Abstract: Atmospheric turbulence degrades decoding and data recovery from optically transmitted signals. For example, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to higher-order modes, resulting in significantly degraded mixing efficiency and system performance. Systems and methods are provided to generate a signal that is a conjugate of the atmospheric noise which is combined with a received data signal to ameliorate atmospheric noise. An optical pilot beam may be transmitted with an optical data beam and received by a receiver which utilizes the optical pilot beam to generate the signal that is a conjugate of the atmospheric noise.

Abstract: A control signal may be modulated on an optical wave. A transmitter may transmit the control signal to a switch/processor location. At the remote node, the control signal is received and converted from an optical signal to an electrical signal to drive the switch/processor. To provide electrical power at the switch/processor location, optical power is transmitted from a distance and converted to electrical power using a series of PDs. Monitoring tones may be sent to the remote node and fed back to the transmitter to realize an operation state and detect a bias drift. Accordingly, an OSP function at a remote node is enabled without using any local electrical power supply.

Abstract: A method for all-optical reduction of inter-channel crosstalk for spectrally overlapped optical signals for maximizing utilization of an available spectrum includes receiving a plurality of spectrally overlapped optical signals modulated with data. The method further includes generating conjugate copies of each of the plurality of optical signals using non-linear optics. The method further includes selecting the conjugate copies and adjusting an amplitude, a phase, and a delay of the conjugate copies. The method further includes performing inter-channel interference (ICI) compensation on the spectrally overlapped optical signals in an optical domain by adding the adjusted conjugate copies to the spectrally overlapped optical signals.

Abstract: A method for all-optical reduction of inter-channel crosstalk for spectrally overlapped optical signals for maximizing utilization of an available spectrum includes receiving a plurality of spectrally overlapped optical signals modulated with data. The method further includes generating conjugate copies of each of the plurality of optical signals using non-linear optics. The method further includes selecting the conjugate copies and adjusting an amplitude, a phase, and a delay of the conjugate copies. The method further includes performing inter-channel interference (ICI) compensation on the spectrally overlapped optical signals in an optical domain by adding the adjusted conjugate copies to the spectrally overlapped optical signals.

Abstract: Methods, systems, and devices for data encoding and channel hopping. The system includes a signal source for providing a signal. The system includes an optical switch having an input port and multiple output paths. The optical switch is configured to receive, at the input port, the signal. The optical switch is configured to route the signal to an output path of the multiple output paths. The system includes a mode converter that is connected to the optical switch and configured to select an orbital angular momentum (OAM) mode. The mode converter is configured to encode or channel hop the signal using the OAM mode and combine the signal from each output path. The system includes a transmitter configured to propagate the signal.

Abstract: A system includes a transmitter with multiple transmit devices each having an OAM multiplexer that converts multiple input signals into an OAM beam. Each transmit device outputs a coaxial group of orthogonal OAM beams. The system also includes a receiver that has multiple receive devices each having an OAM demultiplexer that receives the group of OAM beams from a corresponding transmit device. The OAM demultiplexer also converts the coaxial group of mutually orthogonal OAM beams into a plurality of received signals corresponding to input signals represented by the OAM beams. The receiver also includes a MIMO processor that has an equalizer that determines a transfer function corresponding to crosstalk of each of the plurality of received signals. The MIMO processor also reduces the crosstalk of each of the plurality of received signals based on the transfer function and updates the transfer function.

Abstract: A system includes a transmitter having a first transmit device having a first transmit antenna and a first OAM multiplexer designed to receive two input signals and to convert the input signals to orthogonal OAM beams. The first transmit antenna is designed to transmit a first output signal that includes the OAM beams. The transmitter also includes a second transmit device that functions in a similar manner as the first transmit device. A receiver includes a first receive device having a first receive antenna designed to receive the first output signal and a first OAM demultiplexer designed to convert the first output signal to received signals corresponding to the input signals. The receiver also includes a second receive device having similar features as the first receive device. The receiver also includes a MIMO processor designed to reduce interference between the received signals.

Abstract: Methods, systems, and apparatus for phase-sensitive regeneration of a signal without a phase-locked loop and using Brillouin amplification. The system for phase-sensitive regeneration includes a data channel, one or more pumps and a mixing stage. The one or more pumps are coupled with the data channel. The mixing stage is coupled with the data channel and is for processing a data signal that is combined with an output of the one or more pumps and idler or higher harmonic. The mixing stage is configured to amplify the idler or higher harmonic using Brillouin amplification in a Brillouin gain medium to keep the one or more pumps and the data channel phase-locked.

Abstract: Methods, systems, and devices for data encoding and channel hopping. The system includes a signal source for providing a signal. The system includes an optical switch having an input port and multiple output paths. The optical switch is configured to receive, at the input port, the signal. The optical switch is configured to route the signal to an output path of the multiple output paths. The system includes a mode converter that is connected to the optical switch and configured to select an orbital angular momentum (OAM) mode. The mode converter is configured to encode or channel hop the signal using the OAM mode and combine the signal from each output path. The system includes a transmitter configured to propagate the signal.

Abstract: A system includes a transmitter with multiple transmit devices each having an OAM multiplexer that converts multiple input signals into an OAM beam. Each transmit device outputs a coaxial group of orthogonal OAM beams. The system also includes a receiver that has multiple receive devices each having an OAM demultiplexer that receives the group of OAM beams from a corresponding transmit device. The OAM demultiplexer also converts the coaxial group of mutually orthogonal OAM beams into a plurality of received signals corresponding to input signals represented by the OAM beams. The receiver also includes a MIMO processor that has an equalizer that determines a transfer function corresponding to crosstalk of each of the plurality of received signals. The MIMO processor also reduces the crosstalk of each of the plurality of received signals based on the transfer function and updates the transfer function.

