基于多模光纤对芯熔接的全光纤温度传感器

All-fiber Temperature Sensor Based on Multimode Optical Fiber-to-core Fusion Splicing

传统SMS结构的光纤传感器具有模式单一、损耗较大的问题而导致温度灵敏度较低,文中采用单模-多模-多模-多模-单模结构的新型光纤马赫-曾德尔干涉传感器,对原有结构进行了改进。大芯径多模光纤与两端的单模光纤耦合,实现光的分束和合束,同时将大芯径多模光纤与小芯径多模光纤(MMF_(2))熔接,使高阶模与基模分别进入小芯径多模光纤包层与纤芯进行传输从而产生相位差,最终形成对温度敏感的模式干涉,理论分析了该结构的温度敏感特性。采用MMF_(2)长度分别为8 mm和12 mm的两种该结构传感器,温度灵敏度均能提高到80 pm/℃,同时该结构具有更低的应变灵敏度,可较好的规避应力变化带来的影响。除此之外该结构具有应变交叉敏感度低、制作简单、成本低廉且损耗小等优点,在监测温度方面具有广阔的应用前景。

The optical fiber sensor of traditional SMS structure has such problem as single mode and large loss,thus causing low temperature sensitivity and inaccurate sensing and displaying data of electrical equipment. In this paper,a new optical fiber Mach-Zehnder interference sensor with single-mode-multi-mode-multi-mode-single-mode structure is adopted to improve the original structure. The coupling of large core multi-mode optical fiber with singlemode optical fiber on both ends achieves beam splitting and beam merging and,at the same time,the large core multi-mode optical fiber with small multi-mode fiber(MMF_(2))are spliced so to keep the higher order mode and base mode enter into small core multi-mode fiber cladding and fiber core for transmission,thus generating phase difference and eventually forming mode interference mode which is sensitive to temperature. Moreover,the temperature sensitive characteristic of the structure is theoretically analyzed. The temperature sensitivity can be improved up to 80 pm/℃by using two structures of MMF_(2) sensors with lengths of 8 mm and 12 mm respectively. At the same time,the structure has lower strain sensitivity,which can better avoid the impact due to stress changes. In addition,the structure has such advantages as low strain cross sensitivity,simple fabrication,low cost and low loss and has a broad application prospect in the field of temperature monitoring.