DOPING OPTIMIZED SINGLE-MODE OPTICAL FIBER WITH ULTRA LOW ATTENUATION

Abstract

A doping optimized single-mode optical fiber with ultra low attenuation includes a core layer and cladding layers. The cladding layers has an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary outer cladding layer. The content of fluorine in the core layer is 0.5 wt %, Ge0.12%, n.sub.10.12%. The content of fluorine in the inner cladding layer is 0.5-1.5 wt %, n.sub.20.14%. The content of fluorine in the trench cladding layer is 1-3 wt %, n.sub.30.25%. The content of fluorine in the auxiliary outer cladding layer is 0.5-2 wt %, n.sub.40.14%. The outer cladding layer is a pure silicon dioxide glass layer and/or a metal-doped silicon dioxide glass layer.

Claims

1. A doping optimized single-mode optical fiber with ultra low attenuation, comprising: a core layer and cladding layers, wherein the cladding layers comprises an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary outer cladding layer; wherein a content of fluorine in the core layer is less than or equal to about 0.5 wt %, a relative refractive index contribution Ge of germanium in the core layer is less than or equal to about 0.12%, and a relative refractive index n.sub.1 of the core layer is less than or equal to about 0.12%; wherein a content of fluorine in the inner cladding layer is in a range of about 0.5 wt % to 1.5 wt %, and a relative refractive index n.sub.2 of the inner cladding layer is less than or equal to about 0.14%; wherein a content of fluorine in the trench cladding layer is in a range of about 1 wt % to 3 wt %, and a relative refractive index n.sub.3 of the trench cladding layer is less than or equal to about 0.25%; wherein a content of fluorine in the auxiliary outer cladding layer is in a range of about 0.5 wt % to 2 wt %, and a relative refractive index n.sub.4 of the auxiliary outer cladding layer is less than or equal to about 0.14%; and wherein the outer cladding layer is a pure silicon dioxide glass layer and/or a metal-doped silicon dioxide glass layer.

2. The doping optimized single-mode optical fiber according to claim 1, wherein metal dopants doped in the outer cladding layer comprise aluminum and alkali metals, and a total content of the metal dopants is less than or equal to about 25 ppm, wherein a content of aluminum is in a range of about 1 ppm to 18 ppm, and a total content of the alkali metals is less than or equal to about 2 ppm.

3. The doping optimized single-mode optical fiber with according to claim 2, wherein the alkali metals are one or more of lithium, sodium and potassium.

4. The doping optimized single-mode optical fiber according to claim 2, wherein the metal dopants further comprise one or more of iron, calcium, magnesium and titanium.

5. The doping optimized single-mode optical fiber according to claim 2, wherein a radius r.sub.1 of the core layer is in a range of about 4.0 m to 6.0 m.

6. The doping optimized single-mode optical fiber according to claim 5, wherein a radius r.sub.2 of the inner cladding layer is in a range of about 10 m to 14 m, a radius r.sub.3 of the trench cladding layer is in a range of about 12.5 m to 17 m, and a radius r.sub.4 of the auxiliary outer cladding layer is in a range of about 40 m to 50 m.

7. The doping optimized single-mode optical fiber according to claim 2, wherein a diameter of the outer cladding layer is about 125 m.

8. The doping optimized single-mode optical fiber according to claim 2, wherein the relative refractive index n.sub.1 of the core layer is in a range of about 0.12% to 0.08%, the relative refractive index n.sub.2 of the inner cladding layer is in a range of about 0.14% to 0.35%, the relative refractive index n.sub.3 of the trench cladding layer is in a range of about 0.25% to 0.75%, and the relative refractive index n.sub.4 of the auxiliary outer cladding layer is in a range of about 0.14% to 0.56%.

9. The doping optimized single-mode optical fiber according to claim 2, wherein an attenuation coefficient of the optical fiber at a wavelength of about 1550 nm is less than or equal to about 0.175 dB/km.

10. The doping optimized single-mode optical fiber according to claim 1, wherein a radius r.sub.1 of the core layer is in a range of about 4.0 m to 6.0 m.

11. The doping optimized single-mode optical fiber according to claim 10, wherein a radius r.sub.2 of the inner cladding layer is in a range of about 10 m to 14 m, a radius r.sub.3 of the trench cladding layer is in a range of about 12.5 m to 17 m, and a radius r.sub.4 of the auxiliary outer cladding layer is in a range of about 40 m to 50 m.

12. The doping optimized single-mode optical fiber according to claim 1, wherein a diameter of the outer cladding layer is about 125 m.

13. The doping optimized single-mode optical fiber according to claim 1, wherein the relative refractive index n.sub.1 of the core layer is in a range of about 0.12% to 0.08%, the relative refractive index n.sub.2 of the inner cladding layer is in a range of about 0.14% to 0.35%, the relative refractive index n.sub.3 of the trench cladding layer is in a range of about 0.25% to 0.75%, and the relative refractive index n.sub.4 of the auxiliary outer cladding layer is in a range of about 0.14% to 0.56%.

