Multiparameter sensor based on hollow square core optical fiber

A Fabry Perot (FP) based fiber sensor for multiparameter measurement is proposed. The sensor is constituted by a short section of a hollow square core fiber (HSCF) spliced between a single mode fiber and a long section of a silica capillary tube. In a reflection scheme, several FP cavities are enhanced in different areas of the HSCF. In a single 439 μm long sensing head, three FP cavities are excited. Using the Fourier band-pass filter method, each cavity was individually monitored towards variations of pressure, temperature, and curvature. The maximum sensitivities of (3.23 ± 0.04) nm/MPa, (9.6 ± 0.3) pm/°C, and (-32 ± 1) pm/m-1 were obtained for pressure, temperature, and curvature, respectively within a measurement range of 0.4 MPa, 110°C, and 9 m-1. The distinct responses of the FP cavities to the measurands allow for a triple-hybrid application of the sensor towards simultaneous measurement of pressure, temperature, and curvature. The proposed sensor is robust with simple fabrication and small dimensions, revealing promising to be employed in a wide range of applications where the measurement of several physical parameters is required.