Microstructured Transmission Optical Fiber

• US 20090202211A1
• Filed: 01/16/2009
• Published: 08/13/2009
• Est. Priority Date: 02/07/2008
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Li, Ming-Jun, Bookbinder, Dana Craig, Tandon, Pushkar, Bickham, Scott Robertson
• Granted Patent: US 8,175,437 B2
• Time in Patent Office: Days
• US Class Current: 385/125
• CPC Class Codes: C03B 2203/14 Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
• CPC Class Codes: C03B 2203/23 Double or multiple optical cladding profiles
• CPC Class Codes: C03B 37/02781 Hollow fibres, e.g. holey fibres
• CPC Class Codes: G02B 6/02333 Core having higher refractive index than cladding, e.g. solid core, effective index guiding
• CPC Class Codes: G02B 6/02357 Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals
• CPC Class Codes: G02B 6/0365 arranged - - +

Abstract

Microstructured optical fiber for single-moded transmission of optical signals, the optical fiber including a core region and a cladding region, the cladding region including an annular void-containing region that contains non-periodically disposed voids. The optical fiber provides single mode transmission and low bend loss.

Claims

1. A single mode microstructured optical fiber for transmitting optical signals comprised of light, the optical fiber comprising:

a core region disposed about a longitudinal centerline and having a refractive index profile with a first refractive index, and

a cladding region surrounding the core region, the cladding region comprising an annular void-containing region comprised of non-periodically disposed voids;

wherein said non-periodically disposed voids comprise a percent regional void area percent in said void-containing region which is between 2 and 10 percent, and an average number density of voids in said void-containing region is greater than 0.5 per microns², and said fiber exhibits a 22 meter cutoff wavelength less than 1500 nm.

2. The single mode fiber of claim 1, wherein said annular void-containing region is spaced from said core at least 1 micron and said annular region comprises a width of between 2 and 10 microns.

3. The single mode fiber of claim 1, wherein said fiber exhibits a 22 meter cutoff wavelength less than 1260 nm.

4. The single mode fiber of claim 1, wherein the average number density of voids in said void-containing region is greater than 2 per microns.

5. The single mode fiber of claim 1, wherein the void-containing region comprises a void distribution uniformity throughout the circumference and width of the annular void-containing region and along the length of the fiber sufficient to result in a maximum bend loss less than 2 dB per 10 mm diameter turn for an entire fiber length which is greater than 1 m.

6. The single mode fiber of claim 1, wherein said annular void-containing region comprises greater than 200 voids when said fiber is viewed in cross-section.

7. The single mode fiber of claim 1, wherein said annular void-containing region comprises greater than 300 voids when said fiber is viewed in cross-section.

8. The single mode fiber of claim 1, wherein said annular void-containing region comprises greater than 600 voids when said fiber is viewed in cross-section.

9. The fiber of claim 7, wherein said annular region is less than 10 microns in width.

10. The fiber of claim 8, wherein said annular region exhibits a mean diameter void size less than about 300 nm.

11. The fiber of claim 8, wherein said annular region exhibits a mean diameter void size less than about 200 nm and greater than 5 nm.

12. The single mode fiber of claim 1, wherein the voids in said annular void-containing region comprise krypton gas or sulphur dioxide gas or chlorine gas plus at least one of nitrogen, carbon dioxide, argon, krypton or sulphur dioxide.

13. The single mode fiber of claim 10, wherein the voids in said annular void-containing region comprise plus at least one of nitrogen, carbon dioxide, argon, krypton or sulphur dioxide, and chloride in an amount greater than 2000 ppm by weight.

14. The single mode fiber of claim 10, wherein the voids in said annular void-containing region comprise plus at least one of nitrogen, carbon dioxide, argon, krypton or sulphur dioxide, and chloride in an amount greater than 3000 ppm by weight.

15. The single mode fiber of claim 1, wherein the void-containing region comprises a void distribution uniformity throughout the circumference and width of the annular void-containing region and along the length of the fiber sufficient to result in a maximum bend loss less than 1 dB per turn on a 10 mm diameter mandrel.

16. The single mode fiber of claim 1, wherein the void-containing region comprises a void distribution uniformity throughout the circumference and width of the annular void-containing region and along the length of the fiber sufficient to result in a maximum bend loss less than 0.5 dB per turn on a 10 mm diameter mandrel.

17. A method of making an optical fiber comprising randomly distributed voids therein, the method comprising the step of drawing said fiber from a preform comprising randomly distributed voids therein under conditions effective to result in process parameter Ω

which is less than 5×

10<sup>−

7</sup>, where

$\mathrm{\Omega <br><br>}=\frac{D_{{\mathrm{gas}}_{\left(T_{\mathrm{avg}}\right)}}<br><br>{\mathrm{\phi <br><br>}}_f<br><br>L_{\mathrm{root}}}{V_f<br><br>R_f^2}$

and wherein D_gas in cm²/sec is the void gas diffusivity at T_avg, wherein T_avg is the average of the softening point temperature of the optical fiber preform and the peak draw furnace temperature in °

C., φ

_f is the regional void area fraction, L_root is the draw root length in cm as measured from the beginning of the neck down region and ending when the preform has reached the final fiber draw diameter, V_f is the fiber draw speed in cm/sec and R_f is the final fiber radius in cm.

18. The method of claim 17, further comprising drawing said fiber at a draw tension greater than 200 g.

19. The method of claim 17, further comprising drawing said fiber at a draw tension between 250 and 300 grams.

20. The method of claim 17, wherein 0 is less than 3×

10<sup>−

7</sup>.

21. The method of claim 17, wherein the ratio of number of voids in said preform prior to said drawing step to the number of voids in the resultant optical fiber after the draw step is less than 2000.

22. The method of claim 20, wherein the ratio of number of voids in said preform prior to said drawing step to the number of voids in the resultant optical fiber after the draw step is less than 2000.