Tunable optic fiber bandpass filter using flexural acoustic waves

• US 6,151,427 A
• Filed: 04/20/1999
• Issued: 11/21/2000
• Est. Priority Date: 04/20/1999
• Status: Expired due to Fees

• Current Assignee: National Security Agency Government of The United States of America As Represented By
• Original Assignee: The United States of America As Represented By The Director National Security Agency
• Inventors: Satorius, Duane A.
• Primary Examiner(s): Sanghavi, Hemang
• Application Number:
  US09/294,390
• Time in Patent Office: 581 Days
• Field of Search: 385/1, 385/7, 385/27, 385/28, 385/29, 385/37, 385/123, 385/10
• US Class Current: 385/7
• CPC Class Codes: G02B 6/14 Mode converters
• CPC Class Codes: G02B 6/29389 Bandpass filtering, e.g. 1x1 device rejecting or passing certain wavelengths G02B6/2938 takes precedence
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: G02F 1/0115 in optical fibres
• CPC Class Codes: G02F 1/125 in an optical waveguide structure
• CPC Class Codes: G02F 2201/02 fibre
• CPC Class Codes: G02F 2201/307 Reflective grating, i.e. Bragg grating
• CPC Class Codes: G02F 2203/055 wavelength filtering

Abstract

The present invention is a tunable optic fiber bandpass filter using flexural acoustic waves that includes an optic fiber; a first silica horn; a first acoustic transducer; a first signal generator; a first acoustic absorber; a core blocker; a second acoustic absorber; a second silica horn; a second acoustic transducer; and a second signal generator. The method of the present invention is receiving an optic signal in a core of an optic fiber; inducing a first flexural acoustic wave in the optic fiber where there is no buffer coating; absorbing the first flexural acoustic wave after it has traveled a distance down the optic fiber; causing user-definable wavelengths of the optic signal to exit the core and enter the cladding of the optic fiber; blocking wavelengths of the optic signal that remain in the core of the optic fiber; inducing a second flexural acoustic wave in the optic fiber where there is no buffer coating; absorbing the second flexural acoustic wave after it has traveled a distance down the optic fiber; and causing user-definable wavelengths of the optic signal to exit the cladding and enter the core of the optic fiber. One signal generator may be used to induce both flexural acoustic waves. In an alternate embodiment, one absorber may be used.

Claims

1. A tunable optic fiber bandpass filter using flexural acoustic waves, comprising:

a) an optic fiber, having a core, having a cladding over the core, and having a buffer coating over the optic fiber where bandpass filtering does not occur;

b) a first silica horn, having a first end attached to the optic fiber where no buffer coating is present, and having a second end;

c) a first acoustic transducer attached to the second end of the first silica horn;

d) a first signal generator attached to the first acoustic transducer;

e) a first acoustic absorber deposited on the optic fiber at which no buffer coating is present and to the right of the first silica horn;

f) a core blocker fabricated within the core of the optic fiber at which there is no buffer coating present and to the right of the first acoustic absorber;

g) a second acoustic absorber deposited on the optic fiber at which there is no buffer coating and to the right of the core blocker;

h) a second silica horn, having a first end attached to the optic fiber where no buffer coating is present and to the right of the second acoustic absorber, and having a second end;

i) a second acoustic transducer attached to the second end of the second silica horn; and

j) a second signal generator attached to the second acoustic transducer.

2. The device of claim 1, wherein said optic fiber is comprised of a step index optic fiber.

3. The device of claim 1, wherein said first silica horn and said second silica horn are attached to the optic fiber with acoustic impedance matching epoxy.

4. The device of claim 1, wherein said first acoustic absorber and said second acoustic absorber are both comprised of epoxy deposited on the optic fiber.

5. The device of claim 1, wherein said first acoustic transducer and said second acoustic transducer are both comprised of a piezoelectric material.

6. A tunable optic fiber bandpass filter using flexural acoustic waves, comprising:

a) an optic fiber, having a core, having a cladding over the core, and having a buffer coating over the optic fiber where bandpass filtering does not occur;

b) a first silica horn, having a first end attached to the optic fiber where no buffer coating is present, and having a second end;

c) a first acoustic transducer attached to the second end of the first silica horn;

d) a first acoustic absorber deposited on the optic fiber at which no buffer coating is present and to the right of the first silica horn;

e) a core blocker fabricated within the core of the optic fiber at which there is no buffer coating present and to the right of the first acoustic absorber;

f) a second acoustic absorber deposited on the optic fiber at which there is no buffer coating and to the right of the core blocker;

g) a second silica horn, having a first end attached to the optic fiber where no buffer coating is present and to the right of the second acoustic absorber, and having a second end;

h) a second acoustic transducer attached to the second end of the second silica horn; and

i) a signal generator attached to the first acoustic absorber and the second acoustic transducer.

