High-sensitivity strain sensor with an in-fiber air-bubble Fabry-Perot interferometer

Abstract

We present a laser machining method for fabricating an all-fiber pillar-in-bubble Fabry-Perot interferometer (FPI), which is used for strain sensors with high sensitivity. The micro-structure of the air-bubble is fully controllable, especially the cavity length and sidewall thickness. The measured sensitivity of this strain sensor is as high as 56.69 pm/με, which is several times higher than that of most FPI strain sensors reported to date. This sensor also has a low-temperature sensitivity of 0.682 pm/°C, reducing the cross-sensitivity between tensile strain and temperature to 0.012 με/°C. Furthermore, such a sensor has the benefits of flexible design, simple fabrication, and high reproducibility, making it attractive for practical applications.