Optical fiber strain sensor with high and tunable sensitivity.

We demonstrate a fiber-optic strain sensor with high and tunable sensitivity by constructing a Fabry-Perot interferometer with tunable stretching length. By improving the ratio of stretching length to interference length for the proposed sensor, the measured strain sensitivity is up to 1932 pm/με, which is an order of magnitude higher than the maximum value of reported fiber-optic strain sensors so far. The sensitivity for a prepared sensor could be also tuned conveniently by changing the stretching length, and experimental results show that the sensitivity could be tuned from 1932 to 978 pm/με by reducing the stretching length from 12 to 6 mm. Furthermore, the proposed device is economical, straightforward, robust, and reproducible. The advantages make the proposed device promising in practical applications.