WO2011147272A1

WO2011147272A1 - Anti-bending muti-mode optical fiber

Info

Publication number: WO2011147272A1
Application number: PCT/CN2011/074242
Authority: WO
Inventors: 曹蓓蓓; 张方海
Original assignee: 长飞光纤光缆有限公司
Priority date: 2010-05-28
Filing date: 2011-05-18
Publication date: 2011-12-01
Also published as: CN101840023A; CN101840023B

Abstract

An anti-bending multi-mode optical fiber for an access network and a miniaturized optical device comprises an optical fiber and a coating layer covering the optical fiber. The optical fiber is composed of a quartz glass core layer with a parabola-shape index or a step-index profile structure and a quartz glass cladding layer surrounding the core layer. The core layer is made of quartz glass material doped with germanium and fluorine. The cladding layer is covered with two cured polymer coating layers, wherein the inner coating layer is low-refraction index flexible polymer coating layer, and the outer coating layer is high Young's modulus polymer coating layer. The inner coating layer of the multi-mode optical fiber with low-refraction index avoids the internal stress in the optical fiber, so as to improve the mechanical performance of the optical fiber and guarantee better usage performance and longer service life of the optical fiber working in a small-radius bending state.

Description

Anti-bending multimode optical fiber technical field

The present invention relates to a bending-resistant multimode optical fiber for use in an access network or miniaturized optical device, and more particularly to an optical fiber having a lower bending additional attenuation, which belongs to the field of optical communication technology.

Background technique

In recent years, the development of communication technology and the rise of integrated miniaturized optical devices have made multimode optical fibers in applications often placed in smaller and smaller bending channels and wound in small storage boxes with smaller and smaller spaces, such as telecommunications. Wire boxes, data center cabinets, etc. In this case, the fiber often encounters small angle bends. When the conventional fiber is bent at a small angle, the high-order mode transmitted near the boundary of the multimode fiber core is easily leaked from the core when the fiber is bent, resulting in signal loss, resulting in a costly transmission interruption.

Bending-resistant multimode fiber has been greatly improved in bending performance, minimizing signal loss and enabling faster and more efficient fiber path, cabling and installation. Cabling in a narrow environment requires that the bend-resistant multimode fiber can withstand small angle bends with a radius equal to or less than 10 mm and its signal loss is much less than that of conventional multimode fibers. The new bend-resistant multimode fiber is easier to operate and install than copper, allowing fiber to be deployed in more locations.

In the prior art, an effective way to reduce the additional attenuation of fiber bending is to use a depressed cladding design in which a layer having a lower refractive index is added to the cladding to achieve the effect of confining optical power. The refractive index profiles are mainly "groove type" (shown in Figures 1 and 3) and "double-clad type" (shown in Figure 2). U.S. Patents US20080166094A1, US20090169163A1 and US20090154888A1 are such designs. The design principle is: When the fiber is subjected to small bending, the light leaking from the core is easily confined to the inner cladding and returned to the core, thereby reducing the additional attenuation of the fiber macrobend. However, the addition of a layer having a low refractive index to the cladding has the disadvantage that the range of the layered refractive index is limited, that is, it is difficult to achieve a layered refractive index of less than -1.5%, and the process complexity is high and the product uniformity is poor. How to ensure the optical performance consistency of such fibers and the long-term operation in the small radius bending state remains to be further studied. Existing multimode fibers are difficult to meet the demanding optical performance and reliability requirements at small bend radii.

