Static strain measurement with sub-micro strain resolution and large dynamic range using twin grating Fabry-Perot sensor

摘要

We present experimental results on testing a twin grating fiber optic sensor for measurement of static strain. The sensor is built with two identical Bragg gratings closely spaced in a single mode fiber. It produces a reflection spectrum modulated due to interference. Similar to traditional FBG sensors, strain of the fiber leads to the wavelength shift of the reflection spectrum. This shift can be determined precisely measuring phase changes for corresponding components of Fourier transform of the reflection spectrum. Such an approach allows an absolute strain measurement with an interferometric sensitivity. Resolution of 0.02 deg C and 0.2mu epsilon was demonstrated experimentally for temperature and static strain measurements using a pair of 0.7mm long Bragg gratings with reflectivity of 1 percent each.