Optical Fiber Temperature Sensing Probe Based on F–P Cavity for Human Body Temperature Monitoring

In the exoskeleton-assisted rehabilitation scenarios, sensors need to have strong resistance to environmental interference and long-term monitoring stability. Commonly used body temperature measurement equipment cannot be recorded and worn for long periods. This article highlights the advantages of optical fiber sensors, such as their resistance to electromagnetic interference, strong environmental adaptability, and good stability after being fabricated and packaged in specific structures. Based on these benefits, it proposes an optical fiber temperature sensing probe that encapsulates the F–P cavity within capillary copper tubes. The UV glue is applied at the end of the optical fiber and cured to form an F–P microcavity, which is encapsulated with a copper tube for thermal conductivity and protection. It can be fixed anywhere on the body surface with medical tape. Theoretical derivation and numerical simulation are carried out on the interference principle and temperature sensing principle of the F–P cavity. The characteristics of the sensing probe are tested, and body temperature monitoring is performed on the human wrist and armpit. The experimental results show that the probe has good stability, repeatability, sensitivity, and signal-to-noise ratio. The average standard deviation of the dip wavelength at constant temperature is 16.7 pm. The sensor sensitivity is about $287.3 \text {pm}/^{\circ }\text {C}$ . The capillary structure makes the temperature response speed faster than that of electronic sensors. The proposed F–P sensing probe can be applied to human body sign information monitoring and feedback in rehabilitation, which is conducive to the realization of efficient and intelligent rehabilitation strategies.