Form polarizing fibers and method of fabrication

• US 4,717,225 A
• Filed: 05/15/1985
• Issued: 01/05/1988
• Est. Priority Date: 10/11/1984
• Status: Expired due to Term

• Current Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Furlong, Steven C., Chang, Chin-Lung, Feth, John R.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Ullah, Akm E.
• Application Number:
  US06/734,211
• Time in Patent Office: 965 Days
• Field of Search: 350/96.29, 350/96.30, 350/96.31, 350/96.32, 350/96.33, 350/96.34
• US Class Current: 385/11
• CPC Class Codes: C03B 2203/30 Polarisation maintaining [PM], i.e. birefringent products, e.g. with elliptical core, by use of stress rods, "PANDA" type fibres
• CPC Class Codes: C03B 37/01217 for making preforms of polarisation-maintaining optical fibres polarisation-maintaining optical fibres per se G02B6/105
• CPC Class Codes: G02B 6/105 having optical polarisation effects
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A polarizing optical fiber has a core formed of a plurality of layers of dielectrics having different refractive indices. The dielectric layers form a composite structure having different refractive indices for light of different polarizations. The differing refractive indices cause the polarization states of light guided by the fiber to be non-degenerate so that energy ordinarily will not couple from one polarization to the other. The fiber includes a cladding that may have a refractive index either less than both core indices to provide a polarization maintaining fiber or greater than or equal to one of the core indices to provide a polarizing fiber. The method of fabrication of the layered core form birefringent optical fiber includes forming a structure of a plurality of layers of the dielectrics, heating the structure to form a monolith, stretching the monolith to form the fiber core, and adding the cladding to the core.

Claims

1. A polarizing fiber optic waveguide, comprising:

a core formed of a plurality of alternating dielectric layers, each layer having a characteristic refractive index, said core being formed such that the dielectric layers provide a first core refractive index for light of a first polarization and a second core refractive index for light of a second polarization; and

a cladding surrounding said core, said cladding being formed of a dielectric material having a refractive index at least as large as said first core refractive index and less than said second core refractive index such that said core guides only light of said second polarization and light of all other polarizations propagate from said core into said cladding.

2. The polarizing fiber optic waveguide of claim 1 wherein said core has diameter such that only a single mode of optical energy will be guided by said core.

3. The polarizing fiber optic waveguide of claim 1 wherein said core is formed of alternating layers of SiO₂ and GeO₂.

4. A method for forming a polarizing fiber optic waveguide, comprising the steps of:

forming a core of a plurality of alternating dielectric layers, each layer having a characteristic refractive index, the alternating dielectric layers providing a first core refractive index for light of a first polarization and a second core refractive index for light of a second polarization; and

surrounding the core with a cladding formed of a dielectric material having a refractive index at least as large as the first core refractive index and less than the second core refractive index such that the core guides only light of said second polarization and light of all other polarizations propagate from the core into the cladding.

5. The method of claim 4 wherein the forming step includes:

forming a plurality of alternating layers of SiO₂ and GeO₂ ;

stacking a plurality of the layers; and

supporting the stacked layers with graphite blocks.

6. The process of claim 4 further including the step of encasing the stack of layers in fused silica before heating to form a monolith.

7. The method of claim 4 wherein the drawing step includes drawing the structure through a plurality of rectangular dies.

8. The method of claim 4 further including the step of grinding the monolith into a cylinder.

9. The method of claim 8 wherein the drawing step further includes drawing the cylinder through a series of circular dies.

10. The method of claim 9 further including the step of covering the core with a cladding having a cladding refractive index less than the refractive indices of the core.

11. The method of claim 9 further including the step of covering the core with a cladding having a cladding refractive index that is at least as great as one of the refractive indices of the core.

12. The method of claim 4 further including the step of compressing the structure to reduce the thickness of the layers to predetermined thicknesses.

13. The method of claim 9 further including the step of grinding the monolith into a cylinder.

14. The method of claim 10 wherein the drawing step further includes drawing the cylinder through a series of circular dies.