14. The doping optimized single-mode optical fiber according to claim 1, wherein an attenuation coefficient of the optical fiber at a wavelength of about 1550 nm is less than or equal to about 0.175 dB/km.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings illustrate one or more embodiments of the invention and together with the written description, serve to explain the principles of the invention. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like elements of an embodiment.

[0044] FIG. 1 is a diagram of a refractive-index profile structure distribution of an optical fiber according to an embodiment of the present invention.

[0045] FIG. 2 is a diagram of a fluorine doping concentration distribution in different layers of the optical fiber according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0046] The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

[0047] The terms used in this specification generally have their ordinary meanings in the art, within the context of the invention, and in the specific context where each term is used. Certain terms that are configured to describe the invention are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner regarding the description of the invention. For convenience, certain terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no influence on the scope and meaning of a term; the scope and meaning of a term is the same, in the same context, whether or not it is highlighted. It will be appreciated that same thing can be said in more than one way. Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for certain terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and in no way limits the scope and meaning of the invention or of any exemplified term. Likewise, the invention is not limited to various embodiments given in this specification.

[0048] It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only configured to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the disclosure.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and/or comprising, or includes and/or including or has and/or having when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

[0050] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the invention, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0051] As used herein, around, about or approximately shall generally mean within 20 percent, preferably within 10 percent, and more preferably within 5 percent of a given value or range. Numerical quantities given herein are approximate, meaning that the term around, about or approximately can be inferred if not expressly stated.

[0052] As used herein, the term ppm refers to one-millionth by weight.

[0053] From a central axis of an optical fiber, according to changing of a refractive index, a layer closest to the axis is defined as a core layer, i.e., the core layer refers to a central area of a cross section of the fiber, and an outmost layer of the fiber, i.e., a pure-silicon-dioxide layer and/or a metal-doped silicon dioxide glass layer, is defined as an outer cladding layer of the fiber.

[0054] As used herein, a relative refractive index n.sub.i of a layer of a fiber is defined according to the following formula:

[00002]$.Math..Math.n_i=\frac{n_i-n_c}{n_c}100.Math.\%$

where n.sub.i is a refractive index of the corresponding layer, and n.sub.c is a refractive index of the outer cladding layer, that is, a refractive index of the pure silicon dioxide without dopants of Ge or F.

[0055] A contribution of doped Ge in the core layer of the optical fiber to the refractive index Ge is defined according to the following equation:

[00003]$.Math..Math.\mathrm{Ge}=\frac{n_{\mathrm{Ge}}-n_c}{n_c}100.Math.\%,$

where n.sub.Ge is a change of the refractive index of the silicon dioxide glass caused by the doped substance Ge doped in the core layer, provided that the doped substance Ge doped in the core layer is doped in the pure silicon dioxide that includes no other doped substance.

[0056] The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings. In accordance with the purposes of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to a doping optimized single-mode optical fiber with ultra low attenuation.

[0057] According to one embodiment of the invention as shown in FIGS. 1 and 2, the optical fiber includes a core layer and cladding layers surrounding the core layer.

[0058] The cladding layers comprises an inner cladding layer surrounding the core layer, a trench cladding layer surrounding the inner cladding layer, an auxiliary outer cladding layer surrounding the trench cladding layer, and an outer cladding layer surrounding the auxiliary outer cladding layer.

[0059] In certain embodiments, a content of fluorine in the core layer is less than or equal to about 0.5 wt %, a relative refractive index contribution Ge of germanium in the core layer is less than or equal to about 0.12%, and a relative refractive index An, of the core layer is less than or equal to about 0.12%;

[0060] In certain embodiments, a content of fluorine in the inner cladding layer is in a range of about 0.5 wt % to 1.5 wt %, and a relative refractive index n.sub.2 of the inner cladding layer is less than or equal to about 0.14%. A content of fluorine in the trench cladding layer is in a range of about 1 wt % to 3 wt %, and a relative refractive index n.sub.3 of the trench cladding layer is less than or equal to about 0.25%. A content of fluorine in the auxiliary outer cladding layer is in a range of about 0.5 wt % to 2 wt %, and a relative refractive index n.sub.4 of the auxiliary outer cladding layer is less than or equal to about 0.14%.

[0061] In certain embodiments, metal dopants doped in the outer cladding layer comprise aluminum and alkali metals, and a total content of the metal dopants is less than or equal to about 25 ppm, wherein a content of aluminum is in a range of about 1 ppm to 18 ppm, and a total content of the alkali metals is less than or equal to about 2 ppm.

[0062] In certain embodiments, the alkali metals are one or more of lithium (Li), sodium (Na) and potassium (K).

[0063] In certain embodiments, the metal dopants further comprise one or more of iron (Fe), calcium (Ca), magnesium (Mg) and titanium (Ti).

[0064] In certain embodiments, a radius r.sub.1 of the core layer is in a range of about 4.0 m to 6.0 m.

[0065] In certain embodiments, a radius r.sub.2 of the inner cladding layer is in a range of about 10 m to 14 m, a radius r.sub.3 of the trench cladding layer is in a range of about 12.5 m to 17 m, and a radius r.sub.4 of the auxiliary outer cladding layer is in a range of about 40 m to 50 m.

