Fig. 1. Experimental setup of L-band switchable dual-wavelength passively mode-locked fiber laser based on CNT-SA

Fig. 2. Output of mode-locked fiber laser centered at 1596.6 nm when pump power is about 57.3 mW. (a) Optical spectrum, autocorrelation signal of pulse, and hyperbolic secant fitting curve; (b) frequency spectrum (insert is impulse sequence)

Fig. 3. Output of mode-locked fiber laser centered at 1572.9 nm when pump power is about 67.1 mW. (a) Optical spectrum, autocorrelation signal of pulse, and hyperbolic secant fitting curve; (b) frequency spectrum (insert is impulse sequence)

Fig. 4. Output of dual-wavelength mode-locked fiber laser when pump power is about 64.8 mW.(a)(b) Output before filter; (c)(d) output after filter, and insert in Fig. 4(c) shows autocorrelation signal of pulse

Fig. 5. Stability test results of L-band dual-wavelength mode-locked fiber laser. (a) Spectra; (b) output power

Fig. 6. Numerical simulation results of laser. Simulation results about evolution of single-wavelength mode-locked spectra at (a) 1592 nm-band and (b) 1572 nm-band, respectively; (c) simulation result of dual-wavelength mode-locked spectra (three inserts show spectra of different Lorentz transmissivities)