₂₁, and LP₀₂) are explored under a single Sagnac interferometer and paralleled Sagnac interferometers, respectively. LP₂₁ mode has the highest temperature sensitivity. Compared with fundamental mode (LP₀₁), the temperature sensitivity based on LP₂₁ mode improved by 18.2% at least. In addition, a way to achieve the enhanced optical Vernier effect is proposed. It should be noted that two Sagnac loops are located in two temperature boxes of opposite variation trends, respectively. Both two Sagnac interferometers act as the sensing element, which is different from the traditional optical Vernier effect. The temperature sensitivity of novel enhanced optical Vernier effect is magnified by 8 times, which is larger than 5 times the traditional Vernier effect. The novel approach avoids measurement errors and improves the stability of the sensing system. The focus of this research is on high-order mode interference, which has important guiding significance for the development of highly sensitive Sagnac sensors.

中文翻译：

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基于 Sagnac 干涉的高阶 LP 模式，用于具有增强光学游标效应的温度传感

本文提出并从理论上研究了基于萨格纳克干涉的高阶 LP 模式的温度传感。基于通过模式选择耦合器（MSC）激发的特定高阶LP模式，我们设计了支持4种LP模式的应力诱导熊猫型少模光纤（FMF），并构建了Sagnac干涉仪以实现高灵敏温度传感器。分别在单个萨格纳克干涉仪和并行萨格纳克干涉仪下探讨了不同LP模式（LP ₀₁、LP ₁₁、LP ₂₁和LP ₀₂ ）的性能。 LP ₂₁模式具有最高的温度灵敏度。与基本模式(LP ₀₁ )相比，基于LP ₂₁模式的温度灵敏度至少提高了18.2%。此外，还提出了一种实现增强光学游标效应的方法。值得注意的是，两个萨尼亚克环分别位于两个变化趋势相反的温度箱中。两个萨格纳克干涉仪都充当传感元件，这与传统的光学游标效应不同。新型增强光学游标效应的温度灵敏度放大了8倍，比传统游标效应大5倍。这种新颖的方法避免了测量误差并提高了传感系统的稳定性。本研究的重点是高阶模干扰，对于高灵敏Sagnac传感器的开发具有重要的指导意义。