Abstract: The invention relates to a system (EM, RE) for the optical transmission of a binary code. The invention makes it possible to carry out a coding of the bits transmitted in terms of intensity and phase by choosing a first base in which the signals coding the bits are distinguished only by a first physical quantity, and a second base in which the signals coding the bits are distinguished only by a second physical quantity.

Abstract: The invention relates to a system (EM, RE) for the optical transmission of a binary code. The invention makes it possible to carry out a coding of the hits transmitted in terms of intensity and phase by choosing a first base in which the signals coding the hits are distinguished only by a first physical quantity, and a second base in which the signals coding the hits are distinguished only by a second physical quantity.

Abstract: The invention concerns a device (100) for receiving an optical signal comprising at least one optical signal of angular frequency ?0 modulated by an electrical signal of angular frequency ? whose phase ?1 varies according to the value of at least data bit to be transmitted. The reception device (100) comprises a polarisation separator (105) for separating the modulated optical signal of angular frequency ?0, into first and second optical signals of different polarisation, means (140, 102, 103, 104) of obtaining two electrical signals, means (110a) of modulating the first optical signal from the first electrical signal, means (110b) of modulating the second optical signal from the second electrical signal, and means (115) of combining the first modulated optical signal and the second modulated optical signal in order to form a recombined optical signal.

Abstract: An optical binary code transmission system comprising a sender comprising: means for generating a light beam; phase-shifter means; attenuator means whereby the intensity of the lateral modes is sufficiently low for there to exist at the most only one photon in the lateral modes. The phase-shifter means of the sender impose a phase-shift that is chosen randomly to be equal either to 0 or to ?/2 for a first bit value or either to ? or to 3?/2 for a second bit value, and the receiver comprising means for detecting the presence of a photon in the first lateral mode and means for detecting the presence of a photon in the second lateral mode, a first bit value being detected if the presence of a photon is detected in the first lateral mode and a second bit value being detected if the presence of a photon is detected in the second lateral mode.

Abstract: An optical binary code transmission system comprising a sender comprising: means for generating a light beam; phase-shifter means; attenuator means whereby the intensity of the lateral modes is sufficiently low for there to exist at the most only one photon in the lateral modes. The phase-shifter means of the sender impose a phase-shift that is chosen randomly to be equal either to 0 or to &pgr;/2 for a first bit value or either to &pgr;/or to 3&pgr;/2 for a second bit value, and the receiver comprising means for detecting the presence of a photon in the first lateral mode and means for detecting the presence of a photon in the second lateral mode, a first bit value being detected if the presence of a photon is detected in the first lateral mode and a second bit value being detected if the presence of a photon is detected in the second lateral mode.

Abstract: Device for sending an encrypted signal, including: a source (1) for generating said signal and means (2) for intensity modulating the signal, a feedback loop which includes delay line means and non-linear means, characterized in that the feedback loop includes: an interferometer (5) to which is applied an electric current that corresponds to the delayed generated signal and an auxiliary source of constant intensity that feeds the interferometer optically, the output signal of the interferometer being a non-linear function of the output signal of the delay line means, a photodiode (7) which converts the luminous power at the output of the interferometer to a modulation current, and a summing circuit (8) which adds the message to be encrypted to the modulation current at the output of said photodiode, the output signal of the summing circuit controlling modulator means.

Abstract: Process and device for quantum distribution of an encryption key. According to the invention, a light beam is modulated by a signal, the phase of which can be adjusted at random. On reception, the received beam is modulated by a signal, the phase of which is also adjustable. The intensity of one of the lateral modes is measured, which depends on the difference between the two phases used. The key is distributed by the photons contained in one of the lateral modes. Application to cryptography with secret key.