Sampling circuitry for receiving an analog signal from photodetector circuitry and generating a sample analog signal. Equalization circuitry for generating an equalized signal comprising first and second sample values corresponding with a cursor tap and a first postcursor tap, and one or more third sample values corresponding with taps other than the cursor tap and the first postcursor tap. In the equalized signal, amplitudes of the first and second sample values are substantially equal while the third sample values are attenuated relative to the first and second sample values. The first and second sample values correspond with two or more first symbols of a first alphabet. Data slicer and modulo circuitry to generate a data signal based on the equalized signal and perform a modulo operation on the two or more first symbols and to generate one or more second symbols. The second symbols are according to a second alphabet.

According to one example, errors in a logical signal from a data slicer are detected and a power supply voltage is adjusted based on the detected errors.

A Dual Parallel (DP)-Inphase/Quadrature (I/Q) Mach-Zehnder Modulator (MZM) bias controller configured to generate a pair of orthogonal dither signals; multiply the pair of dither signals to create a second order orthogonal dither signal; and lock an Inphase (I) I MZM of a DP-I/Q MZM to a value of a corresponding I component of a transmission signal by applying the pair of orthogonal dither signal to a Quadrature (Q) MZM and a Phase (P) MZM of the DP-I/Q MZM; applying an I bias signal to the I MZM of the DP-I/Q MZM; detecting an output of the DP-I/Q MZM; and determining an I error signal in the output of the I MZM of the DP-I/Q MZM based on the product of second order dither signal and the output of the DP-I/Q MZM.

There is provided an optical medium reproduction device that optically reproduces an optical medium in which a plurality of tracks are provided, the optical medium reproduction device including: a detection unit configured to divide a cross-section of a beam returning from the optical medium into at least one channel corresponding to an outer region in a radial direction, at least one channel corresponding to a region that is different in position in a tangential direction, and a channel corresponding to the other region, and form detection signals of the channels; a multi-input equalizer unit including a plurality of equalizer units to which the detection signals of the plurality of channels are supplied, respectively, the multi-input equalizer unit being configured to calculate outputs of the plurality of equalizer units and output the outputs as an equalized signal in a manner that a phase difference between two of the regions is set to be a predetermined phase difference; and a binarization unit configured to perform a binarization process on the equalized signal to obtain binary data.

A method for allocating bandwidth to a first ONU, a second ONU, M.sub.1 ONUs, and M.sub.2 ONUs includes, during an allocation cycle, (i) granting a respective upstream time slot to, of a plurality of N ONUs, only each of the M.sub.1 ONUs, and (ii) granting a first upstream time slot to the first ONU. Each of the M.sub.1 ONUs and M.sub.2 ONUs is one of the plurality of N ONUs. The method also includes, during a subsequent cycle, (i) granting a respective upstream time slot to, of the plurality of N ONUs, only each of the M.sub.2 ONUs. The N ONUs includes a skipped-ONU that is one of either, and not both, the M.sub.1 ONUs and the M.sub.2 ONUs. The method includes, during the subsequent allocation cycle, granting a second upstream time slot to a second ONU, which is not one of the plurality of N ONUs.

An optical receiver that includes an input port configured to receive intensity modulated optical signal with multipath interference (MPI); a detector configured to convert the intensity modulated optical signal with multipath interference to an electrical signal; a high pass filter (HPF) configured to filter the electrical signal and suppress carrier-carrier beat noise induced by the MPI to produce a filtered electrical signal; and an output port configured to transmit the filtered electrical signal.

An optical receiver that includes an input port configured to receive intensity modulated optical signal with multipath interference (MPI); a detector configured to convert the intensity modulated optical signal with multipath interference to an electrical signal; a high pass filter (HPF) configured to filter the electrical signal and suppress carrier-carrier beat noise induced by the MPI to produce a filtered electrical signal; and an output port configured to transmit the filtered electrical signal.

Methods and systems for communication with a modified constellation are provided. One of the methods includes coding, by a transmitter in the user equipment, an input data stream into a constellation of symbols having at least two neighboring symbols therein which differ by more than one bit and which are separated by a modified Euclidean distance to increase a Gaussian white noise resiliency of the at least two neighboring symbols with respect to remaining symbols, the remaining symbols being separated by the Euclidean distance of exactly one bit. The method further includes modulating, by the transmitter, the symbol stream into a transmission stream.

Embodiments of the present invention provide a crosstalk suppression method and apparatus. By obtaining a first electrical signal indicating a data bit stream of a first optical signal output by a laser diode (LD) in an optical transceiver module and a transmission parameter of a photodiode (PD), adjusting the first electrical signal based on the transmission parameter of the PD to obtain a third electrical signal indicating an electrical signal transformed by the PD from the first optical signal transmitted by the LD, and subtracting the third electrical signal from a second electrical signal output by the PD in the optical transceiver module, an electrical signal generated by the optical signal transmitted by the LD and reflected or refracted to the PD is removed from the electrical signal output by the PD, thereby suppressing crosstalk and improving the sensitivity of the optical transceiver module.

Methods and systems may mitigate nonlinear noise (NLN) penalties for optical paths using spectral inversion in optical transport networks. Using a tunable dispersion compensator with an optical amplifier at each span in an optical path, the dispersion along the optical path may be modified to a normalized dispersion for each span. In this manner, the dispersion associated with NLN accumulation may be balanced by NLN compensation to reduce overall NLN levels for the optical path.