Novel VCSEL driving technique with virtual back termination for high-speed optical interconnection

In this work, we develop a simple and high-speed VCSEL driving technique with "virtual back termination" for optical interconnect applications. For achieving compact and high-speed optical interconnects, an optical module with the flip-chip bonding structure is effective. To realize flip-chip mounting, the development of the VCSEL driving technique, which can perform impedance matching with the transmission line, is a critical issue. Back termination has to be implemented to reduce signal reflection via the transmission line. Additionally, back termination must have a simple dc coupling. Introducing a virtual GND to the circuit ensures that these requirements are met. The virtual GND is made by a dummy load connected to a complementary output and dc-coupled 50-Omega resisters between output and complementary output. The dummy load has characteristics similar to the load VCSEL. As a result of the virtual GND, the resisters act as the back termination. When we drove the VCSEL with this technique, clear eye opening without the reflectance effects was obtained up to 28-Gb/s despite using a 10-cm transmission These results show that our driving technique is suitable for high-speed optical interconnect applications.