Study On Key Technologies And Applications Of Optical Fiber Sensor Networks For WIT120

WIT120（Wise Information Technology of 120）is a newly developed strategy proposed under the background of"Medical Reform"in China.With rapid development of WIT120,we gradually step into a new era of"precision medicine".The key to achieve precision medicine lies in the development of high-performance medical equipment,which allows physiological parameters to be shown intuitively for comprehensively diagnosis of health conditions.Medical mechanic sensor is one of the most widely used medical sensor,which monitors various physiological activities of human beings,such as heartbeat,breathing,limb movement and intestinal peristalsis.These biological signals are weak and with low frequency,which require high measurement sensitivity and signal-to-noise ratio.At the same time,integrated diagnostics on multiple measurement points are usually required in the definite diagnosis of one disease,so the development of networked and portable mechanical sensing device is becoming the research focus nowadays.Compared with traditional piezoelectric mechanical sensors,optical fiber sensors have many advantages,such as high measurement accuracy,good biocompatibility,immunity to electromagnetic interference,corrosion resistance,small size and ability of networking,making them the preferred solution for the development of new-generation medical diagnosis equipment.In view of the above needs in medical measurement,we proposed two types of optical fiber sensor,one is 2D encoded microstructure based optical fiber sensor,the other one is the diaphragm based miniaturized fiber sensor tip.Through sensitivity enhancement and network construction,multi-point and high-precision sensing systems have been achieved.They are promising in gastrointestinal motility detection and pulse wave monitoring,respectively.The main contents of this thesis are listed as follows:（1）Microstructure based fiber optic pressure sensor network is proposed to meet the requirements of long-distance and high-precision distributed pressure sensing in invasive detection of digestive tract.The microstructured optical fiber consists of quantities of ultra-weak twin-grating-based microstructures,which encoded in wavelength and frequency domains by setting different grating period and spacing of grating pairs.The sensing capacity of one single fiber is theoretically demonstrated to be 243.The lateral pressure sensitivity of the fiber sensor has been significantly improved by polymer encapsulating.Meanwhile,a spectral demodulation system based on wavelength scanning technique has been developed,the wavelength resolution of which is better than 1pm.Pressure signals on multiple microstructure units could be demodulated simultaneously by this means.（2）The application of microstructure fiber optic pressure sensor network in gastrointestinal motility detection has been studied.The microstructure optical fiber with a length of 50cm and 6 sensing units has been fabricated.The multi-point static pressure sensing experiment is carried out to demonstrated a pressure sensitivity of1.032?10^-3/MPa,as well as the measurement resolution of about 0.625kpa.The sensing performance of 6sensing units are in good consistent and with no crosstalk.Moreover,an experimental platform has been built to simulate the gastrointestinal pressure wave.The distribution of pressure wave has been successfully obtained by the optical fiber sensing system,which verified its good practical prospect in the dynamic detection of digestive tract.（3）Diaphragm based fiber sensor array is proposed to meet the requirements of high SNR and multi-point sensing in non-invasive acoustic signal measurement.Based on the mechanical simulation of the diaphragm structure,we introduce the acoustic sensing mechanism of the optical fiber sensor tip.Meanwhile,the phase demodulation system based on heterodyne detection is developed to improve the sensing signal-to-noise ratio.The sensitivity of acoustic sensor tip is better than-136dB re 1rad/μPa in the 300Hz¹5kHz,and the minimum detectable pressure can be calculated to be 75μPa/Hz^1/2.In addition,combined with time-division multiplexing technology,the fiber acoustic sensor array has been realized,and the capacity of which is up to 248.Multipoint acoustic sensing has been successfully realized and applied to sound source localization in two-dimensional space.（4）The application of diaphragm optical fiber acoustic sensor array in human pulse wave detection has been studied.A wearable optical fiber wristband is developed by using aluminum sensing diaphragm,which can recovery the pulse waveform with high fidelity and has the ability of multi-point measurement.Based on morphological analysis,the clinical experiments of pulse wave measurement are carried out.The results preliminarily verify the measurement reliability,which is promising in early diagnosis of cardiovascular diseases.