We have developed a high-speed electroabsorption modulator integrated distributed feedback (EA/DFB) lasers. To realize the high-speed, small-footprint, low-power-consumption and cost-effective semiconductor light source, we have investigated the several key technologies. Newly developed 1.3 µm range 25 Gbps and 43 Gbps EA/DFB laser showed a good transmission performance over 10 km single mode fiber. These devices are suitable for next generation, high speed network systems, 100 Gbps and 40 Gbps Ethernet.