Research On Sensing Characteristics Of FBG/FP Hybrid Sensor At High And Low Temperature

The optical fiber grating sensor has received wide attention and research because of its characteristics in the process of structural monitoring such as resistance to electromagnetic interference,corrosion resistance,small volume,light weight,easy reuse to develop network.Compared to conventional electrical sensor,the FBG does not need to consider the tedious electrical circles and complicated shielding lines.However,the harsh environment of high and low temperature in the area such as aerospace,petroleum and chemical industry,nuclear fusion,there is more stringent requirement for the adaptation and precision of the sensor.Meanwhile,there exits strain and temperature cross sensitivity problem when the FBG and F-P sensor are used in some complex occasions.It heavily limits the application of these sensors.The thesis researches on the characteristics of the FBG sensor at high and low temperature and technology of hybrid sensor,including the decay and wavelength repeat performance of FBG in process of high temperature annealing,the measurement of elastic-optic coefficient at nitrogen temperature and the EFPI-FBG hybrid sensor with temperature compensation.The main content of thesis is as follows:The decay process of FBG was firstly studied through isothermal annealing at500 ?.Then,the multiple isochronal annealing was carried out to research on the wavelength repeat performance of FBG.The wavelength decay curve of hydrogen-loaded FBG at different temperature point was worked out.After that,the function between wavelength shift and temperature of the processed FBG which had good repeat performance was determined in the range from 18? to 500? through temperature characteristic test.The temperature sensitivity of FBG at 500 ? was worked out.The strain characteristic of FBG at low temperature was researched through static stretching in liquid nitrogen environment.Moreover,the same experiment was carried out at common temperature for comparison.The elastic-optic coefficient of FBG at common and liquid nitrogen temperature was finally determined,which is valuable for the research and application of FBG at low temperature.The high temperature resistant EFPI-FBG hybrid sensor was designed and fabricated.Firstly,the temperature self-compensation experiment was carried out at low temperature.Then,the sensor was applied to simultaneously measure the temperature and strain of TC4 titanium alloy at high temperature.It was well proved that the sensor has excellent repeat performance and measurement ability at high temperature through strain experiment.