A transmitter of a binary data stream comprises: a serial/parallel converter to split the binary data stream into m different parallel bit streams, each bit stream having a rate D/m which is m times lower than the initial rate D; m first encoding modules to error-correcting encode each bit stream individually; a time-interleaver to intermix the information bits originating from different encoded bit streams; an encoder to error-correcting encode the m interleaved bit streams into p bit streams; p electro-optical modulators to modulate each of the p bit streams delivered by the interleaver by means of p optical carriers of different wavelengths; and a wavelength-division multiplexer to combine the less p optical carriers into a single optical signal.