Photonic synthesis of RF frequency

Abstract

One approach for the photonic generation of reference signals is the opto-electronic oscillator, OEO, which is based on an electrooptic feedback loop that converts light energy from a laser to highly spectrally pure rf signal. A particular realization of the OEO can provide spectrally pure microwave signals at its electrical output, as well as an ultra-low jitter timing pulses on an optical carrier. The device, named the Coupled Opto-Electronic Oscillator (COEO), acts both as a microwave source and a stable source of short optical pulses. We have demonstrated two different configurations for the COEO, one involving an SOA and an external modulator in the optical loop, and a second utilizing a semiconductor device directly. Both architectures use a long fiber delay as the stabilizing element in the optoelectronic feedback loop. We present a configuration for placing the entire device on the same substrate to produce a chip based COEO. Such a device enables a number of applications in microwave photonics, and exhibits excellent microwave signal purity on a chip.