Fig. 1. Experimental setup of mode-locked erbium-doped fiber laser for generating square pulses

Fig. 2. PID control schematic, where e(t) is the input electrical signal, and u(t) is the output signal calculated by PID algorithm

Fig. 3. Schematic diagram of experimental setup for real-time shaping of optical pulses

Fig. 4. Square wave pulses output from mode-locked fiber lasers. (a) Time-domain waveform; (b) pulse train; (c) spectrum

Fig. 5. Temporal waveforms of single square pulse after being amplified to different levels

Fig. 6. Shaping of square wave pulses with different pulse widths. (a) Waveforms of square pulses with different pulse widths before and after shaping; (b) comparison among ideal,initial,and shaped square pulses with pulse width of 130 ns in time-domain; (c) comparison among ideal, initial, and shaped square pulses with pulse width of 210 ns in time-domain

Fig. 7. Comparison of the spectra of square wave pulses before and after shaping. (a) Spectrum of the 210 ns square wave pulse before shaping; (b) spectrum of the 210 ns square wave pulse after shaping; (c) spectrum of the 400 ns square wave pulse before shaping; (d) spectrum of the 400 ns square wave pulse after shaping