Concatenated Bragg grating fiber-optic sensors for simultaneous measurement of curvature, temperature, and axial pressure

• Published in: Journal of sensors and sensor systems 2024-07, Vol.13 (2), p.147-155
• Main Authors: Shojaei Khatouni, Sohrab, Zakowski, Sven, Hosseini Vedad, Reza, Masjedi, Mustafa, Askar, Akram, Ewald, Jan Christian Eli, Trieu, Hoc Khiem
• Format: Article
• Language: English
• Subjects: Bragg gratings; Cladding; Coating; Curvature; Decision trees; Design; Equipment and supplies; Fiber optics; Measurement; Measuring instruments; Optics; Root-mean-square errors; Sensors; Silicon compounds; Silicon dioxide
• ISSN: 2194-878X; 2194-8771; 2194-878X
• DOI: 10.5194/jsss-13-147-2024

This paper presents the development and evaluation of four sensors based on multiple fiber Bragg grating (FBG) constellations embedded in a silicon dioxide single-mode fiber (SMF) for simultaneous measurement of pressure, temperature, and bending curvature. We applied dimension and material variations – including core, cladding, and coating dimensions; coating material; and the number and arrangement of the FBGs – to optimize the reflected signal response and increase information density. A bootstrap-aggregated ensemble of decision trees was used to evaluate the sensor signal. The results show that adjusting the cladding-to-coating ratio led to significant improvements in pressure and bending prediction performance. Additionally, two combined FBGs were fabricated to form a fiber Bragg grating Fabry–Pérot interferometer, which enabled the detection of curvature with a root-mean-square error (RMSE) of 0.0034 L mm−1 (R2=1), axial pressure with an RMSE of 0.0564 bar (R2=0.99), and temperature with an RMSE of 0.0265 °C (R2=1). At the time of writing, there is no commercially available instrument that can perform these measurements simultaneously.