Tension-tuned acousto-optic bandpass filter

• US 6,647,159 B1
• Filed: 01/25/2002
• Issued: 11/11/2003
• Est. Priority Date: 01/25/2002
• Status: Active Grant

• Current Assignee: The United States of America As Represented By The Director National Security Agency
• Original Assignee: The United States of America As Represented By The Director National Security Agency
• Inventors: Satorius, Duane Anthony
• Primary Examiner(s): Sanghavi, Hemang
• Assistant Examiner(s): PAK, SUNG H
• Application Number:
  US09/683,617
• Time in Patent Office: 655 Days
• Field of Search: 385/7, 385/4, 385/1, 385/27, 385/28, 385/29, 359/308, 359/305
• US Class Current: 385/7
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/14 Mode converters
• CPC Class Codes: G02F 1/01716 Optically controlled superlattice or quantum well devices
• CPC Class Codes: G02F 1/113 Circuit or control arrangements
• CPC Class Codes: G02F 1/125 in an optical waveguide structure
• CPC Class Codes: G02F 2201/02 fibre
• CPC Class Codes: G02F 2203/055 wavelength filtering

Abstract

Device whereby one or more bands of optical wavelengths may be selected for further transmission. All light within the optical bandwidth of operation is first coupled from the core mode of an optical fiber to a specific cladding mode by a chirped broadband cladding mode coupler. These cladding mode lightwaves then enter a narrow-band core mode coupler whereby selected optical bands of wavelengths, tuned by the tension on the optical fiber, are re-coupled back into the core of the optical fiber. The chirped broadband cladding mode coupler is isolated from the narrow-band core mode coupler by an acoustic absorber to limit the acoustic interaction between them.

Claims

1. A tension-tuned acousto-optic bandpass filter, comprising:

a single-mode optical fiber, with a longitudinal axis, core, concentric cladding over the core, and proximal and distal ends;

a broadband cladding mode coupler further comprising a first longitudinal length of the optical fiber closer to the proximal end of the optical fiber, wherein said first longitudinal length has a chirped diameter, and at least one first acoustic-wave generator coupled to the optical fiber within the first longitudinal length;

a narrow-band core mode coupler further comprising a second longitudinal length of the optical fiber closer to the distal end of the optical fiber and at least one second acoustic-wave generator coupled to the optical fiber within the second longitudinal length;

an acoustic absorber deployed and coupled to the optical fiber between said broadband cladding mode coupler and said narrow-band core mode coupler; and

means for applying an adjustable tension to said second longitudinal length of the optical fiber.

2. The filter of claim 1, wherein the diameter of said second longitudinal length of the optical fiber is tapered.

3. The filter of claim 1, wherein said first longitudinal length of the optical fiber, in addition to having a chirped diameter, also has a tapered diameter.

4. The filter of claim 1, wherein said means for applying an adjustable tension includes at least one piezo-electric actuating device.

5. The filter of claim 1, wherein said means for applying an adjustable tension includes at least one mechanical actuating device.

6. The filter of claim 1, wherein said means for applying an adjustable tension includes at least one thermo-electric actuating device.

7. The filter of claim 1, wherein said means for applying an adjustable tension includes at least one magneto-electric actuating device.

8. The filter of claim 1, wherein said means for applying an adjustable tension includes means for dynamically tuning said filter by dynamically adjusting said adjustable tension.

9. The filter of claim 1, wherein said means for applying an adjustable tension includes means for modulating said adjustable tension.

10. The filter of claim 1, wherein said means for applying an adjustable tension is accomplished by applying longitudinal force to at least one of said second acoustic-wave generators.

11. The filter of claim 1, wherein said means for applying an adjustable tension is accomplished by applying longitudinal force to an acoustic wave amplifier mechanically coupled to at least one of said second acoustic-wave generators.

12. The filter of claim 8, wherein said means for dynamically tuning said filter by dynamically adjusting said adjustable tension includes means for performing a power spectral analysis over a bandwidth of interest by varying said adjustable tension such that said narrow-band core mode coupler is tuned across said bandwidth of interest by said dynamically tuning means.

13. The filter of claim 1, wherein at least one of said second acoustic-wave generators is electrically connected to more than one frequency source.

14. A tension-tuned acousto-optic bandpass filter, comprising:

a single-mode optical fiber, with a longitudinal axis, core, concentric cladding over the core, and proximal and distal ends;

a broadband cladding mode coupler further comprising a first longitudinal length of the optical fiber closer to the proximal end of the optical fiber, wherein said first longitudinal length has a chirped diameter, and at least one first acoustic-wave generator coupled to the optical fiber within the first longitudinal length;

a narrow-band core mode coupler further comprising a second longitudinal length of the optical fiber closer to the distal end of the optical fiber and at least one second acoustic-wave generator coupled to the optical fiber within the second longitudinal length;

an acoustic absorber deployed and coupled to the optical fiber between said broadband cladding mode coupler and said narrow-band core mode coupler; and

means for applying an adjustable tension to said single-mode optical fiber.