A coherent detection method, apparatus, and system are disclosed. The method may include: receiving an intensity-modulated optical signal transmitted by a transmitting end, where the intensity-modulated optical signal is obtained by intensity modulation performed by the transmitting end on an original signal; performing phase modulation on a local oscillator optical signal to obtain a phase-modulated local oscillator optical signal; and mixing the intensity-modulated optical signal and the phase-modulated local oscillator optical signal, and then performing photoelectric detection, analog-to-digital conversion, and digital signal receiving processing in sequence to recover the original signal.

A system is provided that can introduce data redundancy into wireless communications, and in particular ultra-wideband (UWB) wireless communications to increase the communication range when transmitting data that has low transmission rates. Multipath degradation, introduced by the extended communications range, can be mitigated by frequency hopping between the orthogonal frequency-division multiplexed symbols of the ultra-wideband waveform. Frequency hopping can place adjacent symbols in different frequency channels for filtering. Data redundancy can be expanded in the time domain and/or the frequency domain, resulting in extended range.

Methods and apparatus to realize high spectral efficiency in optical signals transmitted over long distances.

A method, system, and apparatus for a coherent optical breakout; wherein the optical breakout has a laser; wherein the coherent optical breakout has a set of optical connections; wherein the set has at least two optical connections; wherein the coherent optical breakout enables coherent optical communication of X Gbs across each of the set of optical connections.

Proposed is a receiving UE for receiving a signal in optical wireless communication, according to the present disclosure. The receiving UE may include: a transceiver for receiving an optical signal of an orbital angular momentum (OAM) mode from a transmitting terminal; a demodulator composed of at least one phase shifter; a photoelectricity converter composed of at least one photodiode; and a processor connected to the transceiver, the demodulator, and the photoelectricity converter. In addition, the at least one phase shifter may convert an optical signal of the OAM mode into an optical signal of a Gaussian mode, and the at least one photodiode may convert an optical signal of the Gaussian mode into an electrical signal.

A coherent optical receiver having an analog electrical circuit connected to combine the outputs of multiple photodetectors to generate an electrical output signal from which the data encoded in a received modulated optical signal can be recovered in a robust and straightforward manner. In an example embodiment, the analog electrical circuit includes one or more transimpedance amplifiers connected between the photodetectors and the receiver's output port. The coherent optical receiver may include a dual-polarization optical hybrid coupled to eight photodiodes to enable polarization-insensitive detection of the received modulated optical signal. The signal processing implemented in the analog electrical circuit advantageously enables the use of relatively inexpensive local-oscillator sources that may have relaxed specifications with respect to linewidth and wavelength stability. Different embodiments of the analog electrical circuit can be used to enable the receiver to receive amplitude- and intensity-encoded modulated optical signals.

A measuring method and apparatus of frequency response characteristic imbalance of an optical receiver, in which by transmitting at least one single-frequency signal in an I branch or a Q branch of an optical transmitter, an amplitude ratio and phase imbalance of the I branch and the Q branch of the optical receiver are directly calculated according to at least one pair of received signals extracted from the I branch and the Q branch of the optical receiver of which frequencies are split due to a frequency difference between lasers of the optical transmitter and the optical receiver, with no need of many times of changes of central wavelengths of lasers of the optical transmitter and the optical receiver for performing measurement for many times, and measurement of frequency response characteristic imbalance of the optical receiver may be achieved through one time of measurement, which is simple in process and accurate in measurement result.

A quadrature oscillation circuit includes a plurality of adjacent quadrature oscillators, wherein a first quadrature oscillator includes a first I-phase inductor, a first Q-phase inductor, and a first drive circuit that generates a first I-phase current passing the first I-phase inductor and a first Q-phase current passing the first Q-phase inductor such that phases of a first I-phase differential signal from the first I-phase inductor are different from phases of a first Q-phase differential signal from the first Q-phase inductor, a second quadrature oscillator includes a second I-phase inductor, a second Q-phase inductor, and a second drive circuit that generates a second I-phase current passing the second I-phase inductor and a second Q-phase current passing the second Q-phase inductor such that phases of a second I-phase differential signal from the second I-phase inductor are different from phases of a second Q-phase differential signal from the second Q-phase inductor.

A quadrature oscillation circuit includes a plurality of adjacent quadrature oscillators, wherein a first quadrature oscillator includes a first I-phase inductor, a first Q-phase inductor, and a first drive circuit that generates a first I-phase current passing the first I-phase inductor and a first Q-phase current passing the first Q-phase inductor such that phases of a first I-phase differential signal from the first I-phase inductor are different from phases of a first Q-phase differential signal from the first Q-phase inductor, a second quadrature oscillator includes a second I-phase inductor, a second Q-phase inductor, and a second drive circuit that generates a second I-phase current passing the second I-phase inductor and a second Q-phase current passing the second Q-phase inductor such that phases of a second I-phase differential signal from the second I-phase inductor are different from phases of a second Q-phase differential signal from the second Q-phase inductor.

A receiver convolves an impulse response for compensating for frequency characteristics and a complex impulse response for wavelength dispersion compensation with each of a real component and an imaginary component of each polarized wave of a reception signal. For each polarized wave, the receiver performs complex signal processing of multiplying the imaginary component by the imaginary unit, then branching the resulting component, and adding one imaginary component to the real component. For each polarized wave, the receiver uses, as input signals, the real component and the imaginary component of each polarized wave after complex signal processing and the phase conjugates of them. For each polarized wave, the receiver adds a signal obtained by a process in which each of the real component and the imaginary component of each polarized wave is multiplied by a complex impulse response, the resulting components are added, and a phase rotation is applied and a signal obtained by a process in which each of the phase conjugate of the real component and the phase conjugate of the imaginary component of each polarized wave is multiplied by a complex impulse response, the resulting components are added, and an opposite phase rotation is applied, and adds a transmission data bias correction signal.