7. The device of claim 6, wherein said optic fiber is comprised of a step index optic fiber.

8. The device of claim 6, wherein said first silica horn and said second silica horn are attached to the optic fiber with acoustic impedance matching epoxy.

9. The device of claim 6, wherein said first acoustic absorber and said second acoustic absorber are both comprised of epoxy deposited on the optic fiber.

10. The device of claim 6, wherein said first acoustic transducer and said second acoustic transducer are both comprised of a piezoelectric material.

11. A tunable optic fiber bandpass filter using flexural acoustic waves, comprising:

a) a step index optic fiber, having a core, having a cladding over the core, and having a buffer coating over the optic fiber where bandpass filtering does not occur;

b) a first silica horn, having a first end attached to the optic fiber where no buffer coating is present, and having a second end;

c) a first acoustic transducer attached to the second end of the first silica horn;

d) a first signal generator attached to the first acoustic transducer;

e) an acoustic absorber deposited on the optic fiber at which no buffer coating is present and to the right of the first silica horn;

f) a core blocker fabricated within the core of the optic fiber at which there is no buffer coating present and within the confines of the first acoustic absorber;

g) a second silica horn, having a first end attached to the optic fiber where no buffer coating is present and to the right of the second acoustic absorber, and having a second end;

h) a second acoustic transducer attached to the second end of the second silica horn; and

i) a second signal generator attached to the second acoustic transducer.

12. The device of claim 11, wherein said optic fiber is comprised of a step index optic fiber.

13. The device of claim 11, wherein said first silica horn and said second silica horn are attached to the optic fiber with acoustic impedance matching epoxy.

14. The device of claim 11, wherein said acoustic absorber is comprised of epoxy deposited on the optic fiber.

15. The device of claim 11, wherein said first acoustic transducer and said second acoustic transducer are both comprised of a piezoelectric material.

16. A tunable optic fiber bandpass filter using flexural acoustic waves, comprising:

a) a step index optic fiber, having a core, having a cladding over the core, and having a buffer coating over the optic fiber where bandpass filtering does not occur;

b) a first silica horn, having a first end attached to the optic fiber where no buffer coating is present, and having a second end;

c) a first acoustic transducer attached to the second end of the first silica horn;

d) an acoustic absorber deposited on the optic fiber at which no buffer coating is present and to the right of the first silica horn;

e) a core blocker fabricated within the core of the optic fiber at which there is no buffer coating present and within the confines of the first acoustic absorber;

f) a second silica horn, having a first end attached to the optic fiber where no buffer coating is present and to the right of the second acoustic absorber, and having a second end;

g) a second acoustic transducer attached to the second end of the second silica horn; and

h) a signal generator attached to the first acoustic transducer and the second acoustic transducer.

17. The device of claim 16, wherein said optic fiber is comprised of a step index optic fiber.

18. The device of claim 16, wherein said first silica horn and said second silica horn are attached to the optic fiber with acoustic impedance matching epoxy.

19. The device of claim 16, wherein said acoustic absorber is comprised of epoxy deposited on the optic fiber.

20. The device of claim 16, wherein said first acoustic transducer and said second acoustic transducer are both comprised of a piezoelectric material.

21. A method of bandpass filtering an optical signal using flexural acoustic waves, comprising the steps of:

a) receiving an optic signal in a core of an optic fiber, where the optic fiber includes a cladding around the core, and a buffer coating around the cladding where bandpass filtering does not lake place;

b) inducing a first flexural acoustic wave in the optic fiber where there is no buffer coating on the optic fiber;

c) absorbing the first flexural acoustic wave after it has traveled a distance down the optic fiber and to the right;

d) causing a user-definable frequency of the optic signal to exit the core and enter the cladding of the optic fiber by the first flexural acoustic wave;

e) blocking portions of the optic signal that remain in the core of the optic fiber;

f) inducing a second flexural acoustic wave in the optic fiber where there is no buffer coating on the optic fiber and to the right of the first flexural acoustic wave;

g) absorbing the second flexural acoustic wave after it has traveled a distance down the optic fiber and to the left; and

h) causing a user-definable frequency of the optic signal to exit the cladding and enter the core of the optic fiber by the second flexural acoustic wave.

22. The method of claim 21, wherein said step of receiving an optic signal in a core of an optic fiber is comprised of the step of receiving an optic signal in a core of a step index optic fiber.

23. The method of claim 21, wherein said steps of inducing a first flexural acoustic wave and a second acoustic wave in the optic fiber are both comprised of the step of inducing a first acoustic wave and a second acoustic wave in the optic fiber by vibrating the optic fiber.

24. The method of claim 21, wherein said step of absorbing the first flexural acoustic wave and second flexural acoustic wave are both comprised of the step of absorbing the first flexural acoustic wave and the second flexural acoustic wave by epoxy deposited on the optic fiber.