An optical receiver includes: an optical brancher configured to branch polarization multiplexed light to a first polarization multiplexed light and a second polarization multiplexed light, the polarization multiplexed light in which a pilot signal is superimposed on at least one of a first polarization and a second polarization; an optical fiber configured to transmit the first polarization multiplexed light; a first polarization rotator configured to control a first polarization state of the first polarization multiplexed light output from the optical fiber; a first polarization separator configured to separate the second polarization multiplexed light into a third polarization and a fourth polarization; and a controller configured to control the first polarization rotator based on one of a first pilot signal included in the third polarization and a second pilot signal included in the fourth polarization.

A passive dual polarization unit and coherent transceiver and/or receiver including one or more passive dual polarization units are provided. An example passive dual polarization unit includes a polarization splitter configured to split an input signal into a TE mode and TM mode signals; TE/TM splitters each designed to split the TE/TM mode signals into first TE/TM signals and second TE/TM signals; a first TE signal polarization rotation component for receiving the first TE signal and providing a third TM signal having the same magnitude and time dependence as the first TE signal; a first TM signal polarization rotation component for receiving the first TM signal and providing a third TE signal having the same magnitude and time dependence as the first TM signal; and TE/TM couplers that couple the second TE/TM signals and the third TE/TM signals to generate output TE/TM signals.

An optical receiver is described. Using silicon-photonic components that support a single polarization, the output of an optical receiver is independent of the polarization of an optical signal. In particular, using a polarization-diversity technique, the two orthogonal polarizations in a single-mode optical fiber are split in two and processed independently. For example, the two optical signals may be provided by a polarization-splitting grating coupler. Subsequently, a redistribution element provides mixtures of the two optical signals. Next, a wavelength channel in the two mixed optical signals is selected using a wavelength-selective filter (for example, using ring-resonator drop filters or an echelle grating) and converted into an electrical signal at an optical detector (such as a photodetector) to achieve polarization-independent operation.

Aspects described herein include an optical apparatus comprising a multiple-stage arrangement of two-mode Bragg gratings comprising: at least a first Bragg grating of a first stage. The first Bragg grating is configured to transmit a first two wavelengths and to reflect a second two wavelengths of a received optical signal. The optical apparatus further comprises a second Bragg grating of a second stage. The second Bragg grating is configured to transmit one of the first two wavelengths and to reflect an other of the first two wavelengths. The optical apparatus further comprises a third Bragg grating of the second stage. The third Bragg grating is configured to transmit one of the second two wavelengths and to reflect an other of the second two wavelengths.

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.

An optical transmission/reception unit includes a carrier rotatable around an axis of rotation, an optical receiver arranged at the carrier on the axis of rotation so as to receive an optical reception signal from a first direction, an optical transmitter arranged at the carrier adjacent to the optical receiver so as to emit an optical transmission signal in a second direction, and a transmission/reception optic arranged at the carrier on the axis of rotation above the optical receiver, wherein the transmission/reception optic includes a reception optic and a transmission optic arranged in the reception optic, wherein the reception optic is configured to guide the optical reception signal striking the transmission/reception optic towards the optical receiver on the axis of rotation, and wherein the transmission optic is configured to displace onto the axis of rotation the optical transmission signal emitted by the optical transmitter.

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 herein are optical transceivers with multi-laser modules, as well as related optoelectronic assemblies and methods. In some embodiments, an optical transceiver may include: a first laser and a second laser; an optical output path, wherein an output of the first laser is coupled to the optical output path; and switching circuitry to decouple the output of the first laser from the optical output path and to couple an output of the second laser to the optical output path.

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.