THz-range optical-frequency conversion of 1 Gb/s-signals is demonstrated, for the first time, through the use of cavity-enhanced highly nondegenerate four-wave mixing (HNDFWM) in an InGaAsP semiconductor laser. This conversion is based on a subpicosecond ultrafast nonlinear gain process in the laser. The possibility of applying this phenomenon to an optical fiber dispersion compensator is also discussed.