热光系数与长周期光纤光栅的温度灵敏度研究

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。

Thermo-optic coefficient and temperature sensitivity of long-period fiber gratings

The temperature properties of long period fiber gratings(LPFGs) are investigated theoretically by use of the eigenvalue equations of the fibers affected by temperature and the phase matching condition. The analytical expression of the temperature sensitivity is derived. The temperature properties of LPFG base on the lower-order cladding modes are investigated experimentally. The difference of the thermo-optic coefficient of the fiber material and the effective-thermo-optic coefficient of the modes is analyzed. The thermo-optic coefficient of the core mode of the single-mode fibers is close to that of the fiber core material. The thermo-optic coefficient of the cladding modes is more than that of the cladding material, and the mode order is higher, its value is more. Changing the value of the thermo-optic coefficient of the fiber core and cladding material and selecting the different cladding modes, the LPFGs sensitive or insensitive the temperature can be designed and fabricated.