Aspects of the present disclosure are directed to systems, methods, and structures providing for the accurate measurement of guided acoustic-wave Brillouin scattering in optical fiber transmission systems and facilities.

An optical reception apparatus (1) of the present invention includes: a local oscillator (11) outputting local oscillation light (22); an optical mixer (12) receiving a multiplexed optical signal (21) and the local oscillation light, and selectively outputting an optical signal (23) corresponding to the wavelength of the local oscillation light from the multiplexed optical signal; a photoelectric converter (13) converting the optical signal (23) output from the optical mixer into an electric signal (24); a variable gain amplifier (15) amplifying the electric signal (24) to generate an output signal (25) whose output amplitude is amplified to a certain level; a gain control signal generating circuit (16) generating a gain control signal (26) for controlling the gain of the variable gain amplifier (15); and a monitor signal generating unit (17) generating a monitor signal (27) corresponding to the power of the optical signal (23) using the gain control signal (26).

An optical receiving device that divides receive signals obtained by receiving an optical signal using a coherent detection scheme into a plurality of frequency bands, matches timing of the receive signals along a time axis between the frequency bands resulting from the division, performs a combining process of combining the receive signals contained in the plurality of frequency bands, and compensates the receive signals for waveform distortion either before or after the combining process, includes: a first wavelength dispersion compensation unit adapted to compensate the receive signals for waveform distortion in each of the frequency bands resulting from the division; a first nonlinear compensation unit adapted to compensate the receive signals belonging to each of the frequency bands and timed with each other in a time domain for a nonlinear optical effect; and a second wavelength dispersion compensation unit adapted to compensate the receive signals belonging to each of the frequency bands and compensated for the nonlinear optical effect for wavelength dispersion in each of the frequency bands.

A method for reconfigurable optical signal processing. The method includes generating a first pump pulse by propagating a first input pump through a first dispersive medium, generating a first modulated signal by applying a parametric nonlinear wave mixing process on an input optical signal and the first pump pulse, generating a first transformed signal of the input optical signal by propagating the first modulated signal through a second dispersive medium, generating a multiplied signal by multiplying the first transformed signal by a Green's function, generating a second pump pulse by propagating a second input pump through a third dispersive medium, generating a second modulated signal by applying the parametric nonlinear wave mixing process on the multiplied signal utilizing the second pump pulse, and generating a second transformed signal of the multiplied signal by propagating the second modulated signal through a fourth dispersive medium.

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 method and structure for equalization in coherent optical receivers. Block-based LMS (BLMS) algorithm is one of the many efficient adaptive equalization algorithms used to (i) increase convergence speed and (ii) reduce implementation complexity. Since the computation of the equalizer output and the gradient of the error are obtained using a linear convolution, BLMS can be efficiently implemented in the frequency domain with the constrained frequency-domain BLMS (FBLMS) adaptive algorithm. The present invention introduces a novel reduced complexity constrained FBLMS algorithm. This new approach replaces the two discrete Fourier transform (DFT) stages required to evaluate the DFT of the gradient error, by a simple frequency domain filtering. Implementation complexity can be drastically reduced in comparison to the standard constrained FBLMS. Furthermore, the new approach achieves better performance than that obtained with the unconstrained FBLMS in ultra-high speed coherent optical receivers.

A space optical coupling apparatus, including M first couplers, a phase adjustment apparatus, N beam splitters, M second couplers, a coupling apparatus, and a controller. The first coupler receives a beam, and couples the beam to the phase adjustment apparatus. The phase adjustment apparatus includes M phase adjusters, N beam splitters, and N detectors. Each beam splitter is configured to split a received beam into two beams, one sent to a corresponding detector and the other sent to a corresponding phase adjuster. The second coupler receives output light from the coupling apparatus, and transmits the output light into the space. The coupling apparatus is configured to couple a beam onto a single-mode fiber. The controller is configured to control, based on the beam intensity detected by the detector and the beam intensity on the single-mode fiber, the M phase adjusters to adjust the phases of the received beams.

An optical multiple-input-multiple-output (MIMO) receiver includes an input port configured to receive input light; a Stokes measurement apparatus configured to generate measurements of Stokes parameters; an optical MIMO demultiplexer configured to generate a plurality of demultiplexed output light signals based on (i) the input light and (ii) the measurements of the Stokes parameters generated by the Stokes measurement apparatus; and a plurality of output ports configured to output the plurality of demultiplexed output light signals generated by the optical MIMO demultiplexer. In particular, the Stokes measurement apparatus is connected to the optical MIMO demultiplexer in a parallel arrangement.

An optical apparatus includes an attenuator, a photoelectric convertor, an amplifier, and a processor. the attenuator attenuates signal light. The photoelectric convertor converts the signal light attenuated by the attenuator into an electric signal. The amplifier adjusts a gain of the electric signal. The processor detects a monitor value of a target channel from an output signal of the amplifier, calculates a power value of the target channel from the detected monitor value, calculates a difference value between the power value and a target power value, calculates a attenuation amount by adding a current attenuation amount, which is currently set to the attenuator, to the difference value, controls the gain of the amplifier so that the difference value of the target channel is minimized when the set attenuation amount is less than zero, and sets the attenuation amount to the attenuator when the attenuation amount is zero or more.

An optical signal receiver includes a multimode waveguide for receiving a complex modulated optical signal, an optical resonator that receives the complex modulated optical signal from the multimode waveguide and converts the complex modulated optical signal to an intensity modulated signal, and a detector that is configured to convert the intensity modulated signal into an electrical signal, the electrical signal having an amplitude indicative of an intensity of the intensity modulated signal from the optical resonator, and that provides a detected signal.