Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, a transmitter includes a laser operable to supply an optical signal, a digital signal processor operable to supply first electrical signals based on first data input to the digital signal processor and second data input to the digital signal processor, digital-to-analog conversion circuitry operable to output second electrical signals based on the first electrical signals, modulator driver circuitry is operable to output third electrical signals based on the second electrical signals, and an optical modulator operable to supply first and second modulated optical signals based on the third electrical signals. The first modulated optical signal includes a plurality of optical subcarriers carrying user data. The plurality of optical subcarriers also being amplitude modulated to carry control information.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for performing asymmetric pulse-shaping filtering. In some implementations, a receiver comprises a detector circuit operable to receive optical signal data from an optical link. The receiver comprises a filter circuit, coupled to the detector circuit, operable to (i) filter the optical signal data according to an asymmetric filtering scheme and (ii) output the filtered optical signal data, wherein the asymmetric filtering scheme comprises utilizing a shaping filter with first criteria, the first criteria including one or more values greater than one or more values of second criteria utilized by a shaping filter at a transmitter, the transmitter communicating with the receiver.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for applying non-linearity to digital subcarriers. A receiver includes a detector circuit operable to receive a first optical signal over an optical link, the first optical signal carrying first data. The receiver includes a carrier recovery estimation circuit operable to generate compensated data by correcting errors in the first data. The receiver includes a non-linear coefficient estimation circuit operable to (i) receive the compensated data, and (ii) estimate one or more non-linear coefficients, wherein information indicative of the estimated non-linear coefficients is transmitted over an optical network, such that a second optical signal is transmitted based, at least in part, on the estimated non-linear coefficients, the second optical signal being received by the receiver.

Abstract: Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, a transmitter includes a laser operable to supply an optical signal, a digital signal processor operable to supply first electrical signals based on first data input to the digital signal processor and second data input to the digital signal processor, digital-to-analog conversion circuitry operable to output second electrical signals based on the first electrical signals, modulator driver circuitry is operable to output third electrical signals based on the second electrical signals, and an optical modulator operable to supply first and second modulated optical signals based on the third electrical signals. The first modulated optical signal includes a plurality of optical subcarriers carrying user data. The plurality of optical subcarriers also being amplitude modulated to carry control information.

Abstract: A digital signal processing method and apparatus is described. The digital processing apparatus comprises a coarse carrier recovery module for performing a coarse carrier compensation of a received modulated signal; and a trellis-based equalization module selectable between a first mode for performing a trellis-based equalization to compensate a residual inter-symbol interference of the received modulated signal and a second mode for performing a trellis-based equalization to compensate a residual phase noise of the received modulated signal.

Abstract: An optical device with integrated Optical Time Domain Reflectometer (OTDR) functionality and method for the same is provided. The optical device includes a transmitter and an Optical Time Domain Reflectometer (OTDR) module, The transmitter is configured to generate an Optical Time Domain Reflectometer (OTDR)-modulated optical supervisory channel (OSC) signal by applying an OTDR modulation to an optical supervisory channel (OSC) signal using an OTDR signal and to transmit the OTDR-modulated OSC signal. The OTDR module is configured to generate the OTDR signal, to monitor a returned light signal, to determine transmitter noise compensation information, and to generate OTDR trace information using transmitter noise compensation information and the monitored returned light signal.

Abstract: A digital signal processing method and apparatus is described. The digital processing apparatus comprises a coarse carrier recovery module for performing a coarse carrier compensation of a received modulated signal; and a trellis-based equalization module selectable between a first mode for performing a trellis-based equalization to compensate a residual inter-symbol interference of the received modulated signal and a second mode for performing a trellis-based equalization to compensate a residual phase noise of the received modulated signal.

Abstract: A method and apparatus for performing residual phase noise compensation is described. A coarse carrier compensation of a received modulated signal is performed to obtain a coarse carrier compensated signal and a trellis-based residual carrier recovery is performed to estimate a residual phase noise of the coarse carrier compensated signal. The coarse carrier compensated signal is compensated based on the estimated residual phase noise.

Abstract: An optical device with integrated Optical Time Domain Reflectometer (OTDR) functionality and method for the same is provided. The optical device includes a transmitter and an Optical Time Domain Reflectometer (OTDR) module, The transmitter is configured to generate an Optical Time Domain Reflectometer (OTDR)-modulated optical supervisory channel (OSC) signal by applying an OTDR modulation to an optical supervisory channel (OSC) signal using an OTDR signal and to transmit the OTDR-modulated OSC signal. The OTDR module is configured to generate the OTDR signal, to monitor a returned light signal, to determine transmitter noise compensation information, and to generate OTDR trace information using transmitter noise compensation information and the monitored returned light signal.