Claims
- 1. A method of switching between selected wavelengths transmitted and/or reflected by a fiber-Bragg grating, comprising;
applying effective voltage versus time profiles to a piezoelectric actuator coupled to a selected section of an optical fiber containing a fiber-Bragg grating to vary strain in the selected section of the optical fiber in order to switch the selected wavelengths of light reflected and/or transmitted by said fiber-Bragg grating, the effective voltage versus time profiles being selected to rapidly change the strain in the selected section of the optical fiber in such a way so as to compensate for effects of creep in the piezoelectrc actuator due to the application of voltage thereto and to obtain convergence to a substantially fixed strain in said selected section of the optical fiber in a pre-selected period of time.
- 2. The method according to claim 1 wherein said effective voltage versus time profiles include a step voltage and a series of voltage pulses superimposed on the step voltage to compensate for creep due to the step voltage, the series of voltage pulses including a first voltage pulse with the same polarity as said step voltage and being sufficiently large to stimulate rapid displacement of the piezoelectric element to reach said substantially fixed strain, and wherein subsequent voltage pulses in the series of voltage pulses are of opposite polarity and lower magnitude than the first voltage pulse so that the strain remains within a selected tolerance from said substantially fixed strain until the convergence to said substantially fixed strain is obtained.
- 3. The method according to claim 2 wherein said voltage pulses are exponentially decaying voltage pulses.
- 4. The method according to claim 2 wherein said voltage pulses are stepwise transitions in voltage.
- 5. The method according to claim 2 wherein said pre-selected period time less than about 5 milliseconds.
- 6. The method according to claim 2 wherein said effective voltage versus time profiles are selected to give said rapid switching with pre-selected switching times.
- 7. The method according to claim 1 wherein said selected wavelengths are telecommunication wavelengths, and wherein the fast switching is suitable to ensure that an optical link is not interrupted for an unsuitable long time for telecommunication.
- 8. The method according to claim 2 wherein one of said selected wavelengths is a first Bragg wavelength λBragg1 and a second of said selected wavelengths is a second Bragg wavelength λBragg2.
- 9. An optical switch, comprising;
an optical fiber having at least one fiber-Bragg grating in at least one selected section of said fiber; at least one piezoelectric actuator physically coupled to said at least one selected section of said fiber for applying strain to said at least one selected section of said fiber; and controller means electrically connected to said at least one piezoelectric actuator for applying effective voltage versus time profiles to said piezoelectric actuator coupled to said selected section of an optical fiber containing a fiber-Bragg grating to vary strain in the selected section of the optical fiber in order to switch the wavelengths of light reflected and/or transmitted by said fiber-Bragg grating, the effective voltage versus time profiles being selected to rapidly change the strain in the selected section of the optical fiber in such a way so as to compensate for effects of creep in the piezoelectric actuator due to the application of voltage thereto and to obtain convergence to a substantially fixed strain in said selected section of the optical fiber in a pre-selected period of time.
- 10. The optical switch according to claim 9 wherein said effective voltage versus time profiles include a step voltage and a series of voltage pulses superimposed on the step voltage to compensate for creep due to the step voltage, the series of voltage pulses including a first voltage pulse with the same polarity as said step voltage and being sufficiently large to stimulate rapid displacement of the piezoelectric element to reach said substantially fixed strain, and wherein subsequent voltage pulses in the series of voltage pulses are of opposite polarity and lower magnitude than the first voltage pulse so that the strain remains within a selected tolerance from said substantially fixed strain until the convergence to said substantially fixed strain is obtained.
- 11. The optical switch according to claim 10 wherein said voltage pulses are exponentially decaying voltage pulses.
- 12. The optical switch according to claim 10 wherein said voltage pulses are stepwise transitions in voltage.
- 13. The optical switch according to claim 10 wherein said pre-selected period time less than about 5 milliseconds.
- 14. The optical switch according to claim 10 wherein said effective voltage versus time profiles are selected to give said rapid switching with pre-selected switching times.
- 15. The optical switch according to claim 9 wherein said selected wavelengths are telecommunication wavelengths, wherein said optical switch is a component in a telecommunication network and wherein the switching is sufficiently fast to ensure that an optical link in said network is not interrupted for unsuitable long times.
- 16. The optical switch according to claim 9 wherein one of said selected wavelengths is a first Bragg wavelength λBragg1 and a second of said selected wavelengths is a second Bragg wavelength λBragg2.
