A current blocking structure with semi insulating semiconductors that feature high electrical resistance by way of doping impurity is showing a promising way to develop a distributed feed-back (DFB) laser with high speed response well suited for 25Gbps operation. However the high output power up to now was not possible to achieve due to poor current injection efficiency in the active region. To remedy this short coming Mitsubishi Electric has developed the new current blocking structure with semi-insulating semiconductors that achieves efficient current injection in the active region. The newly developed DFB laser diode which has been manufactured based on this new structure is suitable for 25Gbps optical fiber communication in 100Gbps systems operating in a wide range of temperatures from -20 to 85 degrees Celsius. Four DFB laser diodes can be mounted on 100Gbps high speed communication transceivers for optical fiber communication resulting in lower power consumption and enhanced communication performance making them ideal for use in data centers.