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

A method, system, and apparatus for emulating impairments in a communication system.

A decoding system, a decoding controller, and a decoding control method are provided. In the decoding system, a decoding controller is disposed between two adjacent decoders. The decoding controller determines whether to perform turn-off based on a non-turn-off indication received by a previous-stage decoder, a turn-off indication output by the previous-stage decoder, and historical turn-off probability statistics. This is equivalent to adding a buffer zone between the two adjacent decoders.

Consistent with the present disclosure, the above-described subcarrier noise, which may be characterized as a linear filtering effect, may be reduced or eliminated by providing a first multiple-input multiple output (MIMO) circuits at the transmit end of an optical link and providing a second MIMO circuit at the receive end of the optical link. The first MIMO may include a first plurality of filters, each of which may include a finite-impulse response (FIR) filter having variable coefficients or tap weights that may be changed or adapted to minimize subcarrier noise associated with the modulator, as well as D/A and analog circuitry, at the transmit end of the optical link. In addition, the second MIMO may include a second plurality of filters, each of which may also include an FIR filter having variable coefficients or tap weights that may be changed or adapted to minimized subcarrier noise associated with the optical hybrids, as well as A/D and analog circuitry, at the receive end of the optical link. In one example, a least means square (LMS) technique may be employed to calculate desired coefficients or tap weights whereby an error determined based on the signal detected at the receiver is minimized to update the coefficients of the FIR filters.

A detector coherent-receives a signal being transmitted from a transmitter. A filter group includes a plurality of filters connected in series along a signal path of a reception signal. The plurality of filters include a plurality of non-linear distortion compensation filters and one or more linear distortion compensation filters. A coefficient updating unit controls a filter coefficient of the plurality of non-linear distortion compensation filters and a filter coefficient of at least some of the linear distortion compensation filters. The coefficient updating unit adaptively controls the filter coefficient, by using an error back propagation method, based on a difference between an output signal being output from the filter group and a predetermined value of the output signal.

This disclosure describes digitally generating sub-carriers (SCs) to provide isolation and dynamic allocation of bandwidth between uplink and downlink traffic between transceivers that are communicatively coupled via a bidirectional link including one or more segments of optical fiber. Separate uplink and downlink communication channels may be created using digitally generated SCs and using the same transmitter laser. In some implementations, one or more of the nodes include a transceiver having at least one laser and one digital signal processing (DSP) operable for digitally generating at least two SCs and detecting at least two SCs. The transceiver can transmit selected SCs, and can receive other SCs. Accordingly, the transceiver can facilitate bidirectional communication, for example, over a single optical fiber link. In some instances, techniques can facilitate dynamic bandwidth assignment by facilitating adding or blocking of optical subcarriers from transmission in an uplink or downlink direction.

An ADC (12) in an optical receiver (1) generates a sample signal composed of time series samples by oversampling a received signal that is an electrical signal converted from an optical signal by a light receiving unit (11). A symbol timing detection unit (132) of a DSP unit (13) detects a symbol timing in the sample signal. When it is determined that a symbol timing is appearing at a longer interval than a predetermined interval based on this detection result, a symbol timing adjusting unit (133) skips one or more samples included in the sample signal to read out samples at the predetermined interval, while when it is determined that the symbol timing is appearing at a shorter interval than the predetermined interval, the symbol timing adjusting unit inserts the same samples as one or more samples included in the sample signal immediately after the one or more samples to read out the samples at the predetermined interval.

A communication network includes a coherent optics transmitter, a coherent optics receiver, an optical transport medium operably coupling the coherent optics transmitter to the coherent optics receiver, and a coherent optics interface. The coherent optics interface includes a lineside interface portion, a clientside interface portion, and a control interface portion.

An optical network communication system utilizes a coherent passive optical network (PON). The system includes an optical line terminal (OLT) having a downstream transmitter and an upstream receiver system configured for time-wavelength division coherent detection. The system further includes a splitter in operable communication with the OLT, and a plurality of optical network units (ONUs) in operable communication with the splitter. Each of the plurality of ONUs is configured to (i) receive downstream coherent burst signals from the OLT, and (ii) transmit at least one upstream burst signal to the OLT. The upstream receiver system further includes a power control module and a local oscillator (LO) configured to generate an optical LO signal The power control module is configured to adaptively control, in real-time, a power level of the optical LO signal.

An optical coherent transceiver includes a transmitter and a receiver that share laser light. The transmitter includes a pair of parent MZIs in a modulator, which are parent MZIs configured to perform quadrature modulation on the laser light according to a bias voltage, and two pairs of child MZIs in the modulator, which are child MZIs configured to perform phase modulation on the laser light according to the bias voltage. The transmitter includes a control circuit configured to control the bias voltage to be applied to the parent MZIs and the child MZIs. The control circuit is configured to, when turning light output of the transmitter off, with input of a data signal being set off, control the bias voltage such that a phase difference between the parent MZIs is around 90 degrees and a phase difference between the child MZIs in each of the pairs is 180 degrees.