Smart health monitoring system based on fiber optic sensors

Abstract

As the population ages in modern society, people begin to pay attention to daily medical care. There are already some vital sign monitoring products on the market, such as Xiaomi Smart Band, Fitbit Watch, Apple Watch, etc. However, these products are all wearable devices. Not only will wearing it for a long time cause discomfort, but long-term contact measurements may also trigger allergic reactions. BCG, a signal of tiny vibrations in the body caused by the heart's pumping of blood, can be measured non-invasively by FOSs. In this work, a fiber optic interferometer-based BCG monitoring system was developed. During exercise and sleep states, the BCG signal based on the FOS has a high correlation with the reference signal collected by commercial equipment. Through the BCG signal collected by this system, the health status of the heart, such as myocardial contractility and HRV, can be analyzed. FOSs based on special optical fibers were first proposed for non-contact vital signs monitoring. One is a new online MZI sensor based on self-made SCF, and the other is an SI sensor based on self-made SH-HiBiF. The advantage of the former is that the sensor is simple to manufacture, low in cost, and has high repeatability. The advantage of the latter is that the sensing fiber used is not sensitive to temperature, and the system does not need to use demodulation to solve the signal fading problem. During the experiment, the sensing fiber was packaged under the mattress to monitor vital sign signals for a long time. Through filtering and FFT procedures, accurate RR and HR can be obtained. At the same time, the proposed system can also diagnose premature beats in a non-contact manner with an accuracy of 97.9%. Furthermore, we also propose a single-mode fiber-based MZI for non-contact vital sign monitoring. The system uses 3×3 coupler demodulation scheme to solve the signal fading problem and can be used stably for a long time. And due to its high sensitivity, this sensor can not only be placed under the mattress for sleep monitoring, but can also be attached to the wrist for pulse diagnosis. The measurement results of RR and HR at rest and during exercise showed high accuracy. This work verifies the feasibility of the proposed system in sleep, pulse diagnosis and driver monitoring applications. And the heart health status is evaluated based on the long-term BCG data collected by the proposed system.