A transmission method includes: in a first period, causing a light source to emit light having a first luminance; and in a second period, causing the light source to transmit an optical signal by causing the light source to alternately emit light having a second luminance and light having a third luminance lower than the second luminance.

A communication device includes an interleaving unit that determines an interleaving length of transmit data to be transmitted through free-space optical communication, and interleaves the transmit data based on the determined interleaving length, and a shaping unit that shapes the interleaved transmit data so as to make the interleaving length detectable on a receiving side of the free-space optical communication.

Disclosed are a quantum information transmitter, a quantum communication system including the same, and an operating method of the quantum information transmitter. The quantum information transmitter includes a light source driver, a light source, and a light modulator. The light source driver generates a first light source driving signal having a first level and a second light source driving signal having a second level. The light source generates a first light signal having a first average number of photons in response to the first light source driving signal, and generates a second light signal having a second average number of photons in response to the second light source driving signal. The optical modulator modulates the first light signal to generate a target signal, and modulates the second light signal to generate a decoy signal.

To prevent deterioration in an extinction ratio due to asymmetry between a pair of optical waveguides.

An optical modulator has a Mach-Zehnder optical waveguide including mutually parallel first and second waveguides and a signal electrode for controlling the phase of light propagating in the Mach-Zehnder optical waveguide. The first and second waveguides have a first section in which the second waveguide has a line width smaller than that of the first waveguide and a second section in which the first waveguide has a line width smaller than that of the second waveguide. The first section and the second section are replaced with each other in curved parts.

An optical emitter comprising a primary laser and a plurality of secondary lasers wherein each secondary laser is optically injection locked to said primary laser, the emitter further comprising at least one polarisation controller configured to control the polarisation of the output of at least one of the secondary lasers, the emitter further comprising a combination unit that is configured to combine the outputs of the secondary laser modules into an output signal.

There is provided an optical waveguide device including a substrate, an optical waveguide formed on the substrate, and a working electrode that controls a light wave propagating through the optical waveguide, in which the working electrode includes a first base layer made of a first material, and a first conductive layer on the first base layer, and a conductor pattern including a second base layer made of a second material different from the first material and a second conductive layer on the second base layer is formed in a region other than a path from an input end to an output end of the optical waveguide, in a region on the substrate.

There is provided an optical waveguide device including a substrate, an optical waveguide formed on the substrate, and a working electrode that controls a light wave propagating through the optical waveguide, in which the working electrode includes a first base layer made of a first material, and a first conductive layer on the first base layer, and a conductor pattern including a second base layer made of a second material different from the first material and a second conductive layer on the second base layer is formed in a region other than a path from an input end to an output end of the optical waveguide, in a region on the substrate.

A wavelength converter includes an optical waveguide substrate configured to include a plurality of optical waveguides formed with different design values, an incidence-side optical fiber from which signal light and excitation light are incident to the optical waveguide substrate, and an emission-side optical fiber to which light including converted light having a wavelength different from a wavelength of the signal light is extracted from the optical waveguide substrate, wherein the incidence-side optical fiber and the emission-side optical fiber are optically coupled to one optical waveguide among the plurality of optical waveguides.

A master station device includes a processor that outputs a subcarrier modulation signal, and a transmitter that maps an in-phase (I) component and a quadrature-phase (Q) component of the subcarrier modulation signal to an optical signal to be transmitted to a fronthaul.

A master station device includes a processor that outputs a subcarrier modulation signal, and a transmitter that maps an in-phase (I) component and a quadrature-phase (Q) component of the subcarrier modulation signal to an optical signal to be transmitted to a fronthaul.