A method for compensating the distortions introduced by impairments of MZMz implementing an optical transmitter, according to which the level of total amplitude and phase distortions caused by the optical transmitter is measured and all impairments in the constellation domain are compensated by pre-distorting the input signal to be transmitted by symmetrically adding imbalance to the voltage applied to the MZM arms. The imbalance is determined by introducing a phase rotation in either I or in the Q path of the optical transmitter, which compensates the total amplitude distortion, and also introducing a phase rotation to both I and Q paths of the optical transmitter, which compensate the total phase distortion and the phase shift caused by compensating the amplitude distortion, until reaching a desired operating point, which corresponds to the level of pre-distortion.

A system is provided along a route of a network including a first transponder at a first node and a second transponder at a second node. The system further includes one or more processors configured to detect, in a first waveform measured at the first transponder, a first signature at a first time point, and configured to detect, in a second waveform measured at the second transponder, a second signature at a second time point. The one or more processors may correlate the first waveform and the second waveform, and determine, based on the correlation, that the first signature and the second signature correspond to a same event occurring along the route of the network. Based on comparing the first time point and the second time point, the one or more processors may determine an estimated location of the event.

A receiver is configured to calculate a representation of a received signal conveying symbols at a frequency f.sub.S, the representation comprising a first frequency band and a second frequency band which are disjoint and have non-zero correlation. The receiver calculates a first term comprising a function of a phase difference between the representation at a first pair of frequencies separated by a gap Δ and comprised within the first frequency band, and a second term comprising a function of a phase difference between the representation at a second pair of frequencies separated by the gap Δ and comprised within the second frequency band, wherein the higher frequency of the first pair and the higher frequency of the second pair are separated by a gap G. An estimate of chromatic dispersion in the received signal is calculated based on the first term and the second term.

A method includes modulating a digital signal via pulse amplitude modulation (PAM) and applying Nyquist shaping to the digital signal to generate a filtered digital signal. The method also includes converting the filtered digital signal into an analog signal and transmitting the analog signal in an optical communication channel via a dense wavelength division multiplexing (DWDM) scheme.

A network element includes a client port configured to receive a signal for transmission; a line port configured to transmit the signal to a far end via Optical Transport Network (OTN); circuitry configured to communicate one or more of a fault and a status associated with the signal to the far end via OTN overhead. The circuitry configured to communicate can be for the fault and utilizes one or more Tandem Connection Monitoring (TCM) layers in the OTN overhead. The circuitry configured to communicate can be for the status and utilizes one or more of Optical Data Unit (ODU) Performance Monitoring (PM) and one or more Tandem Connection Monitoring (TCM) layers.

The present disclosure provides signal management with unequal eye spacing by: determining a dispersion slope of a channel between a transmitter and a receiver based on a temperature of the transmitter and a wavelength used by the transmitter to transmit signals over the channel; determining maximum and minimum powers for transmission over the channel; assigning a plurality of rails to a corresponding plurality of power levels, wherein amplitude differences between adjacent rails of the plurality of rails are based on the dispersion slope and produce a first eye pattern with a first Ratio of Level Mismatch (RLM) less than one; encoding, by the transmitter, data onto a conditioned signal according to the plurality of rails; and transmitting the conditioned signal over the channel, so that the conditioned signal demonstrates a second eye pattern with a second RLM greater than the first RLM when received at the receiver.

A reception apparatus includes a dispersion compensation unit configured to acquire an electrical signal resulting from conversion of an optical signal and perform, on the electrical signal, dispersion compensation with a predetermined compensation amount, a clip rate measurement unit configured to measure a clip rate for the electrical signal subjected to the dispersion compensation, and a control unit configured to detect the compensation amount that minimizes the clip rate.

A digital coherent receiver includes: an adaptive equalizer configured to execute, using a first tap coefficient, adaptive equalization processing on a digital signal that corresponds to a signal; a first coefficient updating unit configured to update the first tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a first step size; a second coefficient updating unit configured to update a second tap coefficient based on the digital signal on which the adaptive equalization processing has not been executed, the digital signal on which the adaptive equalization processing has been executed, and a second step size; and a control unit configured to detect a fluctuation speed of a state of polarization of the digital signal based on the second tap coefficient, and change the first tap coefficient to the updated second tap coefficient if it is determined that the fluctuation speed is higher than or equal to a speed threshold.

A system is provided along a route of a network including a first transponder at a first node and a second transponder at a second node. The system further includes one or more processors configured to detect, in a first waveform measured at the first transponder, a first signature at a first time point, and configured to detect, in a second waveform measured at the second transponder, a second signature at a second time point. The one or more processors may correlate the first waveform and the second waveform, and determine, based on the correlation, that the first signature and the second signature correspond to a same event occurring along the route of the network. Based on comparing the first time point and the second time point, the one or more processors may determine an estimated location of the event.

Systems and methods for characterizing an optical fiber performed in part by an optical node (12) in an optical line system (10) include performing one or more measurements to characterize the optical fiber (16, 18) with one or more components (50, 52) at the optical node (12), wherein the one or more components (50, 52) perform functions during operation of the optical node (12) and are reconfigured to perform the one or measurements independent of the functions; and configuring the optical node (12) for communication over the optical fiber (16, 18) based on the one or more measurements. The one or more components can include any of an Optical Service Channel (OSC), an Optical Time Domain Reflectometer (OTDR), and an optical amplifier. The configuring can include setting a launch power into the optical fiber based on the one or more measurements.