Abstract: A system and method involving a coded modulation scheme whereby different spectral efficiencies can be achieved for different transmitters in a WDM system using the same M2-QAM modulation format. A maximum achievable spectral efficiency for the transmitters may be selected and a spectral efficiency step-size of the maximum achievable spectral efficiency may be specified. The spectral efficiency for any transmitter in the system may be individually selected by reducing its spectral efficiency from the maximum achievable spectral efficiencies by a selected number of steps corresponding to the step size.

Abstract: Dispersion may be managed in an optical network by allowing accumulation of dispersion to at least ten thousand ps/nm, and several tens of thousands of ps/nm in some embodiments. The accumulated dispersion may be returned to zero or near zero at a receiver and/or at one or more branch paths coupled to the transmission path.

Abstract: A system and method including a transmitter including digital signal processor for providing a shaped data output in response to an input data stream. The shaped data output is coupled to a modulator that modulates an optical signal in response to the shaped data output to provide a non-rectangular shaped output having channel spacing greater than Nyquist channel spacing. Providing a shaped output consistent the present disclosure mitigates the effects of non-linear impairments in an optical transmission system.

Abstract: A system and method involving a coded modulation scheme whereby different spectral efficiencies can be achieved for different transmitters in a WDM system using the same M2-QAM modulation format. A maximum achievable spectral efficiency for the transmitters may be selected and a spectral efficiency step-size of the maximum achievable spectral efficiency may be specified. The spectral efficiency for any transmitter in the system may be individually selected by reducing its spectral efficiency from the maximum achievable spectral efficiencies by a selected number of steps corresponding to the step size.

Abstract: A system and method for blind equalization of a QAM signal. Equalization is achieved using an algorithm characterized by cost function that is a function the Euclidian distance, e.g. the minimum Euclidian distance, between points of the constellation associated with the QAM signal, i.e. the distance between symbols.

Abstract: A soft decision threshold control system and method may be used with a forward error correction (FEC) scheme to adjust or tune one or more soft decision thresholds in response to one or more bit value averages for the threshold(s) and in response to a bit error rate (BER). The bit value average for a soft decision threshold generally refers to an average number of binary values (e.g., logic ones and/or zeros) occurring in a bit stream detected using the soft decision threshold. For different BER levels in a particular system, for example, one or more of the soft decision thresholds may have a predetermined bit value average, which has been determined to provide a certain level of performance (e.g., an optimum performance). Thus, one or more of the soft decision thresholds may be adjusted such that the bit value averages for the soft decision thresholds are adjusted as a function of the BER.

Abstract: A system and method for blind equalization of a QAM signal. Equalization is achieved using an algorithm characterized by cost function that is a function the Euclidian distance, e.g. the minimum Euclidian distance, between points of the constellation associated with the QAM signal, i.e. the distance between symbols.

Abstract: A detection system and method may be used to detect data transmitted in a signal with data pattern dependent signal distortion such as intersymbol interference. In general, a detection system and method compares samples of a received signal with stored samples of distorted signals associated with known data patterns and selects the known data patterns that correspond most closely with the samples of the received signal. The detection system and method may thus mitigate the effects of data pattern dependent signal distortion.

Abstract: A detection system and method may be used to detect data transmitted in a signal with data pattern dependent signal distortion. In general, a detection system and method compares samples of a received signal with stored samples of distorted signals associated with known data patterns and selects the known data patterns that correspond most closely with the samples of the received signal. The detection system and method may thus mitigate the effects of data pattern dependent signal distortion.

Abstract: Dispersion may be managed in an optical network by allowing accumulation of dispersion to at least ten thousand ps/nm, and several tens of thousands of ps/nm in some embodiments. The accumulated dispersion may be returned to zero or near zero at a receiver and/or at one or more branch paths coupled to the transmission path.

Abstract: An optical amplifier including gain equalization and system incorporating the same. The amplifier includes a Raman portion and an EDFA portion with a gain flattening filter coupled between the Raman portion and the EDFA.

Abstract: A detection system and method may be used to detect data transmitted in a signal with data pattern dependent signal distortion. In general, a detection system and method compares samples of a received signal with stored samples of distorted signals associated with known data patterns and selects the known data patterns that correspond most closely with the samples of the received signal. The detection system and method may thus mitigate the effects of data pattern dependent signal distortion.

Abstract: A detection system and method may be used to detect data transmitted in a signal with data pattern dependent signal distortion such as intersymbol interference. In general, a detection system and method compares samples of a received signal with stored samples of distorted signals associated with known data patterns and selects the known data patterns that correspond most closely with the samples of the received signal. The detection system and method may thus mitigate the effects of data pattern dependent signal distortion.

Abstract: Dispersion may be managed in an optical network configured to transmit differential phase shift keying (DPSK) modulated signals by allowing accumulation of dispersion to thousands of ps/nm before compensating. A dispersion map providing a negative average dispersion and a minimum dispersion wavelength outside of the signal band may be employed.

Abstract: A soft decision threshold control system and method may be used with a forward error correction (FEC) scheme to adjust or tune one or more soft decision thresholds in response to one or more bit value averages for the threshold(s) and in response to a bit error rate (BER). The bit value average for a soft decision threshold generally refers to an average number of binary values (e.g., logic ones and/or zeros) occurring in a bit stream detected using the soft decision threshold. For different BER levels in a particular system, for example, one or more of the soft decision thresholds may have a predetermined bit value average, which has been determined to provide a certain level of performance (e.g., an optimum performance). Thus, one or more of the soft decision thresholds may be adjusted such that the bit value averages for the soft decision thresholds are adjusted as a function of the BER.

Abstract: A WDM optical transmission system and method uses slope compensation at the transmit terminal and/or the receive terminal. The system and method may be used with modulation formats with a short pulse width and a broad optical spectrum.

Abstract: The soft decision thresholds in a soft decision forward error correction (FEC) system may be adjusted based on mutual information of a detected signal. In one embodiment, a recursive algorithm may be used to optimize threshold values by maximizing the mutual information. In another embodiment, an adaptive scheme may be used to optimize threshold values based on a pre-knowledge of the noise in the channel. In a further embodiment, an adaptive scheme may be used to optimize threshold values by without pre-knowledge of the noise in the channel.

Abstract: An optical amplifier including gain equalization and system incorporating the same. The amplifier includes a Raman portion and an EDFA portion with a gain flattening filter coupled between the Raman portion and the EDFA.

Abstract: An optical communication system configured to operate with optical signals at lower signal to noise ratios than previously contemplated. The communication system includes a receiver having an optical pre-processor coupled between a demultiplexer and a detector. The optical pre-processor includes either an optical polarization section having a polarization rotator and an optical polarizer, a phase modulation section that includes a phase modulator and a dispersion element and a clock recovery circuit, or an amplitude modulation section that includes an amplitude modulator clock recovery circuit and a spectral shaping filter.

Abstract: A WDM optical transmission system and method uses slope compensation at the transmit terminal and/or the receive terminal. The system and method may be used with modulation formats with a short pulse width and a broad optical spectrum.