Opto-electronic devices for processing and transmitting RF signals based on brillouin selective sideband amplification

• US 6,417,957 B1
• Filed: 10/27/2000
• Issued: 07/09/2002
• Est. Priority Date: 10/27/1999
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Yao, Xiaotian Steve
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/699,297
• Time in Patent Office: 620 Days
• Field of Search: 359/334, 359/156, 359/187, 359/327, 250/227.11
• US Class Current: 359/334
• CPC Class Codes: H04B 10/25758 between a central unit and a single remote unit by means of an optical fibre
• CPC Class Codes: H04B 10/2916 using Raman or Brillouin amplifiers

Abstract

Systems and techniques for transmitting and processing an electrical signal through an opto-electronic system with an optical Brillouin amplifier.

Claims

1. A system, comprising:

an input terminal to receive an input electrical signal; and

an opto-electronic module comprising an optical amplifier with a Brillouin medium which produces a pump beam in said Brillouin medium to generate a Brillouin signal, and an optical ring unit having an optical modulator coupled to said input terminal to superimpose said input electrical signal onto an optical signal,

wherein said optical ring unit is adapted to couple said optical signal into said Brillouin medium with a polarization substantially identical to a polarization of said pump beam to selectively amplify a sideband in said optical signal, and

wherein said opto-electronic module further includes a photodetector to convert said amplified optical signal into an output electrical signal.

2. The system as in claim 1, wherein said opto-electronic module includes an optical subcarrier generator coupled to generate said optical signal with local oscillator sidebands.

3. The system as in claim 2, wherein said optical subcarrier generator includes a signal laser, a local oscillator circuit to produce a local oscillator signal, an optical modulator to modulate a laser beam from said signal laser in response to said local oscillator signal to produce said optical signal.

4. The system as in claim 3, wherein said optical subcarrier generator includes an opto-electronic oscillator which comprises an electrically controllable optical modulator and at least one active opto-electronic feedback loop that comprises an optical part with an optical delay element to receive a portion of an optical signal form said modulator and an electrical part interconnected by a photodetector to produce a control signal to said modulator.

5. The system as in claim 4, wherein said optical delay element includes a fiber loop.

6. The system as in claim 4, wherein said optical delay element includes an optical resonator.

7. The system as in claim 4, wherein said optical part of said opto-electronic feedback loop includes a Brillouin medium to amplify a selected modulation sideband in said optical signal.

8. The system as in claim 4, wherein said opto-electronic oscillator further includes an optical loop in which said optical modulator is disposed to modulate an optical gain in said optical loop.

9. The system as in claim 2, wherein said optical ring unit includes:

a polarization beam splitter coupled to receive said optical signal that transmits through said Brillouin medium from said subcarrier generator to split said optical signal into a first and a second optical signals with orthogonal polarizations;

a first polarization maintaining fiber having a first terminal to receive said first optical signal and a second terminal coupled to one terminal of said optical modulator;

a 90-degree Faraday rotator coupled to rotate a polarization of said second optical signal; and

a second polarization maintaining fiber having a first terminal to receive said second optical signal from said Faraday rotator and a second terminal coupled to another terminal of said optical modulator so that said first and said second optical signals have the same polarization inside said optical modulator.

10. The system as in claim 9, wherein said optical modulator is a phase modulator.

11. The system as in claim 9, wherein said opto-electronic module further includes:

a pump laser to produce said pump beam with a pump polarization orthogonal to a polarization of said optical signal; and

a first polarization beam splitter in an optical path between said subcarrier generator and said Brillouin medium and orientated with respect to said polarization of said optical signal to direct both said optical beam and said pump beam to said Brillouin medium and to direct said amplified optical signal to a direction opposite to said pump beam.

12. The system as in claim 11, wherein said opto-electronic module further includes an optical circulator to direct said pump beam to said first polarization beam splitter and to direct said amplified optical signal to said photodetector.

13. The system as in claim 11, wherein said opto-electronic module further includes:

an electronic unit to split DC and low frequency components from said output electrical signal from said photodetector to provide a control signal to said laser control unit, wherein said laser control unit is operable to control said pump according to said control signal; and

a laser control unit operable to control said pump laser according to said control signal.

14. The system as in claim 1, wherein said optical modulator is an amplitude modulator.

15. The system as in claim 1, wherein said optical modulator is a phase modulator.

16. The system as in claim 1, wherein said Brillouin medium includes an optic fiber.

34. The system as in claim 1, further comprising a RF antenna coupled to said optical modulator to covert a RF wave signal into said input electrical signal.

