Research On Polarization-maintaining Photonic Crystal Fiber Loop Mirror Sensing Technology

Polarization-maintaining photonic crystal fiber (HiBi-PCF) is made of micro-structured cladding with air holes and pure silica core. It has many characteristics, such as single endless mode, unusual chromatic dispersion, excellent nonlinear effects, and good birefringence effect. And the characteristic of birefringence can be used for interferometric sensors. Fiber loop mirror has been extensively studied in recent years because of its simple structure, small size and high sensitivity. There are more and more advantages of this structure, and so, there become more and more sensors based on such structure. However, flaws still exist. For example, the sensor output will be affected seriously or even wrong if the fiber loop mirror is squeezed, bended or twisted by external circumstances. Therefore, this structure is far less practical. Fiber loop mirror with an output probe can ensure not only the embedded use, but also the stability in measurement process of the fiber loop mirror, which makes it able to be a sensing unit in practice.In this thesis, the fiber loop mirror and HiBi-PCF are combined based on lots of domestic and international literatures. To explore the advantages of the combination, a displacement sensor and a angle sensor based on fiber loop mirror with an output probe using HiBi-PCF are designed here. In view of the above problems, the thesis finishes the following four parts of work:Firstly, the present situation of HiBi-PCF and conventional fiber loop mirror are given at home and abroad, and then a summar of the research on the combination of sensing applications, which will provide the reference for the design of the displacement sensor and the angle sensor;Secondly, polarization properties of HiBi-PCF are given, as well as fiber loop mirror theory analysis tool:Jones matrix. Then the basic structure and theory analysisof conditional fiber loop mirror and its improved form are described to provide the basis theory analysis for the displacement sensor and the angle sensor. Besides, the application of finite element and Mathematica in this design are also described in this part;Then comes the core of theoretical analysis in the thesis. The two kinds of sensors’ theory are deduced in detail with the help of Matlab and Mathematica based on Jones matrix, and then simulation results are analyzed. For displacement sensor, a higher resolution can be demodulated by the mobile of interference spectrum generally; And for angle sensor, there are two kinds of demodulation method. They’re based on the mobile and energy change of interference spectrum, respectively. And they have each advantages and disadvantages;The last part of the thesis is the experiment of the angle sensor based on HiBi-PCF fiber loop mirror with an output probe. The experiment system and the production of the part devices and the experiment procedures are described here. Besides, the data collected from spectrometer is filtered, processed, integrated, then the resolution is demodulated based on the mobile and energy change of interference spectrum. And the two kinds of demodulation methods are compared.It’s wise to combine HiBi-PCF and fiber loop mirror, the best value, the best match. Traditional sensor is difficult to achieve the level number of μm, even could, volume and sensitivity are constrained. However, the combination of HiBi-PCF and improved fiber loop mirror can achieve this using birefringence with a small volume, and without the affect of temperature, which is the direction of precision sensors in future.