At present, the development of new communication bands to meet the needs of large communication transmission capacity in the current era is one of the key research topics. The conventional erbium-doped laser is limited by its structure which has the problem of short luminous bandwidth and can not cover a large communication band. Therefore, there is growing interest in designing bismuth-doped glass and fiber with ultra-wide gain bandwidth for fiber laser applications. By utilizing its ultra-wide gain bandwidth characteristics, important communication devices such as broadband fiber amplifiers and broadband tunable fiber lasers can be designed to operate in the L+band, thereby solving the problem that the ultra-wide bandwidth of the optical communication window cannot be achieved in the future high-speed communication systems. In this study, the 1550nm pump source is used to excite the bismuth-doped fiber, and the MATLAB numerical simulation modeling is used to design a bismuth-doped fiber laser with a central wavelength of 1650nm and a threshold power of 10W. To a certain extent, this design addresses the research gap in L+ band bismuth-doped fiber lasers.