Opto-Electronic Oscillator Circuit Working and Applications

Opto -Electronic Oscillator
Circuit Operation and
Applications

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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.

 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?

Opto-Electronic Oscillator

Basic Operation of the OEO
 The following figure shows the operation of the Opto-electronic
oscillator.

 By observing the circuit, the 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.

 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.

 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.

 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.

Multi-Loop Opto-Electronic Oscillator
 The figure shows the dual loop Optoelectronic oscillator with the cavity
mode within the band pass filter.

 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.

 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.

 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.

 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

Single Loop Phase Noise Spectrum
 Hence, both the loops support the side modes and they are completely not
eliminated, but they are suppressed.

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

 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

Opto-Electronic Oscillator Circuit Working and Applications

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