Fig. 1. (a) ASE transmission spectrum of the EDF; (b) varied intensity differences of the ASE transmission spectrum (VOA device) with the increase of the additional intracavity loss (labeled); inset, the original spectrum of the BBS.

Fig. 2. (a) Schematic diagram of SMF-NCF-GIMF-SMF structure; (b) nonlinear saturable absorption curve of the NCF-GIMF device; inset, the transmission spectrum of the NCF-GIMF device.

Fig. 3. Schematic diagram of the experimental setup. The red arrow represents the laser direction.

Fig. 4. Conventional mode-locked single soliton outputs. (a) Optical spectrum; (b) autocorrelation trace; (c) pulse train; (d) RF spectrum.

Fig. 5. Output power of the fiber laser versus pump power.

Fig. 6. (a)–(k) Tunable spectra of the mode-locking operation in the C + L band at different additional insertion losses.

Fig. 7. Evolution of relevant parameters during tuning process. (a) Corresponding central wavelengths at different intracavity losses; (b) pulse energy and average power after subtracting the CW light as functions of the tuning wavelength; (c) pulse width and 3-dB bandwidth as functions of the tuning wavelength.

Fig. 8. (a)–(e) Different spectra of dual wavelength; (a1)–(e1) corresponding autocorrelation traces; insets: wide-range autocorrelation trace diagram.

Fig. 9. (a) Pulse train of the dual-wavelength; (b) corresponding RF spectrum.

Fig. 10. Controllable pulse energies of the dual wavelength. (a), (b) The spectra; (c), (d) corresponding autocorrelation traces; insets: wide-range autocorrelation trace diagram.