Simple Optoelectronic Oscillators Using Direct Modulation of Dual-Section Distributed-Feedback Lasers

Dual-section distributed-feedback laser diodes, in which the electrode on the top of the gain medium is split into two electrically isolated sections, can emit multiple optical modes by self-sustained pulsation at gigahertz frequencies. Here, we report that by directly modulating the laser in an optoelectronic oscillator (OEO) loop, a pure OEO signal can be obtained without the need for external modulators. In experiments, we successfully generate an 8-GHz OEO signal with a phase noise of -108 dBc/Hz at a 5-kHz offset and a radio-frequency threshold gain of 29 dB.