The present invention relates to a fiber branch structure for spatial optical communication for transmitting information by emitting communication light. The fiber branch structure is provided with: a light emitter configured to emit communication light; a light emission controller configured to control the light emitter; an optical fiber configured to transmit the light emitted from the light emitter; a distributor configured to distribute the light, the distributer being optically coupled to an output terminal of the optical fiber; and an optical fiber group optically coupled to a plurality of output terminals of the distributor. According to the present invention, a communication area can be established without blind spots. That is, the fiber branch structure for spatial optical communication according to the present invention includes an optical fiber group optically coupled to a plurality of output terminals of the distributor. A communication area can be established more assuredly by such an optical fiber group, which prevents the optical communication from being interrupted.

An optical communication device 1 is provided with: a plurality of light-receiving elements 11 each configured to receive light and output a light detection signal; a plurality of optical fibers 13 provided to correspond to the plurality of light-receiving elements 11, respectively, the plurality of optical fibers each being configured to guide the light to the corresponding light-receiving element 11; a plurality of amplifiers 18 provided to correspond to the plurality of light-receiving elements 11, respectively, the plurality of amplifiers each being configured to generate optical communication information by performing signal processing on the light detection signal; a light intensity information collection unit 25 configured to collect intensity of the light received by each of the plurality of optical fibers 13 as light intensity information; an optical fiber identification unit 27 configured to identify the optical fiber 13 that is receiving relatively strong light out of the plurality of optical fibers 13, based on the light intensity information La to Le collected by the light intensity information collection unit 25; and a switch controller 29 configured to control to turn on the amplifier 18, the amplifier 18 being provided to correspond to the optical fiber 13 identified by the optical fiber identification unit 27.

An optical communication device 1 is provided with: a plurality of light-receiving elements 11 each configured to receive light and output a light detection signal; a plurality of optical fibers 13 provided to correspond to the plurality of light-receiving elements 11, respectively, the plurality of optical fibers each being configured to guide the light to the corresponding light-receiving element 11; a plurality of amplifiers 18 provided to correspond to the plurality of light-receiving elements 11, respectively, the plurality of amplifiers each being configured to generate optical communication information by performing signal processing on the light detection signal; a light intensity information collection unit 25 configured to collect intensity of the light received by each of the plurality of optical fibers 13 as light intensity information; an optical fiber identification unit 27 configured to identify the optical fiber 13 that is receiving relatively strong light out of the plurality of optical fibers 13, based on the light intensity information La to Le collected by the light intensity information collection unit 25; and a switch controller 29 configured to control to turn on the amplifier 18, the amplifier 18 being provided to correspond to the optical fiber 13 identified by the optical fiber identification unit 27.

In order to improve free space optical communications, an optical communication terminal includes a laser source, a photo detecting apparatus and an optical input/output assembly. These components are controlled by a control logic. In order to have the optical communication terminal to be self-compatible, the optical input/output assembly selectively routes the outgoing beam and incoming beam depending on their respective beam polarization. To this end, the optical input/output assembly may include a polarizing beam splitter together with a quarter-wave plate.

An electronic device may include an antenna that conveys wireless signals at frequencies greater than 100 GHz. The antenna may include a radiating element coupled to a uni-travelling-carrier photodiode (UTC PD). An optical path may illuminate the UTC PD using a first optical local oscillator (LO) signal and a second optical LO signal. An optical phase shift may be applied to the first optical LO signal. A Mach-Zehnder modulator (MZM) may be interposed on the optical path. During signal transmission, the MZM may modulate wireless data onto the second optical LO signal while control circuitry applies a first bias voltage to the UTC PD. During signal reception, the control circuitry may apply a second bias voltage to the UTC PD that configures the UTC PD to convert received wireless signals into intermediate frequency signals and/or optical signals.

An electronic device may include an antenna that conveys wireless signals at frequencies greater than 100 GHz. The antenna may include a radiating element coupled to a uni-travelling-carrier photodiode (UTC PD). An optical path may illuminate the UTC PD using a first optical local oscillator (LO) signal and a second optical LO signal. An optical phase shift may be applied to the first optical LO signal. A Mach-Zehnder modulator (MZM) may be interposed on the optical path. During signal transmission, the MZM may modulate wireless data onto the second optical LO signal while control circuitry applies a first bias voltage to the UTC PD. During signal reception, the control circuitry may apply a second bias voltage to the UTC PD that configures the UTC PD to convert received wireless signals into intermediate frequency signals and/or optical signals.

A High Bandwidth Individual Channel Control via Optical Reference Interferometry (HICCORI) system actively controls the phase and/or polarization of the optical emission of each element in a tiled optical array. It can also actively align any high-frequency broadening waveform applied to the array beams for spectral broadening or data transmission. By maintaining consistent polarization and manipulating the phase relationships of the beams emitted by the array elements, the HICCORI system can manipulate the spatial pattern of constructive and destructive interference formed as the individual emissions coherently combine. Active feedback control allows the desired phase, polarization, and/or spectral broadening alignment to be maintained in the presence of external disturbances.

The present disclosure aims to enable communication to be performed with stable quality even when a user uses a terminal while moving. In the wireless communication system according to the present disclose, a switching control unit 15 sets switching illuminance p.sub.th for maintaining illuminance of an optical signal received by a terminal 91 at requested illuminance corresponding to throughput or higher during the time until connection switching between the communication with an optical wireless access point 92 and the communication with an RF wireless access point 93 is completed, and when the received illuminance p becomes lower than the switching illuminance p.sub.th during connection with the optical wireless access point 92, the switching control unit 15 performs connection switching from the optical wireless communication to the RF wireless communication.

The present disclosure aims to enable communication to be performed with stable quality even when a user uses a terminal while moving. In the wireless communication system according to the present disclose, a switching control unit 15 sets switching illuminance p.sub.th for maintaining illuminance of an optical signal received by a terminal 91 at requested illuminance corresponding to throughput or higher during the time until connection switching between the communication with an optical wireless access point 92 and the communication with an RF wireless access point 93 is completed, and when the received illuminance p becomes lower than the switching illuminance p.sub.th during connection with the optical wireless access point 92, the switching control unit 15 performs connection switching from the optical wireless communication to the RF wireless communication.

A method of receiving, by a receiving terminal, a signal in optical wireless communication is proposed. The method may comprise: establishing a communication link for performing the optical wireless communication with a transmitting terminal; receiving an optical signal from the transmitting terminal through the communication link; and performing interference cancelation on the optical signal. Here, establishing the communication link comprises transmitting and receiving initial information with the transmitting terminal, wherein the initial information may include an orbital angular momentum (OAM) mode applied to the optical signal. In addition, the interference cancelation may be performed on the basis of the OAM mode.