Silicone-Encapsulated Wearable Fiber Optic Sensor for Respiratory and Heart Rate Measurement

This paper proposes a silicone-encapsulated wearable fiber-optic sensor based on a single-mode-multimode -few-mode-multimode-single-mode fiber-optic Mach-Zehnder interferometer configuration, achieving simultaneous extraction of respiratory and heartbeat signals through the variational mode decomposition algorithm. The sensing region is fully encapsulated within a soft and elastic silicone layer, improving the durability and maintaining high biocompatibility. The proposed sensor exhibits high curvature sensitivity, achieving an average sensitivity of -17.45 dB/m⁻¹, with a maximum sensitivity of -69.42 dB/m⁻¹ within the curvature range of 2.77-3.92 m⁻¹, and an average of 22.76 dB/m⁻¹ with a maximum of 65.25 dB/m⁻¹ in the extended range of 3.92-4.96 m⁻¹. Experimental results show that the sensor can be freely worn at different positions on the chest, and it successfully acquires both respiratory and heartbeat signals under various breathing patterns. The respiratory and heart rates measured by the system show good agreement with manual breath counting and a commercial heart rate monitor, respectively. With advantages including cost-effective fabrication, simplified manufacturing process, and low temperature cross-sensitivity, this design provides a practical approach for implementing fiber-optic sensors in clinical respiration and heart rate monitoring.