A high-performance optically injected synchronous oscillator

An improved optical injection network incorporating a high-speed p-i-n photodiode into a microwave synchronous oscillator (SO) is presented. The p-i-n photodiode directly injects current converted from a modulated optical signal into the SO tank circuit. The SO possesses an adaptive gain function to amplify a low-level input signal to +7 dBm, and tracks the frequency deviation of the input signal to achieve synchronization. A tracking bandwidth up to 8 MHz has been observed, which is a factor of 10 better than previous results with the same optical injection power. Within the tracking bandwidth, the FM noise is significantly reduced and frequency/phase jitter is substantially removed. This technique is applicable to fiber-optic communication systems for the applications of clock/carrier recovery and coherent demodulation.< >