Coating for light-diffusing optical fibers

Patent metadata

Field	Value
Publication number	US-10627558-B2
Application number	US-201615358232-A
Country	US
Kind code	B2
Filing date	Nov 22, 2016
Priority date	Nov 25, 2015
Publication date	Apr 21, 2020
Grant date	Apr 21, 2020

Abstract

A light-diffusing optical fiber that provides a symmetric intensity distribution of forward and backward scattered light is described. The fiber includes a secondary coating that contains scattering centers. Control of the thickness of the secondary coating and concentration of scattering centers provides control over the distribution of scattered intensity. More symmetric distributions of scattered light intensity are realized by increasing the thickness of the secondary coating and/or the concentration of scattering centers in the secondary coating. Representative scattering centers include oxide nanoparticles.

First claim

What is claimed is:

1. A light-diffusing optical fiber comprising:
a glass core, said glass core comprising a volume fraction of voids of between 0.5% and 20%; and
a cladding surrounding said glass core;
a primary coating surrounding the cladding, wherein the primary coating has a Young's modulus, when configured as a cured film with 80 μm thickness, of less than 1.5 MPa and wherein the primary coating is the cured product of a primary composition that includes a curable crosslinker, a curable diluent, and a polymerization initiator, the curable crosslinker being essentially free of urethane and urea functional groups; and
a secondary coating surrounding said primary coating, wherein said secondary coating has a Young's modulus, when configured as a cured rod having a diameter of 0.022″, of at least 500 MPa;
wherein said secondary coating comprises an inner portion without scattering centers and an outer portion with scattering centers, said scattering centers having a concentration of at least 0.5 wt % in said outer portion of the secondary coating;
wherein said light-diffusing optical fiber is configured to scatter light propagating in said glass core; and
wherein a maximum intensity of scattered light occurs at a peak azimuthal angle, said peak azimuthal angle being in the range from 80°-100°.

2. The light-diffusing optical fiber of claim 1 , wherein said glass core has a cross-sectional dimension greater than 50 μm.

3. The light-diffusing optical fiber of claim 1 , wherein said cladding comprises a polymer.

4. The light-diffusing optical fiber of claim 1 , wherein said cladding has a thickness of at least 10 μm.

5. The light-diffusing optical fiber of claim 1 , wherein said core has a first refractive index and said cladding has a second refractive index, said second refractive index being at least 0.003 less than said first refractive index.

6. The light-diffusing optical fiber of claim 1 , wherein said scattering centers include nanoparticles, said nanoparticles having a cross-sectional dimension of at least 25 nm.

7. The light-diffusing optical fiber of claim 1 , wherein said secondary coating is the outermost coating.

8. An illumination system comprising the light-diffusing optical fiber of claim 1 and a light source, said light-diffusing optical fiber having a first end and a second end, said light source being coupled to said first end.

9. The light-diffusing optical fiber of claim 1 , wherein the primary composition comprises from 1 wt % to 20 wt % of the curable crosslinker, from 10 wt % to 60 wt % of the curable diluent, and from 0.5 wt % to 10.0 wt % of the polymerization initiator.

10. The light diffusing optical fiber of claim 1 , wherein the primary coating has a thickness in the range of from 5 μm to 50 μm.

11. The light-diffusing optical fiber of claim 6 , wherein said nanoparticles have an average transmittance, per mm thickness, over the wavelength range from 400 nm-700 nm of greater than 90%.

12. The light-diffusing optical fiber of claim 6 , wherein said secondary coating comprises a polymer.

13. The light diffusing optical fiber of claim 9 , wherein the curable crosslinker has a molecular weight of from 150 g/mol to 15000 g/mol.

14. The light diffusing optical fiber of claim 13 , wherein the curable diluent has a molecular weight of from 120 g/mol to 600 g/mol.

15. A light-diffusing optical fiber comprising:
a glass core, said glass core comprising a volume fraction of voids of between 0.5% and 20%; and
a cladding surrounding said glass core;
a primary coating surrounding the cladding, wherein the primary coating has a Young's modulus, when configured as a cured film with 80 μm thickness, of less than 1.5 MPa and wherein the primary coating is the cured product of a primary composition that includes a curable crosslinker, a curable diluent, and a polymerization initiator, the curable crosslinker being essentially free of urethane and urea functional groups; and
a secondary coating surrounding said primary coating, said secondary coating comprising an inner portion without scattering centers and an outer portion with scattering centers;
wherein said light-diffusing optical fiber is configured to scatter light propagating in said glass core in a first azimuthal direction having an azimuthal angle θ 1 and in a second azimuthal direction having an azimuthal angle 180°-θ 1 ;
wherein the ratio of the intensity of light scattered in said first azimuthal direction to the intensity of light scattered in said second azimuthal direction is in the range from 0.5-1.5; and
wherein the maximum intensity of scatter light occurs at a peak azimuthal angle, said peak azimuthal angle being in the range from 80°-100°.

16. The light-diffusing fiber of claim 15 , wherein said scattering centers include nanoparticles.

17. The light-diffusing optical fiber of claim 15 , wherein said azimuthal angle θ 1 is an angle in the range from 5°-90°.

18. An illumination system comprising the light-diffusing optical fiber of claim 15 and a light source, said light-diffusing optical fiber having a first end and a second end, said light source being coupled to said first end.

19. A light-diffusing optical fiber comprising:
a glass core, said glass core comprising a volume fraction of voids of between 0.5% and 20%; and
a cladding surrounding said glass core;
a primary coating surrounding the cladding, wherein the primary coating has a Young's modulus, when configured as a cured film with 80 μm thickness, of less than 1.5 MPa and wherein the primary coating is the cured product of a primary composition that includes a curable crosslinker, a curable diluent, and a polymerization initiator, the curable crosslinker being essentially free of urethane and urea functional groups; and
a secondary coating surrounding said primary coating, said secondary coating comprising an inner portion without scattering centers and an outer portion with scattering centers;
wherein said light-diffusing optical fiber is configured to scatter light propagating in said glass core in a first plurality of azimuthal directions spanning a first plurality of azimuthal angles and in a second plurality of azimuthal directions spanning a second plurality of azimuthal angles, said second plurality of azimuthal angles corresponding to supplements of said first plurality of azimuthal angles;
wherein the ratio of the intensity of light scattered in two or more of said first plurality of azimuthal directions to the intensity of light scattered in two or more of said second plurality of azimuthal directions is in the range from 0.5-1.5, said two or more of said first plurality of azimuthal directions corresponding to two or more of said first plurality of azimuthal angles and said two or more of said second plurality of azimuthal directions having azimuthal angles corresponding to supplements of said two or more of said first plurality of azimuthal angles; and
wherein the maximum intensity of scatter light occurs at a peak azimuthal angle, said peak azimuthal angle being in the range from 80°-100°.

20. An illumination system comprising the light-diffusing optical fiber of claim 19 and a light source, said light-diffusing optical fiber having a first end and a second end, said light source being coupled to said first end.

Assignees

• Corning Inc

Inventors

• Bennett Kevin Wallace
• Hesch Trista Nicole
• Logunov Stephan Lvovich
• Ocampo Manuela

Classifications

• G02B6/001 Primary

  the light being emitted along at least a portion of the lateral surface of the fibre · CPC title

• G02B6/03694

  Multiple layers differing in properties other than the refractive index, e.g. attenuation, diffusion, stress properties · CPC title