Research On The Multi-Wavelength Fiber Laser Based On The Strong Coupled Twin-Core Fiber And The Few-Mode Fiber For The High-Power Fiber Laser

On one hand, for WDM system in the high-speed optical transmission network, we have designed and fabricated Er-doped strong coupled twin-core fibers, fabricated some comb filters based on these twin-core fibers and then set up some multi-wavelength fiber lasers based on these comb filters. On the other hand, for high power fiber lasers, we have proposed some few-mode fiber designs and investigated numerically their great potential, we have analyzed numerically the gain competition between different modes in few-mode active fibers, and we have set up a measurement system of rare-earth ion concentration in silica preforms and measured the longitudinal and radial concentrations of rare-earth ions in the preform cores. This work is supported by National Natural Science Foundation of China, the National 973 Program, Fundamental Research Funds for the Central Universities. The main achievements are listed as follows:1. Based on home-made Er doped strong coupling twin-core fiber, we fabricated a fiber device with the functions of comb filter and gain medium and set up multi-wavelength fiber lasers.2. We proposed some rod few-mode fiber designs for high power fiber lasers. The HOM suppression and large mode area is investigated.3. We proposed the modified multi-trench fibers with gaps. The effective mode area is about 920μm2 at 20cm bending radius and 50μm fiber core. In the modified multi-trench fiber with four gaps, the excellent HOM suppression is over ±22° bending orientation. To simplify the fiber structure, in the modified multi-trench fiber with two gaps, the excellent HOM suppression is over ±14° bending orientation, the ratio between the core diameter and the gap width reduces and the fabrication difficulty reduces.4. We proposed a two-layer low-index trench fiber with parabolic profile core. The effective mode area in this fiber is independent on the bending radius, 890μm2. The excellent high order mode (HOM) suppression is investigated. Given the fabrication, our design can be fabricated by conventional processes, such as MCVD with careful control, and the rare-earth ions can also be easily doped simultaneously.5. We set up a measurement system of rare-earth ion concentration in silica preforms. And we measured the longitudinal and radial concentrations of rare-earth ions in the preform cores. We have analyzed numerically the gain competition between different modes in the few-mode active fiber with forward pump light, and these results could help optimize fiber designs and fiber lasers.