Summary of the invention

To facilitate the introduction of the present invention, define some terms:

Mandrel: a quartz glass piece containing a core or core layer and a partial cladding;

Preform: A quartz glass component that has a reasonable geometric and optical parameter that can be melt drawn into an optical fiber; Refractive index: When light is refracted from a vacuum injection medium, the ratio of the sine of the incident angle to the sine of the refraction angle is called the "absolute refractive index" of the medium. Relative refractive index difference: X 100% *" ~~ °- X 100 %, and 3⁄4 are each

Corresponding part and the refractive index of pure quartz glass, unless otherwise specified, the maximum refractive index of each corresponding part;

Refractive index profile: The relationship between the refractive index of the glass and its radius, as indicated by a graph of the fiber or fiber preform (including the mandrel);

Low refractive index: The refractive index of the material is smaller than that of pure quartz glass, which is called low refractive index. Pure quartz glass has a refractive index of 1.458 at 589 nm and a refractive index of 1.457 at 630 nm. The refractive index is lower than that of pure quartz glass at the same wavelength. The coating is called a low refractive index coating;

Radius: the distance between the outer boundary of the layer and the center point;

Power exponential refractive index profile: a refractive index profile that satisfies the power exponential function below, where is the refractive index of the fiber axis; r is the distance from the fiber axis; a is the fiber core radius; a is the distribution index; Δ is the core /package relative refractive index difference;

n ² (r) = n^[l - 2A(-) ^a ] r<a

a

The technical problem to be solved by the present invention is to provide a bending-resistant multimode optical fiber having a lower bending additional attenuation in view of the deficiencies of the prior art described above.

The technical solution of the multimode optical fiber proposed by the invention comprises: an optical fiber and a coating coated on the outer surface of the optical fiber, the optical fiber being composed of a quartz glass core layer having a parabolic or step-shaped refractive index profile structure and surrounding the core layer Quartz glass cladding composition, the difference is: the core layer diameter 2R1 is 20~200μηι, composed of ytterbium-doped (Ge) and fluorine (F) quartz glass materials, the cladding is covered with double The layer-cured polymer coating, the inner coating coated on the outer surface of the cladding is a low refractive index flexible polymer coating, and the outer coating is a high Young's modulus polymer coating.

According to the above scheme, the cladding layer is a pure quartz glass cladding layer surrounding the core layer, or a sum of pure quartz and a doped quartz glass cladding layer, and the outermost quartz glass cladding layer has a diameter of 80 μm to 230 μm.

According to the above scheme, the inner coating layer has a Young's modulus of less than or equal to 10 MPa in the range of -65 ° C to 85 ° C, a typical Young's modulus range is 0.5 MPa to 2 MPa, and a refractive index (589 nm wavelength sodium yellow) The range of light is 1.37 to 1.455; the outer coating is in the range of -65 ° C to 55 ° C. The Young's modulus ranges from 500 MPa to 1500 MPa, the typical range is from 700 MPa to 1000 MPa, and the refractive index ranges from 1.47 to 1.78. The layer refractive index has no significant effect on the fiber properties. According to the above scheme, the inner coating layer is a UV-curable or heat-curable flexible silicone rubber coating, and the inner coating layer has a thickness of 10 μm to 40 μm _; the outer coating layer is ultraviolet light curing or heat curing. Polyacrylate coating, the outer coating has a diameter of 160μηι~260μηι.

According to the above scheme, the multimode fiber has a typical additional bending attenuation of less than or equal to 0.15 dB, or even less than or equal to 0.05 dB, at a wavelength of 850 nm with a radius of 10 mm around one turn.

According to the above scheme, the refractive index profile of the core layer is parabolic, (1.9 to 2.2, the relative refractive index difference Δ1 is 0.9% to 1.2%, the inner coating refractive index range is 1.40 to 1.43, and the core diameter is 47μηι~53μηι. The dynamic fatigue parameter Nd is equal to or greater than 26; at a wavelength of 850nm and a wavelength of 1300nm with a bandwidth of 500MHz-km or more, by adjusting the power exponential refractive index profile, the optimized 850nm wavelength window can reach 2000MHz-km or even 5000MHz. Bandwidth above -km.

According to the above scheme, the refractive index profile of the core layer is parabolic, (1.9 to 2.2, the relative refractive index difference Δ1 is 1.8% to 2.3%, and the core layer diameter is 60 μηι to 65 μηι.

According to the above scheme, the refractive index profile of the core layer is stepped, and the relative refractive index difference Δ1 is 0.3% to 2.2%.

