Highly sensitive strain sensor based on a sealed optical microfiber coupler

A simple, high-sensitivity strain sensor based on a sealed optical microfiber coupler (OMC) was proposed and demonstrated. Affected by the strain, the effective refractive index (RI), microfiber length, microfiber diameter changes the coupling coefficient of the OMC. Due to the uneven force of the port3 and port4, the strain sensitivity after encapsulation will improve, which is proved in the experiment. The mechanical simulation demonstrates that there is a dependence between strain sensitivity and waist diameter. The sensor with a 2.3 μm waist diameter presents a sensitivity of −18.351 pm/με regarding the variation of axial strain from 10 to 1200με, which was one order of magnitude higher than that of optical strain sensors based on fiber Bragg gratings. Experimental results demonstrate that the OMC sensor exhibits high sensitivity, strong stability and the capability of simultaneous measurement of strain and temperature.