Optical single sideband (SSB) technique has recently attracted considerable attentions as an alternative transmitter for metro-haul applications. The optical SSB technique can double the spectral efficiency and is free from dispersion-induced power fading, compared with conventional double-sideband (DSB) signals. However, the optical SSB transmitter is much more complicated than that of the optical DSB system. In this paper, we review the monolithically integrable optical single sideband (SSB) transmitters that are potentially used for cost-sensitive inter-datacenter interconnects. The focus will be on the optical SSB transmitter scheme of modulating a directly modulated laser and an electro-absorption modulator simultaneously.