Research On The Performance Of The Refractive Index Sensor Based On Photonic Crystal Fiber Grating

The fiber grating refractive index sensing technology is a novel technology thatemploys the fiber grating as signal converter. It determines the biological and chemicalparameters by measuring biological and chemical sensitive films directly or indirectly. Ifbiological and chemical parameters change, the refractive index of biological or chemicalsensitive films changes accordingly due to chemical reactions. The air-holes of photoniccrystal fiber can be treated as thin passages for measured medium. Only nano-liter of gasor liquid is required to be sensed. By optimizing the structure of the fibers, higher sensingsensitivity can also be achieved. Nowadays, photonic crystal fiber grating is more andmore promising in fiber sensing area with the development of experimental condition. Inthis thesis, the sensing sensitivity of two fiber grating, namely grapefruit photonic crystalfiber Bragg grating and grapefruit photonic crystal fiber long period grating is researched.Their performance on refractive index sensing is studied. The main contents include:Firstly，the concepts of photonic crystal fiber and its properties are introducedbriefly. Several numerical methods for photonic crystal fiber analyzing are deduced.Their differences are compared. Coupling-mode theory and transmission matrix method,which are two of methods for analyzing transmission property of photonic crystal fibergrating, are introduced.Secondly，the reflectance spectrum of grapefruit photonic crystal fiber Bragg gratingis simulated by transmission matrix method. The relation between resonance oscillatingwavelength of the fiber grating and the refractive index of liquid filled in its air-holes isstudied. By considering the thermal expansion and thermo-optic effect, the temperaturesensing sensitivity of grapefruit photonic crystal fiber Bragg grating is obtained.Thirdly, the transmission spectrum of grapefruit photonic crystal fiber long periodgrating is simulated by transmission matrix method. The relation between resonanceoscillating wavelength of the fiber grating and the refractive index of liquid filled in itsair-holes is studied. By considering the thermal expansion and thermo-optic effect, thetemperature sensing sensitivity of grapefruit photonic crystal fiber long period grating is obtained.At last, the refractive property and temperature property of grapefruit photoniccrystal fiber Bragg grating and long period grating is investigated experimentally. Theexperimental results are analyzed thoroughly. The feasibility by using photonic crystalfiber grating as sensor is validated.