Single mode optical fiber with ultra-low attenuation and bend insensibility

Abstract

An optical fiber with ultra-low attenuation and bend insensitivity includes a core layer and cladding layers. The cladding layers have 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 core layer has a radius of 3.0-3.9 m, and a relative refractive index difference of 0.04% to 0.12%. The inner cladding layer has a radius of 8-14 m, and a relative refractive index difference of about 0.35% to 0.10%. The trench cladding layer has a radius of about 14-20 m, and a relative refractive index difference of about 0.6% to 0.2%. The auxiliary outer cladding layer has a radius of about 35-50 m, and a relative refractive index difference of about 0.4% to 0.15%. The outer cladding layer is a pure silicon-dioxide glass layer.

Claims

1. A single-mode optical fiber with ultra low attenuation and bend insensitivity, 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 the core layer has a radius r.sub.1 in a range of about 3.0 to 3.9 m, and a relative refractive index difference n.sub.1 in a range of about 0.04% to 0.12%; wherein the inner cladding layer has a radius r.sub.2 in a range of about 8 to 14 m, and a relative refractive index difference n.sub.2 in a range of about 0.35% to 0.10%; wherein the trench cladding layer has a radius r.sub.3 in a range of about 14 to 20 m, and a relative refractive index difference n.sub.3 in a range of about 0.6% to 0.2%; wherein the auxiliary outer cladding layer has a radius r.sub.4 in a range of about 35 to 50 m, and a relative refractive index difference n.sub.4 in a range of about 0.4% to 0.15%; and wherein the outer cladding layer is a pure silicon dioxide glass layer, and wherein the core layer is a silicon dioxide glass layer co-doped with germanium fluorine and alkali metals, or a silicon dioxide glass layer co-doped with germanium and alkali metals, wherein a relative refractive index contribution Ge of the germanium in the core layer is in a range of about 0.02% to 0.10%, and the doping quantity of the alkali metals is in a range of about 5 to 3000 ppm.

2. The single-mode optical fiber according to claim 1, having a mode field diameter at a wavelength of about 1310 nm being in a range of about 8.4 to 9.1 m.

3. The single-mode optical fiber according to claim 1, having a cabling cutoff wavelength being equal to or smaller than 1260 nm.

4. The single-mode optical fiber according to claim 1, having a zero dispersion point of the optical fiber is in a range of 1300 to 1324 nm, and the zero dispersion slope of the optical fiber is smaller than or equal to 0.092 ps/(nm.sup.2*km).

5. The single-mode optical fiber according to claim 1, having a dispersion at a wavelength of about 1310 nm being equal to or smaller than 18 ps/(nm*km).

6. The single-mode optical fiber according to claim 1, having an attenuation at a wavelength of about 1310 nm being equal to or smaller than 0.314 dB/km.

7. The single-mode optical fiber according to claim 1, having an attenuation at a wavelength of 1550 nm being equal to or smaller than 0.174 dB/km.

8. The single-mode optical fiber according to claim 1, having a microbending loss with a bend radius of R 15 mm for 10 circles at a wavelength of about 1550 nm being equal to or smaller than 0.03 dB, and the microbending loss with a bend radius of R 10 mm for 1 circle being equal to or smaller than 0.1 dB.

9. The single-mode optical fiber according to claim 1, wherein the alkali metals in the core layer comprise one or more of lithium, sodium, potassium, rubidium, cesium and francium alkali metal ions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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.

(2) FIG. 1 is a diagram of a refractive-index profile structure distribution of an optical fiber according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) 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.

(4) 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.

(5) 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.

(6) 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.

(7) 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.

(8) 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.

(9) As used herein, the term ppm refers to one-millionth by weight.

(10) 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, is defined as an outer cladding layer of the fiber.

(11) As used herein, a relative refractive index n.sub.1 of a layer of a fiber is defined according to the following formula:

(12) $n_i=\frac{n_i-n_c}{n_c}100\%$
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.

