The Sensing Characteristics Of Microstructure Optic Fiber Interferometer

Photonic crystal fiber, also known as microstructure fiber, has strong flexibility in the structure design, and unique optical waveguide characteristics, known as "a new generation of optical Fiber. In 1996, photonic crystal fiber has been firstly successfully drawn, it is being paid close attention to, becomes a hot research topic in the field of optical communication, fiber sensors and fiber lasers. The types and applications of optical fiber sensors have been greatly enriched by using the transmission properties of photonic crystal fiber with interferometry and the coupled mode theory. Optical fiber Mach-Zehnder interferometer and Fabry-Perot interferometer are the most widely used for optical fiber sensors. This paper studies two different kinds of optical fiber Mach-Zehnder interferometer sensors and one optical fiber Fabry-Perot interferometer sensor, the sensing characteristics of these kinds of optical fiber interferometer sensors are analyzed by theory and experiment. The main contents are arranged as follows: 1. We introduces the classification and the research status of optical fiber sensor. Optical fiber Mach-Zehnder interferometer sensors and optical fiber Fabry-perot interferometer sensor are an emphasis on. Mainly discusses the general steps of analysis of photonic crystal fiber mode field characteristics by use of the finite element method（FEM）.2. Using commercial splicing machine, arc discharge is applied to collapse the air holes of photonic crystal fiber to product optical fiber Mach-Zehnder interferometer. Theoretical and experimental analysis of the mode characteristics of 7 layers of air hole photonic crystal fiber. The bending sensitivity of 0.53nm/m^–1 is obtained at 1586 nm for the curvature range from 2 to 8.514 m^–1. The temperature sensitivity is very low. 3. A Mach-Zehnder interferometer has been constructed by lateral offset splicing. It shows the capacity for recognizing positive and negative directions. Within a curvature range of-7.13 m^-1 to 7.13 m^-1, at 1531 nm and 1591 nm with opposite fiber orientations the bending sensitivities are obtained to be 0.484 nm/m^-1 and 0.246 nm/m^-1, respectively. 4. We introduces the optical fiber Fabry-Perot interferometer, the structure and the principle of interferometer sensor. A micro Fabry-Perot interferometer is obtained by splicing both ends of a short section simplified hollow-core photonic crystal fiber with single mode fibers. Then use a femtosecond laser micromachining a micro-channel in the simplified hollow-core photonic crystal fiber which is drilled. A Fabry-Perot interferometer with a length of 272 μm demonstrates a pressure sensitivity of 4.071 nm/MPa at 1580 nm, and a low temperature sensitivity of 1.1 pm/°C, corresponding to a low temperature cross-sensitivity of 0.27 k Pa/°C.