Tunable optical structure featuring feedback control

• US 6,563,968 B2
• Filed: 09/10/2001
• Issued: 05/13/2003
• Est. Priority Date: 03/16/2000
• Status: Expired due to Term

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Cidra Sarl (Nordic Cultural & Educational Foundation)
• Inventors: Putnam, Martin A., Davis, Michael A., Bellemore, David G.
• Primary Examiner(s): Ullah, Akm E.
• Application Number:
  US09/950,509
• Publication Number:
  US 20020071626A1
• Time in Patent Office: 610 Days
• Field of Search: 385/1-16, 385/147, 250/231.18, 250/237.G, 250/306, 731/05, 356/613, 356/614
• US Class Current: 385/12
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• CPC Class Codes: G01D 5/35377 Means for amplifying or modifying the measured quantity
• CPC Class Codes: G01L 1/246 using integrated gratings, e.g. Bragg gratings
• CPC Class Codes: G02B 6/022 using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131
• CPC Class Codes: G02F 1/011 in optical waveguides, not otherwise provided for in this subclass

Abstract

A tunable optical device has a compression tuned optical structure and a displacement sensor. The compression tuned optical structure responds to an optical signal, and further responds to a displacement sensor signal, for providing a compression tuned optical structure signal containing information about a change in an optical characteristic of the compression tuned optical structure, and for also further providing an excitation caused by a change in a displacement of the compression tuned optical structure. The displacement sensor responds to the excitation, for providing a displacement sensor signal containing information about the change in the displacement of the compression tuned optical structure. The compression tuned optical structure may be in the form of a dogbone structure that is an all-glass compression unit having wider end portions separated by a narrower intermediate portion. The displacement sensor includes a capacitance sensor affixed to the compression tuned optical structure for measuring a change in capacitance between two parallel and opposing plates that depends on a change in a gap or an area with respect to the two parallel and opposing plates.

Claims

1. A tunable optical device comprising:

a first optical waveguide having a first grating disposed therein, the first grating having a first reflection wavelength; and

a sensor including;

a second optical waveguide attached to the first optical waveguide, the second optical waveguide having a second grating disposed therein, the second grating having a second reflection wavelength; and

a light source optically coupled to the second optical waveguide;

wherein the second grating filters light provided by the light source, the filtered light being indicative of the stain provided to the first optical waveguide.

2. The tunable optical device of claim 1, further including:

an actuator that strains the first optical waveguide to change the reflection wavelength of the first grating in response to a control signal; and

a controller that provides the control signal in response to the filtered light and an input signal indicative of a desired reflection wavelength.

3. The tunable optical device of claim 1, wherein the first optical waveguide has an outer transverse dimension of at least 0.3 mm.

4. The tunable optical device of claim 3, when the first optical waveguide comprises a cane element.

5. The tunable optical device of claim 3, wherein the first optical waveguide comprises a tube, having an optical fiber and the first grating cased therein along a longitudinal axis of the tube, the tube being fused to at least a portion of the optical fiber.

6. The tunable optical device of claim 1, wherein the second optical waveguide has an outer transverse dimension of at least 0.3 mm.

7. The tunable optical device of claim 6, wherein the second optical waveguide comprises a cane element.

8. The tunable optical device of claim 6, wherein the second optical waveguide comprises a tube, having an optical fiber and the second grating cased therein along a longitudinal axis of the tube, the tube being fused to at least a portion of the optical fiber.

9. The tamable optical device of claim 1, wherein the second optical waveguide is attached at opposite ends to the first optical waveguide.

10. The tunable optical device of claim 1, wherein the second optical waveguide is attached to the first optical waveguide at a region of the second optical waveguide having the second grating.

11. The tunable optical device of claim 1, wherein the first grating comprises a Bragg grating written in a core of the first optical waveguide.

12. The tunable optical device of claim 2, wherein the actuator compresses axially the first optical waveguide to tune the first grating to the desired reflection wavelength.

13. The tunable optical device of claim 12, wherein the actuator is at least one of a piezoelectric device, a stepper motor and a magnetostrictive device.

