Ultra-high-speed PLL-type clock recovery circuit based on all-optical gain modulation in traveling-wave laser diode amplifier

A new phase lock loop (PLL) is developed for very-high-speed optical timing extraction using traveling-wave laser-diode amplifier (TW-LDA) as a phase detector. The all-optical gain modulation of the TW-LDA is utilized to detect the relative phase difference between an optical signal and an optical clock The frequency response of the optical gain modulation measured with the optical heterodyne technique agrees with the theoretical results based on a rate equation model. With the developed PLL, 10-GHz optical timing clock is successfully extracted from randomly modulated optical signal pulses and the measured bit-error-rate performance shows no power penalty. Influence of the received optical noise on the phase variance of the PLL is also evaluated and it is concluded that 100 GHz operation is possible by increasing the input optical power to 10 mW