Systems, devices and techniques for receiving a signal comprising a quadrature duobinary modulated signal include performing channel equalization of the received signal using a constant multi-modulus to obtain a set of channel estimation coefficients and a stream of symbols, partitioning, based on modulus, the stream of symbols into three partitions, estimating carrier frequency based on the partitioned stream of symbols, recovering a phase of the signal using a maximum likelihood algorithm, and decoding the partitioned stream of symbols to recover data.

Disclosed are a chromatic dispersion estimation method and device in optical coherent communication, wherein, the method includes: performing a fast Fourier transform on IQ-imbalance compensated data to obtain frequency-domain data in two polarization directions; calculating autocorrelation sequences of the frequency-domain data and performing an inverse fast Fourier transform on the values of the autocorrelation sequences; calculating modulus squares of the results of the inverse fast Fourier transform, and adding the results in the two polarization directions to obtain; determining a mean value of s of a plurality of data sets; calculating an index of the maximum value of, and estimating a dispersion value of the optical fiber link according to the index of the maximum value of. The abovementioned technical solution allows a significantly accurate and rapid estimation of dispersion values.

Systems and methods for autonomous signal modulation format identification are disclosed. In an example embodiment of the disclosed technology, a method includes applying higher-order statistics to an input signal to identify the input signal's modulation format. The method may include applying higher-order statistics to the input signal to calculate higher-order cumulant values for the input signal as higher-order cumulants are indicative of a particular modulation format signature. The method may further include employing a decision tree to determine the modulation format of the input signal.

A carrier recovery unit is provided including: separation-and-output section that outputs separated symbol group formed into block; a priori state-estimation section that obtains a priori estimate acquired by estimating values processed this time from among values of intra-block frequency and central phase processed last time; provisional compensation section that provisionally compensates the phase of each separated symbol based on the a priori estimation phase; decision section that performs decision based on the reference signal for the symbol before decision, and obtains symbol after decision; error-estimation section that calculates the frequency and phase errors; a posteriori state-estimation section that obtains a posteriori estimate based on the frequency and phase errors; actual compensation section that actually compensates the phase based on the a posteriori estimation phase; and feedback processing section that feeds back the a posteriori estimate as the values processed last time to the a priori state estimation section.

In an inter-vehicle communication system, a first terminal included in a first vehicle includes a first control unit that receives a first relative phase between a third vehicle and a second vehicle transmitted by a second terminal included in the second vehicle and calculates, based on the received first relative phase and a second relative phase between the first vehicle and the second vehicle, a third relative phase between the first vehicle and the third vehicle, and the second terminal includes a second control unit that transmits the first relative phase to the first vehicle.

An optical receiver including: a phase modulation unit that generates local oscillation light and modulates a phase of the local oscillation light; a coherent detection unit that causes a received optical signal and the local oscillation light phase-modulated by the phase modulation unit to interfere and converts the optical signal to an electrical signal; a polarization separation/adaptive equalization unit that performs polarization separation and adaptive equalization on the electrical signal after coherent detection; and decoding units that decode the polarization-separated electrical signals outputted from the polarization separation/adaptive equalization unit.

A phase difference multiplier circuit is disclosed that includes first and second delay circuits to apply two different quantities of delay to first and second input signals. The first and second delay circuits may operate in a first mode where a first and smaller amount of delay is imparted to the respective input signals. The first and second input signals differ in phase, and a transition in the first signal will be followed by a similar transition in the second signal. Following the transition of the first signal reaching the input of the first delay circuit, the similar transition will reach the input of the second delay circuit. In response to the transition reaching the input of the second delay circuit, the first and second delay circuits are then operated to impart a second and larger amount of delay to the first and second signals. At the output of the first and second delay circuits, the duration of the difference in phase between the first and second signals is increased by a multiplication factor. Extending the duration in such a manner may, for example, make the initial difference in phase easier to measure.

Aspects of the present disclosure describe systems, methods. and structures for vibration detection using phase recovered from an optical transponder with coherent detection. Advantageously, our systems, methods, and structures leverage contemporary digital coherent receiver architecture in which various adaptive DSP operations performed to recover transmitted data track optical phase. The phase is extracted at low overhead cost, allowing a digital coherent transponder to perform vibration detection/monitoring as an auxiliary function to data transmission. Demonstration of vibration detection and localization based on the extraction of optical phase from payload-carrying telecommunications signal using a coherent receiver in a bidirectional WDM transmission system is shown and described.

The method includes receiving, at a first optical communication device, feedback information on training of a neural network from at least one second optical communication device, the neural network configured to process a signal received from the first optical communication device, the feedback information at least including a training performance indication for training of the neural network conducted at the at least one second optical communication device; updating, based on the feedback information, a first initial parameter value set for the neural network maintained at the first optical communication device, to obtain a second initial parameter value set for the neural network; and transmitting the second initial parameter value set to at least one further second optical communication device, for training of the neural network to be conducted at the at least one further second optical communication device based on the second initial parameter value set.

An apparatus includes an optical source of an optical wavelength carrier, an optical modulator to receive the optical wavelength carrier, and an optical data receiver. The optical data modulator is configured to produce, from the optical wavelength carrier, an optical signal to carry separate data on different first and second components thereof in individual modulation periods during data transmission and to carry a training sequence on one of the components during time slots for calibration. The first component is relatively phase offset from the second component in the optical signal. The optical data modulator alternates the one of the components between the first and second components over the time slots for calibration. The optical receiver is connected to receive a portion of the optical signal and to temporally interleave a measurement of a characteristic of the first component and a measurement of a characteristic of the second component over the time slots for calibration. The optical receiver is configured to feedback information to the optical data modulator based on the measured characteristics. The optical data modulator is configured to reduce an imbalance between the two components of the optical carrier during data transmission based on the information.