Abstract: The invention relates to an optical transmission system that implements encrypting of an information carrying signal by deterministic chaos. The system includes a transmitter (1), a receiver (4), and one transmission channel coupled between the transmitter (1) and the receiver (4). The transmitter (1) includes a deterministic chaos generator (3) coupled to an encoding system (2). The deterministic chaos generator (3) includes a wavelength tunable laser-emitting diode (33) and a feedback loop (34). The active layer of laser diode (33) is offset controlled by a laser signal passed through a non-linear optical element (32) and a delay line (31). The receiver (4) has a deterministic chaos generator (7) coupled to a synchronizer (6) and a decoder coupled to the synchronizer (6). Preferably, chaos generator (3) is the same as chaos generator (7). Other features are disclosed.