Design And Analyze Of Optical Fiber Microbend Displacement Sensor

As an intensity modulated optical fiber sensor, optical fiber microbend sensor can obtain under test environmental parameters such as displacement, pressure, temperature, acceleration, strain, rate of flow and speed, by measuring the transmitted light intensity changes caused by micro-bending of the optical fiber. It has such advantages as simple structure, low cost and convenience installation, etc.The main contents of this paper are as follows:(1)The state of domestic and international development of optical fiber microbend sensor is firstly reviewed and factors affecting the sensitivity of the sensor are analyzed using coupled-mode theory.(2)The design, preparation and debugging of a kind of fiber microbend displacement sensor are accomplished as the choices of period, number of teeth and pitch in microbending are determined according to the best microbending period and the fiber deformation attenuation coefficient.(3)Design of the differential fiber microbend sensor as well as programming of PC software are fulfilled in which the photoelectric detection circuit is devised using photodiode trans impedance amplification and two amplifiers.(4)taking screw micrometer and laser interferometer as displacement benchmarks, experiments on displacement measurement of the sensor are carried out and the effect on displacement measurement range and sensitivity from pitch and the number of teeth is analyzed.Experiment results show that the displacement measurement range increases while the sensitivity decreases with the increase of pitch and the number of teeth. The measuring range of the designed sensor is up to 0~300μm and the sensitivity is about 0.240.24mv/um at the range of 150~250μm with relative measurement error less than 3%.