Research On Propagation Characteristics Of Micro-structure Fiber And Its Sensing Demodulation Technology

Microstructure fiber were fabricated periodic structure into traditionary fiber through the exposal, etch or draw technology, such as the production of photonic crystals fiber, Fabry-Perot Cavity and so on. Microstructure fiber have rich microstructure and optical properties, greatly change the structure and properties of microstructure fiber device. Colloidal photonic crystal is the sub-micron level of monodisperse colloidal microspheres with the suitable conditions, spontaneous formation of three-dimensional periodic structure in an orderly array, which have particular optical properties. Based on these microstructures, fiber was modified by colloidal crystal to form three dimensional photonic crystal fiber optical device. Because it was fabricated in common single mode fiber, the fabrication is simple and the cost is low. The research have important significance.Based on optical properties of colloidal crystals and micro-optical fiber, this paper numerically analyze structure of colloidal crystal, energy band characteristics and transmission characteristics of colloidal crystal microstructure fiber using the finite difference time domain method (FDTD). The numerical result will guide the design, production and application of colloidal crystal microstructure fiber.In this paper, the structure of colloidal crystal and transmission characteristics are presented. The structure model of colloidal crystal is established by finite difference time domain method. The transmission spectra and transmission mode of colloidal crystal are numerically simulated. The position of the photonic band gap is analyzed and the impact of different parameters on the location of band gap are discussed. The relationship of transmission characteristics and the refractive index modulation, the lattice constant and the external environment are analyzed.Based on study of colloidal crystal and micro-fiber, a new type of colloidal crystal micro-fiber is presented. Its structure and parameters are theoretically analyzed. The model of colloidal crystal micro-fiber is established by finite difference time domain method. The transmission spectrum of the structure are calculated and measured. Experimental result and theoretical calculation show that this structure exists photonic band gap in the communication band. The effect of different wavelengths on the transmission mode of microstructure fiber are analyzed. The results show that the colloidal crystals have certain impact on transmission patterns of light. In addition, the demodulation technique of microstructure fiber sensor is researched in this paper. A neural network based peak tracking demodulation method is presented and applied in the demodulation system of micro-fiber pressure sensor. The basic principles of neural network and demodulation method are theoretically analyzed, and pressure testing system is established to progress demodulation tests. The results show that the neural network method can achieve higher precision and meet the actual demand.