Contactless vital signs monitoring based on few-mode and multi-core fibers

Few-mode and multi-core fibers are proposed and demonstrated for contactless vital signs monitoring in this paper. In-line optical fiber interferometers using few-mode and multi-core fibers are designed and offset splicing is utilized for mode excitation. Extinction ratio and insertion loss are analyzed experimentally under different offset distances. The fabricated in-line interferometers are packaged under the mattress to realize contactless vital signs signals collection. By using filtering techniques, both respiration and heartbeat signals can be recovered successfully, and respiration as well as heartbeat ratio are obtained. Mode excitation and interference are theoretically analyzed in few-mode fiber while curvature sensing experiments using multi-core fiber interferometer are performed to verify its excellent performance on vital signs monitoring. The successful demonstration on contactless vital signs monitoring makes few-mode and multi-core fibers promising candidates for healthcare applications.