High-performance ultra-wideband Phased Array Antennas (PAA) are disclosed, having unique capabilities, enabled through photonic integrated circuits and novel optical architectures. Unique capabilities for PAA systems are enabled by photonic integration and ultra-low-loss waveguides. Novel aspects include optical multiplexing combining wavelength division multiplexing and/or a novel extension to array photodetectors, providing the capability to combine many RF photonic signals with very low loss. Architectures include tunable optical up-conversion and down-conversion systems, moving a chosen frequency band between baseband and a high RF frequency band with high dynamic range. Simultaneous multi-channel RF beamforming is achieved through power combining/splitting of optical signals.

A system and method for ultrashort signal detection adds an optical weighting element upstream of a detector within a direct detection receiver. The optical weighting element is configured to generate an optical pulse that closely matches at least one ultrashort pulse within the input signal so that portions of the input signal that are nonoverlapping with the at least one ultrashort pulse are rejected.

A signal processing method and apparatus are provided. The method includes: receiving an optical signal in a target receive channel, and converting the optical signal into an electrical signal; determining, in the converted electrical signal, an electrical signal associated with a non-overlapping frequency band between the target receive channel and another channel, where the another channel is a channel that overlaps the target receive channel; and determining, based on the electrical signal associated with the non-overlapping frequency band, an electrical signal corresponding to a valid received optical signal that does not include an interfering optical signal in the target receive channel. According to the application, the target transmit channel and the another channel are set to channels that overlap each other, thereby reducing bandwidths occupied by the channels. In the method provided in the embodiments of this disclosure, spectrum utilization can be improved, thereby improving a data transmission rate.

A system comprising an optical receiver for multi-wavelength-channel optical communication, an optical source of spontaneous emission light and a tunable optical filter connected to receive the light at an input. The tunable optical filter can have a filter spectrum with spectral passbands separated by spectral notches. The system also includes an optical fiber link connecting an output of the optical filter to the optical receiver for multi-wavelength-channel optical communication. The receiver can be configured to make a measurement indicative of an optical power level in at least one of the notches or to make measurements of optical power levels and at least one of the passbands and at least one of the notches in response to the optical source transmitting the filtered light to the optical fiber link. Another embodiment includes an apparatus comprising an optical test module including a source of spontaneous emission light and an optical filter connected to receive the spontaneous emission light from the source.

A circuit and method for mitigating multi-path interference in direct detection optical systems is provided. Samples of an optical signal having a pulse amplitude modulated (PAM) E-field are processed by generating a PAM level for each sample. For each sample, the sample is subtracted from the respective PAM level to generate a corresponding error sample. The error samples are lowpass filtered to produce estimates of multi-path interference (MPI). For each sample, one of the estimates of MPI is combined with the sample to produce an interference-mitigated sample.

A symbol-determining device according to an embodiment includes: a transmission line shortening unit that multiplies each symbol value of a symbol array that is part of an input signal by a tap gain of a linear digital filter and outputs a symbol array representing a sum of values acquired through the multiplication; a transmission line estimating unit that estimates a transfer function of a transmission line using an adaptive nonlinear digital filter on the basis of a symbol array representing a state of the transmission line; an addition comparison processing unit that calculates a minimum value of a distance function in a Viterbi algorithm on the basis of a metric that is calculated on the basis of the output of the transmission line shortening unit and the transfer function; and a path tracing-back determination unit that performs symbol determination by tracing back a trellis path in the Viterbi algorithm on the basis of the minimum value of the distance function.

A system and method for ultrashort signal detection adds an optical weighting element upstream of a detector within a direct detection receiver. The optical weighting element is configured to generate an optical pulse that closely matches at least one ultrashort pulse within the input signal so that portions of the input signal that are nonoverlapping with the at least one ultrashort pulse are rejected.

A circuit for detecting an optical data signal includes a photonics substrate and first and second photodiodes formed in the photonics substrate. The first photodiode is configured to receive, via an input port formed in the photonics substrate, a first portion of the optical data signal and convert light power of the first portion of the optical data signal to generate a first current based on the optical data signal. The second photodiode is configured to output a second current without receiving any portion of the optical data signal. The second current corresponds to a dark current induced in the second photodiode. The circuit is configured to subtract the second current from the first current to generate an output signal corresponding to a power of the optical data signal without dark current induced in the first photodiode.

Provided is a burst mode optical transmitter capable of preventing an optical signal from being output from a light source during burst mode disable time through an arithmetic circuit configured to remove an idle signal included in a MAC electrical signal by using a MAC electrical signal and a burst mode control signal.

This application provides a receiver optical sub-assembly, a bi-directional optical sub-assembly, and an optical network device to improve anti-electromagnetic crosstalk performance of the receiver optical sub-assembly. The receiver optical sub-assembly includes: a photodiode, a trans-impedance amplifier, and a first filter component. The photodiode is configured to convert an optical signal into an electrical signal, a positive electrode of the photodiode is connected to an input terminal of the trans-impedance amplifier, and a negative electrode of the photodiode is configured to connect to a power supply. The trans-impedance amplifier is configured to amplify the electrical signal output by the photodiode, a power terminal of the trans-impedance amplifier is configured to connect to a power supply, and a first ground terminal of the trans-impedance amplifier is configured to connect to an external ground.