The double-coated composite structure used in the present invention combines the advantages of the two coatings, can improve the mechanical properties of the optical fiber and minimize the microbending loss: the flexible inner coating can alleviate the pressure on the outer surface of the glass cladding and reduce the microbending loss. The optical power loss, high Young's modulus of the outer coating can withstand large mechanical forces, the fiber is protected from mechanical damage during processing, transportation and use.

The method for manufacturing the multimode optical fiber of the present invention comprises: fixing a pure quartz glass liner on a plasma enhanced chemical vapor deposition (PCVD) lathe for doping deposition, and introducing a gas containing F into the reaction gases SiCl ₄ and ₀₂ ; Introducing F doping, introducing GeCl ₄ to introduce Ge doping, ionizing the reaction gas in the liner into a plasma by microwave, and finally depositing it on the inner wall of the liner in the form of glass; according to the doping of the fiber waveguide structure Miscellaneous requirements, the waveguide structure curve is subdivided into thousands to 10,000 layers of thin layer step-by-step deposition, and the core layer with precise refractive index distribution is realized by programmatically controlling the flow rate and ratio of the doping gas in each mixed gas; Upon completion, the deposition tube is melted into a solid mandrel using an electric heating furnace.

The solid mandrel is placed in a pure quartz glass hollow tube with suitable size parameters to form a preform for preparing the optical fiber, or a pure quartz glass layer is deposited on the surface of the mandrel by an OVD process as a cladding and then fired into a preform. The preform is placed in a drawing tower to form a fiber, and the inner and outer layers of the polymer coating are coated on the surface of the fiber to form an optical fiber.

The additional bending attenuation of the fiber consists of both macrobend additional attenuation and microbend additional attenuation. Increasing the fiber's resistance to bending can be achieved by optimizing the structure to reduce both attenuations. The inner coating material uses a low refractive index polymer The low refractive index of the elastomer, which limits the light leaking from the core, is confined to the quartz glass cladding and returned to the core, thereby reducing the additional attenuation of the fiber macrobend. On the other hand, it has a Young's modulus of less than 10 MPa in the range of -65 ° C to 85 ° C, and a typical Young's modulus range of 0.5 MPa to 2 MPa. This property minimizes the glass cladding and the inner layer. The stress at the coating and the optical power loss caused by the irregular deformation reduce the additional attenuation of the microbend, thereby improving the bending resistance of the fiber.

The beneficial effects of the present invention are as follows: 1. The design of the low refractive index inner coating avoids the introduction of additional stress in the quartz glass cladding and the core layer, and the low refractive index characteristic can limit the light leaked from the core to the quartz. The glass cladding is returned to the core, thereby reducing the additional attenuation of the fiber macrobend, avoiding the attenuation and bandwidth loss caused by the additional stress; 2. The design of the low refractive index inner coating avoids the internal stress of the fiber and greatly improves the fiber. The mechanical properties ensure the performance and service life of the fiber working under small radius bending conditions, and have excellent bending resistance. 3. The design of the low refractive index inner coating is equivalent to the introduction of the "sag layer" outside the quartz glass cladding. ", this can change the parameters of the "sag layer" by flexibly adjusting the properties of the coating, such as the diameter and depth of the trap layer, etc., and the parameters can be adjusted in the drawing process without adding unstable factors in the complicated preform design. Thereby, the reliability of the wire drawing manufacturing process is improved; 4. The manufacturing method of the invention is simple and effective, and is suitable for mass production.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the structure of a refractive index profile in a first embodiment of the present invention

Fig. 2 is a schematic view showing the structure of a refractive index profile in a second embodiment of the present invention.

Fig. 3 is a schematic view showing the structure of a refractive index profile in the third embodiment of the present invention.

Fig. 4 is a view showing the structure of a refractive index profile of a fourth embodiment of the present invention.

Fig. 5 is a view showing the structure of a refractive index profile in a fifth embodiment of the present invention.

Fig. 6 is a view showing the structure of a refractive index profile of a sixth embodiment of the present invention.

