Research On Cylindrical Microbending Optical Fiber Sensor

With the optical fiber and optical fiber communication technology continues to evolveand mature, the optical fiber sensing technology has been rapidly developed. As an importantoptical fiber sensors, micro-bending optical fiber sensors have many advantages, such ashigh sensitivity, small size, low price, simple structure and suitable for application in harshenvironment, etc. This thesis mainly focuses on A Cylindrical Micro-bending Optical FiberSensor that based on light intensity modulation.This thesis described the principle of the optical fiber micro-bending loss, which mainlyanalyses by the light theory and mode coupling theory. Mode coupling theory providedseveral micro-bending loss functions with different micro-bending curvature pulse functions.The author designed a new cylindrical micro-bending sensor, whose sensitivity was highlyimproved compared with the previous micro-bending optical fiber sensors. And itssensitivity can be adjusted as request by changing the number of serrated, the slot pitch ofthe inner shell and the turns of winding optical fiber, which can be adjusted in a wide rangesimply. In this thesis, on the one hand, the author built the theoretical model of the newstructure, and established the relationship between displacement and loss from the differentdirection of the force and carried out the simulation by matlab. From the simulation picturewe can see the sensitivity of the sensor can be adjusted more than two orders of magnitudeby changing the slot pitch of the inner shell. The sensitivity is9.3887dB/μ mwhen the slotpitch of the inner shell is1.11mm and the turns of winding optical fiber are100. On the otherhand, the author also used OptiBPM simulate the fiber optical field distribution in the bentfiber, influenced by the fiber bending cycle, the fiber radius, the wavelength of incident light.The author has tested the cylindrical micro-bending optical fiber sensor. And the resultsshow that the changing trend of the experimental data and theoretical data is consistent, butthere is a gap between them, with an average error of12.7%. At last the author analyzed theerror in experiment and gave the improving measure.