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利用受温度影响的光纤的本征方程和相位匹配条件,从理论上研究了长周期光纤光栅(LPFGs)的温度响应特性,给出了LPFGs的温度灵敏度的解析表达式。对利用低模序包层模的LPFG进行了实验研究。结果表明,利用不同包层模的LPFGs具有不同的温度灵敏度。分析了光纤的材料热光系数和模的热光系数的差别。单模光纤导模的热光系数接近纤芯的材料热光系数,而包层模的热光系数比包层的材料热光系数大,模序越大,其值越大。适当调整纤芯和包层的热光系数,并选用不同的包层模,可以得到对温度灵敏或不灵敏的LPFGs。
The temperature response characteristics of long period fiber gratings (LPFGs) are theoretically studied by using the eigen equations and phase matching conditions of the fiber affected by temperature, and the analytical expression of temperature sensitivity of LPFGs is given. An experimental study of LPFG using a low-mode cladding modeler has been carried out. The results show that LPFGs with different cladding modes have different temperature sensitivities. The difference between the thermo-optic coefficient of the material and the thermo-optic coefficient of the fiber is analyzed. The thermal coefficient of the single-mode fiber is close to the thermal coefficient of the core, while the thermal coefficient of the cladding mode is larger than the thermal coefficient of the cladding material. The larger the mode is, the larger the value is. Appropriate adjustment of the thermal coefficient of the core and the cladding, and the choice of different cladding modes can result in temperature-sensitive or insensitive LPFGs.