液氮温度下裸光纤布拉格光栅弹光系数实验测量

Experimental measurement of elastic-optic coefficient of bare fiber Bragg grating at liquid nitrogen temperature

研究了裸光纤布拉格光栅(FBG)的低温应变特性,采用静态拉伸实验逐对记录FBG中心波长和加载应力,通过理论推导得到理论应变,并将其与相对波长变化量的关系曲线进行线性拟合,求出裸光纤布拉格光栅在常温和液氮温度下的有效弹光系数.此种实验方式消除了传统实验方式(将光栅粘在金属基片上)应变传递对测量结果的影响,使测量结果更准确.结果发现液氮温度下相对波长变化量ΔλB/λB与应变ε呈线性关系,测得常温和液氮温度下弹光系数分别为0.25和0.23.

The strain characteristics of bare fiber Bragg grating （FBG） at cryogenic temperature are studied. The static tensile experiments are carried out to record the central wavelength of FBG and the force in pair. Then, the linear fitting of relative wavelength variation and strain which is worked out through theoretical derivation can be performed. Afterwards, the valid elastic-optic coefficients of bare fiber Bragg grating at normal and liquid nitrogen temperature are determined. This experimental way eliminates the influence caused by the traversal of stress in traditional experiment （adhering FBG to metal chip） and makes the result preciser. It turns out that it is linear relationship between the relative wavelength variation △λB/λB and the strain ε at liquid nitrogen temperature. Moreover, the measured elastic-optic coefficient at normal and liquid nitrogen temperature is respectively 0. 25 and 0. 23.