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The optoelectronic oscillator (OEO) has emerged in recent years as an excellent low-noise source that rivals the best RF oscillators over broad offset frequencies. NIST scientists Craig Nelson, Archita Hati, and Dave Howe, along with Weimin Zhou of Army Research Laboratory, have developed an optoelectronic oscillator (OEO) at microwave frequencies utilizing only optical gain. NIST’s OEO is unique compared to conventional OEOs or radio-frequency (RF) oscillators in that it does not fundamentally require a RF gain element in order to satisfy the amplitude threshold condition for oscillation. All of the energy required for oscillation is obtained from the optical carrier. The light from optoelectronic modulator is detected by a photodetector, filtered, and fed back to the electrical input port of the modulator. If the modulator and photodiode efficiencies are high enough, sustained self electro-optic oscillation will start without the use of a RF gain element. The main feature of this OEO with no amplifier is that it completely eliminates the noise contribution of an RF amplifier, which is one of the main sources of noise in a conventional OEO. OEOs are important for communications, navigation, radar, precise tests and measurements, and other applications.
1. C.W. Nelson, A. Hati, D.A. Howe, and W. Zhou, “Microwave Optoelectronic Oscillator with Optical Gain,” Proc. 2007 Joint Mtg. IEEE Intl. Freq. Cont. Symp. and EFTF Conf., pp. 1014-1019, 29-MAY-07.