▎ 摘　　要

NOVELTY - The system has an optical fiber laser (101) that adopts polarization-preserving fiber resonant cavity. A coupler (104) welds the polarization-preserving fiber and polarization device along precise alignment. A circulator (105) has high isolation so that laser is transmitted as one-way in the cavity. A laser diode (106) is composed with single mode tail fiber output reverse pump. A mirror (103) is effectively accessed via cavity to reflect using five-layer graphene as saturable absorber to obtain basic order mode locking pulse and to obtain second order mode-locked pulse. USE - Optical fiber laser system capable of switching base and second order harmonic mode locking. ADVANTAGE - The structure is compact. The structure has high stability, high conversion efficiency, good light beam quality. The maintenance of the structure is easy and the cost of the structure is low and the structure has wide application prospect. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the structure of optical fiber laser system. (Drawing includes non-English language text) Polarization-maintaining erbium-doped optical fiber laser (101) Saturable absorption mirror (103) Output polarization maintaining coupler (104) Polarization maintaining circulator (105) Laser diode (106)