Tunable RF signal generation

• US 20030114117A1
• Filed: 11/06/2002
• Published: 06/19/2003
• Est. Priority Date: 11/07/2001
• Status: Abandoned Application

• Current Assignee: Nanyang Technological University
• Original Assignee: Nanyang Technological University
• Inventors: Yao, Jianping, Zhou, Yan, Lam, Yee Loy
• Application Number:
  US10/288,723
• Publication Number:
  US 20030114117A1
• Time in Patent Office: Days
• US Class Current: 455/77
• CPC Class Codes: H03D 9/00 Demodulation or transference of modulation of modulated electromagnetic waves demodulating light, transferring modulation in light waves G02F2/00

Abstract

There is provided a tunable radio frequency (RF) signal generator comprising: a bi-directional ring laser and a photodetector. The ring laser includes a phase modulator driven by an electrical signal. In use, the modulator imparts a phase shift in dependence on the electrical signal to at least one of a mutually coherent clockwise and counter-clockwise propagating optical signal in the ring laser so as to produce a predetermined difference in the frequency of the clockwise and counter-clockwise propagating signals. The photodetector is optically coupled to an optical output of the ring laser, and in use the photodetector generates a radio frequency signal in dependence on the difference in frequency of the clockwise and counter-clockwise propagating optical signals.

There is also provided a method for generating a tunable radio frequency signal using the tunable radio frequency (RF) signal generator.

Claims

1. A tunable radio frequency (RF) generator comprising:

a bi-directional ring laser, the ring laser including;

a phase modulator driven by an electrical signal, in use the modulator imparting a phase shift in dependence on the electrical signal to at least one of a mutually coherent clockwise and counter-clockwise propagating optical signal in the ring laser so as to produce a predetermined difference in the frequency of the clockwise and counter-clockwise propagating signals; and

,

a photodetector optically coupled to an optical output of the ring laser, in use the photodetector generating a radio frequency signal in dependence on the difference in frequency of the clockwise and counter-clockwise propagating optical signals.

2. An RF generator according to claim 1, in which the bi-directional ring laser is mode-locked.

3. An RF generator according to claim 2, in which the ring laser is mode-locked by means of an intensity modulator.

4. An RF generator according to claim 1, further comprising a Bragg reflector optically coupled to an optical output from the ring laser, the Bragg reflector reflecting a portion of the optical spectrum of the optical output back into the ring laser.

5. An RF generator according to claim 1, in which the ring laser includes a 2×

2 optical coupler.

6. An RF generator according to claim 1, in which the phase modulator modulates at a frequency substantially the same as a round-trip frequency of the ring laser or a sub-multiple thereof.

7. An RF generator according to claim 1, in which the phase modulator imparts a constant phase shift.

8. An RF generator according to claim 1, in which the phase modulator imparts a time-varying phase shift.

9. An RF generator according to claim 1, in which the radio frequency signal is in the microwave wavelength range.

10. An RF generator according to claim 1, in which the radio frequency signal is in the millimeter wavelength range.

11. An RF generator according to claim 1, comprising fibre optic components.

12. An RF generator according to claim 1, comprising a photonic integrated circuit.

13. An RF generator according to claim 1, comprising discrete optical components.

14. A method of generating a tunable radio frequency signal comprising the steps of:

generating two mutually-coherent counter-propagating optical signals in a bi-directional ring laser;

imparting a phase shift to at least one of the two optical signals so as to produce a predetermined difference in the frequency of the two optical signals; and

,

heterodyning the two optical signals at a photodetector so as to produce a radio frequency signal in dependence on the difference in frequency of the two optical signals.

15. A method according to claim 14, further comprising the step of mode-locking the bi-directional ring laser.