Based On The Taper Method Preparation And Application Research Of Long Period Fiber Grating

The period of Long period fiber grating is relatively long. The phase matching conditionmeets with the core mode and cladding modes of the same direction to transmission,whichfeatures leads to the resonant wavelength and amplitude of the LPFG are very sensitive tochanges in the external environment.In this paper,we achieve the preparation of long period fiber grating by using electricheating fused method. This method has many advantages, such as ease of fabrication, goodthermal stability. Moreover, this method does not require special process,such as dopedhigh-sensitive, hydrogen loaded fiber. Electric heating fused prepared fiber grating is amodulated fiber grating structure, the structure of the fiber grating is stable at hightemperatures, and as the temperature increases, the sensitivity will be even greater,particularly suitable for the production of high temperature sensors. We carried outpreparation and sensing characteristics of long-period fiber grating based on the taperingmethod,the main research work are as follows:1. We analysis the formation mechanism and the coupling characteristics of thestructural modulation of LPFG by using an improved coupled mode theory-localcoupled-mode theory. Moreover, we give the fundamental mode of the core with a ordercladding mode coupling through simulate mode coupling characteristics. In finally, we drawthe the effective refractive index change of tapering region.2. We establish fiber fused viscoelastic finite element analysis model with ANSYS, andanalyses fiber stress-strain behavior with high temperature. The nearer to the center from theheating element, the more uniform temperature field. In the opposite, along radial direction ofthe fiber, the fiber stress distribution is unevenly far away from the heating element center.And gradually increases with the surface of the stress differential, especially in the taper waistfiber stress gradient maximum.3. We verified the viability and stability of electric heating fused prepared long periodfiber grating by experiment. And we analyze the process parameters impact on the taper areas,such as the different number of tapering, tapering depth, tapering power and tapering speed,etc. We prepare for the controllable long period fiber grating which resonant depth of20-30dB through optimization design for the parameters. 4. We launched the experimental research of temperature sensing,the axial stress andbending characteristics of the LPFG. LPFG written in a standard single-mode optical fiberbased on electric heating fused method, the resonant wavelength decreases as the temperaturerises, the sensitivity about63pm/°C. LPFG resonant wavelength and axial strain of a linearrelationship with the axial strain increases the resonance wavelength drift towards theshorter,and the sensitivity about-1.40pm/με. The sensitivity of bending characteristic about10.52nm m.