An optical receiver includes a processor. The processor calculates first through fourth optical intensities that respectively indicate input optical intensities of in-phase component in the first polarization, quadrature component in the first polarization, in-phase component in the second polarization and quadrature component in the second polarization. The processor calculates polarization dependent intensity ratio and phase dependent intensity ratio based on the first through fourth optical intensities. The processor calculates an input optical intensity of a polarization multiplexed optical signal based on an optical intensity of one of the first through fourth amplifiers, the polarization dependent intensity ratio, and the phase dependent intensity ratio.

An optical relay apparatus includes a first signal converting unit that converts a received optical signal into an electric signal and demodulates and outputs the electric signal and modulates an input electric signal in a first modulation scheme, converts the electric signal into an optical signal, and transmits the optical signal and a second signal converting unit that modulates the electric signal output from the first signal converting unit in a second modulation scheme, converts the electric signal into an optical signal, and transmits the optical signal and converts a received optical signal into an electric signal, demodulates the electric signal, and outputs the electric signal as an electric signal input to the first signal converting unit.

Apparatus and method for digital signal constellation transformation are provided herein. In certain configurations, an integrated circuit includes an analog front-end that converts an analog signal vector representing an optical signal into a digital signal vector, and a digital signal processing circuit that processes the digital signal vector to recover data from the optical signal. The digital signal processing circuit generates signal data representing a signal constellation of the digital signal vector. The digital signal processing circuit includes an adaptive gain equalizer that compensates the signal data for distortion of the signal constellation arising from biasing errors of optical modulators used to transmit the optical signal.

In a coherent optical receiver device, the dynamic range considerably decreases in the case of selectively receiving the optical multiplexed signals by means of the wavelength of the local oscillator light, therefore, a coherent optical receiver device according to an exemplary aspect of the invention includes a coherent optical receiver receiving optical multiplexed signals in a lump in which signal light is multiplexed; a variable optical attenuator; a local oscillator connected to the coherent optical receiver; and a first controller controlling the variable optical attenuator by means of a first control signal based on an output signal of the coherent optical receiver; wherein the coherent optical receiver includes a 90-degree hybrid circuit, a photoelectric converter, and an impedance conversion amplifier, and selectively detects the signal light interfering with local oscillation light output by the local oscillator out of the optical multiplexed signals; and the variable optical attenuator is disposed in the optical path of the optical multiplexed signals in a stage preceding the photoelectric converter, inputs the optical multiplexed signals, and outputs them to the coherent optical receiver controlling the intensity of the optical multiplexed signals based on the first control signal.

There is provided a system for generating a spectrogram signal representative of a spectrogram of an initial signal, the system comprising: a temporal phase modulator for receiving the initial signal and quadratically modulating a temporal phase of the initial signal in a periodic series of consecutive quadratic time lenses in order to obtain a temporal phase modulated signal; a spectral phase modulator for quadratically modulating a spectral phase of the temporal phase modulated signal to obtain a given signal representative of a series of consecutive spectra; and a sensor for detecting the given signal in a temporal domain in order to obtained a sensed signal and outputting the sensed signal, the sensed signal being representative of the spectrogram of the initial signal.

An optical signal processing method and a coherent receiver, wherein an in-phase signal XI in a first polarization direction and an in-phase signal YI in a second polarization direction are added up to obtain a signal I; a quadrature signal XQ in the first polarization direction and a quadrature signal YQ in the second polarization direction are added up to obtain a signal Q; and quantization, combination, and digital signal processing are performed on the I and the Q. After summation, two signals need to be quantized. Therefore, a quantity of ADCs is reduced by half. In addition, because power consumption of a summation component is less than that of an ADS, power consumption of optical signal processing can be reduced. In addition, because there is a preset value, the summation may be performed after phase-inversion is performed on one analog signal, thereby avoiding a signal loss caused by the summation.

An optical receiver circuit includes: a substrate; and an optical waveguide device that is formed on the substrate. The optical waveguide device includes: a first optical splitter section branching the signal light into a first signal light propagation waveguide and a second signal light propagation waveguide and; a second optical splitter section branching the local-oscillator light into a first local-oscillator light propagation waveguide and a second local-oscillator light propagation waveguide; a first optical coupler section that combines the signal light propagating through the first signal light propagation waveguide and the local-oscillator light propagating through the first local-oscillator light propagation waveguide with each other; a second optical coupler section that combines the signal light propagating through the second signal light propagation waveguide and the local-oscillator light propagating through the second local-oscillator light propagation waveguide with each other.

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.

An optical channel between a coherent optical transmitter and a coherent optical receiver may include one or more components that act as a bandpass filter with a passband that is narrower than the signal bandwidth. Such a narrow filter may significantly attenuate the signal content close to the band edge of the data signal. As a result, timing error detection may work less effectively, and therefore clock recovery may be less effective or fail. Methods and systems are disclosed in which a single optical carrier is used to transmit a data signal that has multiple bands, and timing error detection is performed at the receiver using one or more inner bands of the multiple bands. The timing error detection may therefore be made more robust to the effects of the narrow filtering.

An optical receiver includes a processor. The processor calculates first through fourth optical intensities that respectively indicate input optical intensities of in-phase component in the first polarization, quadrature component in the first polarization, in-phase component in the second polarization and quadrature component in the second polarization. The processor calculates polarization dependent intensity ratio and phase dependent intensity ratio based on the first through fourth optical intensities. The processor calculates an input optical intensity of a polarization multiplexed optical signal based on an optical intensity of one of the first through fourth amplifiers, the polarization dependent intensity ratio, and the phase dependent intensity ratio.