Encoding element (100) at least selectively transparent to an infrared or ultraviolet light radiation, incident thereon on a first incidence surface (101), whereinin the volume defined by said encoding element (100)a plurality of areas (104) is provided, previously selected and arranged according to a predefined pattern wherein at least one polarisation characteristic of the optical radiation (200) that is incident thereon is varied, wherein the variation of said polarisation characteristic of said incident radiation is varied according to a localised alteration pattern biunivocally associated to a predefined ciphering key, and wherein said plurality of areas is arranged between said first incidence surface (101) on which said infrared or ultraviolet light radiation is incident in use, and a second output surface (102) of said infrared or ultraviolet light optical radiation.

Encoding element (100) at least selectively transparent to an infrared or ultraviolet light radiation, incident thereon on a first incidence surface (101), whereinin the volume defined by said encoding element (100)a plurality of areas (104) is provided, previously selected and arranged according to a predefined pattern wherein at least one polarisation characteristic of the optical radiation (200) that is incident thereon is varied, wherein the variation of said polarisation characteristic of said incident radiation is varied according to a localised alteration pattern biunivocally associated to a predefined ciphering key, and wherein said plurality of areas is arranged between said first incidence surface (101) on which said infrared or ultraviolet light radiation is incident in use, and a second output surface (102) of said infrared or ultraviolet light optical radiation.

Certain aspects provide a method for radar detection by an apparatus. The method including transmitting a radar waveform in transmission time intervals (TTIs) to perform detection of a target object. The method further includes varying the radar waveform across TTIs based on one or more radar transmission parameters.

Quantum key distribution device includes a transmitter, including a light source, a first polarization controller, a phase modulator and an optical attenuator, all connected in series using a first optical fiber; a receiver, including a second polarization controller, a second phase modulator, a third polarization controller, a beamsplitter, and two single photon detectors, all connected in series using a second optical fiber; and a communication channel providing a light path from the transmitter to the receiver. The first and/or second optical fiber is a polarization maintaining fiber. The first and second phase modulators are actively controlled Pockels cell crystals, lithium niobate crystals or gallium arsenide crystals. The polarization controllers include a piezo-driven fiber compression device, a Pockels cell controller, a piezo-driven fiber twist device, or a non-linear optical crystal. The first and third polarization controllers use a /2 plate, or 45 fiber splice polarizer.

Quantum key distribution device includes a transmitter, including a light source, a first polarization controller, a phase modulator and an optical attenuator, all connected in series using a first optical fiber; a receiver, including a second polarization controller, a second phase modulator, a third polarization controller, a beamsplitter, and two single photon detectors, all connected in series using a second optical fiber; and a communication channel providing a light path from the transmitter to the receiver. The first and/or second optical fiber is a polarization maintaining fiber. The first and second phase modulators are actively controlled Pockels cell crystals, lithium niobate crystals or gallium arsenide crystals. The polarization controllers include a piezo-driven fiber compression device, a Pockels cell controller, a piezo-driven fiber twist device, or a non-linear optical crystal. The first and third polarization controllers use a /2 plate, or 45 fiber splice polarizer.

Provided is a polarization decomposition device. The polarization decomposition device includes a polarization beam splitter configured to split an optical signal into a first polarized light having a first polarization direction and a second polarized light having a second polarization direction different from the first polarized light, a phase shifter configured to delay a phase of the first polarized light, a polarization rotator configured to rotate the second polarized light so that the polarization direction of the second polarized light is changed, and an interference beam splitter configured to allow the first polarized light in which the phase is delayed and the second polarized light in which the polarization direction is rotated to interfere with each other and split them into a third polarized light and a fourth polarized light.

Provided is a polarization decomposition device. The polarization decomposition device includes a polarization beam splitter configured to split an optical signal into a first polarized light having a first polarization direction and a second polarized light having a second polarization direction different from the first polarized light, a phase shifter configured to delay a phase of the first polarized light, a polarization rotator configured to rotate the second polarized light so that the polarization direction of the second polarized light is changed, and an interference beam splitter configured to allow the first polarized light in which the phase is delayed and the second polarized light in which the polarization direction is rotated to interfere with each other and split them into a third polarized light and a fourth polarized light.

A highly-secure wireless communication system has a transmitter for transmitting the same information at predetermined polarized wave angles having different rotation-polarized waves for rotating the polarized waves of a carrier wave, and a receiver for restoring the reception information at the aforementioned predetermined polarization wave angles and for comparing the restoration results of the predetermined polarization wave angles with one another.

A highly-secure wireless communication system has a transmitter for transmitting the same information at predetermined polarized wave angles having different rotation-polarized waves for rotating the polarized waves of a carrier wave, and a receiver for restoring the reception information at the aforementioned predetermined polarization wave angles and for comparing the restoration results of the predetermined polarization wave angles with one another.

A communication apparatus includes a reference signal generating section, a transmitting section, a propagation estimating section, a first data acquiring section, and a decoding section. The reference signal generating section generates a first reference signal to enable a communicating party to estimate a propagation environment. The transmitting section transmits the first reference signal. The propagation estimating section estimates a first propagation estimation value of the propagation environment using a second reference signal transmitted from the communicating party. The first data acquiring section generates first data using the first propagation estimation value. The decoding section decodes a transmission signal encoded using a second propagation estimation value that is estimated by the communicating party using the first reference signal, to obtain second data using the first data.