A technique for calibrating an optical receiver is described. During this technique, a front-end circuit in the optical receiver receives an optical signal that corresponds to a sequence with alternating groups of symbol types that correspond to binary values, where durations of the groups of a given symbol type, which can correspond to a first binary value or a second binary value, progressively decrease during the sequence. Then, the output of the feedback circuit is adjusted based at least on the sequence. When the durations of groups corresponding to the first binary value and the second binary value reach their minimum values in the sequence, a calibration value corresponding to the output of the feedback circuit is stored for use during a normal operating mode of the optical receiver.