Low-Cost Optoelectronic Self-Injection-Locked Oscillators

We demonstrate a new configuration for an optoelectronic self-injection-locked (SIL) oscillator, where a part of the electrical output signal is self-injected after passing through a long optical delay line for output phase-noise reduction. The SIL oscillator consists of an electrical free-running oscillator and a long optical feedback loop. For the compact and low cost configuration, the free-running oscillator is realized with an InP HPT-based monolithic oscillator and electrical-to-optical conversion is carried out by two low-speed and low-cost laser diodes. With this new configuration, we achieve more than 55-dB phase-noise reduction at 10-kHz frequency offset from the center frequency of about 10.8 GHz by injecting 8-dBm optical signals without using any high-speed optoelectronic components.