Fig. 1. Structure schematic of fiber filter

Fig. 2. Transmittance curve of GIMF under the length of 4.5π and 4.6π

Fig. 3. (a) Schematic setup of mode-locked fiber laser; (b) Nonlinear transmittance curves of saturable absorption; (c) SMF-GIMF-SMF under a microstretched length of GIMF of 70 μm

Fig. 4. Output characterizations of stretched pulses. (a) Output spectrum; (b) Temporal trains of pulses; (c) Radio frequency spectrum; (d) Autocorrelation curve

Fig. 5. Output characteristic at a pump current of 296 mA. (a) Output spectrum; (b) Radio frequency spectrum; (c) Temporal pulse trains; (d) Time-domain waveform of pulse

Fig. 6. Evolutionary trends under pump current in the range of 300 mA to 800 mA, measured at 100 mA intervals. (a) Evolution of pulse waveform; (b) Full width at half maximum and average power of output port