High-speed 340 Gbps PAM4 and 450 Gbps PAM6 Operations of Narrow High-Mesa EML. - Shinya Okuda; Asami Uchiyama; Toshiya Tsuji; Yohei Hokama; Koki Kihara; Mizuki Shirao; Takeshi Yamatoya; Yasuhiro Yamauchi (OFC, 2025)