Optical communication device and method and transmitting antenna in free-space optical communication system

An optical communication device and method and transmitting antenna in a free-space optical communication system for use in antenna alignment. The optical communication device comprises: a light emitting unit, for transmitting a first optical signal having a first wavelength; an optical conversion unit, for receiving the first optical signal transmitted by the light emitting unit, converting a first-part optical signal in the first optical signal into a second optical signal having a second wavelength, and outputting a second-part optical signal in the first optical signal and the second optical signal, wherein the second optical signal serves as a beacon light for performing signal tracking and the second-part optical signal serves as a communication light for carrying client data; and atransmitting unit, for transmitting the second-part optical signal and the second optical signal output from the optical conversion unit to a first peer communication device.