A signal processing arrangement generates optical stimulation signals to optical stimulation contacts in an implanted cochlear implant array. An input sound signal is transformed into band pass signals that each represent an associated band of audio frequencies, with each band pass signal includes an envelope component characterizing loudness of the band pass signal, and a fine structure component characterizing temporal details of the band pass signal. One or more of the signal components of each band pass signal is half wave rectified to remove negative phase signals. Signal slope is determined that corresponds to rate of change of the rectified one or more signal components. Then constant-rate optical stimulation pulses are generated for one or more given band signals only when the rectified one or more signal components has a positive signal slope.
