Opto-Electronic Oscillator Circuit Operation and Applications

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This article tells about what is an Opto electronic oscillator, working of the oscillator, multi-loop Opto-electronic oscillator, and its applications.

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Opto -Electronic Oscillator Circuit Operation and Applications

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Introduction: The Opto-electronic oscillator circuit is comparable to the optoelectronic feedback circuits which are established by the Neyer and Voges in the 1982 year. In 1984 by Nakazawa and later on in the year 1992 by Lewis. The Opto-electronic oscillator is based on the converting continuous light energy from the pump laser to radio frequency, microwave or mm-wave signal.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications The Optoelectronic oscillator is an Opto-electronic circuit. The output of the circuit is in the form of the sine wave or modulated continuous wave signal.  It is a device where the phase noise of the oscillator does not increase the frequency. It is subject to the implementation of the electronic oscillators like crystal oscillator, dielectric resonator, and sir dielectric resonator. What is an Opto-Electronic Oscillator?

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Opto-Electronic Oscillator

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Basic Operation of the OEO The following figure shows the operation of the Opto-electronic oscillator.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Basic Operation of the OEO By observing the circuit, t he Optoelectronic oscillator starts with continuous wave laser is penetrating into the intensity modulator.  The output of optical intensity modulator is passed through a long optical fiber delay line and into a photodiode. The improved electrical signal is applied and approved through an electronic bandpass filter.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Basic Operation of the OEO To complete the Opto electronic cavity the output of the filter is connected to the RF input of intensity modulator. If the gain of the cavity is greater than the loss, then the optoelectronic oscillator is will start the oscillation.  The electronic band pass filter selects the frequency of the diminished the other free running modes of the cavity which is below the threshold.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Basic Operation of the OEO The OEO is different from the before Optoelectronic circuit by using the very low loss of the optical fiber delay line to produce a cavity with a huge high Q factor.  The Q factor is the ratio of the stored energy in the cavity over the loss of cavity. Thus the loss of the fiber delay line is in the order of the 0.2dB/ km with a less little loss a very long fiber is stored in a large amount of energy.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Basic Operation of the OEO Because of the Q factor, the OEO can achieve the level easily of 108. It can translate to 10GHz clock signal with a phase noise of 140 dBc/Hz at 10kHz offset.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Multi-Loop Opto -Electronic Oscillator The figure shows the dual loop Optoelectronic oscillator with the cavity mode within the band pass filter.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Multi-Loop Opto -Electronic Oscillator To achieve the high Q factor for the Optoelectronic oscillator there should be the maximum fiber length.  If the fiber length increases the space between the cavity modes will be decreased.  For an example, a 3 km length of the fiber will yield a cavity mode spacing of 67 kHz approximately. 

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Multi-Loop Opto -Electronic Oscillator The high-quality electrical band pass filter is at 10GHz has 3dB bandwidth of 10MHz. Hence there will be many nonoscillating modes to continue through the electrical band pass filter. It can present in the phase noise measurement. There is another method to reduce this problem by second fiber length into the Opto-electrical oscillator. 

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications There will be the own set of cavity modes for the second loop of the OEO. If the length of the second loop is not a harmonic multiple of the first loop. Then the cavity modes will not overlap with each other. On the other hand the modes from each loop which are closest each other will lock and hold back the band pass the other cavity modes. Multi-Loop Opto -Electronic Oscillator

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications The single loop phase noise spectrum with the side modes next to the dual loop spectrum with the side mode suppressed below.  The exchange of the system is the phase noise. It is an average of the noise of the two loops independently. There is no phase noise just a long loop. Single Loop Phase Noise Spectrum

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Single Loop Phase Noise Spectrum Hence, both the loops support the side modes and they are completely not eliminated, but they are suppressed.

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications Application of OEO The high-performance Optoelectric oscillator is a major element in many applications. Such as Aerospace engineering Satellite communication links Navigation systems. Precise meteorological time and frequency measurement Wireless communication links Modern radar technology

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http://www.elprocus.com/ Opto-Electronic Oscillator Circuit Operation and Applications The Opto-Electronic Oscillator is an optoelectronic circuit  that produces repetitive electronic sine wave and/or modulated optical continuous wave signals. An opto-electronic oscillator is based on converting the continuous light energy from a pump laser to radio frequency (RF), microwave or mm-wave signals. Conclusion

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