Research On Sensing Properties Of Seven Core Fiber

Fiber optic sensor is one of the more mature sensors.It has the advantages of high sensitivity,anti-electromagnetic interference,corrosion resistance,and adapting to harsh environment.In recent years,it has widely been used in the sensing field.Multi-core optical fiber is a new kind of special optical fiber in recent years.Using this kind of optical fiber,the mode interferometer can be fabricated and applied in sensing field.At the same time,there are cross-sensitivity problems in any sensing process,so the measurement of composite parameters has important research significance.In this thesis,the characteristics of seven-core optical fibers for sensing liquid level and temperature are studied.The simultaneous measurement of temperature and liquid level is also studied.It is helpful to further use the advantages of seven-core optical fibers in sensing field and expand its applications.Firstly,the background and significance of our work and optical fiber sensors are described.The classification and research hotspots of optical fiber mode interference sensors are introduced.The research status of optical fiber composite parameter sensors,which focus on the multi-core optical fiber,are described in detail.Secondly,the theory of optical fiber mode is expounded,and the sensing principle of the mode interference in optical fiber is explained.The sensing principle and error analysis of multiple parameters measurement are discussed.The resolution calculation formula of the sensor for simultaneous measurement of two parameters is given.Thirdly,the sensing characteristics of mode interferometer with seven-core fiber are studied.Four kinds of optical fiber sensors are designed and fabricated.The first sensor has two up-tapers.The second sensor consists of an up-taper and MMF.The third sensor is composed of an up-taper and a spherical reflection end.The final sensor is combined by MMF and a spherical reflection end.The liquid level and temperature characteristics of the four sensors are measured experimentally.Finally,in order to solve the cross-sensitive problem of the temperature in liquid level sensing,we use the optical fiber sensor with two up-tapers or with an up-taper and MMF to measure composite parameters.These two kinds of sensors are cascaded respectively with FBG to realize the simultaneous measurement of both temperature and liquid level.