Simulation And Analysis Of Side-polished Photonics Crystal Fiber And Its Coupling Device

Photonic crystal fiber (PCF) is extensive studies as a new type of optical fiber,with its compact microstructure and unique optical properties. The side-polishedphotonic crystal fiber (SPPCF) offers the new research direction for design andfabrication of new fiber optic device. The simulation calculation of side-polishedphotonics crystal fiber’s optical propagation characteristics and its coupled device canprovide the theoretical basis for the experiment.In this thesis, we research optical propagation characteristics of side-polishedphotonics crystal fiber and the coupling characteristics of its coupled device by usingthe method of numerical analysis, the primary research work and achievements are asfollows:1、We built the optical model of D type of side-polished photonics crystal fiberwith side-polished transition area. Both the attenuation of optical power and the fielddistribution of propagation modes in the device of SPPCF were calculated andanalyzed with the variation of the factors, such as: residual radius after sidepolishing, axial rotation angle, the length of side-polished area, and refractive index ofexternal environment, by using the three-dimensional finite difference beampropagation method (3D-FDBPM) in Rsoft software. The analysis results show thatthe shorter the residual radius is, the larger the attenuation of the optical power inSPPCF is; the optical power of LP01of the SPPCF is attenuated in the side-polishedarea, and recovered after light pass through the side-polished area. When the residualradius is longer than0.5μm, there is a smaller difference between the attenuations ofoptical power of PCFs polished at different axial rotation angles. When residual radiusis small enough, the high order modes appear during the light pass through theside-polished area. The mode field distribution is the most dispersive one and manyhigh order modes appear in side polished area when axial rotation angle is30o.Whenthe residual radius is longer than1.5μm, the change of the side-polished length has alittle impact on the attenuation of optical power in SPPCF; when the residual radius is shorter than1.5μm, the attenuation of optical power changes in oscillation as theside-polished length varies from shorter to longer. when the refractive indexabsorption factor in side-polished area is1, the shorter the residual radius is, the largerthe attenuation of the optical power in SPPCF is, as R in the range of7.5μm to1.5μm.when the refractive index in side-polished area is close to1.45, which is the refractiveindex of PCF, there is a great and quickly attenuation of optical power inside-polished area. The mode field distribution is shifted toward the high refractiveindex side-polished area, when polishing fluid in side-polished area infiltrate into theair holes which have been polished; As the residual radius is shorter than6.5μm, theoptical power of LP01of the SPPCF is attenuated rapidly to zero in the side-polishedarea.2、Based on the optical model of the side-polished single-mode fiber (SPF), thecoupling optical model of SPF and micro optical fiber (MF) is established. Thecoupling efficiency were calculated and analyzed with the variation of the factors,such as: residual thickness of SPF after side polishing, the diameter of MF, the radiusof curvature of MF’s bending part, by using the finite difference beam propagationmethod (FDBPM) in Rsoft software. The analysis results show that when the launchlight input from MF, the coupling efficiency is higher. The short the residual thicknessof SPF, the larger the optical power transmittance, which is coupled into SPF. Whenthe diameter of MF is6μm, the coupling efficiency is highest. As the radius ofcurvature of MF’s bending part increase from360μm to1000μm, the optical powertransmittance, which is coupled into SPF, is reduced first，and increased soonafterwards.3、Based on the coupling optical model of SPF and MF，the coupling opticalmodel of SPPCF and MF is established. The coupling efficiency were calculated andanalyzed with the variation of the factors, such as: residual radius of SPPCF after sidepolishing, the diameter of MF, the radius of curvature of MF’s bending part. Theanalysis results show that when the launch light input from MF, the short the residualradius of SPPCF, the larger the optical power transmittance, which is coupled intoSPPCF. When the diameter of MF is9μm, and the radius of curvature of MF’s bending part is1000μm, the optical power transmittance which is coupled into SPPCFis the largest, the coupling efficiency is the highest.The innovations of this research work are:1、The optical model of D type of SPPCF has been built, and the opticalpropagation characteristics of SPPCF are calculated and analyzed.2、The coupling optical model of SPF and MF, and similarly the coupling opticalmodel of SPPCF and MF are established. The coupling efficiency were calculated andanalyzed with the variation of the factors.