We report an all-optical processing scheme which generates a strong spectral component at the bit rate frequency of a high-speed nonreturn-to-zero data stream. The processed signal can be used for timing extraction by direct optical injection locking. The scheme is based on multiplying the data signal by its delayed replica. A dispersion compensating fiber serves as a delay line and the multiplication is performed by four-wave mixing in a dispersion-shifted fiber. Simulated results and experimental confirmations are demonstrated.