All-fiber asymmetrical interferometric sensor for simultaneous dual-parameter measurements

An inline fiber sensor is proposed for simultaneously measure refractive index (RI) and axial strain or temperature and axial strain. The proposed sensor consists of a microcavity and a fiber core-offset attenuator. The microcavity with the diameter of 6μm and the depth of 2.5 μm is embedded in the fiber core fabricated by a femtosecond laser. High quality interference spectra with a fringe visibility around 20 dB are observed. For attenuation peak wavelengths at 1496.68 nm and 1533.18 nm, the RI sensitivities are -29.91 nm/RIU and -16.72 nm/RIU, the strain sensitivities are -1.55 pm/με and -0.31 pm/με, respectively. The experimental results demonstrate that the sensor is able to achieve simultaneous measurements of refractive index and axial-strain or temperature by sensitivity matrix.