A coherent optical receiver, and an optical communication device and system, and relates to the field of optical communication. A polarization control component in the coherent optical receiver can deflect, driven by a feedback control circuit, a state of polarization of local oscillator light, and decompose the local oscillator light into two channels of light having equal or similar optical power. Therefore, the state of polarization of the local oscillator light is not deflected randomly and thereby coherent detection is not affected. Moreover, an azimuth of a half-wave plate device in the polarization control component can be deflected continuously, allowing continuous tracking and adjustment for the state of polarization of the local oscillator light.

An adaptive receiver comprising a current buffer, an inverter-based transimpedance that receives input from the current buffer, an average current control loop that feeds back from the inverter-based transimpedance to the current buffer, a variable gain circuit that receives input from the inverter-based transimpedance, a differential voltage amplifier that receives input from the variable gain circuit, an automatic gain control loop that feeds back from the differential voltage amplifier to the inverter-based transimpedance and variable gain circuit, and a differential buffer that receives input from the differential voltage amplifier.

A method communicates data with a platform. A platform receives modulated coherent optical signals modulated using radio frequency signals encoding sensor data and generates an input current in response to receiving the modulated coherent optical signals at a receiver system in the platform. The platform recovers the radio frequency signals from the input current in a manner that adjusts for changes in the modulated coherent optical signals caused by variations in received optical intensity occurring during propagation of the modulated coherent optical signals. The platform outputs the radio frequency signals encoding the data.

A signal processing device includes: a memory; and a processor coupled to the memory and configured to: compensate an electric field signal representing an electric field component in an optical signal input from a transmission channel for an optical frequency offset between light sources on a transmission side and a reception side of the optical signal based on a compensation value; calculate an estimated value of the optical frequency offset from data having a fixed pattern in the electric field signal; generate a plurality of candidates for the compensation value from the estimated value; calculate power of the optical signal compensated for the optical frequency offset based on each of the plurality of candidates; and select an initial value of the compensation value from the plurality of candidates based on the power of the optical signal.

Upon receipt of a coherent optical signal that includes a training signal generated using a code sequence constituted by multi-value phase modulation symbols, in which a deviation angle of a vector average of a one-symbol delay differential component of a signal generated on the basis of the code sequence has a prescribed angle and a modulation phase difference between adjacent symbols has a fixed, repeated pattern, a reception training signal corresponding to a training code sequence for frequency offset estimation is detected within a reception signal acquired by converting the received coherent optical signal into an electric signal, a plurality of delay differential components are calculated on the basis of the detected reception training signal and at least two delay signals of the reception training signal, each delay signal having a different number of delay symbols, and an averaged frequency offset amount is calculated using the calculated plurality of delay differential components.

Joint estimation of the framer index and the frequency offset in an optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. By identifying the beginning of the header portion of a data frame, the receiver can then process data received from the transmitter in a manner synchronous to the manner in which the data was transmitted by the transmitter.

A digital receiver is configured to process a polarization multiplexed carrier from a communication network. The polarization multiplexed carrier includes a first polarization and a second polarization. The receiver includes a first lane for transporting a first input signal of the first polarization, a second lane for transporting a second input signal of the second polarization, a dynamic phase noise estimation unit disposed within the first lane and configured to determine a phase noise estimate of the first input signal, a first carrier phase recovery portion configured to remove carrier phase noise from the first polarization based on a combination of the first input signal and a function of the determined phase noise estimate, and a second carrier phase recovery portion configured to remove carrier phase noise from the second polarization based on a combination of the second input signal and the function of the determined phase noise estimate.

Upon receiving a communications signal conveying symbols at a symbol period T, a receiver applies filter coefficients to a digital representation of the communications signal, thereby generating filtered signals having a shape in the frequency domain characterized by a bandwidth expansion factor α, where components of the filtered signals correspond to angular frequencies $\omega =-\frac{\pi \left(1+\alpha \right)}{T}\mathrm{.Math.}-\frac{\pi \left(1-\alpha \right)}{T},+\frac{\pi \left(1-\alpha \right)}{T}\mathrm{.Math.}+\frac{\pi \left(1+\alpha \right)}{T}.$
The receiver calculates first-order components from a first phase derivative of the components at a first differential distance, second-order components from a second phase derivative of the first-order components at a second differential distance, and composite second-order components from an average of the second-order components over multiple time in

A signal processing device includes: a memory; and a processor coupled to the memory and configured to: compensate an electric field signal representing an electric field component in an optical signal input from a transmission channel for an optical frequency offset between light sources on a transmission side and a reception side of the optical signal based on a compensation value; calculate an estimated value of the optical frequency offset from data having a fixed pattern in the electric field signal; generate a plurality of candidates for the compensation value from the estimated value; calculate power of the optical signal compensated for the optical frequency offset based on each of the plurality of candidates; and select an initial value of the compensation value from the plurality of candidates based on the power of the optical signal.

When a frequency deviation compensation amount is compensated for by use of frequency shift, a phase offset occurs between adjacent input blocks included in a plurality of input blocks as divided, with the result that an error occurs in a reconstructed bit sequence. A frequency deviation compensation system of the invention is characterized by comprising: a frequency deviation compensation means for compensating for a frequency deviation occurring in a signal by use of frequency shift; and a phase offset compensation means for compensating for a phase offset occurring, in the signal, due to the frequency shift.