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EP-4741893-A2 - MULTI-CLAD OPTICAL FIBERS

EP4741893A2EP 4741893 A2EP4741893 A2EP 4741893A2EP-4741893-A2

Abstract

The present invention relates to an optical fiber (100, 200, 300, 400) comprising one or more cores (102), a clad enveloping the one or more cores and a buffer clad layer (202, 302, 402) between the first clad layer and the second clad layer. Particularly, the clad includes a first clad layer (104) is made of silica with less than 0.1% metallic impurity and a second clad layer (106) is made of silica with greater than 0.1% of metallic impurity. Further, the first clad layer has less than 800 ppm OH content, less than 10 ppm aluminium and less than 2 ppm sodium and the second clad layer has less than 50 ppm OH content, more than 10 ppm aluminium and more than 2 ppm sodium.

Inventors

  • KAPOOR, SAURABH
  • Balakrishnan, Ranjith
  • PANDEY, ANAND

Assignees

  • Sterlite Technologies Limited

Dates

Publication Date
20260513
Application Date
20230323

Claims (15)

  1. An optical fiber (100, 200, 300, 400) characterized in that : one or more cores (102); and a clad enveloping the one or more cores (102), wherein the clad comprising at least two clad layers (104, 106), wherein a first clad layer (104) of the at least two clad layers (104,106) is made of silica with less than 0.1% metallic impurity. and a second clad layer (106) of the at least two clad layers (104,106) is made of silica with greater than 0.1% metallic impurity.
  2. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the core (102) is either based of pure silica or of germanium doped silica.
  3. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the core (102) has less than 1 ppm OH content.
  4. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the first clad layer (104) and second clad (106) has OH content of less than 5 ppm.
  5. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the first clad layer has a radius in a range of 10-20 microns.
  6. The optical fiber (100, 200, 300, 400) as claimed in claim 1, further comprising a buffer clad layer (202, 302, 402) between the first clad layer (104) and the second clad layer (106).
  7. The optical fiber (100, 200, 300,400) as claimed in claim 1, wherein the first clad layer (104) has less than 800 ppm OH content.
  8. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the first clad layer (104) has less than 10 ppm aluminium and less than 2 ppm sodium.
  9. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the second clad layer (106) has less than 50 ppm OH content.
  10. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the second clad layer (106) has more than 10 ppm aluminium and more than 2 ppm sodium.
  11. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the at least two clad layers comprise the first clad layer (104) and the second clad layer (106).
  12. The optical fiber (100,200,300,400) as claimed in claim 11, wherein the first clad layer (104) surrounds the one or more cores (102) and the second clad layer (106) surrounds the first clad layer (104).
  13. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the first clad layer (104) and the second clad layer (106) are defined by a first purity level of silica and a second purity level of silica.
  14. The optical fiber (100, 200,300,400) as claimed in claim 1, wherein the first purity level is higher than the second purity level.
  15. The optical fiber (100, 200, 300, 400) as claimed in claim 1, wherein the first clad layer (104) is made of type 3 silica and the second clad layer (106) is made of type 1 silica or type 2 silica.

Description

TECHNICAL FIELD Embodiments of the present disclosure relate to the field of optical fiber communications, and more particularly to a multi-clad optical fiber suitable for transmission of high-power light and the like, and an optical fiber module, a fiber laser, and a fiber amplifier having the optical fiber. This application claims the benefit of Indian Application No. 202211017573 titled "MULTI-CLAD OPTICAL FIBERS" filed by the applicant on March 26th, 2022, which is incorporated herein by reference in its entirety. BACKGROUND ART The fields of data communications and telecommunications, optical fibers with small diameters are attracting attention as optical fibers that realize dense optical fiber cables. An optical fiber with a small diameter is in general an optical fiber in which a portion made of glass has a small diameter and the cladding diameter is small. Note that optical fibers with small diameters also include one whose outer circumference with a coating, formed such that the coating covers the outer circumference of a cladding, included is small because the cladding diameter is small. Optical fiber cables have secured an important position in building the optical network of modern communication systems across the globe. An optical fiber cable consists of one or more optical fibers that use light to transfer information from one end of the one or more optical fibers to other. The one or more optical fibers are made by optical fiber preforms which are manufactured by depositing layers of specially formulated silicon dioxide using chemical vapor deposition (CVD) processes, such as outside vapor deposition (OVD) and vapor axial deposition (VAD) processes. Such processes often utilize only a portion of a starting raw material due to limitations in deposition efficiency of the deposition processes. A lower deposition efficiency for the deposition processes leads to wastage of generated silica soot. Thus, resulting in significant increase in raw material cost. Some of the prior art references are given below: Prior art US5076825A teaches about preform having three-layer construction, wherein a support layer made of a silica glass having a drawable temperature of at least 1800°C. In order to eliminate the problem that the cores of some adjacent optical fibers come into direct contact with each other i.e. to avoid sticking of cores of optical fiber. Another prior art US5090979A discloses a manufacturing process for an optical fiber preform whose cladding layer is doped in order to prevent loss of useful light from the optical fiber without reducing range of light wavelength over which the fiber provides effective transmission. Yet another prior art US20030026584A1 discloses an optical fiber having cladding made of nanoparticles in order to bear mechanical stresses and is hydrophobic in nature. While the prior arts cover various solutions for the aforesaid drawbacks related to material wastage and high production cost. However, there still remains a need of material that can be used for producing the optical fiber preforms and incurs low cost without reducing function, performance and quality of the optical fiber preforms. In light of the above-stated discussion, there is a need to provide a technical solution that overcomes the aforementioned problems of the traditional optical fibers. SUMMARY OF THE DISCLOSURE According to the first aspect of the present disclosure, an optical fiber comprising: one or more cores and a clad enveloping the one or more cores. The clad further comprises at least two clad layers where the first clad layer is made of silica with less than 0.1% metallic impurity, and a second clad layer of the at least two clad layers is made of silica with greater than 0.1% metallic impurity. According to the second aspect of the present disclosure, the core is either based of pure silica or of germanium doped silica. Moreover, the first clad layer and second clad have OH content of less than 5 ppm. According to the third aspect of the present disclosure, the optical fiber comprising a buffer clad layer between the first clad layer and the second clad layer. The first clad layer has a radius in a range of 10-20 microns. The first clad layer has less than 800 ppm OH content, less than 10 ppm aluminium and less than 2 ppm sodium. According to the fourth aspect of the present disclosure, the second clad layer has less than 50 ppm OH content, more than 10 ppm aluminium and more than 2 ppm sodium. According to the fifth aspect of the present disclosure, the at least two clad layers comprise the first clad layer and the second clad layer. The first clad layer surrounds one or more cores and the second clad layer surrounds the first clad layer. In particular, the first clad layer and the second clad layer are defined by a first purity level of silica and a second purity level of silica. Moreover, the first purity level is higher than the second purity level. Further, the first clad layer is made of