[2] [2] Xiao Y, Liu Y, Zhang Y, et al. 35 km amplifier-less four-level pulse amplitude modulation signals enabled by a 23 GHz ultrabroadband directly modulated laser[J]. Journal of Semiconductors: English Edition, 2020, 41(3): 4.

[12] [12] Moon, Byunghyuck Kim, Yong SooJu, et al. Pulse-amplitude equalization in the monotonic region of the modulator of a rational-harmonically mode-locked fiber ring laser[J]. Laser Physics: An International Journal devoted to Theoretical and Experimental Laser Research and Application, 2020, 30(11): 126-132.

[14] [14] Won Y Y, Sang M Y, Kang J, et al. Simultaneous optical transmission of pulse amplitude modulation and discrete multitone signals in passive optical link using derivative and subtractive equalization[J]. Optical Engineering, 2021, 60(11): 116101-116109.