- 17. A method of rapidly adjusting strain in a piezoelectric actuator which compensates for strain creep, comprising;
applying effective voltage versus time profiles to said piezoelectric actuator, the effective voltage versus time profiles being selected to rapidly change the strain in the piezoelectric actuator in such a way as to compensate for effects of strain creep in the piezoelectric actuator due to the application of voltage thereto and to obtain convergence to a substantially fixed strain in said piezoelectric actuator in a pre-selected period of time.
- 18. The method according to claim 17 wherein said effective voltage versus time profiles include a step voltage and a series of voltage pulses superimposed on the step voltage to compensate for creep due to the step voltage, the series of voltage pulses including a first voltage pulse with the same polarity as said step voltage and being sufficiently large to stimulate rapid displacement of the piezoelectric element to reach said substantially fixed strain, and wherein subsequent voltage pulses in the series of voltage pulses are of opposite polarity and lower magnitude than the first voltage pulse so that the strain remains within a selected tolerance from said substantially fixed strain until the convergence to said substantially fixed strain is obtained.
- 19. The method according to claim 18 wherein said voltage pulses are exponentially decaying voltage pulses.
- 20. The method according to claim 18 wherein said voltage pulses are stepwise transitions in voltage.
- 21. A piezoelectric actuator system, comprising;
a piezoelectric actuator; and controller means electrically connected to said piezoelectric actuator for applying effective voltage versus time profiles to said piezoelectric actuator, the effective voltage versus time profiles being selected to rapidly change the strain in the piezoelectric actuator in such a way as to compensate for effects of strain creep in the piezoelectric actuator due to the application of voltage thereto and to obtain convergence to a substantially fixed strain in said piezoelectric actuator in a pre-selected period of time.
- 22. The piezoelectric actuator system according to claim 21 wherein said effective voltage versus time profiles include a step voltage and a series of voltage pulses superimposed on the step voltage to compensate for strain creep due to the step voltage, the series of voltage pulses including a first voltage pulse with the same polarity as said step voltage and being sufficiently large to stimulate rapid displacement of the piezoelectric element to reach said substantially fixed strain, and wherein subsequent voltage pulses in the series of voltage pulses are of opposite polarity and lower magnitude than the first voltage pulse so that the strain remains within a selected tolerance from said substantially fixed strain until the convergence to said substantially fixed strain is obtained.
- 23. The piezoelectric actuator system according to claim 22 wherein said voltage pulses are exponentially decaying voltage pulses.
- 24. The piezoelectric actuator system according to claim 22 wherein said voltage pulses are stepwise transitions in voltage.
- 25. A positioning system for positioning an object, comprising;
a piezoelectric actuator physically attachable to an object to be positioned at a pre-selected position; controller means electrically connected to said piezoelectric actuator for applying effective voltage versus time profiles to said piezoelectric actuator for applying strain to said object to move a selected portion of said object, the effective voltage versus time profiles being selected to rapidly change the strain in the piezoelectric actuator in such a way as to compensate for effects of strain creep in the piezoelectrc actuator due to the application of voltage thereto and to obtain convergence to a substantially fixed strain in said piezoelectric actuator in a pre-selected period of time.
- 26. The positioning system according to claim 25 wherein said effective voltage versus time profiles include a step voltage and a series of voltage pulses superimposed on the step voltage to compensate for strain creep due to the step voltage, the series of voltage pulses including a first voltage pulse with the same polarity as said step voltage and being sufficiently large to stimulate rapid displacement of the piezoelectric element to reach said substantially fixed strain, and wherein subsequent voltage pulses in the series of voltage pulses are of opposite polarity and lower magnitude than the first voltage pulse so that the strain remains within a selected tolerance from said substantially fixed strain until the convergence to said substantially fixed strain is obtained.
- 27. The positioning system according to claim 26 wherein said voltage pulses are exponentially decaying voltage pulses.
- 28. The positioning system according to claim 26 wherein said voltage pulses are stepwise transitions in voltage.
CROSS REFERENCE TO RELATED U.S PATENT APPLICATIONS
[0001] This patent application relates to U.S. provisional patent application Serial No. 60/337,164 filed on Dec. 10, 2001 entitled METHOD OF DRIVING PIEZOELECTRIC CERAMICS FOR FAST SWITCHING OF SINGLE OR MULTIPLE BANDWIDTHS OF LIGHT IN A FIBER-BRAGG GRATING
Provisional Applications (1)
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Number |
Date |
Country |
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60337164 |
Dec 2001 |
US |