A digital receiver is configured to process a polarization multiplexed carrier from a communication network. The polarization multiplexed carrier includes a first polarization and a second polarization. The receiver includes a first lane for transporting a first input signal of the first polarization, a second lane for transporting a second input signal of the second polarization, a dynamic phase noise estimation unit disposed within the first lane and configured to determine a phase noise estimate of the first input signal, a first carrier phase recovery portion configured to remove carrier phase noise from the first polarization based on a combination of the first input signal and a function of the determined phase noise estimate, and a second carrier phase recovery portion configured to remove carrier phase noise from the second polarization based on a combination of the second input signal and the function of the determined phase noise estimate.

A demodulator can include an optical resonator. The optical resonator can include a resonant cavity that extends between a first surface that is partially reflective and a second surface that is at least partially reflective. The first surface can receive a phase-modulated optical signal that has a time-varying phase. The resonant cavity can accumulate resonant optical signal energy based at least in part on the phase-modulated optical signal. The first surface can direct a fraction of the resonant optical signal energy out of the optical resonator to form an intensity-modulated optical signal that has a time-varying intensity. A data detector can receive at least a portion of the intensity-modulated optical signal and, in response, generate an intensity-modulated electrical signal that has a time-varying intensity that corresponds to the time-varying phase of the phase-modulated optical signal.

Disclosed are optical communications systems and optical receivers including one or more optical cavity resonators. In particular, disclosed are methods and apparatus that allow for beam pointing to be maintained while permitting the receiver to tune the optical resonator to suit the wavelength, data rate and modulation format of the incoming optical signal, without requiring a coherent receiver or adaptive optics in addition to optical resonators.

The present invention is directed to a communication signal tracking system comprising an optical receiver including one or more delay line interferometers (DLIs) configured to demultiplex incoming optical signals and a transimpedance amplifier configured to convert the incoming optical signals to incoming electrical signals. The communication signal tracking system further includes a control module configured to calculate a bit-error-rate (BER) of the incoming electrical signals before forward-error correction decoding, and use the BER as a parameter for optimizing settings of the one or more DLIs in one or more iterations in a control loop and generating a back-channel data.

An optical communication method is an optical communication method for performing optical communication with a light-emitting device serving as a communication target. The optical communication method includes: a first step of reading information relating to a distance to the light-emitting device and information relating to a size of a light-emitting region included in the light-emitting device, the information relating to the distance and the information relating to the size being stored in advance; a second step of controlling an imaging range of a camera based on the information relating to the distance and the information relating to the size, the camera capturing an image of light from the light-emitting device; and a third step of extracting a signal from light emitted from the light-emitting device based on image data that the camera has captured in the imaging range.

A wavelength detection system may include one or more wavelength detection stages configured to receive at least a portion of an input light signal, where each stage may include a splitter to split a portion of the input light signal into two arms, a 90-degree optical hybrid, and two differential detectors configured to generate I-channel and Q-channel differential signals based on the outputs from the 90-degree optical hybrid. Further, a free spectral range is associated with an optical path length difference between the two arms of each stage. The system may further include a logic device to receive at least one set of detection signals including I and Q channel differential signals associated with different free spectral ranges and determine the wavelength of the input light signal based on an arctangent of a ratio of the Q-channel and I-channel differential signals for at least one set of detection signals.

An optical communication method is an optical communication method for performing optical communication with a light-emitting device serving as a communication target. The optical communication method includes: a first step of reading information relating to a distance to the light-emitting device and information relating to a size of a light-emitting region included in the light-emitting device, the information relating to the distance and the information relating to the size being stored in advance; a second step of controlling an imaging range of a camera based on the information relating to the distance and the information relating to the size, the camera capturing an image of light from the light-emitting device; and a third step of extracting a signal from light emitted from the light-emitting device based on image data that the camera has captured in the imaging range.

A digital receiver is configured to process a polarization multiplexed carrier from a communication network. The polarization multiplexed carrier includes a first polarization and a second polarization. The receiver includes a first lane for transporting a first input signal of the first polarization, a second lane for transporting a second input signal of the second polarization, a dynamic phase noise estimation unit disposed within the first lane and configured to determine a phase noise estimate of the first input signal, a first carrier phase recovery portion configured to remove carrier phase noise from the first polarization based on a combination of the first input signal and a function of the determined phase noise estimate, and a second carrier phase recovery portion configured to remove carrier phase noise from the second polarization based on a combination of the second input signal and the function of the determined phase noise estimate.

Provided are a communication method and apparatus using a hybrid modulation scheme in a communication system. The communication node uses a hybrid modulation scheme in the communication system and includes a processor, a first light-emitting diode (LED) array configured to transmit a first signal by blinking a first LED set according to control of the processor, a second LED array configured to transmit a second signal by blinking a second LED set according to control of the processor, and a memory configured to store one or more instructions executed by the processor. Therefore, performance of the communication system can be improved.

An apparatus includes an optical data receiver to receive a phase-modulated optical signal and to demodulate data therefrom. The optical data receiver includes an optical power splitter, first and second optical intensity detectors, and a digital signal processor. The digital signal processor is connected to receive digital values of intensity measurements of each of the optical intensity detectors. The first optical intensity detector is connected to receive light from the optical power splitter via a first optical path, and the second optical intensity detector is connected to receive light from the optical power splitter via a second optical path. The first and second optical paths have channel functions with different frequency dependencies.