Intensity modulation type fiber-optic strain sensor based on a Mach–Zehnder interferometer constructed by an up-taper with a LPG

•The sensor is based on an in-line fiber Mach–Zehnder interferometer (MZI), which is constructed by connecting a long-period fiber grating (LPG) with an up-taper.•The proposed sensor shows a sensitivity of 0.026 dB/με, which is almost 2 times of the existing similar strain sensor.•The results of the experiment were confirmed by theoretical simulations.

A highly sensitive and compact fiber-optic strain sensor was presented and experimentally demonstrated. The sensor is based on an in-line fiber Mach–Zehnder interferometer (MZI), which is constructed by connecting a long-period fiber grating (LPG) with an up-taper. With the increasing of the axial strain on the sensor, both of the up-taper's diameter and the light coupling efficiency decreased. By measuring the transmission intensity changes of the resonant dips at wavelength ~1553.4 nm under the fiber axial strain ranging from 0 to 590 με, the sensitivity of 0.026 dB/με was obtained, which is almost 2 times of the existing similar strain sensor. And the results were also confirmed by simulations.