The Research Of Novel Large Mode Field Diameter Bend Insensitive Single Mode Fiber And Few Mode Fiber

Large-mode-field-diameter bend-insensitive single-mode fibers and few-mode fibers are the key components of the next generation of ultra high-speed large-capacity optical network, optical mode division multiplexing system, optical space division multiplexing system and high-power compact optical devices. They also have broad application prospects in the fields of optical fiber sensing, medical treatment, material processing and national defense. Under the supports of the Major State Basic Research Development Program of China (973):"Research on the theory and key techniques of optical fiber devices towards the optical switching networks", the National High Technology Research and Development Programs of China (863):"Research on160Gbit/s optical transmission technology with several fibers amplified by a pump source", and the the National Natural Science Foundation of China:"Development of new type fiber and large area active fiber for efficient enhancing anti-Stokes Raman scattering efficiency", this thesis is devoted to depth theoretical and experimental research of novel large-mode-field-diameter bend-insensitive single-mode fibers and few-mode fibers. The main achievements of this thesis are listed as follows:1. A single-mode large-mode-field-diameter bend-insensitive fiber (DIC-LMFD-BIF) is proposed. Using simple structure to achieve the performance integration of single mode propagation, large mode area and bend insensitivity. A novel semi-analytical method that we called Frustrated Total Reflection method is proposed to calculate the cutoff wavelength of DIC-LMFD-BIF. Compared with the simulation results of other numerical methods and experimental results, it proves that FTRM has accuracy and superiority.2. The samples of Er-Yb co-doped DIC-LMFD-BIF are manufactured experimentally. Put forward a simple and convenient method named Transverse Splice Loss Technique which is applicable to bend insensitive fibers to accurately measure the cutoff wavelength of samples, and compare advantages and disadvantages with other methods. A measurgin method for accurate measurement of macro-bend loss is proposed, which is applicable to bend insensitive fibers and normal optical fibers. The samples guarantee single mode characteristic at C-band. The mode field diameter increases nearly four times compared with the commercially available commercial erbium ytterbium co-doped fiber. The macro-bend loss reduces close to65times compared with standard single mode fiber at bend radius of5mm. Meanwhile, good absorption effect of rare earth ions and C-band gain flatness are achieved.3. A novel Few-Vector-Mode Fiber (FVMF) is proposed. It realizes splitting mode degeneracy group. The vector modes are effective separated. The effective refractive index difference reaches6×10-4-magnitude. The vector mode is supported to excite and transmit independently, and takes into account the large mode area. The contained stable vortex beams have the ability to generate and carrying orbital angular momentum modes. The samples of FVMF are manufactured experimentally. The experimental results verify vector-mode separation characteristic. The tested effective refractive index difference between TEO1and HE21modes of samples reach10-4-magnitude. The simulation of generating OAM modes in the FVMF is realized.4. A hole-assisted strong-coupling multi-core fiber (HA-SC-MCF) is proposed. We clearly demonstrate that the strong-coupling multi-core structure can achieve single-mode operation. This fiber has unique modal characteristic of single-mode operation, strict dual-mode operation (propagation in HE11mode and HE21mode only), and few-mode operation by flexible design. The large mode area is obtained in supermodel form. It solves the trade off between bending loss and mode area which can not be improved in ordinary multi-core structure. The bending performance is greatly improved.