An apparatus for managing clock-data recovery for a modulated signal from a communication channel, the apparatus comprising: an input module configured to receive the modulated signal and provide one or more analog signals; one or more analog-to-digital converters, ADCs, configured to provide one or more digital input streams from samples of the analog signals; and a digital signal processing module configured to process the digital input streams to provide decoded digital data, the processing comprising: determining the decoded digital data based on information modulated over a plurality of frequency elements associated with the modulated signal, based at least in part on transforms of the digital input streams; determining a clock signal based on clock recovery from the digital input streams; and determining a clock phase error estimate associated with the determined clock signal based at least in part on a sum that includes different weights multiplied by different respective summands corresponding to different sets of frequency elements, wherein the digital signal processing module is configured to determine one or more of the weights based at least in part on measurements characterizing one or more conditions of the communication channel; and wherein the measurements include at least one of: a plurality of measurements of signal-to-noise ratio, SNR, for different respective frequency elements, a measurement of a condition associated with a time-dependent frequency response, a measurement of a condition associated with polarization mode dispersion, a measurement of a condition associated with polarization dependent loss, a measurement of a condition associated with optical-to-electrical signal conversion, a measurement of a condition associated with electrical-to-optical signal conversion, a measurement of a condition associated with digital-to-analog conversion, a measurement of a condition associated with analog-to-digital conversion, or a measurement of a condition associated with frequency-selective fading. an input module configured to receive the modulated signal and provide one or more analog signals; one or more analog-to-digital converters, ADCs, configured to provide one or more digital input streams from samples of the analog signals; and a digital signal processing module configured to process the digital input streams to provide decoded digital data, the processing comprising: determining the decoded digital data based on information modulated over a plurality of frequency elements associated with the modulated signal, based at least in part on transforms of the digital input streams; determining a clock signal based on clock recovery from the digital input streams; and determining a clock phase error estimate associated with the determined clock signal based at least in part on a sum that includes different weights multiplied by different respective summands corresponding to different sets of frequency elements, determining the decoded digital data based on information modulated over a plurality of frequency elements associated with the modulated signal, based at least in part on transforms of the digital input streams; determining a clock signal based on clock recovery from the digital input streams; and determining a clock phase error estimate associated with the determined clock signal based at least in part on a sum that includes different weights multiplied by different respective summands corresponding to different sets of frequency elements, wherein the digital signal processing module is configured to determine one or more of the weights based at least in part on measurements characterizing one or more conditions of the communication channel; and wherein the measurements include at least one of: a plurality of measurements of signal-to-noise ratio, SNR, for different respective frequency elements, a measurement of a condition associated with a time-dependent frequency response, a measurement of a condition associated with polarization mode dispersion, a measurement of a condition associated with polarization dependent loss, a measurement of a condition associated with optical-to-electrical signal conversion, a measurement of a condition associated with electrical-to-optical signal conversion, a measurement of a condition associated with digital-to-analog conversion, a measurement of a condition associated with analog-to-digital conversion, or a measurement of a condition associated with frequency-selective fading.