CN116990902A - Ultra-low loss large effective area optical fiber and preparation method thereof - Google Patents

Abstract

The invention provides an ultra-low loss large effective area optical fiber and a preparation method thereof. The ultra-low loss large effective area optical fiber includes a core layer, an inner cladding layer, a concave cladding layer and an outer cladding layer from the inside to the outside; the concave cladding layer includes a deep concave layer, a concave platform layer and a concave platform layer. The ultra-low loss large effective area optical fiber with the above-mentioned specific refractive index profile structure provided by this application has good bending resistance, a fiber cut-off wavelength of no more than 1520nm, small macro-bending loss, and is in the short wavelength C band 1520nm~ The difference in attenuation coefficient from 1565nm to long wavelength L-band 1565nm~1625nm is small, which can meet the G.654.E optical fiber standard and can be used for ultra-high-voltage power communications, submarine cables or land trunk ultra-high-speed communication lines.

Description

Ultra-low loss large effective area optical fiber and preparation method thereof

Technical field

The present invention relates to the field of optical communication technology, and specifically to an ultra-low loss large effective area optical fiber and a preparation method thereof.

Background technique

The deterioration of signal-to-noise ratio and the nonlinear effect of optical fiber are the main factors limiting the optical transmission distance. Reducing fiber loss can reduce the number of relay stations, thereby reducing overall link loss and construction costs. The increase in the effective area can reduce the nonlinear effect and increase the fiber input power, thus improving the transmission performance of the optical fiber. In addition to improving single-channel transmission capabilities, increasing the number of wavelength division multiplexing (WDM) system channels and expanding the transmission band can also increase system capacity to meet continued growth in business needs.

At present, step structure design is often used to reduce the loss of optical fibers. However, the attenuation coefficients of existing optical fibers vary greatly from short wavelength to long wavelength range, and the attenuation consistency of the communication window of optical fibers needs to be improved.

Therefore, it is urgent to research and develop a low-loss optical fiber with a small difference in attenuation coefficient from the short-wavelength C-band 1520nm to 1565nm to the long-wavelength L-band 1565nm to 1625nm, which is of great significance for improving the transmission performance of the optical fiber.

Contents of the invention

The main purpose of the present invention is to provide an ultra-low loss large effective area optical fiber and a preparation method thereof, so as to solve the problem in the prior art that the attenuation coefficients of optical fibers in the short wavelength to long wavelength range are greatly different, and the attenuation consistency of the communication window of the optical fiber is relatively poor. Bad question.

In order to achieve the above object, on the one hand, the present invention provides an ultra-low loss large effective area optical fiber. The ultra-low loss large effective area optical fiber includes a core layer, an inner cladding layer, a recessed cladding layer and an outer cladding layer from the inside to the outside; the recessed cladding layer is The layers include a deep recessed layer, a recessed platform layer and a recessed platform layer; the maximum relative refractive index difference of the core layer material is △1 _max , the minimum relative refractive index difference of the inner cladding material is △2 _min , and the relative refractive index of the deep recessed layer material The difference is △3; the maximum relative refractive index difference of the recessed platform layer material is △4 _max , and the minimum relative refractive index is △4 _min , the maximum relative refractive index difference of the recessed platform layer material is △5 _max , and the minimum relative refractive index is △5 _min ; △3＜△2 _min , △3＜△4 _min , and △3＜△5 _min ; r represents the radial distance between a certain position in the ultra-low loss large effective area fiber and the center of the fiber;

△1(r) represents the relative refractive index difference between a certain position in the core layer and the material from the center of the optical fiber. △1(r) and r satisfy the following relationship (1):

Among them, R ₀ represents the radius of the core layer, g represents the refractive index distribution parameter of the core layer, 2≤g≤6;

△2(r) represents the relative refractive index difference between a certain position in the inner cladding and the center of the fiber. △2(r) and r satisfy the following relationship (2):

Among them, R ₁ represents the radial distance between the contact interface between the inner cladding and the recessed cladding and the center of the fiber, h represents the refractive index distribution parameter of the inner cladding, 3≤h≤10;

△4(r) represents the relative refractive index difference between a certain position in the recessed platform layer and the center of the optical fiber. △4(r) and r satisfy the following relationship (3):

