Injection locked dual opto-electronic oscillator

• US 7,151,415 B1
• Filed: 02/01/2005
• Issued: 12/19/2006
• Est. Priority Date: 03/05/2004
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Zhou, Weimin
• Primary Examiner(s): Lee, John D.
• Application Number:
  US11/046,789
• Time in Patent Office: 686 Days
• Field of Search: 331 65- 66, 331135-136, 359328-330, 372/18, 372/32
• US Class Current: 331/66
• CPC Class Codes: G02F 2/002 using optical mixing
• CPC Class Codes: H03B 17/00 Generation of oscillations using radiation source and detector, e.g. with interposed variable obturator

Abstract

An injection locked dual opto-electronic oscillator having a master oscillator which generates a high Q RF output signal with a plurality of harmonic signals within a predetermined pass band. A slave oscillator has a modulation input coupled to the output signal from the master oscillator as well as an output signal. The slave oscillator has a cavity length selected to produce a single mode operation within the pass band. An electronic phase shifter in the slave oscillator is adjustable to produce constructive interference at a single harmonic of the output signal from the master oscillator and destructive interference of all other harmonics within the pass band and to bring the slave oscillator into injection locked condition with the master oscillator. Therefore the slave OEO is used as a filter for the spurious radiation generated by the master OEO and at the same time preserves the high Q of the RF carrier signal from the master OEO.

Claims

1. An injection locked opto-electronic oscillator comprising:

an opto-electronic master oscillator with a high Q cavity which generates an RF output signal with a plurality of harmonic signals within a predetermined pass band,

an opto-electronic slave oscillator having an RF input coupled to said output signal from said master oscillator and an output RF signal, said slave oscillator having a cavity length selected to produce only a single mode operation within said pass band, and an electronic phase shifter adjustable to produce constructive interference at a single harmonic of said output signal from said master oscillator and destructive interference of all other harmonics within said pass band during an injection lock condition.

2. The invention as defined in claim 1 wherein said master oscillator comprises:

a laser which generates an optical output signal,

an optical modulator having an optical input which receives the optical output signal from the laser, an RF modulation input and a modulated optical output,

a photodetector having an input and an output, said photodetector operable to convert an optical signal at its input to an RF output signal on its output,

an optical fiber which optically couples said optical modulator output to said photodetector input,

wherein a portion of said RF output signal is coupled as a feedback signal to said optical modulator'"'"'s RF modulation input.

3. The invention as defined in claim 2 and comprising an RF filter connected in series with said photodetector output signal, said RF filter having a pass band less than or equal to said predetermined pass band.

4. The invention as defined in claim 3 and comprising an RF amplifier connected in series with said RF filter.

5. The invention as defined in claim 2 wherein said optical fiber has a length selected to produce a Q factor in excess of one million.

6. The invention as defined in claim 1 wherein said slave oscillator comprises:

a laser which generates an optical output signal,

a optical modulator having an optical input which receives the optical output signal from the laser, an RF modulation input and an optical output,

a photodetector having an input and an output, said photodetector operable to convert an optical signal at its input to an RF output signal on its output,

an optical fiber which optically couples said optical modulator optical output to said photodetector input,

wherein a portion of said photodetector RF output signal is coupled to said optical modulator RF modulation input.

7. The invention as defined in claim 6 and comprising an RF filter connected in series with said photodetector output signal, said RF filter having a pass band less than or equal to said predetermined pass band.

8. The invention as defined in claim 7 and comprising an RF amplifier connected in series with said RF filter.

9. The invention as defined in claim 8 and comprising an adjustable RF phase shifter connected in series with said RF filter and said RF amplifier to facilitate the injection locking condition for the slave oscillator.

10. The invention as defined in claim 7 wherein the optical fiber has its length selected so that only one RF oscillation mode is allowed in the oscillator loop with the pass band of said RF filter.