Data communication over 300 m of distance, such as Ethernet standards, where the required data rate per channel reaches 10 Gb/s or more, demand optical transmission. Vertical-cavity surface-emitting laser (VCSEL) and multimode optical fiber (MMF) are usually used in such optical transmission systems, because they offer several advantages such as ease of assembly and optical alignment for cost reduction. The modulation frequency of commercial VCSEL devices is limited to approximately 10 GHz. To overcome this limitation, solutions have been reported by Palermo et al. (2006, 2007). However, these papers merely describe that the modulation frequency of VCSEL can be extended by equalization. On the other hand, the transmission performance of MMF is generally defined by the product of transmission distance and modulation frequency. In a commercial graded-index (Gl) MMF, the transmission performance stays about 500 MHz-km due to modal dispersion. In the case of 10 Gb/s data transmission, the required bandwidth for transmission medium is 10 GHz or more. Therefore, when using these commercial Gl MMF, the transmission distance will be limited to 50 m. Thus, when several hundred meters of transmission is achieved using MMF, the modal dispersion of MMF becomes a rather predominant transmission bottleneck than the use of VCSEL. To overcome this bottleneck, a 4-PAM VCSEL driver with an equalization scheme to compensate the modal dispersion of MMF is described in this paper. The driver is fabricated in 90 nm CMOS and achives 10 Gb/s 500 m 4-PAM transmission using conventional MMF having a 500 MHz-km of transmission bandwidth. Using this driver, the transmission distance with 10 Gb/s is extended by 10times (5 GHz-km).