Timing extraction of a 10-gb/s NRZ signal using an electrooptic multiplication scheme

We report a new scheme for timing extraction of a 10-Gb/s nonreturn-to-zero signal. The scheme uses electrooptical multiplication of the optical signal by its delayed electrical replica in a Mach-Zehnder modulator. The modulator output injection locks an oscillator whose output is a high-quality 10-GHz clock used to synchronize a bit-error-rate (BER) measurement receiver. The quality of the clock signal depends on the modulator nonlinearity which is controlled by its dc bias and the delay between the two multiplied signals. BER performances with the extracted clock signal were found to be essentially identical to measurements with a clock from the BER system, proving the high quality of extracted timing signal.