Dielectric waveguide with elongate cross-section

• US 4,307,938 A
• Filed: 03/03/1980
• Issued: 12/29/1981
• Est. Priority Date: 06/19/1979
• Status: Expired due to Term

• Current Assignee: Fleet Capital Corporation (Bank of America Corp.)
• Original Assignee: Andrew Corporation (CommScope Holding Company, Inc.)
• Inventors: Dyott, Richard B.
• Primary Examiner(s): Lee, John D.
• Application Number:
  US06/126,416
• Time in Patent Office: 666 Days
• Field of Search: 350/96.15, 350/96.16, 350/96.30, 350/96.31, 350/96.32, 350/96.34
• US Class Current: 385/123
• CPC Class Codes: G02B 6/10 of the optical waveguide type G02B6/02, G02B6/24 take precedence; devices or arrangements for the control of light by electric, magnetic, electro-magnetic or acoustic means G02F1/00; transferring the modulation of modulated light G02F2/00; optical logic elements G02F3/00; optical analogue/digital converters G02F7/00
• CPC Class Codes: G02B 6/105 having optical polarisation effects

Abstract

A dielectric waveguide comprises a wave propagating member having a core with a refractive index n₁ and a cladding with a refractive index n₂, the core having an elongate cross-section with a major axis a and a minor axis b. The values of n₁, n₂, a and b are such that only the two orthogonally polarized fundamental modes of a wave with a prescribed wavelength can propagate through the core, thereby avoiding propagation of unwanted higher order modes of the wave, and such that the group velocities of the two orthogonally polarized fundamental modes are substantially equal so that any accidental coupling between the fundamental modes does not reduce the bandwidth of the waveguide.

Claims

1. A dielectric waveguide comprising a wave propagating member having a core with a refractive index n₁ and a cladding with a refractive index n₂, said core having an elongate cross section with a major axis a and a minor axis b, the values of n₁, n₂, a and b being such that

(1) only the two orthogonally polarized fundamental modes of a wave with a prescribed wavelength can propagate through said core, thereby avoiding propagation of unwanted higher order modes of said wave and

(2) the group velocities of said two orthogonally polarized fundamental modes are substantially equal so that any accidental coupling between said fundamental modes does not reduce the bandwidth of the waveguide.

2. A dielectric waveguide as set forth in claim 1 wherein the propagation constants of said fundamental modes are substantially different so as to minimize coupling therebetween.

3. A dielectric waveguide as set forth in claim 1 wherein said wave propagating member is an optical fiber having a core with an elliptical cross section.

4. A dielectric waveguide as set forth in claim 1 wherein the ratio of the length of the major axis to the length of the minor axis of said elongate cross-section is in the range of from about 2.0 to about 3.5.

5. A method of propagating electromagnetic waves along a dielectric waveguide, said method comprising the steps of applying the polarized electromagnetic wave as an input to a wave propagating member having a core with a refractive index n₁ and a cladding with a refractive index n₂, said core having an elongate cross section with a major axis a and a minor axis b, the values of n₁, n₂, a and b being such that

(1) only the two orthogonally polarized fundamental modes of a wave with a prescribed wavelength can propagate through said core, thereby avoiding propagation of unwanted higher order modes of said wave and

(2) the group velocities of said two orthogonally polarized fundamental modes are substantially equal so that any accidental coupling between said fundamental modes not does reduce the bandwidth of the waveguide.

6. A method as set forth in claim 5 wherein the propagation constants of said fundamental modes are substantially different so as to minimize coupling therebetween.

7. A method as set forth in claim 5 wherein said wave propagating member is an optical fiber having a core with an elliptical cross section.

8. A method as set forth in claim 5 wherein the ratio of the length of the major axis to the length of the minor axis of said elongate cross-section is in the range of from about 2.0 to about 3.5.