Fig. 1. Structural schematic of breath soliton Er-doped fiber laser based on mode locking by NPR

Fig. 2. Output spectra of laser under different repetition rates

Fig. 3. Simulated results of pulse width. (a) ZDF2 with length of 0 cm; (b) ZDF2 with length of 107.5 cm; (c) output pulse width of laser for SMF1 with different lengths

Fig. 4. Output characteristics of the laser. (a) Direct output spectra and (c) output spectra after compression in linear (solid line) and logarithmic (dashed line) coordinates; distributions of pulse time domain (solid line) and phase (dashed line) for (b) direct output and (d) output after compression

Fig. 5. Output of mode-locking fiber laser. (a) Pulse trains; (b) frequency spectrum