Fig. 1. Experimental setup for realizing the rectangular SBS filter. PC, polarization controller; AWG, arbitrary waveform generator; DML, directly modulated laser; EDFA, erbium-doped fiber amplifier; TLS, tunable laser source; MZM, Mach–Zehnder modulator; FBG, fiber Bragg grating; ISO, isolator; EVNA, electrical vector network analyzer; PD, photodiode; ATT, optical attenuator.

Fig. 2. In-band gain ripple and average current waveform repetition period relation with different fiber lengths of 0.2, 10.2, 20.4 km.

Fig. 3. Gain profile versus frequency at different current waveform repetition periods, including (a) 100 ns, (b) 33 ns, (c) 20 ns, (d) 14.29 ns, (e) 12.5 ns, (f) 10.53 ns, (g) 9.091 ns, (h) 8.33 ns, (i) 6.25 ns, (j) 5 ns, (k) 2.5 ns, and (l) 2 ns.

Fig. 4. Relation between temporal current waveform and chirped light spectrum of DML.

Table 1. Comparison Between External Modulation Scheme and Direct Modulation Scheme