The paper presents a realization of our optical-connected realtime VLBI (very long baseline interferometer) observation testbed with the highest sensitivity in the world. Today's rapid deployment of high-speed wide area optical networks will give a major breakthrough in VLBI astronomy in terms of its observational sensitivity and immediateness. VLBI requires a huge amount of data transfer from several, separately located, radio telescopes for calculating cross-correlation. High-speed networks can be applied to such data transfer instead of conventional magnetical tape recording and physical transportation, which cause a serious performance bottleneck. We have newly designed and implemented a special component named gigabit network access node, which can exchange 2.048 Gbps telescope data through a 2.488 Gbps OC-48c/STM-16c SONET/SDH link. We have also constructed the world's first multi-gigabit-rate VLBI testbed using actual wide area optical networks and successfully conducted several real observations.