17. A system, comprising:

an optical subcarrier generator to generate a linearly-polarized optical signal with local oscillator sidebands;

a pump laser to produce a pump beam whose polarization is orthogonal to said optical signal;

a first polarization beam splitter to combine said optical signal and said pump beam to overlap and to copropagate;

an optic fiber line coupled to receive said optical signal and said pump beam and responsive to said pump beam to produce a Brillouin signal in a direction against said pump beam;

an optical ring unit coupled to one end of said optic fiber line to receive said pump beam and said optical signal that transmit through said fiber line, said ring unit having an optical modulator to superimpose an input electrical signal onto said optical signal and said pump beam and adapted to return said optical signal into said fiber line, wherein said returned optical signal has a polarization substantially identical to said polarization of said pump beam that propagates in said fiber line from said first polarization beam splitter to said ring unit to selectively amplify a sideband in said returned optical signal, and wherein said returned pump beam has polarization substantial orthogonal to said polarization of said pump beam that propagates in said fiber line from said first polarization beam splitter to said ring unit; and

a photodetector to convert said amplified returned optical signal into an output electrical signal.

18. The system as in claim 17, wherein said ring unit includes:

a second polarization beam splitter coupled to receive said optical signal that transmits through said fiber line to split said optical signal into a first and a second optical signals with orthogonal polarizations;

a first polarization maintaining fiber having a first terminal to receive said first optical signal and a second terminal coupled to one terminal of said optical modulator;

a 90-degree Faraday rotator coupled to rotate a polarization of said second optical signal; and

a second polarization maintaining fiber having a first terminal to receive said second optical signal from said Faraday rotator and a second terminal coupled to another terminal of said optical modulator so that said first and said second optical signals have the same polarization inside said optical modulator.

19. The system as in claim 18, wherein said optical modulator in said ring unit is a phase modulator.

20. The system as in claim 18, wherein said optical subcarrier generator includes a signal laser, a local oscillator circuit to produce a local oscillator signal, an signal optical modulator to modulate a laser beam from said signal laser in response to said local oscillator signal to produce said optical signal.

21. The system as in claim 20, wherein said signal optical modulator in a phase modulator.

22. The system as in claim 18, wherein said optical subcarrier generator includes an opto-electronic oscillator which comprises an electrically controllable optical modulator and at least one active opto-electronic feedback loop that comprises an optical part with an optical delay element to receive a portion of an optical output signal form said electrically controllable optical modulator and an electrical part interconnected by a converting photodetector to produce a control signal to said electrically controllable optical modulator.

23. The system as in claim 22, wherein said optical delay element includes a fiber loop.

24. The system as in claim 22, wherein said optical delay element includes an optical resonator.

25. The system as in claim 22, wherein said optical part of said opto-electronic feedback loop includes a Brillouin medium to amplify a selected modulation sideband in said optical output signal in said optical part.

26. The system as in claim 22, wherein said opto-electronic oscillator further includes an optical loop in which said electrically controllable optical modulator is disposed to modulate an optical gain in said optical loop.

35. The system as in claim 17, further comprising a RF antenna coupled to said input terminal to covert a RF wave signal into said input electrical signal.

27. A method, comprising:

modulating a laser beam in response to a local oscillator signal to produce an optical signal having local oscillator signal sidebands;

directing said optical signal into a Brillouin medium which is pumped by a pump beam propagating in the same direction in said medium as said optical signal;

transmitting said optical signal through said medium;

modulating said optical signal that transmits through said medium to superimpose information in an electrical signal onto said optical signal to produce signal modulation sidebands;

returning said optical signal back to said medium with a polarization substantially identical to a pump polarization of said pump in an opposite direction to amplify a sideband in said returned optical signal based on a Brillouin amplification process in said medium; and

converting said amplified optical signal into an output electrical signal.

28. The method as in claim 27, comprising:

adjusting a frequency of said pump beam to a desired sideband in said returned optical signal to obtain frequency up conversion.

29. The method as in claim 27, comprising:

adjusting a frequency of said pump beam to a desired sideband in said returned optical signal to obtain frequency down conversion.

30. The method as in claim 27, wherein said signal modulation sidebands are produced by a phase modulation, further comprising adjusting a frequency of said pump beam to a desired sideband away from a carrier frequency of said returned optical signal to obtain a phase-to-amplitude conversion.

31. The method as in claim 27, further comprising actively controlling a frequency of a pump laser that produces said pump beam to maximize a DC component in said output electrical signal.

32. The method as in claim 27, wherein said Brillouin medium includes a fiber line.

33. The method as in claim 32, further comprising using said fiber line to spatially separate a location where the input electrical signal is received and a location where the output electrical signal is produced.

36. The method as in claim 27, further comprising using a RF antenna to convert a RF wave signal into said electrical signal.