Today, one of the key challenges of graphene devices is establishing fabrication processes that can ensure performance stability and repeatability and that can eventually enable production in high volumes. In this paper, we use up-scalable fabrication processes to demonstrate three five-channel wavelength-division multiplexing (WDM) transmitters, each based on five graphene-silicon electro-absorption modulators. A passivation-first approach is used to encapsulate graphene, which results in hysteresis-free and uniform performance across the five channels of each WDM transmitter, for a total of 15 modulators. Open-eye diagrams are obtained at 25 Gb/s using $ 2.5\;{{\rm V}_{{\rm pp}}} $2.5Vpp, thus demonstrating potential for multi-channel data transmission at ${5}\times {25}\;{\rm Gb/s}$5×25Gb/s on each of the three WDM transmitters.