Building coarse wavelength division multiplexing (WDM), 4x10 Gbps VCSEL transmitter modules has the promise for dramatic decreasing power consumption. Over the last years, we have demonstrated continuous improvements of parameters and reliability of wafer fused long-wavelength VCSELs. Progress and challenges in industrial fabrication of wafer-fused VCSELs emitting in the 1310 nm band for high speed WDM applications are reviewed.