Two-parameter Sensing Performance Based On Fiber Intermode Interference Structure

In recent years,due to the advantages of simple structure,low cost,strong anti-electromagnetic interference ability,and easy to realize multiple physical quantity measurement,the dual parameter sensor composed of special fiber cascaded single-mode fiber inter-mode interference structure has attracted the attention of many scientists.Combined with the simulation software Rsoft,the optical transmission path of optical signal is simulated,and different sensing structures are built to realize the simultaneous measurement of temperature and refractive index.The main work contents are as follows:1.Firstly,the four traditional interferometric sensing structures are briefly introduced,and the advantages and disadvantages of Mach-Zehnder interferometric structures are analyzed,and the current research status of multi-parameter optical fiber sensing structures is introduced.Then the interference principle of optical fiber inter-mode interference is analyzed,and simulation software Rsoft is used to simulate the energy distribution of light field under different external refractive index,which provides an important basis for the design ideas and theoretical research of optical fiber sensor in the following chapters.2.A temperature-insensitive refractive index fiber sensor based on thin-core fiber and coreless fiber is designed and studied.The laser beam propagation method was used to simulate the internal optical field distribution with external refractive index of 1 and 1.3333,and the sensing structure was built.The theoretical simulation and experimental results were in good agreement.The dipA and dipB refractive index sensitivities were 101.9446 nm/RIU,R~2=0.9904 and R~2=0.9845,respectively.3.A kind of fiber sensor based on taper cascaded fiber gratings(FBG)for temperature and refractive index measurement is designed and studied.The experimental results show that when the diameter of taper waist is 29.6?m,the measurement sensitivity can reach the best.The MZI sensitivity to refractive index was 201.7157 nm/RIU,R~2=0.9823,and the FBG sensitivity to refractive index was 80.6 pm/RIU,R~2=0.9911.The temperature response sensitivity of MZI and FBG were 87.4 pm/?,R~2=0.9911 and 13.5 pm/?,R~2=0.9832,respectively.4.A kind of double-parameter sensor based on the refractive index and temperature of coreless fiber hollow fiber coreless fiber is designed and studied.The temperature sensitivity of the fiber sensor is 99.2 pm/?,R~2=0.9874 in the temperature range of 35??145?.Under the refractive index range of 1.3333?1.3794,its refractive index sensitivity is-58.2439 d Bm/RIU,R~2=0.9736,which effectively realizes the simultaneous measurement of liquid refractive index and temperature under the external environment.5.Design and study a kind of fiber sensor based on the temperature and refractive index of double MZI of the misplaced coreless fiber cascaded photonic crystal,and use Rsoft to simulate the distribution of the internal light field of different lengths of the misplaced coreless fiber.In terms of the experimental results,two physical quantities,temperature and refractive index,are explored.In terms of temperature,wavelength drift is represented,and in terms of refractive index,intensity change is represented.In the range of 1.3333?1.3534,the refractive index sensitivity of the optical fiber sensor can reach-218.5606 d B/RIU,R~2=0.9916.In the temperature range of 30??120?,the temperature sensitivity can reach0.0809 nm/RIU,R~2=0.9859.