Study On The Fundamental Properties Of Tapered Microstructure Optical Fibers

Tapered microstructure optical fibers based on microstructure optical fiber are drawn by the second processing technology, the microstructure structure in the cladding and the tapered shape have resulted in some unusual properties unattainable with conventional tapered fiber. Therefore, tapered microstructure optical fibers with these unusual properties have great potential applications in many fields, such as optical communication and optical device. The fundamental properties of tapered microstructure optical fibers are investigatedtheoretically in this paper, the main content includes that:First, several numerical simulating methods are introduced. The fully vectorial effective index method simulating tapered microstructure optical fibers is analyzed in detail, and the parameters which are important in the simulating process are optimized. The nonlinear characteristic equation of tapered microstructure optical fibers successfully is resolved by Monte Carlo method and Fortran language.Second, the principle properties of tapered microstructure optical fibers is investigated by the fully vectorial effective index method, including the effective normalized frequency, the power fraction of the fundamental mode in the core, the dispersion and the nonlinear coefficient. It is found that the structure parameters at two ends and the shape of tapered microstructure optical fibers have an important influence on its properties. The multi-single mode conversion can be achieved by the difficulty between the thick end and the thin end, and convex tapered microstructure optical fibers with higher air-filling fraction have higher transmission efficiency.Third, the adaptive split-step Fourier method basing on the split-step Fourier method for tapered microstructure optical fibers is established, and the propagation and evolution of super-short pulse with different parameters at different dispersion regions in tapered microstructure optical fibers are simulated by this method. The initial peak power, duration and frequency chirping affect the pulse evolution at different dispersion regions are mainly investigated and analyzed. It is found that the effect of self phase modulation is stronger than that of group velocity dispersion for high peak power, frequency spectrum at any regions is expanded, the expansion of frequency spectrum and the smoothness are determined by the initial peak power, durations and frequency chirping.