A 224 Gb/s EML Sub-Assembly With Electro Optical Bandwidth of 60 GHz for 800GbE Applications

An EML sub-assembly with a terminating resistor optimized for maximum electro-optical bandwidth was successfully demonstrated for 800 GbE applications. To improve the 3-dB electro-optical bandwidth, we employed a newly developed EML with a shorter EA modulator less than 120 $\mu \text{m}$ long, and adjusted the terminating resistance of the transmission line. The fabricated EML sub-assembly exhibited a wide 3-dB bandwidth of 60 GHz without resorting to special assembly techniques such as flip-chip bonding and very short wiring. Furthermore, clear eye openings were obtained for 98 Gbaud PAM4 operation and also 112 Gbaud PAM4 with no sign of excess jitter or overshoot due to pattern effects caused by the modified terminating resistor.