Fig. 7 is a view showing the structure of a refractive index profile of a step type energy transmission fiber according to Embodiments 7 and 8 of the present invention.

Generally, the refractive index parameter of the coating is expressed by the absolute refractive index. In the drawing, the relative refractive index difference δ of the coating is indicated in order to compare the refractive index of the coating with the core layer and the cladding. The drawing uses Δ to indicate the relative refractive index difference of the quartz glass fiber core layer or cladding layer.

detailed description

Embodiments of the present invention are further described below in conjunction with the accompanying drawings.

1 is a schematic view showing the refractive index profile of a double-coated bending insensitive multimode fiber according to Embodiment 1 of the present invention. The solid line in the figure indicates the refractive index structure of the quartz glass core and the cladding, and the broken line indicates the refractive index structure of the inner and outer coatings in the optical fiber. Δ1 represents the relative refractive index difference of the doped quartz glass core center, quartz in the structure The relative refractive index difference of the glass cladding is 0; δ ΐ and δ 2 represent the relative refractive indices of the inner and outer coatings, respectively. R1 and R2 represent the radii of the core layer and the cladding, respectively, and rl and r2 represent the radii of the inner and outer coatings, respectively.

Fig. 2 is a schematic view showing the structure of a refractive index profile of the second embodiment. In this structure, the quartz glass cladding is divided into three layers, wherein the first and third layers are pure quartz layers, and the second layer is a depressed cladding layer. Δ1 and Δ3 represent the relative refractive index difference between the core and the depressed cladding, respectively; δ ΐ and δ 2 represent the relative refractive indices of the inner and outer coatings, respectively. Rl, R2, R3, and R4 represent the core, the first cladding layered pure quartz layer, the second cladding layer, that is, the depressed cladding layer, and the radius of the third cladding layer, and the second layer radius R3 is 28 μm. 〜58μηι; The relative refractive index difference Δ3 is -0.50% to -0.90%. Rl and r2 represent the radius of the inner and outer coatings, respectively.

Fig. 3 is a schematic view showing the structure of a refractive index profile of the third embodiment. In this structure, the quartz glass cladding is divided into two layers, wherein the first layer is a pure quartz layer, and the second layer is a low refractive index depressed cladding. Δ1 and Δ3 represent the relative refractive indices of the core and the depressed cladding, respectively; δ ΐ and δ 2 represent the relative refractive indices of the inner and outer coatings, respectively. Rl, R2, and R3 respectively represent the core, the first cladding layered pure silica layer, and the second cladding layer, that is, the radius of the depressed cladding layer, and the second layering radius R3 is 28 μηι to 63 μηι; the relative refractive index difference Δ3 is -0.40% to -1.00%. Rl and r2 represent the radius of the inner and outer coatings, respectively.

Fig. 4 is a view showing the structure of a refractive index profile of the fourth embodiment. In this structure, the quartz glass cladding is divided into two layers, wherein the first layer is a low refractive index depressed cladding layer, and the second layer is a pure quartz layer. Δ1 and Δ2 represent the relative refractive indices of the core and the depressed cladding, respectively; δ ΐ and δ 2 represent the relative refractive indices of the inner and outer coatings, respectively. Rl, R2, and R3 respectively represent the core, the first cladding layer, that is, the depressed cladding layer, and the radius of the second cladding layer. The first layering radius R2 is 21μηι~58μηι; the relative refractive index difference Δ2 is -0.40%. To -0.80%. Rl and r2 represent the radius of the inner and outer coatings, respectively.

