| Pulse signal is generated by the heart beat which spread along the outer peripheral arteries and blood, it contains a lot of information about the characterize health, it can reflect the physiological characteristics of blood diseases. Wearable health monitoring device is a kind of portable device which uses wearable biosensor collecting human movement and physiological parameters. The device can realize human healtly detection at low physiological, psychological load conditions. Researching on wearable health monitoring device with the function of pulse detection has high application value on cardiovascular disease detection and treatment.In this thesis, the pulse wave detection system of fiber grating based on mode interferometer is studied. On the basis of analyzing the principle of fiber Bragg garting sensing and compared with different demodulation methods of fiber Bragg grating, a pulse wave detection system based on In-line MZI is presented and its system is designed. The In-line MZI is fabricated by photonic crystal fiber (PCF) under the collapse fusing process. The optical path part of the system is designed by using the SLED light source, circulator, coupler, In-line MZI and photodetector. The hardware of the demodulation circuit is designed with the microcontroller of STM32F103RCT6, which includes the photo-electric conversion circuit, signal conditioning circuit, STM32 processor (ARM) circuit, A/D conversion circuit, TF card storage circuit and WiFi transmission circuit. The software of the ARM processor is written in C language, including the main program, A/D conversion program, TF card storage program and WiFi transmission program. The program of host-computer is written in G language under the Lab View environment. The program can realize the function of pulse signal demodulation, collection, storage and transmission. A platform of fiber grating pulse wave detection system based on mode interferometer is built to do experiments, the experiment results indicate that the system can achieve linear demodulation within the range of 2nm, with a wavelength sensitivity of 0.055nm-1 and a wavelength resolution of 2.2pm. The detection system can meet the requirements of human pulse signal detection.The fiber grating pulse wave detection system based on the mode interferometer can realize the detection of the pulse signal successfully with the advantages of simple structure, low cost, small size, high stability and so on. The system meet requirements of wearable health monitoring devices which detecting fiber grating pulse wave. It has important theoretical significance and high application value on the detection and treatment of cardiovascular disease. |
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