An optical network unit, abbreviated ONU, for downstream data reception in a passive optical network, abbreviated PON, of a first data frame stream sent by an optical line termination, abbreviated OLT, wherein said first data frame stream is converted into a second data frame stream by propagation from said OLT to said ONU along a dispersive communication channel comprised in said PON, wherein said ONU comprises: - a receiver configured to process said second data frame stream, wherein said second data frame stream comprises samples positioned at sample indices along data frames of said second data frame stream; - a correlation determining unit configured to determine for each sample index a correlation value between a sequence of samples around a sample with said sample index and a predetermined sequence of symbols indicative of a frame boundary of a data frame in said first data frame stream; CHARACTERIZED IN THAT said ONU further comprises: - a hunting unit configured to identify a sample index corresponding to a correlation value with largest absolute value, thereby: o detecting frame boundaries of said data frames within said second data frame stream and thereby synchronizing said ONU with said OLT; and o estimating the coefficient with largest absolute value of a channel impulse response of said dispersive communication channel and thereby providing a channel estimation of said dispersive communication channel; and - a training unit configured to, when said hunting unit synchronizes said ONU with said OLT and when said training unit receives said channel estimation from said hunting unit, configure an equalizer in accordance with said channel estimation for said downstream data reception. - a receiver configured to process said second data frame stream, wherein said second data frame stream comprises samples positioned at sample indices along data frames of said second data frame stream; - a correlation determining unit configured to determine for each sample index a correlation value between a sequence of samples around a sample with said sample index and a predetermined sequence of symbols indicative of a frame boundary of a data frame in said first data frame stream; - a hunting unit configured to identify a sample index corresponding to a correlation value with largest absolute value, thereby: o detecting frame boundaries of said data frames within said second data frame stream and thereby synchronizing said ONU with said OLT; and o estimating the coefficient with largest absolute value of a channel impulse response of said dispersive communication channel and thereby providing a channel estimation of said dispersive communication channel; and o detecting frame boundaries of said data frames within said second data frame stream and thereby synchronizing said ONU with said OLT; and o estimating the coefficient with largest absolute value of a channel impulse response of said dispersive communication channel and thereby providing a channel estimation of said dispersive communication channel; and - a training unit configured to, when said hunting unit synchronizes said ONU with said OLT and when said training unit receives said channel estimation from said hunting unit, configure an equalizer in accordance with said channel estimation for said downstream data reception.