In a method for transmission of digital data in an optical free-space transmission system in which a binary code sequence produced from the digital data is used to transmit amplitude-modulated light waves across an optical free space between a transmitter and a receiver, according to a first aspect, the binary code sequence is produced such that a modulation frequency of the light waves determined by the binary code sequence has a value of 70 Hertz. According to a second aspect, ‘t’ light waves are modulated with the binary code sequence and binary data are transmitted in blocks during a first time period, and non-modulated light waves are emitted during second time periods, wherein the light intensities of the time periods are selected so that the quantities of light transmitted in two periods correspond to predetermined quantities of light.