A decoding method includes: receiving a plurality of subcarrier signals each including encoded data; acquiring a predetermined amount of data from each of the plurality of subcarrier signals; correcting errors in the plurality of subcarrier signals by performing decoding arithmetic processing on the respective predetermined amounts of data acquired from the plurality of subcarrier signals in a time-division manner; and causing the decoding arithmetic processing to be consecutively performed on each of the predetermined amounts of data a predetermined number of times.

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 in an optical receiver, for decoding a received M-level pulse-amplitude-modulated, PAM-M, optical signal. An example method comprises, for a first interval, decoding (510) the received PAM-M optical signal using a standard PAM-M decoder with M-1 thresholds, using first sampling times, to obtain a first set of decoded bits, and decoding (520) the received PAM-M optical signal using a duobinary decoder with 2M-2 thresholds, at second sampling times offset from the first sampling times, to obtain second set of decoded bits. The method further comprises calculating (530) first and second error metrics corresponding to the first and second sets of decoded bits, respectively, and selecting (540) the standard PAM-M decoder or the duobinary decoder for subsequent decoding of the received PAM-M optical signal, based on the first and second error metrics.

A communications system may include a transmitter node, a receiver node, and an optical communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter and a pulse divider downstream therefrom. The receiver node may include a pulse recombiner and a pulse receiver downstream therefrom.

The present invention relates to a method for optimizing performance of a multi-span optical fiber network. Each span has an associated optical transmission fiber connected to an associated optical amplifier. Gain and output power of the associated optical amplifier are respectively controlled independently. An amplifier noise figure respectively depends on the gain of the associated optical amplifier, with each associated optical amplifier further connected to launch optical signals into a remainder of a corresponding optical transmission line. The method includes the steps of for each span, computing the amplifier noise figure and a non-linear noise generated in the span based on information about the span and using the computed amplifier noise figure and the computed non-linear noise to compute an optimum launch power, and optimizing performance of the multi-span optical fiber network based on the computed optimum launch powers of all spans.

A circuit and method for mitigating multi-path interference in direct detection optical systems is provided. Samples of an optical signal having a pulse amplitude modulated (PAM) E-field are processed by generating a PAM level for each sample. For each sample, the sample is subtracted from the respective PAM level to generate a corresponding error sample. The error samples are lowpass filtered to produce estimates of multi-path interference (MPI). For each sample, one of the estimates of MPI is combined with the sample to produce an interference-mitigated sample.

Described are, among other things, a method and a receiver for receiving a management data signal in an optical transmission system where a traffic data signal is transmitted as a NRZ modulated signal. The traffic data signal has a management data signal superimposed thereon as a pulse width modulation of the symbols of the NRZ modulated signal. The NRZ modulated signal is received with the data signal superimposed thereon and the traffic data signal is recovered. The recovered traffic data signal in anti-phase is added to the received signal. The management data signal is detected from the added signals.

A circuit and method for mitigating multi-path interference in direct detection optical systems is provided. Samples of an optical signal having a pulse amplitude modulated (PAM) E-field are processed by generating a PAM level for each sample. For each sample, the sample is subtracted from the respective PAM level to generate a corresponding error sample. The error samples are lowpass filtered to produce estimates of multi-path interference (MPI). For each sample, one of the estimates of MPI is combined with the sample to produce an interference-mitigated sample.

We disclose an optical receiver for direct detection of an intensity-modulated optical signal, the digital signal processor of which employs a clock-recovery circuit capable of reliably recovering the internal clock of the received optical signal without relying on dispersion-compensation processing even if the signal's eye pattern is substantially closed. In an example embodiment, the clock-recovery circuit comprises a frequency-domain phase detector that operates to determine and track in time the sampling phase using only a subset of the digital spectral components corresponding to the received optical signal. The determined sampling phase is then used to synchronize the digital electrical samples of the received optical signal with the internal clock thereof by way of digital interpolation or through appropriate control of the sampling frequency and phase of the receiver's analog-to-digital converter. Some embodiments of the clock-recovery circuit can beneficially be used in a two-channel optical receiver.

Systems, methods, architectures, mechanisms or apparatus for analyzing cable modem termination system (CMTS) streams by correlating anomalies found in full spectrum CMTS upstream data to changes in cable modem operational settings to identify and correct network fault conditions, model CMTS behavior, improve network performance and the like.