In this work, 4-level pulse amplitude modulation (PAM4) by using commercial dual-drive Mach-Zehnder Modulator (DD-MZM) is experimentally investigated. We have demonstrated the generation of PAM4 signal up to 50 Gbaud (100 Gbps). The transmission of the PAM4 signal over 5-Km standard single mode fiber (SSMF) is achieved with error-free below the FEC limit (3.8E-3), without employing digital equalization at 90 Gbps. The linear-amplifier-free configuration by DD-MZM leads to simplified implementation and improved performance for high speed PAM4 signal generation, which would be of great significance for short reach optical interconnection.