Contactless vital signs monitoring
based on few-mode and multi-core fibers
Vital signs, such as body temperature, respiration and heartbeat, play an important role in human health condition assessment. Among these vital signs, respiration and heartbeat are the most common indicators since they can directly reflect the working state of the lung and heart. Due to this remarkable importance, monitoring of respiration and heartbeat attracts increasing concern in both research and industry area and many kinds of schemes have been proposed. Currently, the most popular monitoring scheme is wearable sensor, which requires close contact to the skin. This method is not convenient and unfriendly to specific users like the elderly and children. Thus, contactless vital signs monitoring becomes preferred and various schemes have been also investigated. In this work, optical fiber sensors are proposed to detect human vital signs in a contactless way owing to their unique advantages of lightweight, high sensitivity and electromagnetic immunity. The specialty optical fibers utilized here are few-mode and multi-core fibers. The offset structure between single mode fibers and specialty optical fibers are used to introduce interference between modes or cores, which is utilized to detect vital signs signals. The dimension of sensor structure is optimized, and these in-line interferometers are fabricated and packaged under the mattress, as shown in Fig. 1. Based on the collected data, common filtering techniques are introduced and both respiration and heartbeat ratio can be obtained eventually with low errors. This work successfully demonstrates the feasibility of optical fiber sensors on contactless vital signs monitoring.
Fig. 1. Vital signs monitoring experimental setup
The research group of Prof. Changyuan YU from The Hong Kong Polytechnic University reviews the investigation on the application of specialty optical fibers on vital signs monitoring. Healthcare has been drawing wide concern in modern society, especially in the developing country like China. Human health condition is usually assessed by some physical indicators, such as body temperature, respiration and heartbeat. Among these vital signs, respiration and heartbeat are the most widely used indicators. Respiration and heartbeat can reflect the working condition of lung and heart in order to pre-diagnose specific cardiac and pulmonary diseases. Thus, reliable as well as accurate monitoring on respiration and heartbeat become more and more necessary, and various schemes have been proposed. Currently, wearable sensors like ECG devices for heartbeat monitoring, are the most popular methods and has been widely used in hospitals. However, these sensors require close contact or attachment on skin, which is not convenient to specific users like the elderly and children. Thus, contactless sensing schemes are drawing attention and one of them is the optical fiber sensor. Optical fiber sensor owns the advantages of high sensitivity, lightweight and electromagnetic immunity, which can be a potential candidate in healthcare applications. To explore its application on contactless vital signs monitoring, specialty optical fibers, namely few-mode and multi-core fibers are investigated in this work. Based on these two kinds of optical fibers, in-line interferometers are designed and packaged as smart mats under the mattress. The results show that vital signs signals can be detected in a contactless way, and both respiration and heartbeat ratio can be obtained with low errors. This work successfully demonstrates that optical fiber sensors can be desirable candidates on contactless health condition monitoring.
About The Group
Prof. Changyuan Yu’s research group from Department of Electronic and Information Engineering in The Hong Kong Polytechnic University mainly focus on the investigation of optical fibers applications, including high-speed communication and optical sensing. In recent years, optical fiber sensors show excellent performance on the biomedical and healthcare applications. Dr. Yu’s group proposed to use optical fiber interferometric sensors for contactless vital signs monitoring, including respiration and heartbeat. Various sensing schemes have also been demonstrated with outstanding performance, such as conventional optical fiber interferometers and novel specific few-mode and multi-core fibers-based sensors. Dr. Yu is with Department of Electronic and Information Engineering, The Hong Kong Polytechnic University in 2015. And he also continues as an adjunct faculty member of National University of Singapore. His research focuses on photonic devices, subsystems, optical fiber communication and sensor systems, and biomedical instruments. As the PI/co-PI, he secured over 7 million US dollars grants, and supervised 10+ postdocs and 20+ PhD students. He has authored/co-authored 1 US patent, 6 book chapters, 400+ journal and conference papers (82 keynote/invited, including OFC2012 in USA). His group won 6 best paper awards in conferences and the championship in biomedical area in the 3rd China Innovation and Entrepreneurship Competition in 2014.
Tan F Z, Lyu W M, Chen S Y, Liu Z Y, Yu C Y. Contactless vital signs monitoring based on few-mode and multi-core fibers. Opto-Electron Adv 3, 190034 (2020).