Compression-tuned bragg grating and laser

• US 6,229,827 B1
• Filed: 12/06/1999
• Issued: 05/08/2001
• Est. Priority Date: 12/04/1998
• Status: Expired due to Term

• Current Assignee: Weatherford Technology Holdings, LLC (Weatherford International PLC)
• Original Assignee: Cidra Sarl (Nordic Cultural & Educational Foundation)
• Inventors: Kersey, Alan D., Fernald, Mark R., Bailey, Timothy J., Putnam, Martin A., Davis, Michael A., Sanders, Paul E., Brucato, Robert N., Sullivan, James M., Miller, Matthew B.
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US09/456,112
• Time in Patent Office: 519 Days
• Field of Search: 372/20, 372/64, 372/92, 372/6, 385/37, 385/24, 359/568, 359/569
• US Class Current: 372/20
• CPC Class Codes: G02B 6/0218 using mounting means, e.g. by using a combination of materials having different thermal expansion coefficients
• 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 1/0115 in optical fibres
• CPC Class Codes: G02F 1/0128 based on electro-mechanical, magneto-mechanical, elasto-optic effects
• CPC Class Codes: G02F 2201/307 Reflective grating, i.e. Bragg grating

Abstract

A compression-tuned bragg grating includes a tunable optical element 20,600 which includes either an optical fiber 10 having at least one Bragg grating 12 impressed therein encased within and fused to at least a portion of a glass capillary tube 20 or a large diameter waveguide grating 600 having a core and a wide cladding. Light 14 is incident on the grating 12 and light 16 is reflected at a reflection wavelength λ1. The tunable element 20,600 is axially compressed which causes a shift in the reflection wavelength of the grating 12 without buckling the element. The shape of the element may be other geometries (e.g., a “dogbone” shape) and/or more than one grating or pair of gratings may be used and more than one fiber 10 or core 612 may be used. At least a portion of the element may be doped between a pair of gratings 150,152, to form a compression-tuned laser or the grating 12 orgratings 150,152 may be constructed as a tunable DFB laser. Also, the element 20 may have an inner tapered region 22 or tapered (or fluted) sections 27. The compression may be done by a PZT, stepper motor or other actuator or fluid pressure.

Claims

1. A compression-tuned optical device, comprising:

a tunable optical element, having outer dimensions along perpendicular axial and transverse directions, said outer dimension being at least 0.3 mm along said transverse direction;

said tunable optical element receiving and propagating input light and having at least one reflective element disposed therein along said axial direction, said reflective element reflecting a reflection wavelength of said input light;

at least a portion of said tunable element having a transverse cross-section which is contiguous and comprises a substantially homogeneous material; and

said reflective element being axially strain compressed so as to change said reflection wavelength without buckling said tunable element in said transverse direction thereby tuning said optical device.

2. The apparatus of claim 1 wherein said tunable element comprises

an optical fiber, having said reflective element embedded therein; and

a tube, having said optical fiber and said reflective element encased therein along a longitudinal axis of said tube, said tube being fused to at least a portion of said fiber.

3. The apparatus of claim 2 wherein said tube is fused to said optical fiber where said reflective element is located.

4. The apparatus of claim 2 wherein said tube is fused to said optical fiber on opposite axial sides of said reflective element.

5. The apparatus of claim 2, wherein said device further comprises a plurality of said optical fibers encased in said tube.

6. The apparatus of claim 2, wherein said inner core is a single mode core.

7. The apparatus of claim 1 wherein said tunable element comprises a large diameter optical waveguide having an outer cladding and an inner core disposed therein.

8. The apparatus of claim 7, wherein said device further comprises a plurality of said cores disposed in said waveguide.

9. The apparatus of claim 1 wherein said tunable element comprises:

a tube fused to at least a portion of an optical fiber along a longitudinal axis of said tube;

a large diameter optical waveguide having an outer cladding and an inner core disposed therein; and

said tube and said wavguide being axially fused and optically coupled together.

10. The apparatus of claim 9 wherein said reflective element is disposed in said fiber and encased in said tube along said longitudinal axis of said tube.

11. The apparatus of claim 9 wherein said reflective element is disposed in said optical waveguide.

12. The apparatus of claim 1 wherein said material comprises a glass material.

13. The apparatus of claim 1, wherein said tunable element has a plurality of reflective elements disposed therein.

14. The apparatus of claim 1, wherein said tunable element has at least one pair of reflective elements disposed therein and at least a portion of said tunable element is doped with a rare-earth dopant between said pair of elements to form a laser.

