Competence Center for Specialty Optical Fibers

A multiparameter sensor based on a single section of a hollow square core fiber (HSCF) spliced between a single mode fiber and a silica capillary tube is proposed. In a reflection scheme, several Fabry-Perot (FP) cavities are enhanced in different areas of the HSCF. In a 439 µm long sensing head, three FP cavities are excited. Using the Fourier band-pass filter method, each cavity is individually monitored towards the measurand variation. The distinct responses of the FP cavities allow for a hybrid application for simultaneous measurement of pressure, temperature, and curvature. Additionally, a sinusoidal behavior is found in the curvature response when bending is applied for different relative positions of the fiber. The proposed sensor is robust with simple fabrication and small dimensions, demonstrating promising potential for applications where the simultaneous measurement of several physical parameters is required.