[0066] In certain embodiments, the relative refractive index n.sub.1 of the core layer is in a range of about 0.12% to 0.08%, the relative refractive index n.sub.2 of the inner cladding layer is in a range of about 0.14% to 0.35%, the relative refractive index n.sub.3 of the trench cladding layer is in a range of about 0.25% to 0.75%, and the relative refractive index n.sub.4 of the auxiliary outer cladding layer is in a range of about 0.14% to 0.56%.

[0067] In certain embodiments, an attenuation coefficient of the optical fiber at a wavelength of about 1550 nm is less than or equal to about 0.175 dB/km.

[0068] In certain embodiments, the outer cladding layer is a pure silicon dioxide glass layer and/or a metal-doped silicon dioxide glass layer. A diameter of the outer cladding layer is about 125 m.

[0069] In certain embodiments, the optical fiber is manufactured by drawing a preformed rod. The preformed rod mainly includes two parts: an optical fiber core layer rod prepared by using a plasma chemical vapor deposition (PCVD) process/method, and a large hollow tube of a natural quartz sand material. The optical fiber core layer rod and the large tube are assembled by inserting the core layer rod into the tube.

[0070] The core layer rod of the optical fiber preformed rod includes a fiber core layer, an inner cladding layer, a trench cladding layer, and an auxiliary inner cladding layer. The optical fiber core layer manufactured by means of the PCVD process includes quartz glass doped with fluorine and germanium. The inner cladding layer tightly surrounds the core layer, and is manufactured by using the PCVD process that is the same as the core layer. The trench cladding layer includes silicon dioxide quartz glass doped with fluorine deposited by using the PCVD process. The third cladding is the auxiliary outer cladding layer, and includes silicon dioxide quartz glass doped with fluorine deposited by using the PCVD process, and a liner tube obtained by means of the PCVD process.

[0071] The large tube made of natural quartz sand is manufactured by using natural quartz sand of four different grades as raw materials. Numbers and specific dopant content are shown in Table 1. Table 2 shows designs of an optical fiber sleeved with different materials thereon and corresponding attenuation coefficients thereof.

TABLE-US-00001 TABLE 1 The content of raw material dopants of the large hollow tube Nos. of outer cladding layer Total materials Al Fe Ca Mg Ti Mn Cu Li Na K B Ge (ppm) A 7.3 0.1 0.7 0 1.3 0 0 0.2 0.1 0.1 <0.1 0.9 10.5 B 10.8 0.2 0.6 0 1.3 0 0 0.4 0.1 0.1 <0.1 1.3 14.8 C 14.8 0 0.4 0 1.1 0 0 0.5 0.2 0.2 <0.1 1.1 18.3 D 17.8 0.2 0.7 0 1.1 0 0 0.7 0.4 0.3 <0.1 1.3 22.3 Note: 0.5 0.1 0.1 0.05 0.05 0.05 0.05 0.05 0.1 0.1 0.1 0.1 Measurement threshold

TABLE-US-00002 TABLE 2 Parameters of optical fibers and corresponding attenuation coefficients according to embodiments of the present invention Content of F doped in Content of Content of the F doped in F doped in auxilialy Type of the inner the trench inner the outer Ge in the cladding cladding cladding cladding core layer layer layer layer layer Att.@1550 nm Nos. r1 [m] [%] r2 [m] [wt %] r3 [m] [wt %] r4 [m] [wt %] materials [dB/km] 1 5.5 0.02 11 0.9 13.5 1.9 42 1.2 A 0.162 2 5.4 0.05 11.5 1 15.5 1.5 48 1.3 B 0.168 3 6 0.05 12.5 1.1 15.5 1.7 45 1.5 D 0.174 4 4.7 0.06 12 1.2 14.5 2.2 38 1 A 0.166 5 5.2 0.14 10.5 0.74 14 1.35 41 0.9 C 0.173 6 6 0.09 13 0.85 16 2.1 40 1.5 B 0.172 7 5.3 0.07 10 1.3 12.8 1.8 46 1.6 B 0.165 8 4.5 0.04 11 1.5 16.5 2.7 47 2.0 A 0.164 9 4 0.12 10 1.4 13.7 2.3 44 1.8 B 0.169 10 4.2 0.05 11.5 0.8 16.5 2.1 42 1.1 C 0.170

[0072] According to the present invention, the viscosity of the core layer is decreased, so that the core layer can better match the inner cladding layer and the trench cladding layer. In addition, the core layer is combined with the metal-doped outer cladding layer having a matching viscosity. In this way, the virtual temperature of the optical fiber is overall decreased. Moreover, by means of the trench cladding layer design, fundamental mode leakage is restrained, thereby achieving ultra low attenuation performance.

[0073] The foregoing description of the exemplary embodiments of the invention has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

[0074] The embodiments were chosen and described in order to explain the principles of the invention and their practical application so as to enable others skilled in the art to utilize the invention and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present invention pertains without departing from its spirit and scope. Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.