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High resolution static strain measurement using distributed feedback fiber laser and beat frequency technique

A high resolution static strain measurement system using distributed feedback fibre lasers (DFB-FLs) and beat frequency technique is demonstrated. Two independent fibre lasers are used in the sensor head. One fibre laser is used to sense the strain and the other is stress-free and used as a reference. In the interrogation system, a third fibre laser is used to generate the beat notes with the two fibre lasers in the sensor head. The beat frequency difference of the two fibre laser is detected and the strain can be calculated. The experiment result shows that the static strain resolution is better than 0.25 nano-strain (nε).