Fig. 5 is a view showing the structure of a refractive index profile of the fifth embodiment. In this structure, the quartz glass cladding is divided into four layers, wherein the first layer is a pure quartz layer, the second layer is a low refractive index depressed cladding layer, and the third layer is a doped high refractive index quartz layer, the fourth layer. The layer is a layer of pure quartz. Δ1, Δ3, and Δ4 represent the relative refractive indices of the core, the depressed cladding, and the high refractive index doped quartz layer, respectively, the second layering radius R3 is 28 μηι to 55 μηι, and the relative refractive index difference Δ3 is -0.40% to -1.10%. The third layering radius R4 is 31 μm to 58 μm, and the relative refractive index difference Δ4 is 0.1% to 0.8%. δ ΐ and δ 2 represent the relative refractive indices of the inner and outer coatings, respectively. R1, R2, R3, R4, and R5 respectively represent a core, a first cladding layer, a second cladding layer, that is, a depressed cladding layer, a third cladding layer, that is, a high refractive index doped quartz layer, and a fourth package. Layer stratification is the radius of the pure quartz layer. Rl and r2 represent the radius of the inner and outer coatings, respectively.

Fig. 6 is a schematic view showing the refractive index profile of a double-coated bending insensitive multimode fiber according to Embodiment 6 of the present invention. The solid line in the figure indicates the refractive index structure of the quartz glass core and the cladding, and the dotted line indicates the inner and outer coatings. The refractive index structure in the fiber. Δ1 represents the relative refractive index difference of the center of the doped quartz glass core, and the relative refractive index difference of the quartz glass cladding in the structure is 0; δ ΐ and δ 2 represent the relative refractive indices of the inner and outer coatings, respectively. R1 and R2 represent the radii of the core layer and the cladding, respectively, and rl and r2 represent the radii of the inner and outer coatings, respectively.

Fig. 7 is a view showing the structure of a refractive index profile of a step type energy transmission fiber according to Embodiments 7 and 8 of the present invention. The solid line in the figure indicates the refractive index structure of the quartz glass core and the cladding, and the broken line indicates the refractive index structure of the inner and outer coatings in the fiber. The relative refractive index difference Δ1 of the doped quartz glass core is 0.3% to 1.2%. In this structure, the cladding is a doped quartz glass cladding with a low refractive index, and the relative refractive index difference Δ2 of the cladding is -0.1% to -1.1. %. δ ΐ and δ 2 represent the relative refractive indices of the inner and outer coatings, respectively. Rl and R2 represent the radii of the core and cladding, respectively, and rl and r2 represent the radii of the inner and outer coatings, respectively.

The following table shows the specific parameters of the above embodiment:

Table 1

Example No. 1 2 3 4 5 6 7 8 Core diameter (μηι) 50 50 50 50 50 62.5 105 200 Core layer α 1.90 2.03 2.02 2.03 2.19 1.92 - - Core refractive index Δ1 ( % ) 1.04 1.10 0.90 0.96 1.02 1.97 0.58 0.46 cladding layer number 1 3 2 2 4 1 1 cladding diameter (μηι) 80.5 125.4 127.0 125.0 123.0 125.9 124.8 230.5 depressed cladding relative refractive index (%) 0 -0.59 -0.52 -0.44 -0.45 0 -0.57 - 0.69 inner coating diameter (μηι) 123 185 190 195 192 210 185 325 outer coating diameter (μη) 165 240 250 249 251 250 250 500 inner coating refractive index 1.45 1.42 1.44 1.45 1.45 1.40 1.37 1.41 full injection bandwidth

4328 6218 2850 2296 5336 350 - - @850nm (MHz-km)

Full injection bandwidth

640 637 521 489 631 553 - - @1300nm(MHz-km)

1 turn 10mm bend radius macro bend

0.02 0.03 0.01 0.02 0.01 0.02 0.02 0.01 Additional attenuation @85(^^1(()

1 turn 5mm bend radius macro bend

0.10 0.07 0.03 0.07 0.09 0.04 0.05 0.03 Additional attenuation @85(^^1(()

Claims

Claim

A bend-resistant multimode optical fiber comprising an optical fiber and a coating coated on an outer surface of the optical fiber, the optical fiber being composed of a quartz glass core layer having a parabolic or stepped refractive index profile structure and quartz surrounding the core layer The glass cladding composition is characterized in that: the core layer has a diameter of 2R1 of 20 to 200 μm, and is composed of an erbium-doped and fluoroquartz glass material, and the cladding layer is coated with a double-layer cured polymer coating and coated. The inner coating on the outer surface of the cladding is a low refractive index flexible polymer coating and the outer coating is a high Young's modulus polymer coating.

