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.

An optical detector system provides beam positioning data to an optical tracking system to facilitate optical communications. The optical detector system comprises a plurality of optical photodetectors. For example, a two-by-two array may be used. Incoming light passes through one or more optical elements, such as a lens and a dispersive optical element. A first portion of the beam entering the optical elements is directed into a first spot having a first area on the array. A second portion of the beam entering the optical elements is dispersed to form a second spot having a second area on the array that is larger than the first area. This combination of first portion and second portion of the beam incident on the array provides unambiguous information in the output of the photodetectors that is indicative of a position of the incoming beam with respect to the array.

An optical detector system provides beam positioning data to an optical tracking system to facilitate optical communications. The optical detector system comprises a plurality of optical photodetectors. For example, a two-by-two array may be used. Incoming light passes through one or more optical elements, such as a lens and a dispersive optical element. A first portion of the beam entering the optical elements is directed into a first spot having a first area on the array. A second portion of the beam entering the optical elements is dispersed to form a second spot having a second area on the array that is larger than the first area. This combination of first portion and second portion of the beam incident on the array provides unambiguous information in the output of the photodetectors that is indicative of a position of the incoming beam with respect to the array.

Methods, systems, and devices for quantum key distribution (QKD) in passive optical networks (PONs) are described. A PON may be a point-to-multipoint system and may include a central node in communication with multiple remote nodes. In some cases, each remote node may include a QKD transmitter configured to generate a quantum pulse indicating a quantum key, a synchronization pulse generator configured to generate a timing indication of the quantum pulse, and filter configured to output the quantum pulse and the timing indication to the central node via an optical component (e.g., an optical splitter, a cyclic arrayed waveguide grating (AWG) router). The central node may receive the timing indications and quantum pulses from multiple remote nodes. Thus, the central node and remote nodes may be configured to communicate data encrypted using quantum keys.

Methods, systems, and devices for quantum key distribution (QKD) in passive optical networks (PONs) are described. A PON may be a point-to-multipoint system and may include a central node in communication with multiple remote nodes. In some cases, each remote node may include a QKD transmitter configured to generate a quantum pulse indicating a quantum key, a synchronization pulse generator configured to generate a timing indication of the quantum pulse, and filter configured to output the quantum pulse and the timing indication to the central node via an optical component (e.g., an optical splitter, a cyclic arrayed waveguide grating (AWG) router). The central node may receive the timing indications and quantum pulses from multiple remote nodes. Thus, the central node and remote nodes may be configured to communicate data encrypted using quantum keys.

An optical communication device includes a WDM optical transmission reception unit that receives an optical signal and converts the optical signal to an electric signal, a MUX/DEMUX unit that converts the electric signal obtained by the conversion to a plurality of electric signals, signal detection units, a switch unit that changes paths, client IF units, and a control unit. A first signal detection unit among the signal detection units detects a first electric signal among the plurality of electric signals. When the first electric signal is a signal to be processed based on a first communication standard, the control unit controls the switch unit so that the first electric signal is inputted to a client IF unit that executes a process based on the first communication standard among the client IF units.

An optical receiver device includes a boost converter circuit, an optical receiver circuit, and a pulse width modulation controller circuitry. The boost converter circuit is configured to convert a supply voltage according to a pulse width modulation signal, in order to generate an output voltage. The optical receiver circuit is configured to set a gain according to the output voltage, in order to convert an optical signal to a data signal according to the gain. The pulse width modulation controller circuitry is configured to perform a digital to analog conversion according to a control code to gradually adjust a current associated with the output voltage, and to compare the output voltage with a reference voltage to generate the pulse width modulation signal.

An optical receiver device includes a boost converter circuit, an optical receiver circuit, and a pulse width modulation controller circuitry. The boost converter circuit is configured to convert a supply voltage according to a pulse width modulation signal, in order to generate an output voltage. The optical receiver circuit is configured to set a gain according to the output voltage, in order to convert an optical signal to a data signal according to the gain. The pulse width modulation controller circuitry is configured to perform a digital to analog conversion according to a control code to gradually adjust a current associated with the output voltage, and to compare the output voltage with a reference voltage to generate the pulse width modulation signal.

A system and method includes receiving, via a fiber optic cable, an analog fiber optic signal that preserves native radio frequency (RF) energy characteristics of at least one first RF signal associated with at least one wireless device, and converting, by a light-to-RF converter, the received analog fiber optic signal into at least one second RF signal. The system and method can further comprise analyzing, by a processor, the at least one second RF signal and generating, by the processor, at least one digital signature associated with the at least one wireless device, respectively, based on the analysis of the at least one second RF signal. The system and method yet further comprise determining, by the processor, if the at least one wireless device associated with the at least one digital signature, respectively, is one of an authorized device and an unauthorized device.

A system and method includes receiving, via a fiber optic cable, an analog fiber optic signal that preserves native radio frequency (RF) energy characteristics of at least one first RF signal associated with at least one wireless device, and converting, by a light-to-RF converter, the received analog fiber optic signal into at least one second RF signal. The system and method can further comprise analyzing, by a processor, the at least one second RF signal and generating, by the processor, at least one digital signature associated with the at least one wireless device, respectively, based on the analysis of the at least one second RF signal. The system and method yet further comprise determining, by the processor, if the at least one wireless device associated with the at least one digital signature, respectively, is one of an authorized device and an unauthorized device.