Abstract: An adaptive optics compensation approach for an OAM multiplexed FSO communication system is described, in which a Gaussian beam is used to probe the turbulence-induced wavefront distortions and derive the correction pattern for compensating the OAM beams. Using this approach, we demonstrate simultaneous compensation of multiple OAM beams each carrying a 100-Gbit/s data channel through emulated atmospheric turbulence. The results indicate that the turbulence-induced crosstalk and power penalty could be efficiently mitigated by ˜12.5 dB and ˜11 dB respectively.

Abstract: Methods, systems, and apparatus for phase-sensitive regeneration of a signal without a phase-locked loop and using Brillouin amplification. The system for phase-sensitive regeneration includes a data channel, one or more pumps and a mixing stage. The one or more pumps are coupled with the data channel. The mixing stage is coupled with the data channel and is for processing a data signal that is combined with an output of the one or more pumps and idler or higher harmonic. The mixing stage is configured to amplify the idler or higher harmonic using Brillouin amplification in a Brillouin gain medium to keep the one or more pumps and the data channel phase-locked.

Abstract: In at least one aspect, a device for Orbital Angular Momentum (OAM) based optical communication includes a first spatial light modulator configured to down-convert a first plurality of higher-order OAM modes from a communication signal to a second plurality of higher-order OAM modes and a first Gaussian mode, a second spatial light modulator configured to drop the first Gaussian mode and add a second Gaussian mode to the second plurality of higher-order OAM modes, and a third spatial light modulator configured to up-convert the second plurality of higher-order OAM modes and the second Gaussian mode to a third plurality of higher-order OAM modes for further communications.

Abstract: A system includes a transmitter having a first transmit device having a first transmit antenna and a first OAM multiplexer designed to receive two input signals and to convert the input signals to orthogonal OAM beams. The first transmit antenna is designed to transmit a first output signal that includes the OAM beams. The transmitter also includes a second transmit device that functions in a similar manner as the first transmit device. A receiver includes a first receive device having a first receive antenna designed to receive the first output signal and a first OAM demultiplexer designed to convert the first output signal to received signals corresponding to the input signals. The receiver also includes a second receive device having similar features as the first receive device. The receiver also includes a MIMO processor designed to reduce interference between the received signals.

Abstract: Systems and techniques relating to automatically-locked homodyne detection are described. A described system includes a first nonlinear element, a filter, and second nonlinear elements. The first nonlinear element can produce, based on an input signal and a first continuous wave (CW) signal, a first output signal that includes the input signal and a phase conjugate copy of the input signal. The filter can produce a filtered signal based on the first output signal and can be programmable to adjust an induced delay between the input signal and the phase conjugate signal. The second nonlinear elements can produce second output signals based on a second CW signal and differently weighted combinations of signal components within the filtered signal. The second output signals can include an in-phase output signal based on an in-phase version of the filtered signal and a quadrature output signal based on a quadrature version of the filtered signal.

Abstract: A device for optical-signal-to-noise (OSNR) monitoring can include: a delay-line interferometer configured to connect with a tunable optical filter; and two or more power detectors to measure outputs of the interferometer; wherein one or more parameters are optimized for different transmission baud rates to improve accuracy. In addition, a method can include: connecting an input of a delay-line interferometer with an output of a tunable optical filter, and an output of the delay-line interferometer with an input of a power detector, to form an optical-signal-to-noise (OSNR) monitoring apparatus; optimizing one or more parameters of the OSNR monitoring apparatus for different transmission baud rates to improve accuracy.

Abstract: Systems and techniques relating to automatically-locked homodyne detection are described. A described system includes a first nonlinear element, a filter, and second nonlinear elements. The first nonlinear element can produce, based on an input signal and a first continuous wave (CW) signal, a first output signal that includes the input signal and a phase conjugate copy of the input signal. The filter can produce a filtered signal based on the first output signal and can be programmable to adjust an induced delay between the input signal and the phase conjugate signal. The second nonlinear elements can produce second output signals based on a second CW signal and differently weighted combinations of signal components within the filtered signal. The second output signals can include an in-phase output signal based on an in-phase version of the filtered signal and a quadrature output signal based on a quadrature version of the filtered signal.

Abstract: An adaptive optics compensation approach for an OAM multiplexed FSO communication system is described, in which a Gaussian beam is used to probe the turbulence-induced wavefront distortions and derive the correction pattern for compensating the OAM beams. Using this approach, we demonstrate simultaneous compensation of multiple OAM beams each carrying a 100-Gbit/s data channel through emulated atmospheric turbulence. The results indicate that the turbulence-induced crosstalk and power penalty could be efficiently mitigated by ˜12.5 dB and ˜11 dB respectively.

Abstract: In at least one aspect, a device for Orbital Angular Momentum (OAM) based optical communication includes a first spatial light modulator configured to down-convert a first plurality of higher-order OAM modes from a communication signal to a second plurality of higher-order OAM modes and a first Gaussian mode, a second spatial light modulator configured to drop the first Gaussian mode and add a second Gaussian mode to the second plurality of higher-order OAM modes, and a third spatial light modulator configured to up-convert the second plurality of higher-order OAM modes and the second Gaussian mode to a third plurality of higher-order OAM modes for further communications.

Abstract: The present disclosure includes systems and techniques relating to reconfigurable optical transmitters. In some implementations, an apparatus, systems, or methods can include multiple ports to receive independent optical data signals or independent electrical signals that are converted into independent optical data signals, at least one optical pump laser, and one or more nonlinear optics elements configured and arranged to generate a phase conjugate for each of the independent optical data signals at least by combining the respective independent optical data signal with an output of the optical pump, and generate an output optical signal from the independent optical data signals at least by combining each of the independent optical data signals with its corresponding generated phase conjugate.