Abstract: Disclosed herein is an optical transport system configured to transport an amplitude-modulated optical signal generated at the transmitter using single-sideband modulation of an optical carrier and detected at the receiver using direct optical detection. The receiver is configured to estimate the level of signal-signal beat interference (SSBI) in the electrical signal generated upon direct detection of the received optical signal by first converting this electrical signal into a modified baseband signal configured for single-sideband modulation and then squaring and appropriately scaling this modified baseband signal. The receiver is further configured to subtract the estimated level of SSBI from the electrical signal generated by the direct optical detector and to process the resulting corrected electrical signal to recover the data encoded in the amplitude-modulated optical signal. Example analog and digital circuits for estimating the level of SSBI at the receiver are disclosed.

Abstract: Disclosed herein is an optical transport system configured to transport an amplitude-modulated optical signal generated at the transmitter using single-sideband modulation of an optical carrier and detected at the receiver using direct optical detection. The receiver is configured to estimate the level of signal-signal beat interference (SSBI) in the electrical signal generated upon direct detection of the received optical signal by first converting this electrical signal into a modified baseband signal configured for single-sideband modulation and then squaring and appropriately scaling this modified baseband signal. The receiver is further configured to subtract the estimated level of SSBI from the electrical signal generated by the direct optical detector and to process the resulting corrected electrical signal to recover the data encoded in the amplitude-modulated optical signal. Example analog and digital circuits for estimating the level of SSBI at the receiver are disclosed.

Abstract: An optical receiver having an electronic dispersion-compensation module with two parallel signal-processing branches configured to provide a greater range of dispersion compensation than that provided by a prior-art device of comparable implementation complexity. In an example embodiment, each of the signal-processing branches includes a respective bank of finite-impulse-response filters that are configured in accordance with a different respective approximation of the group delay that needs to be compensated. The two group-delay approximations used by the filter banks rely on different respective step functions, each having a respective plurality of quantized steps, with the transitions between adjacent steps in one step function being spectrally aligned with the flat portions of the corresponding steps in the other step function.

Abstract: An optical receiver comprising an optical-to-electrical converter and a digital processor having first and second equalizer stages. The optical-to-electrical converter is configured to mix an optical input signal and an optical reference signal to generate a plurality of electrical digital measures of the optical input signal. The digital processor is configured to process the electrical digital measures to recover the data carried by the optical input signal. The first equalizer stage in the digital processor is configured to perform chromatic-dispersion-compensation processing in a manner that does not mix different electrical digital measures prior to signal-equalization processing in the second equalizer stage, which enables the first equalizer stage to operate using real-valued arithmetic.

Abstract: In a representative embodiment, a disclosed receiver of an optical multicarrier offset-quadrature-amplitude-modulated (MC-OQAM) signal is configured to track and compensate for the phase error in the local-oscillator (LO) signal with respect to a carrier wave of a modulated subcarrier of the optical MC-OQAM signal by tracking a minimum of a cost function that is sensitive to crosstalk between in-phase and quadrature components of the modulated subcarrier and/or crosstalk between the modulated subcarrier and at least one other modulated subcarrier of the optical MC-OQAM signal. The receiver can operate based on pure feed-forward processing and compensate the phase error in real time and without relying on pilot symbols or a PLL circuit coupled to the LO source.

Abstract: An optical receiver comprising an optical-to-electrical converter and a digital processor having one or more equalizer stages. The optical-to-electrical converter is configured to mix an optical input signal and an optical local-oscillator signal to generate a plurality of electrical digital measures of the optical input signal. The digital processor is configured to process the electrical digital measures to recover the data carried by the optical input signal. At least one of the equalizer stages is configured to perform signal-equalization processing in which the electrical digital measures and/or digital signals derived from the electrical digital measures are being treated as linear combinations of arbitrarily coupled signals, rather than one or more pairs of 90-degree phase-locked I and Q signals.

Abstract: An optical receiver having an electronic dispersion-compensation module with two parallel signal-processing branches configured to provide a greater range of dispersion compensation than that provided by a prior-art device of comparable implementation complexity. In an example embodiment, each of the signal-processing branches includes a respective bank of finite-impulse-response filters that are configured in accordance with a different respective approximation of the group delay that needs to be compensated. The two group-delay approximations used by the filter banks rely on different respective step functions, each having a respective plurality of quantized steps, with the transitions between adjacent steps in one step function being spectrally aligned with the flat portions of the corresponding steps in the other step function.

Abstract: An optical receiver comprising an optical-to-electrical converter and a digital processor having one or more equalizer stages. The optical-to-electrical converter is configured to mix an optical input signal and an optical local-oscillator signal to generate a plurality of electrical digital measures of the optical input signal. The digital processor is configured to process the electrical digital measures to recover the data carried by the optical input signal. At least one of the equalizer stages is configured to perform signal-equalization processing in which the electrical digital measures and/or digital signals derived from the electrical digital measures are being treated as linear combinations of arbitrarily coupled signals, rather than one or more pairs of 90-degree phase-locked I and Q signals.

Abstract: In a representative embodiment, a disclosed receiver of an optical multicarrier offset-quadrature-amplitude-modulated (MC-OQAM) signal is configured to track and compensate for the phase error in the local-oscillator (LO) signal with respect to a carrier wave of a modulated subcarrier of the optical MC-OQAM signal by tracking a minimum of a cost function that is sensitive to crosstalk between in-phase and quadrature components of the modulated subcarrier and/or crosstalk between the modulated subcarrier and at least one other modulated subcarrier of the optical MC-OQAM signal. The receiver can operate based on pure feed-forward processing and compensate the phase error in real time and without relying on pilot symbols or a PLL circuit coupled to the LO source.