EDFA-based coupled opto-electronic oscillator (COEO) and its phase noise
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phase noise↗
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Stabilizing Microwave Frequency of a Photonic Oscillator
A scheme for stabilizing the frequency of a microwave signal is proposed that exploits the operational characteristics of a coupled optoelectronic oscillator (COEO) and related optoelectronic equipment. An essential element in the scheme is a fiber mode-locked laser (MLL), the optical frequency of which is locked to an atomic transition. In this scheme, the optical frequency stability of the mode-locked laser is transferred to that of the microwave in the same device. Relative to prior schemes for using wideband optical frequency comb to stabilize microwave signals, this scheme is simpler and lends itself more readily to implementation in relatively compact, rugged equipment. The anticipated development of small, low-power, lightweight, highly stable microwave oscillators based on this scheme would afford great benefits in communication, navigation, metrology, and fundamental sciences. COEOs of various designs, at various stages of development, in some cases called by different names, have been described in a number of prior NASA Tech Briefs articles. A COEO is an optoelectronic apparatus that generates both short (picosecond) optical pulses and a steady microwave signal having an ultrahigh degree of spectral purity. The term "coupled optoelectronic" in the full name of such an apparatus signifies that its optical and electronic oscillations are coupled to each other in a single device. The present frequency-stabilization scheme is best described indirectly by describing the laboratory apparatus used to demonstrate it. The apparatus (see figure) includes a COEO that generates a comb-like optical spectrum, the various frequency components of which interfere, producing short optical pulses. This spectrum is centered at a nominal wavelength of 1,560 nm. The spectrum separation of this comb is about 10 GHz, as determined primarily by the length of an optical loop and the bandpass filter in the microwave feedback loop. The optical loop serves as microwave resonator having a very high value of the resonance quality factor (Q). The optical frequency of MLL is then stabilized by locking it to an atomic transition as described below. The COEO contains a tunable 1-nm band-pass optical filter and a piezoelectric-transducer (PZT) drum over which a stretch of fiber is wound. The 1-nm-wide pass band of the filter provides coarse tuning to overlap the frequency comb with the atomic transition frequency. Controlled stretching of the fiber by means of the PZT drum can be used in conjunction with temperature control for locking the laser frequency. To reference to an atomic resonance at 780 nm in this demonstration setup, the optical output of the COEO at 1,560 nm is fed through an erbium-doped-fiber amplifier (EDFA) to a frequency doubler in the form of a periodically poled lithium niobate (PPLN) crystal. The frequency-doubled output is combined with the output of a separate frequency-stabilized diode laser at a photodetector. As described thus far, the two 780-nm laser subsystems are nominally independent of each other and can, therefore, operate at different frequencies. Hence, at the photodetector, the two laser beams interfere, so that the output of the photodetector includes a beat note (a component at the difference between the two laser frequencies).
Maleki, Lute↗
Ultra-low phase noise optical pulses generated by coupled opto-electronic oscillator
EDFA-based coupled opto-electronic oscillator (COEO) can generate picosecond optical pulses and microwave signals. The phase noise of COEO is better than -135 dBc/Hz at 10 kHz away from the carrier.
oscillator↗
EDFA-based coupled opto-electronic oscillator and its phase noise
EDFA-based coupled opto-electronic oscillator (COEO), an integrated optical and microwave oscillator that can generate picosecond optical pulses, is presented. the phase noise measurements of COEO show better performance than synthesizer-driven mode-locked laser.
mode-locked laser↗
Coupled Opto-Electronic Oscillators
These experiments demonstrate that COEOs are promising compact sources for generating low jitter optical pulses and low phase noise RF/millimeter wave signals.
opto-electronic oscillator (COEO) ring laser mode-↗
Recent results with coupled opto-electronic oscillator
We present experimental results of coupled opto-electronic oscillators (COEO) constructed with a semiconductor optical amplifier based ring laser, a semiconductor Fabry-Perot laser, and a semiconductor colliding pulse mode-locked laser.
coupled↗
Semiconductor Laser Based Coupled Opto-Electronic Oscillators
These experiments demonstrate that COEOs are promising compact sources for generating low jitter optical pulses and low phase noise RF/millimeter wave signals.
Opto-Electronic Oscillator optical pulse RF photon↗
Optical Techniques for Low Noise Microwave Frequency Sources
Optical techniques and mathematical models are described for low noise microwave frequency sources. The contents include: 1) Why Optical Techniques; 2) Wavemixing: Advantages and Disadvantages; 3) Wavemixing with Feedback: The OEO; 4) Feedback in both loops: COEO; and 5) State of the Art and Future Prospects.
microwave oscillators↗
A Dual Microwave and Optical Oscillator
We describe and demonstrate a novel device in which a microwave oscillation is generated and is directly coupled with an optical oscillation, and vise versa.
Coupled Opto-Electronic Oscillator (COEO)↗