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The OEO utilizes the transmission
characteristics of a modulator together with a fiber optic delay line to
convert light energy into spectrally pure rf/microwave reference
signals. The OEO’s schematic diagram
is shown above. Light from a laser is
introduced into an electrooptical (E/O) modulator, the output of which is
passed through a long fiber optic link, and detected with a
photodetector. The output of the
photodetector is amplified, filtered and fed back to the electrical port of
the modulator. This configuration
supports self-sustained oscillations at a frequency determined by the fiber
delay length, bias setting of the modulator, and the bandpass characteristics
of the filter. It also provides for
both electrical and optical outputs.
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The noise of an OEO has been measured to be
-140 dBc/Hz at 10 kHz from a 10 GHz carrier. This is the highest spectral purity
demonstrated by an open loop oscillator in this frequency range (as of
1999). How stable an OEO can be with
respect to other parameters, such as temperature, acceleration and humidity,
is being investigated.
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S. Yao and L.
Maleki, “New Results with the Opto-electronic Oscillators (OEO),” Proc. 1996
IEEE Int’l Frequency Control Symposium, pp. 1219-1222, 1996.
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X. S. Yao and L.
Maleki, "Optoelectronic Oscillator for Photonic Systems," IEEE
Journal of Quantum Electronics, 32, 1141, 1996.
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X. S. Yao, L. Maleki
and L. Davis, ”Coupled Opto-electronic Oscillators,” Proc. 1998 IEEE Int’l
Frequency Control Symposium, pp. 540-544, 1998.
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