Fiber optic continuous true time-delay modulator

• US 5,526,170 A
• Filed: 08/06/1993
• Issued: 06/11/1996
• Est. Priority Date: 08/06/1993
• 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 navy
• Inventors: Monsma, Michael J., Esman, Ronald D.
• Primary Examiner(s): Moskowitz, Nelson
• Application Number:
  US08/102,934
• Time in Patent Office: 1,040 Days
• Field of Search: 359/276, 359/278, 359/279, 359/326, 359/332, 385/3, 385/122, 250/227.23, 356/318
• US Class Current: 359/279
• CPC Class Codes: G02B 6/2861 using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering delay lines in general H03H, H01P9/00; optical computing devices G06E
• CPC Class Codes: H01Q 3/2676 Optically controlled phased array

Abstract

The fiber optic true time delay modulator generates a continuously variable true time-delay (i.e., phase shift) by utilizing the dispersion characteristic of a single mode optical fiber. The signal to be variably delayed modulates a continuous wave optical signal from a tunable laser source which is applied to a dispersive optical fiber wherein the phase shift occurs. The optical intensity output of the dispersive optical fiber is converted back into electrical energy by a photodetector for use in radio frequency, microwave and millimeter wave electronic devices. The invention can be used to generate multiple synchronized output signals by using a multiple wavelength laser or by combining outputs from several independently tuned lasers. Also. frequency and phase shifting is inherently provided by modulating the time delay.

Claims

1. A fiber optic continuous true time-delay modulator for producing a continuously variable propagation delay in an electrical circuit comprising:

means for producing an optical carrier signal of a predetermined optical wavelength;

means for producing a first electrical signal;

means for modulating said optical carrier signal with said first electrical signal to produce a modulated optical signal;

means for controlling the wavelength of the optical carrier signal thereby setting and varying the propagation delay of the first electrical signal;

means for propagating the modulated optical signal at a velocity dependent on the optical wavelength of the modulated optical signal; and

means for converting the modulated optical signal into a second electrical signal.

2. A fiber-optic true time-delay modulator for producing a continuously variable propagation delay in an optical circuit comprising:

a laser optical source with wavelength controllable elements producing an optical carrier with a spectral linewidth of less than 0.08 nm;

means for controlling the wavelength controllable elements of the laser optical source;

means for receiving and modulating the optical carrier with a first electrical signal that is to be variably delayed thereby producing a modulated optical signal output;

an optical fiber exhibiting wavelength dependent optical velocity to propagate and delay said modulated optical signal and thereby produce a variable delayed modulated optical signal; and

means for receiving and converting said variably delayed modulated optical signal into a second electrical signal.

3. A fiber optic continuous true time-delay modulator, as in claim 2, wherein said optical fiber is a dispersive optical fiber.

4. A fiber optic continuous true time-delay modulator, as in claim 2, wherein said receiving means is an optical intensity sensitive photodetector for converting the variably delayed modulated optical signal to a second electrical signal.

5. A fiber optic continuous true time-delay modulator, as in claim 2 wherein said receiving means is an optically coherent photodetection means for converting frequency modulated signals to a second electrical signal.

6. A fiber optic continuous true time-delay modulator, as in claim 2 wherein said receiving means is an optically coherent photodetection means for converting a phase modulated optical signal into a second electrical signal.

7. A fiber optic continuous true time-delay modulator, as in claim 2, wherein said receiver means is further comprised of a means for converting a frequency modulated optical carrier signal into an intensity modulated optical signal and an optically sensitive photodetector to convert the intensity modulated optical signal into a second electrical signal.

8. A fiber optic continuous true time-delay modulator, as in claim 2, wherein said receiver means further comprises a means to convert a phase modulated optical carrier signal into an intensity modulated optical carrier signal and an optically sensitive photodetector for converting the intensity modulated optical signal to a second electrical signal.

9. A fiber optic continuous true time-delay modulator, as in claim 2, wherein the laser optical source is a continuously-tunable laser.

10. A fiber optic continuous true time-delay modulator, as in claim 9, wherein the tunable laser is a sigma (σ

) laser.

11. A fiber optic continuous true time-delay modulator, as in claim 9, wherein the tunable laser is a semiconductor laser.

12. A fiber optic continuous true time-delay modulator, in claim 2, wherein the laser optical carrier source is a multiple-wavelength laser producing a plurality of optical carriers providing a plurality of time-shifted replicas of the input signal.

13. A fiber optic continuous true time-delay modulator, as in claim 12, wherein the multiple-wavelength laser source is a plurality of single-wavelength laser optical carrier sources having narrow spectral width.

14. A fiber optic continuous true time-delay modulator, as in claim 13, further comprising a means for combining the plurality of optical carriers having a narrow spectral width into a single multiple-wavelength optical carrier.

15. A fiber optic continuous true time-delay modulator, as in claim 13, wherein the single-wavelength laser optical carrier sources are independently tunable.

16. A fiber optic continuously true time-delay modulator, as in claim 2, wherein said modulator means is an optical intensity modulator.

17. A fiber optic continuous true time-delay modulator, as in claim 2, wherein said modulator means is a optical frequency modulator.

18. A fiber optic continuous true time-delay modulator, as in claim 2, wherein said modulator means is an optical phase modulator.

19. A fiber optic continuously true time-delay modulator, as in claim 2, wherein said means for controlling the wavelength controllable elements is an electrical controller with a constant voltage power supply.

20. A fiber optic continuous true time-delay modulator, as in claim 19, wherein the electrical controller is an electrical signal generator.

21. A fiber optic continuous true time-delay modulator, as in claim 19, wherein the electrical controller is a digital-to-analog converter.

22. A fiber optic continuous true time-delay modulator, as in claim 19, wherein the electrical controller produces a frequency shift in the first electrical signal by utilizing a ramp signal.

23. A fiber optic continuous true time-delay modulator, as in claim 19, wherein the electrical controller is an electrical circuit for producing complex electrical waveforms.