A method of receiving, by a receiving terminal, a signal in optical wireless communication is proposed. The method may comprise: establishing a communication link for performing the optical wireless communication with a transmitting terminal; receiving an optical signal from the transmitting terminal through the communication link; and performing interference cancelation on the optical signal. Here, establishing the communication link comprises transmitting and receiving initial information with the transmitting terminal, wherein the initial information may include an orbital angular momentum (OAM) mode applied to the optical signal. In addition, the interference cancelation may be performed on the basis of the OAM mode.

A receiver system is provided for receiving a coherent Pulse Amplitude Modulation (PAM) encoded signal. The receiver system may include an optical polarization component configured to modulate a polarization of the received coherent PAM encoded signal. The receiver system may further include a digital signal processor (DSP) configured to perform polarization recovery between the received coherent PAM encoded signal and the LO signal using a first control loop, and to perform phase recovery between the received coherent PAM encoded signal and the LO signal using a second control loop.

A quantum communication system that includes a multiphoton entanglement generator, a plurality of photon detector units, and a plurality of optical fiber links. The plurality of photon detector units include a first photon detector unit and a second photon detector unit. The multiphoton entanglement generator is structurally configured to output more than two entangled photons. The plurality of optical fiber links comprise a first optical fiber link optically coupled to the multiphoton entanglement generator and disposed between the multiphoton entanglement generator and the first photon detector unit. The plurality of optical fiber links comprise a second optical fiber link optically coupled to the multiphoton entanglement generator and disposed between the multiphoton entanglement generator and the second photon detector unit. Further, at least one of the plurality of optical fiber links has a core, a cladding, and a scattering region having a plurality of scattering structures.

The method includes sending a first frame of a first modulation format that is suitable for a first group of receivers before sending a second frame of a second modulation format that is suitable for a second group of receivers, wherein the first modulation format is a higher modulation format than the second modulation format, and wherein the method further includes inserting into the first frame at least one symbol of the second modulation format at at least one outer edge of the first frame.

An optical module configured to electrically connect to a host. A linear equalizer performs equalization on a host equalized signal to create a module equalized signal, and a driver configured to present the module equalized signal from the linear equalizer to an optical conversion device at a magnitude suitable for the optical conversion device. An optical conversion device receives the module equalized signal from the driver, converts the module equalized signal to an optical signal, and transmit the optical signal over an optical channel. Also part of the optical module is an interface which communicates supplemental equalizer settings to the host. A memory stores the supplemental equalizer settings which reflect the optical modules effect on a signal passing through the optical module. A controller oversees communication of the supplemental equalizer settings to the host such that the host uses the supplemental equalizer settings to modify host equalizer settings.

A system for correcting phase noise and/or drift, the system includes an optical signal module being capable of amplitude modulating the optical signal while being phase- and/or frequency-shifted. Further, the system includes a beam splitter capable of separating at least backward travelling waves based on polarization. Moreover, a fiber connected to the beam splitter and a polarization rotator capable of changing the polarization of the optical signal are provided. The system has a partially reflecting reflector capable of creating a backward travelling wave as well as a photodiode capable of receiving the backward travelling wave. The photodiode is capable of generating a detection signal used for detecting phase noise and/or drift in the backward travelling wave.

A system for correcting phase noise and/or drift, the system includes an optical signal module being capable of amplitude modulating the optical signal while being phase- and/or frequency-shifted. Further, the system includes a beam splitter capable of separating at least backward travelling waves based on polarization. Moreover, a fiber connected to the beam splitter and a polarization rotator capable of changing the polarization of the optical signal are provided. The system has a partially reflecting reflector capable of creating a backward travelling wave as well as a photodiode capable of receiving the backward travelling wave. The photodiode is capable of generating a detection signal used for detecting phase noise and/or drift in the backward travelling wave.

The disclosed systems, structures, and methods are directed to a single-stage frequency-domain equalization (FDEQ) structure implemented on a processor, comprising a data preprocessing unit configured to concatenate received data samples in time-domain digital signals, transform the concatenated data samples in the time-domain digital signals to frequency-domain digital signals, and an adaptive equalizer comprising 2×2 multiple-input multiple output (MIMO) configured to compensate for non-time-varying fixed impairments and time-varying adaptive impairments in the frequency-domain digital signals.

The disclosed systems, structures, and methods are directed to a single-stage frequency-domain equalization (FDEQ) structure implemented on a processor, comprising a data preprocessing unit configured to concatenate received data samples in time-domain digital signals, transform the concatenated data samples in the time-domain digital signals to frequency-domain digital signals, and an adaptive equalizer comprising 2×2 multiple-input multiple output (MIMO) configured to compensate for non-time-varying fixed impairments and time-varying adaptive impairments in the frequency-domain digital signals.

The invention is directed to the characterization of an optical channel, such as an optical fiber, in an optical network. The method includes calibrating a transmitter by measuring its transmitter and dispersion eye closure (TDEC, in the case of non-return to zero optical (NRZ) optical systems or transmitter and dispersion eye closure quaternary (TDECQ, in the case of 4-level pulse amplitude modulation (PAM4) optical systems). That calibrated transmitter is used to characterize the optical channel being tested by providing a measure of its stressed eye closure (SEC) or stressed eye closure quaternary (SECQ). A loss deficit for the optical channel can be calculated by subtracting the SEC or SECQ value from the maximum TDEC or TDECQ value.