2. The anti-bending multimode optical fiber according to claim 1, wherein: said cladding is a pure quartz glass cladding surrounding the core layer, or a sum of pure quartz and a doped quartz glass cladding. The outermost quartz glass cladding has a diameter of 80 μm to 230 μm.

The anti-bending multimode optical fiber according to claim 1 or 2, wherein: the inner coating layer has a Young's modulus of less than or equal to 10 MPa in a range of -65 ° C to 85 ° C, and a refractive index range It is 1.37 to 1.455; the outer coating has a Young's modulus in the range of -65 ° C to 55 ° C of 500 MPa to 1500 MPa, and a refractive index ranging from 1.47 to 1.78.

The anti-bending multimode optical fiber according to claim 1 or 2, wherein: the inner coating layer is a UV-curable or heat-curable flexible silicone rubber coating, and the thickness of the inner layer of the inner coating layer is ΙΟμπ ! ~ 40μπι _; The outer coating is UV-cured or heat-cured polyacrylate coating, the outer coating diameter is 160μπ! ~ 260μπι.

The anti-bending multimode optical fiber according to claim 3, wherein: said core layer has a refractive index profile of a parabolic shape, α is 1.9 to 2.2, and relative refractive index difference A 1 is 0.9% to 1.2%. , the inner coating refractive index range is 1.40 to 1.43, and the core layer diameter is 47μπ! ~ 53μπι _; dynamic fatigue parameter Nd is equal to or greater than 26; has a bandwidth of 500 MHz_km or more at a wavelength of 850 nm and a wavelength of 1300 nm.

The anti-bending multimode optical fiber according to claim 3, wherein: said core layer has a refractive index profile of a parabolic shape, α is 1.9 to 2.2, and relative refractive index difference A 1 is 1.8% to 2.3%. The core layer has a diameter of 60 μm to 65 μm.

The anti-bending multimode optical fiber according to claim 5, wherein the cladding layer is divided into three layers, wherein the first layer and the third layer are pure quartz glass layers, and the second layer is a depressed cladding layer. 2 层的半径R2 is 28 μ m 58 μ m Relative refractive index difference Δ 3 is -0. 50% to -0.90%

8. The anti-bending multimode optical fiber according to claim 5, wherein: the cladding layer is divided into two layers, wherein the first layer is a pure quartz glass layer, and the second layer is a low refractive index depressed cladding layer, 2 The layering radius R3 is 28 μ πι 63 μ m, and the relative refractive index difference Δ 3 is -0.40% to -1· 00%

9. The anti-bending multimode optical fiber according to claim 5, wherein: the cladding layer is divided into two layers, wherein the first layer is a low refractive index depressed cladding layer, and the second layer is a pure quartz glass layer, The layered radius R2 is 21 μ πι 58 μ m, and the relative refractive index difference Δ 2 is -0.40% to -0.80%

10. The anti-bending multimode optical fiber according to claim 5, wherein: the cladding layer is divided into four layers, wherein the first layer and the fourth layer are pure quartz glass layers, and the second layer is a low refractive index sinking package. Layer, the third layer is a doped high refractive index quartz layer, the second layer radius R3 is 28 μ n 55 μ m, and the relative refractive index difference Δ 3 is -0.40% to -1. 10% 1%至0. 8%。 8% 。 8% 8% 8% 8% 8%

3%。 The core layer is a layer of quartz glass cladding, the relative refractive index difference Δ 1 of the core layer is 0. 3% 1%至-1. 1%, the cladding relative refractive index difference Δ 2 is -0. 1% to -1. 1%

The bending-resistant multimode optical fiber according to claim 3, wherein the multimode fiber has a bending attenuation of less than or equal to 0.15 dB at a wavelength of 850 nm and a radius of 10 turns of one turn.