Narrow linewidth fiber laser capable of alternately emitting continuous waves and pulse waves

The invention discloses a narrow-linewidth optical fiber laser capable of alternately emitting continuous waves and pulse waves. The narrow-linewidth optical fiber laser comprises a narrow-linewidth seed light source, a laser pre-amplification unit, a continuous and pulse light switching unit and a laser power amplification unit, the output end of the narrow linewidth seed light source is connected with the input end of the laser pre-amplification unit through an optical fiber patch cord, and the output end of the laser pre-amplification unit is connected with the continuous light input end and the pulsed light input end of the continuous and pulsed light switching unit through a first beam splitter. The continuous light output end and the pulsed light output end of the continuous and pulsed light switching unit are coupled through the first coupler, the output end of the first coupler is connected with the input end of the laser power amplification unit, and the output end of the laser ...