| :In the early1980’s, since the advent of hollow core optical fiber, because of its special transmission performance、optical properties、spatial single mode、 polarization control、low loss and other characteristics, researchers have carried out researches on this novel fiber. So far, the hollow optcial fiber can be divided into Bragg fiber、hollow core photonic crystal fiber (HC-PCFs)、the ring structure of the Bragg fiber.The hollow optical fiber has been applied to many fields, including military and optical information storage areas etc. Obviously, the application succes based on hollow optical fiber can’t do without the reasonable design of its structure. But, there are not a good many related report for the mode characteristics based on the parameters change of hollow optical fiber. This article is precisely based on this point, aiming at the typical three layer structure of hollow optical fiber(ie,hollow area(filled with air)、core regin、 cladding region), the author has done mainly in the following aspects:1)calculate the characteristic equation of each model based on hollow optical fiber, such as, the eigen value equation of HEmn and EHmn、the eigen value equation of TEom and TM0m、the mode field distribution of each mode and transmission characteristics2) simulation analysis of structure parameters of hollow optical fiber, such as analysis of the effective area of HEmn and the effective index of HEmn based on the parameters change of hollow radius、core thickness、refractive index difference、 wavelength、the number of cladding layerOn the basis of above analysis, the hollow optical fiber is applied to the mode conversion device; So, two kinds of mode conversion structure will be devised:1)the mode converter based on SMF+HCF+MMF2) the mode converter based on SMF+HCF+LMFLPo1has been converted into LP02through hollow optical fiber. Based on several important parameters, including air diameter、length、refractive index difference, are analyzed on the output power of LP02mode、mode conversion efficiency、extinction ration, optimization of structural parameters. Getting the better effect of mode conversion. |
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