Design And Research Of Composite Structure Optical Fiber Interferometer Strain Sensor

With the development of our society,sensors play an increasingly important role in infrastructure construction,aerospace industry,ultra-precision control machining industry.Optical fiber sensors feature small volume,low cost,and easy to integration.They are more popular than traditional electronic sensors in several areas,for instance,structural monitoring,aerospace industry and ultra-precision machining control industry.In this paper,two types of composite structure fiber strain sensors were proposed by introduce Mach-Zehnder-interferometer(MZI)and Fiber Sagnac interferometer(FSI),respectively,in a Fabry–Pérot interferometer.Hence,the measurement error of FPI strain sensor at high temperature caused by temperature cross-sensitivity and the problem of inaccurate measurement caused by low sensitivity could be overcome.The main contents and innovations of this paper are as follows:(1)MZI mechanism and FPI mechanism are simultaneous realized in a sensor only by introduce a section of micro-cavity.The output signal of the two mechanisms output from two different ports,so that the signal would not hamper by each other and easy to demodulation.Take advantage of the different response characteristics of strain and temperature of MZI and FPI.The temperature cross-sensitivity is successfully alleviate by simultaneously measured the temperature and strain with the help of matrix method.Experiment shows that the strain sensitivity of the proposed sensor is 4.24 pm/?? and it can work steadily at 800?.Such a sensor is helpful to solve the problem of measurement error of FPI strain sensor caused by high temperature environment.(2)A composite structure fiber strain sensor is proposed by introduced a FSI on the basis of FPI and the FPI is built-in FSI.The vernier effect would generate in output spectral by reasonably design the free spectral region of two interferometers.The sensitivity of the proposed sensor is amplified by vernier effect thus the measurement error caused by low sensitivity of FPI strain sensor can be alleviated.Experiment results show that the sensitivity the proposed sensor base on vernier effect is 65.1 pm/??,which is 19.7 times higher than that of the traditional single FPI sensor.It is the highest sensitivity of FPI strain sensor so far as known.The proposed sensor plays an important role in solving the problem of inaccurate measurement caused by low sensitivity of optical fiber strain sensor in engineering.