Research On Optical Fiber Sensors Based On The Theory Of Interference And Bragg Grating

Optical fiber sensor technology is playing a more and more important role in the modern time when information technology changes quickly with each passing day. But in the practical application of fiber-optic sensors, there remain lots of problems to be solved. Among them, fiber-optic sensors’character of cross sensitivity to different parameters at the same time catches considerable attention of many researchers. Meanwhile, this character is also the bottleneck of restricting the further development of optical fiber sensors. Two different kinds of optical fiber sensors are proposed and fabricated in this paper and the sensitivities to strain and temperature of the sensors are measured experimentally. The two sensors we made solve the problem of cross sensitivity to strain and temperature of fiber-optic sensors successfully form different aspects, respectively. The main content of the paper includes the following fields:The first chapter, the main characters, the classification and development tendency of optical fiber sensors are introduced. The features and ways to fabrication of modular interferential Mach-Zehnder and Fabry-Perot optical fiber sensors are introduced highlighted. The characters and applications of fiber Bragg grating are also introduced. In this paper, fiber-optic sensors’ character of cross sensitivity to different parameters is stated and four main solutions are proposed to solve the problem. The main content of the paper and several innovation points are also stated.The second chapter, the coherence theory of light and the conditions for effecting of light interference are summarized. The basic principles of sensing of modular interferential Mach-Zehnder sensors, Fabry-Perot optical fiber sensors and fiber Bragg grating are expounded. The advance analysis will supply theoretical guidance and gist for the subsequent experiment.The third chapter, two kinds of optical fiber temperature sensors which are insensitive to strain are proposed. The different point of the two sensors lies in that one of them is fabricated by using simple-mode fiber, while the other sensor includes photo-sensitive fiber. The procedures of fabrication of two sensors are introduced firstly and the responses to strain and temperature of the two sensors are measured afterwards. Experiment results show that the temperature sensitivity of the sensor using simple-mode fiber is 49.73pm/℃, while the other sensor 100.64pm/℃. The strain sensitivities of the two sensors are both below 1pm/με. The two sensors can be regarded as strain-insensitive optical fiber temperature sensors.The fourth chapter, a kind of dual-parameter optical sensor based on cascade Fabry-Perot cavity and fiber Bragg grating is introduced. The process of fabricating and sensing theory of the sensor is also introduced. This kind of dual-parameter optical fiber sensor can percept fiber strain and surround temperature at the same time. Further, the sensor is considerably compact and economical in cost. The strain sensitivities of FPI and FBG are 8.63 pm/με and 1.11 pm/με, and the temperature sensitivities of them are-1.60 pm/℃ and 9.75 pm/℃, respectively. As FBG and FPI have different sensitivities to strain and temperature, they can be utilized together for simultaneous measurement of dual parameters. The maximal errors in our test are 6.72με and 0.98 ℃ for strain and temperature measurements of the sensor, respectively.The fifth chapter, the venation of the whole paper is reviewed and the paper is summarized in this chapter. The shortcomings of the paper are discussed and analyzed and several new ideas are proposed towards the sensors in this paper, which can be regarded as the reference for subsequent experiments.