A system and method for applying a time-varying phase shift to an optical signal is described. Such a phase shift results in a frequency shift of the optical signal, which can be useful for instance in sensing applications. The design uses cross phase modulation (XPM) in a nonlinear medium such as optical fiber. The pump producing the XPM experiences a change in energy along the medium, for instance due to loss. The pump and signal have mismatched group velocities such that they walk-off each other in time, and the pump pulse repetition rate is chosen so that it has a specific relationship with respect to the walk-off. The design is compatible with very low signal loss and does not require high fidelity electrical control signals. It is capable of high-efficiency one-directional serrodyne frequency shifts, as well as producing symmetric frequency shifts. It can also be made polarization independent.

An optical system, comprising a first wavelength conversion module to: adjust a power of a first pump wavelength; couple an input signal with the first pump wavelength to generate a first coupled signal; perform a first wavelength conversion of the first coupled signal to generate a first wavelength converted signal, the power of the first pump wavelength is adjusted such that the first wavelength conversion is performed with 0 dB conversion efficiency; the optical amplifier to amplify the first wavelength converted signal; a second wavelength conversion module to: adjust a power of a second pump wavelength; couple the amplified first wavelength converted signal with the second pump wavelength to generate a second coupled signal; perform a second wavelength conversion of the second coupled signal to generate a second wavelength converted signal with 0 dB conversion efficiency.

A continuous-variable quantum key distribution (CV-QKD) method and system is provided. The CV-QKD method includes: step 1: transmitting a quantum signal and a local oscillation signal synchronously based on time and polarization multiplexing, and performing detection to obtain detection data; and step 2: compensating for the detection data based on a phase compensation algorithm and public data. In this way, a phase can be compensated accurately in channel fading, so as to improve performance of the CV-QKD system.

A modulator comprises one or more resonators. Each resonator has a light confining closed loop structure, such as a ring structure, and two, three or more electrodes associated with the light-confining structure, and may be a micro-resonator. An optical signal is modulated by a digital signal using the resonator. The procedure comprises obtaining the digital signal, mapping the signal using a mapping function to produce a transformed digital signal, the transformed digital signal being selected to produce, say linear, output from the resonator, inputting the transformed digital signal via electrodes onto the resonator; and modulating the optical signal via coupling from the resonator. Suitable mapping produces 16 QAM and other modulation schemes.

An optical receiver including an optical resonator and a steering mechanism coupled to the at least one optical resonator is disclosed. The optical resonator is configured to receive a phase modulated input optical signal and to produce an intensity modulated output optical signal. An intensity modulation of the output optical signal is representative of the phase modulation of the input optical signal. The optical receiver further comprises an optical-electrical converter that detects the intensity modulated output optical signal and converts the intensity modulated output optical signal to an electrical signal, and signal processor that receives the electrical signal, performs symmetric phase change measurements based on the electrical signal, and provides a control signal to actuate the steering mechanism to steer the optical resonator to maintain normal incidence of the phase modulated input optical signal on a surface of at least one optical resonator.

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 machine-implemented method of constructing multidimensional constellations having increased minimum distances between the constellation symbols thereof compared to those of comparable conventional constellations, e.g., QPSK and QAM constellations. An example multidimensional constellation so constructed may have eight or more dimensions and may be mapped onto degrees of freedom selected from, e.g., time, space, wavelength, polarization, and the in-phase and quadrature-phase components, of the optical field. The disclosed method is beneficially used to generate multidimensional modulation formats characterized by constant total optical transmit power per modulation time slot and/or applicable to the transmission of multidimensional constellation symbols having separate parts thereof primarily carried by different respective guided modes of the optical fiber. Example methods and apparatus for implementing such multidimensional modulation formats are also disclosed herein.

Controller and control method are provided. In particular, a controller is disclosed as being configured to hold intensities of a monitor signal, which changes according to an output from a region in a device, before and after altering a state of a portion in the region and control the state of the portion based on a difference between the held intensities.

In a first embodiment, a method and apparatus for encoding a first spectral efficiency into a second spectral efficiency; wherein the second spectral efficiency has a higher order than the first spectral efficiency. In a second embodiment, a method and apparatus for achieving at least two spectral efficiencies using a single type of modulation.

A method for operating an optical modulator includes receiving a narrowband radio frequency (“RF”) signal. The method further including, responsive to receiving the narrowband RF signal, modulating the narrowband RF signal using a double sideband suppressed carrier (“DSBSC”) modulation scheme to generate a DSBSC optical signal. The method further including transmitting the DSBSC optical signal to an optical transmitter.