15. The apparatus of claim 14 wherein said laser lases at a lasing wavelength which changes as force on said tunable element changes.

16. The apparatus of claim 1, wherein at least a portion of said tunable element is doped with a rare-earth dopant where said reflective element is located and said reflective element is configured to form a DFB laser.

17. The apparatus of claim 16 wherein said DFB laser lases at a lasing wavelength which changes as force on said tunable element changes.

18. The apparatus of claim 1, wherein said material comprises silica.

19. The apparatus of claim 1 wherein at least a portion of said tunable element comprises a cylindrical shape.

20. The apparatus of claim 1 wherein said tunable element has at least one tapered axial section.

21. The apparatus of claim 1 wherein said reflective element has a characteristic wavelength and wherein said tunable element comprises a shape that provides a predetermined sensitivity to a shift in said wavelength due to a change in force on said tunable element.

22. The apparatus of claim 21 wherein said shape of said tunable element comprises a dogbone shape.

23. The apparatus of claim 1, further comprising a compressing device, which axially compresses said waveguide element.

24. The apparatus of claim 23, wherein said compressing device comprises an actuator.

25. The apparatus of claim 23, wherein said compressing device comprises an actuator mechanically connected to at least one axial end of said tunable element.

26. The apparatus of claim 23, wherein said actuator comprises:

a stepper motor, a piezoelectric actuator, a solenoid, or a pneumatic force actuator.

27. The apparatus of claim 23, wherein said compressing device comprises a housing surrounding at least a portion of said compressing device and said waveguide element.

28. The apparatus of claim 23, wherein said compressing device comprises a fluid-filled pressurized housing surrounding at least a portion of said waveguide element.

29. The apparatus of claim 1, wherein said outer dimension of said tunable element along said axial direction is greater than said outer dimension of said tunable element along said transverse direction.

30. A method for wavelength-tuning an optical device, comprising the steps of:

a) obtaining a tunable optical element, having outer dimensions along perpendicular axial and transverse directions, said outer dimension being at least 0.3 mm along said transverse direction, said tunable optical element receiving and propagating input light and having at least one reflective element disposed therein along a longitudinal axis of said element, at least a portion of said tunable element having a transverse cross-section which is contiguous and comprises a substantially homogeneous material; and

b) axially compressing said tunable element so as to change the reflection wavelength of said reflective element without buckling said tunable element in said transverse direction thereby tuning said optical device.

31. The method of claim 30 where said element comprises a tube, having an optical fiber and said reflective element encased therein along a longitudinal axis of said tube, said tube being fused to at least a portion of said fiber.

32. The method of claim 31, wherein said tube comprises a plurality of said optical fibers encased in said tube.

33. The method of claim 30 wherein said tunable element comprises a large diameter optical waveguide having an outer cladding and an inner core disposed therein.

34. The method of claim 33, wherein said waveguide comprises a plurality of said cores.

35. The method of claim 33, wherein said inner core is a single mode core.

36. The method of claim 30, wherein said tunable element has a plurality of reflective elements disposed therein.

37. The method of claim 30, wherein said tunable element has at least one pair of reflective elements disposed therein and at least a portion of said tunable element is doped with a rare-earth dopant between said pair of elements to form a laser.

38. The method of claim 37 wherein said laser lases at a lasing wavelength which changes as force on said tunable element changes.

39. The method of claim 30, wherein at least a portion of said tunable element is doped with a rare-earth dopant where said reflective element is located and said reflective element is configured to form a DFB laser.

40. The method of claim 39, wherein said DFB laser lases at a lasing wavelength which changes as said tunable element is compressed.

41. The method of claim 30 wherein said reflective element has a characteristic wavelength and wherein said tunable element has a shape that provides a predetermined sensitivity to a shift in said wavelength due to a change in force on said tunable element.

42. The method of claim 41 wherein said shape of said tunable element comprises a dogbone shape.

43. The method of claim 30 wherein said step of compressing comprises compressing said tunable element with an actuator.

44. The method of claim 43 wherein said actuator comprises:

a stepper motor, a peizoelectric actuator, a solenoid, or a pneumatic force actuator.

45. The method of claim 30 wherein said step of compressing comprises compressing said tunable element with a fluid pressure.

46. The method of claim 30 wherein said material comprises a glass material.

47. The Method of claim 30, wherein said outer dimension of said tunable element along said axial direction is greater than said outer dimension of said tunable element along said transverse direction.

48. The Method of claim 30, wherein said material comprises silica.