All-Fiber Michelson Interferometer for Heart Rate and Breath Monitoring

Heart rate (HR) and breath monitoring technology based on optical fiber sensors have been widely developed in the field of healthcare due to their high sensitivity, flexibility, adaptability, and lightweight, however exploring exquisite and robust sensors and enhancing integration remain challenges. In this article, an all-fiber Michelson interferometer (MI) for HR and breath monitoring is presented. A fiber cylinder and a fiber sphere are employed in the configuration of the sensor, which not only improves its perception of human physiological signals but also holds robustness and compactness. Microbending significantly modulates the mode interference intensity, providing accurate detection of vital signs. The experimental test demonstrates that the sensor could detect human HR and breath signals and identify these physiological signals under different modes (static, posture, and dynamic). Moreover, the influence of wearing position on physiological detection is investigated, thereby expanding its wearable potential applications. The work is expected to offer a practical strategy for using optical fiber sensors in healthcare applications.