Application Of Optical Fiber Sensing Structure In Measurement Of Human Cardiopulmonary Physiological Parameters

Optical fiber sensor,as the most popular representative of sensors,is one of the most potential optical devices.Large dynamic range,high sensitivity,good stability,anti-electromagnetic interference and multiple reuse are its unique advantages,which have broad application prospects in the field of human key physiological parameters measurement and biochemical detection.However,there are some bottlenecks in the application of optical fiber sensing structure in the measurement of key parameters of human body:first,how to develop a sensing structure with high sensitivity and stable performance;second,how to measure and demodulate multi-parameters simultaneously;third,how to improve the accuracy and signal-to-noise ratio of demodulation scheme.In view of this,two novel measurement schemes are proposed in this paper,which are passive sensing technology based on fiber Bragg grating and active sensing technology based on single-mode-coreless-single-mode fiber structure.In view of the related problems existing in the actual measurement of the two methods,the detailed experimental research is carried out from the three core contents of signal demodulation and denoising,sensing principle and characteristics,the fabrication of overall sensing structure and so on.The related research achievements of this paper are as follows:(1)Considering the physiological background of human breathing,heartbeat and pulse,a wavelet threshold de-noising scheme based on db wavelet is adopted to deal with the noise characteristics of the photoelectric signal conversion and receiving equipment used in the experiment.Experiments show that the scheme has good noise reduction effect on human cardiopulmonary physiological signal processing.(2)According to the development status of fiber optic human cardiopulmonary system parameter sensing at home and abroad,the measurement method based on fiber Bragg grating(FBG)is simplified and improved.A passive measurement scheme using self-luminous wave of fiber demodulator to collect pulse,breathing and heartbeat signals is proposed,which can effectively detect the important information of these three parameters.At the same time,in the data processing of this scheme,it is verified that the best denoising effect is achieved under the 8th decomposition and reconstruction of db10wavelet basis function.This effect will lay a foundation for the signal processing of the full text.(3)A novel wavelength demodulation sensing technique based on single-mode-no-core-single-mode fiber(SNS)structure is proposed for human respiration and pulse monitoring.The axial stress and transverse pressure of the SNS structure are measured.The axial stress sensitivity is about 0.634 pm/μεand the transverse pressure sensitivity is about 16 nm/N.The linearity R~2of the two structures reaches 0.9995 and0.9993 respectively.The low frequency vibration signals of 0.5 Hz-0.6 Hz can be clearly measured.The technique has the advantages of high sensitivity and compact sensor head,which can simultaneously obtain the information of respiratory and pulse parameters of human cardiopulmonary system.The waveform is clear and reliable,and has good medical reference value.The measurement results of pulse respiration in this scheme are in good agreement with the actual measurement.The measurement errors of pulse and respiration are±0.8 bpm and±1 rpm.