Four-channel 200 Gb/s PAM-4 electro-absorption-modulated laser module

In this paper, we propose a four-channel 200-Gb/s four-level pulse amplitude modulation (PAM-4) optical transmitter module. Electro-absorption-modulated laser (EML) transmitting optical sub-assemblies (TOSAs) were used as the light sources. The performance and eye diagrams of the EML TOSAs were measured and verified to be operated at 25 Gb/s non-return to zero (NRZ) and 53 Gb/s PAM-4. Using four EML TOSAs and a commercial quad-channel linear EML driver, we design the four-channel 200-Gb/s PAM-4 optical transmitter module. The printed circuit board (PCB) of this module used a four-layer board, and the high-frequency board material is Rogers 3003. The electrical interface of this module used a SMPM connector. The 53 Gb/s PAM-4 eye diagrams of this module were measured; the extinction ratios of four channels were 6.32, 6.33, 6.31, and 6.46 dB, respectively; the TDECQs were 2.75, 2.65, 2.57, and 3.1 dB; and the OMAs were 3.74, 3.76, 3.75, and 2.65 dBm. The PAM-4 eye diagrams without equalization meet the 200GBASE-ER4 Ethernet specification. Our optical transmitter module could be applied to 200G Ethernet.