Acceleration-insensitive opto-electronic oscillators

• US 6,594,061 B2
• Filed: 06/11/2001
• Issued: 07/15/2003
• Est. Priority Date: 06/09/2000
• Status: Expired due to Term

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Tu, Meirong, Huang, Shouhua, Yao, X. Steve
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): HASAN, MOHAMMED A
• Application Number:
  US09/879,795
• Publication Number:
  US 20020106142A1
• Time in Patent Office: 764 Days
• Field of Search: 359/239, 359/245, 359/276, 359/279, 385/1-3, 385/27-29, 385/136, 385/137
• US Class Current: 359/239
• CPC Class Codes: G02F 1/0123 Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops
• CPC Class Codes: H01S 5/0265 Intensity modulators intra-cavity modulators H01S5/0625
• CPC Class Codes: H01S 5/06832 Stabilising during amplitude modulation
• CPC Class Codes: H04B 10/503 Laser transmitters
• CPC Class Codes: H04B 10/50577 to control the phase of the modulating signal
• CPC Class Codes: H04B 10/58 Compensation for non-linear transmitter output

Abstract

Techniques for reducing frequency shifts in an oscillating frequency of an opto-electronic oscillator by having at least two separate optical delay elements in an optical portion of an opto-electronic feedback loop.

Claims

1. A device, comprising:

an optical modulator operable to receive and modulate a signal beam to produce modulation signals in said signal beam in response to a modulation control signal; and

a feedback loop having an optical portion that receives a portion of said signal beam output from said optical modulator, an optical delay module in said optical portion, and an optical-to-electrical converter converting said portion into an output signal, wherein said feedback loop produces said modulation control signal from said output signal, and wherein said optical delay module includes a first optical delay element responsive to an acceleration of the device to cause a first frequency shift in said modulation control signal and a second optical delay element optically connected to said first optical delay element and responsive to said acceleration to cause a second frequency shift in said modulation control signal that is opposite to said first frequency shift.

2. The device as in claim 1, wherein one of said first and said second optical delay elements is an optical resonator.

3. The device as in claim 2, wherein said optical resonator includes a fiber resonator.

4. The device as in claim 2, wherein said optical resonator is operable in a whispering-gallery mode.

5. The device as in claim 1, wherein one of said first and said second optical delay elements is a fiber delay line.

6. The device as in claim 1, further comprising a second feedback loop having an optical portion that receives a portion of said signal beam output, a second optical delay module in said optical portion, and a second optical-to-electrical converter converting said portion into a second output signal, wherein said second feedback loop is coupled to said feedback loop to produce said modulation control signal by combining said second output signal and said output signal.

7. The device as in claim 1, wherein at least one of said first and said optical delay elements includes a Brillouin optical medium, and further comprising:

a pump laser operable to produce a pump laser beam, and

a coupler engaged to couple said pump laser beam into said Brillouin optical medium to produce a Brillouin optical signal.

8. A method, comprising:

providing an opto-electronic feedback loop that has an optical portion, an electrical portion, and an optical-to-electrical converter interconnecting the optical and electrical portion, wherein the opto-electronic feedback loop is coupled to an optical modulator to form a closed loop which is operable to produce a signal oscillation at an oscillating frequency;

designing the optical portion to have at least a first optical delay element and a second optical delay element that are optically connected to each other in series so that the total optical delay is a sum of delays in the first and the second optical delay elements; and

mechanically engaging and optically coupling the first and second optical elements to experience a common acceleration and to produce frequency shifts in opposite directions in the oscillating frequency to reduce a dependence of the oscillating frequency on the common acceleration.

9. The method as in claim 8, wherein one of the first and said second optical delay elements is an optical resonator.

10. The method as in claim 8, wherein one of the first and said second optical delay elements includes a fiber delay line.

11. The method as in claim 8, further comprising:

coupling a second feedback loop, which is similarly constructed as the opto-electronic feedback loop, to the optical modulator; and

combining output signals from the opto-electronic feedback loops to produce a control signal that controls the optical modulator.

12. A device, comprising:

an optical modulator operable to receive and modulate a signal beam to produce modulation signals in said signal beam in response to a modulation control signal; and

a feedback loop having an optical portion that receives a portion of said signal beam output from said optical modulator, an optical delay module in said optical portion, and an optical-to-electrical converter converting said portion into an output signal, wherein said feedback loop produces said modulation control signal from said output signal, and

wherein said optical delay module includes a first fiber coil as a first optical delay element formed on a first spool along a first axis, and a second fiber coil as a second optical delay element formed on a second spool along a second axis, said first and said second fiber coils being optically connected to said first fiber coil in series and mechanically fixed relative to each other to have said first and said second axes be substantially parallel to respond to an acceleration of the device to cause a first frequency shift in said modulation control signal and a second, opposite frequency shift in said modulation control signal, respectively.

13. The device as in claim 12, wherein said first and said second fiber coils have substantially the same fiber length.

14. The device as in claim 12, further comprising a fixture have two opposing surfaces to which said first and said second fiber coils are mechanically fixed, respectively, with said first and said second axes substantially perpendicular to said opposing surfaces.

15. The device as in claim 12, further comprising:

a pump laser to produce a pump laser beam, and

a pump coupler engaged to couple said pump laser beam into said first and said second fiber coils to produce a Brillouin optical signal.

16. The device as in claim 12, further comprising a second feedback loop having an optical portion that receives a portion of said signal beam output from said optical modulator, a second optical delay module in said optical portion, and a second optical-to-electrical converter converting said portion into a second output signal, wherein said second feedback loop is coupled to said feedback loop to produce said modulation control signal by combining said second output signal and said output signal.

17. A device, comprising:

a laser, having an active optical feedback loop with a first loop gain which supports laser oscillation to produce a laser output and which changes in response to a modulation control signal; and

an opto-electronic feedback loop coupled to said active optical feedback loop to produce said modulation control signal in response to said laser output,

wherein said opto-electronic feedback loop comprises an optical portion that receives a portion of said laser output, an optical delay module in said optical portion, and an optical-to-electrical converter converting said portion into an output signal, wherein said feedback loop produces said modulation control signal from said output signal, and

wherein said optical delay module includes a first optical delay element responsive to an acceleration of the device to cause a first frequency shift in said modulation control signal and a second optical delay element optically connected to said first optical delay element and responsive to said acceleration to cause a second frequency shift in said modulation control signal that is opposite to said first frequency shift.

18. The device as in claim 17, wherein one of said first and said second optical delay elements includes an optical resonator.

19. The device as in claim 18, wherein said optical resonator includes a fiber resonator.

20. The device as in claim 18, wherein said optical resonator is operable in a whispering-gallery mode.

21. The device as in claim 17, wherein one of said first and said second optical delay elements is a fiber delay line.

22. The device as in claim 17, wherein at least one of said first and said optical delay elements includes a Brillouin optical medium, and further comprising:

a pump laser operable to produce a pump laser beam, and

a coupler engaged to couple said pump laser beam into said Brillouin optical medium to produce a Brillouin optical signal.

23. The device as in claim 17, further comprising a second opto-electronic feedback loop having an optical portion that receives a portion of said laser output, a second optical delay module in said optical portion, and a second optical-to-electrical converter converting said portion into a second output signal, wherein said second opto-electronic feedback loop is coupled to said opto-electronic feedback loop to produce said modulation control signal by combining said second output signal and said output signal.