(13) 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:

(14) $\mathrm{Ge}=\frac{n_{\mathrm{Ge}}-n_c}{n_c}100\%,$
where n.sub.Ge is an absolute 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.

(15) As defined in the IEC (International Electrotechnical Commission) standard 60793-1-44, a cable cutoff wavelength .sub.cc is a wavelength for which an optical signal no longer transmits as a single-mode signal after transmitting about 22 meters in a fiber. During a test, a fiber needs to be bent into a circle with a radius of about 14 cm and two circles with a radius of 4 cm to obtain data.

(16) 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.

(17) According to one embodiment of the invention as shown in FIG. 1 the optical fiber includes a core layer and cladding layers surrounding the core layer. The core layer is a silicon dioxide glass layer co-doped with germanium fluorine and alkali metals, or a silicon dioxide glass layer co-doped with germanium and alkali metals. The alkali metals in the core layer include one or more of lithium, sodium, potassium, rubidium, cesium and francium alkali metal ions. The cladding layers have 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 outer cladding is a pure silicon dioxide glass layer, and the diameter of the outer cladding is 125 m.

(18) Table 1 lists parameters of the optical fiber according to the preferred embodiments of the present invention, where Ge is a refractive index contribution of Ge doping in the core layer, and K is the content of potassium in the core layer. Table 2 lists optical parameter properties corresponding to the optical fiber in the Table 1.

(19) TABLE-US-00001 TABLE 1 Optical parameters of the optical fiber of embodiments of the invention Fiber No. r1[m] n1[%] Ge[%] K[ppm] r2[m] n2[%] r3[m] n3[%] r4[m] n4[%] 1 3.5 0.04 0.07 300 10 0.25 13.5 0.52 42 0.2 2 3.7 0.03 0.02 100 11.2 0.33 15.5 0.4 48 0.38 3 3.6 0.01 0.06 200 12.1 0.25 15.5 0.45 45 0.4 4 3.1 0.02 0.05 500 11.1 0.24 14.5 0.38 38 0.36 5 3.2 0.1 0.1 300 9.2 0.15 14 0.38 41 0.18 6 3.8 0.04 0.05 2000 12.1 0.18 17 0.55 40 0.22 7 3.4 0 0.08 50 10.2 0.28 12.8 0.51 46 0.25 8 3.6 0.05 0.01 1000 12 0.21 18 0.45 47 0.27 9 3.2 0.03 0.03 400 8.5 0.32 13.7 0.58 44 0.38 10 3.4 0.02 0.02 900 12.2 0.21 19 0.5 42 0.3

(20) TABLE-US-00002 TABLE 2 Optical fiber parameters of the optical fiber of embodiments of the invention R15 mm R10mm Att. Att. 10turn 1turn Cable Zero @1310 @1550 Macrobending Macrobending Fiber MFD@1310 Cutoff Disp nm nm loss loss No. [m] [nm] [nm] [dB/km] [dB/km] @1550 nm @1550 nm 1 8.6 1242 1316 0.292 0.161 0.17 0.53 2 8.4 1209 1319 0.288 0.166 0.08 0.23 3 8.6 1231 1315 0.294 0.165 0.2 0.61 4 8.7 1240 1319 0.292 0.159 0.13 0.42 5 8.6 1221 1308 0.313 0.164 0.16 0.41 6 8.8 1252 1312 0.311 0.156 0.14 0.43 7 8.5 1232 1310 0.313 0.167 0.20 0.58 8 8.7 1247 1320 0.296 0.158 0.06 0.29 9 8.9 1240 1311 0.301 0.164 0.21 0.66 10 9 1238 1306 0.313 0.160 0.17 0.57

(21) According to the present invention, a core/cladding section structure of the optical fiber and internal viscosity matching of the optical fiber are properly designed. Alkali metal doping is added into the core layer to optimize the core layer viscosity. The optical fiber not only has a low attenuation coefficient and excellent bending performance, but also can be compatible with the G657.A2 standard. The manufacturing cost of the optical fiber is low.

(22) 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.

(23) 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.