The National Astronomical Observatory of Japan (NAO), has an Optical Linked VLBI Experiment Project named OLIVE that directly connects a correlation site wit h some other VLBI observation stations in network by optical fiber, and correlates in real time. 2 Gbps (1 Gsps 2-bit or 2 Gsps 1-bit) or 8 Gbps (4 Gsps 2-bit) VLBI correlator is necessary in OLIVE. We are developing Gigabits correlators (XF type) using special-purpose correlation chips developed by NAO. We have already completed the Ultra Wideband Correlator named UWBC (2 Gsps 2-bit 256 lags) of 15 baselines for the Nobeyama Millimater Array (NMA). The Nobeyama Radio Observatory (NRO) offered the common use of a new wide-band observation system to astronomers since March 1997. We consider that the 2-Gbps VLBI correlator, which is needed in the OLIVE project, is possible to manufacture. It is also possible to manufacture a 8 Gbps-VLBI correlator using the UWBC chip.