14. A tunable optical device comprising:

an optical waveguide having a first core and a second core disposed within a cladding, the first and second cores being spaced to be substantially optically non-coupling;

the first core having a first grating disposed therein, the second core having a second grating disposed therein; and

a light source optically coupled to the second core;

wherein the second grating filters light provided by the light source, the filtered light being indicative of the strain provided to the optical waveguide.

15. The tunable optical device of claim 14, further including:

an actuator that strains the optical waveguide to change the reflection wavelength of the first grating in response to a control signal; and

a controller that provides the control signal in response to the filtered light and an input signal indicative of a desired reflection wavelength.

16. The tunable optical device of claim 14, wherein the optical waveguide has an outer transverse dimension of at least 0.3 mm.

17. The tunable optical device of claim 16, wherein the optical waveguide comprises a cane element.

18. The tunable optical device of claim 16, wherein the optical waveguide comprises a tube, having an optical fiber with the first and second cores disposed therein along a longitudinal axis of the tube, the tube being fused to at least a portion of the optical fiber.

19. The tunable optical device of claim 14, wherein each of the first and second gratings comprises a Bragg grating written in the respective first and second cores.

20. The tunable optical device of claim 15, wherein the actuator compresses axially the optical waveguide to tune the first grating to the desired reflection wavelength.

21. The tunable optical device of claim 20, wherein the actuator is at least one of a piezoelecide device, a stepper motor and a magnetostrictive device.

22. The tunable optical device of claim 14, further comprises an optical detector for receiving the filtered light and providing a control signal, wherein the second grating is blazed to direct the filtered light to the optical detector.

23. The tunable optical device of claim 22, wherein the optical detector is a CCD array.

24. A tunable optical device comprising:

an optical waveguide having a grating disposed therein, the grating having a reflection wavelength; and

a sensor for providing a displacement signal indicative of the strain provided to the optical waveguide, the sensor including;

an element disposed at one end of the optical waveguide, the element providing a magnetic field; and

a detector including a conductive coil disposed at another end of the optical waveguide, wherein the detector provides the displacement signal in response to an electric current induced by the element.

25. The tunable optical device of claim 24, further including:

an actuator that strains the optical waveguide to change the reflection wavelength of the grating in response to a control signal; and

a controller that provides the control signal in response to the displacement signal and an input signal indicative of a desired reflection wavelength.

26. A tunable optical device comprising:

a optical waveguide having a grating disposed therein, the grating having a reflection wavelength; and

a sensor including;

an optical transmitter that provides an optical signal, the optical transmitter being disposed on the optical waveguide; and

an optical receiver that receives the optical signal, the optical receiver being disposed on the optical waveguide;

a processing unit that measures the time between transmitting the optical signal and receiving the optical signal to provide a sense signal indicative of the strain provided to the optical waveguide.

27. A tunable optical device of claim 26, further including a reflective surface disposed at on end of the optical waveguide, and the optical transmitter and optical receiver disposed at an other end of the optical waveguide, wherein the reflective surface reflects the optical signal from the optical transmitter to the optical receiver.

28. The tunable optical device of claim 26, further including:

an actuator that strains the optical waveguide to change the reflection wavelength of the grating in response to a control signal;

wherein the processor provides the control signal in response to the sense signal and an input signal indicative of a desired reflection wavelength.

29. A tunable optical device comprising:

an optical waveguide having a grating disposed therein, the grating having a reflection wavelength; and

a sensor including;

a light source that projects light onto the optical waveguide;

at least one reflective surface disposed on the optical waveguide; and

an optical detector that detects the position of the light reflected from the at least one reflective surface;

wherein the optical detector provides, sense signal indicative of the strain provided to the optical waveguide in response to the position of the reflected light.

30. The tunable optical device of claim 29, further including:

an actuator that strains the optical waveguide to change the reflection wavelength of the grating in response to a control signal; and

a processor that provides the control signal in response to the sense signal and an input signal indicative of a desired reflection wavelength.