布喇格中心波长的偏移与轴向应力、径向应力和温度等变化量均呈极好的线性比例关系，且在较大的测量范围内一直保持线性关系。

The relative shift of Bragg center wavelength increased linearly with the change of axial stress, radial stress or temperature, and it kept the linear relationship in a large range.

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因此，进行应变测量时，应用常规的杠杆引伸仪，受到安装方式和测量标距等条件的限制，往往只能测量轴向一定范围内的平均应变。

So, in the process of strain-measuring, when we apply the normal lever extension meter, it is confined by conditions, such as the install pattern, measurement standard and so on.

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