Configurations of a light signal communication apparatus and an optical communication system suitable for speeding-up of the transmission of information based on a light signal and an increase in the capacity for the information transmission are disclosed. On the light signal transmitting side, excitation light is supplied to an active medium in accordance with a transmission signal to cause induced emission within the active medium, thereby generating signal light. The excitation light causes spontaneously-emitted light to fall on a semiconductor layer, and a voltage pulse corresponding to transmission information is applied to modulate the refractive index of the semiconductor layer, thereby Bragg-reflecting a specific wavelength component, after which it is sent to the active medium as the excitation light. The Bragg reflection and induced emission incident to it exhibit excellent response to a voltage signal having a pulse width of 1×10−9 seconds or less. It is therefore possible to implement an optical communication system having a transmission rate up to 100 Gb/s with one light signal.