Arbitrary waveform can be synthesized by two orthogonal components: in-phase and quad-rature components. Thus, if we can manipulate the two components independently, various complicat-ed modulation can be achieved. This technique is called vector modulation, which is commonly used in wireless radio communication systems where the carrier frequency is lower than 100GHz. On the other hand, in lightwave transmission systems,the carrier frequency is higher than 100THz, and the stability of the signal sources would be much poorer than in radio systems, so that the simplest modulation format (on-off-keying) was often used in commercial systems. However, recently, various modulation techniques such as quadrature ampli-tude modulation, etc., have been demonstrated by using precise and rapid lightwave control. In this report, we review recent progress in optical vector modulation technologies which can generate high-speed and complicated optical signals. Integrated optical modulators can synthesize multi-level sig-nals in photonic circuits.