A new temperature fiber ring laser (FRL) sensor based on a cascaded Sagnac loops fiber structure is proposed and experimentally demonstrated. The optical FRL sensor consists of cascaded Sagnac loops by inserting two polarization-maintaining optical fibers (PMF) with slightly different lengths. PMF with length of 56 cm and 75 cm are used in Sagnac loops as a filter and sensing unit in laser cavity. The working principle of the sensor is based on the phase shift (θ) caused by birefringence between two principal polarization modes and enhance the sensitivity by constructing a Vernier-scale. In an appropriate temperature range (25 °C - 31 °C), the detection sensitivity of FRL sensor based on a cascaded Sagnac structure is significantly higher than other FRL sensors. Thanks to the laser sensing system, the sensitivity can be modulated by changing the free spectral range (FSR). The experimental results show that the temperature sensitivity of the cascade Sagnac structure sensor is - 4.031 nm / °C, which is five times higher than that of FRL sensor base on the single Sagnac structure.

中文翻译：

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级联光纤Sagnac干涉仪的基于光纤环形激光器的温度传感器

提出了一种基于级联萨格纳克环光纤结构的新型温度光纤环形激光传感器，并进行了实验验证。光学FRL传感器由级联的Sagnac环组成，通过插入两条长度稍有不同的保偏光纤（PMF）。在Sagnac回路中使用长度分别为56 cm和75 cm的PMF作为激光腔中的过滤器和传感单元。传感器的工作原理基于两个主要偏振模之间的双折射引起的相移（θ），并通过构造游标刻度来提高灵敏度。在适当的温度范围（25°C-31°C）中，基于级联Sagnac结构的FRL传感器的检测灵敏度明显高于其他FRL传感器。得益于激光感应系统，灵敏度可以通过改变自由光谱范围（FSR）进行调节。实验结果表明，级联Sagnac结构传感器的温度灵敏度为-4.031 nm /°C，是基于单Sagnac结构的FRL传感器的温度灵敏度的五倍。