Among them, R ₂ represents the radial distance between the contact interface between the deep recessed layer and the recessed platform layer and the center of the optical fiber, R ₃ represents the radial distance between the contact interface between the recessed platform layer and the recessed platform layer and the center of the optical fiber, and m represents the radial distance between the recessed platform layer and the center of the optical fiber. Refractive index distribution parameter, 0.5≤m≤3;

△5(r) represents the relative refractive index difference between a certain position in the recessed platform layer and the center of the optical fiber. △5(r) and r satisfy the following relationship (4):

Among them, R ₄ represents the radial distance between the contact interface between the recessed platform layer and the outer cladding and the center of the optical fiber, and n represents the refractive index distribution parameter of the recessed platform layer, 0.5≤n≤3;

The outer cladding is a silicon dioxide layer, and the refractive index of the outer cladding is 0.

In order to achieve the above object, another aspect of the present invention also provides a method for preparing an ultra-low loss large effective area optical fiber. The preparation method includes: preparing an optical fiber preform, which sequentially includes a core preparation layer from the inside to the outside. Inner cladding preparation layer, recessed cladding preparation layer and outer cladding preparation layer; the optical fiber preform is subjected to drawing and annealing treatment so that the core layer preparation layer, inner cladding preparation layer, recessed cladding preparation layer and outer cladding preparation layer are sequentially transformed into The core layer, inner cladding, recessed cladding and outer cladding are defined in the above content of this application, thereby obtaining ultra-low loss and large effective area optical fiber.

By applying the technical solution of the present invention, by designing the recessed cladding of the above-mentioned specific cladding structure, the relative refractive index difference Δ1(r) of the core layer material, the relative refractive index difference Δ2(r) of the inner cladding material, and the recessed cladding are simultaneously designed. The relative refractive index difference △4(r) of the platform layer material and the relative refractive index difference △5(r) of the recessed platform layer material respectively satisfy the relationships (1) to (4), and the deep recessed layer material The relative refractive index difference △3 is limited to the above range, which can effectively constrain the optical fiber guided wave transmission, improve the attenuation performance of the optical fiber, and make the optical fiber have high bending resistance and a cut-off wavelength of no more than 1520nm.

In short, the ultra-low loss large effective area optical fiber with the above-mentioned specific refractive index profile structure provided by this application has good bending resistance, a cable cut-off wavelength of no more than 1520nm, small macro-bending loss, and is in the short-wavelength C band The difference in attenuation coefficient from 1520nm to 1565nm to the long wavelength L-band 1565nm to 1625nm is small, which can meet the G.654.E optical fiber standard and can be used for ultra-high voltage power communications, submarine cables or land trunk ultra-high-speed communication lines.

Description of the drawings

The description and drawings that constitute a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached picture:

Figure 1 shows a schematic structural cross-sectional view of the optical fiber produced in Example 1;

Figure 2 shows a cross-sectional view of the refractive index structure of the optical fiber produced in Example 1;

Figure 3 shows a schematic structural diagram of an optical fiber drawing annealing device in a preferred embodiment of the present application;

Figure 4 shows a schematic structural diagram of the device used in the optical fiber preparation process in a preferred embodiment of the present application.

Among them, the above-mentioned drawings include the following reference signs:

10. Core layer; 20. Inner cladding; 30. Recessed cladding; 31. Deep recessed layer; 32. Recessed platform layer; 33. Recessed platform layer; 40. Outer cladding; 51. First coating; 52. Second coating;

100. Inner cavity heating section; 110. Preheating component; 120. Melting component; 200. Drawing annealing section; 210. First annealing unit; 220. Second annealing unit; 300. Annealing tube; 301. Optical fiber annealing tube outlet.

Detailed ways

It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of this application can be combined with each other. The present invention will be described in detail below with reference to examples.

As described in the background art, existing optical fibers have problems such as large differences in attenuation coefficients from short wavelength to long wavelength ranges, and poor attenuation consistency in communication windows, resulting in poor optical fiber transmission performance. In order to solve the above technical problems, this application provides an ultra-low loss large effective area optical fiber. As shown in Figure 1, the ultra-low loss large effective area optical fiber includes a core layer 10, an inner cladding layer 20, and a recessed cladding layer from the inside to the outside. Layer 30 and outer cladding 40; the recessed cladding 30 includes a deep recessed layer 31, a recessed platform layer 32 and a recessed platform layer 33; the maximum relative refractive index difference of the material of the core layer 10 is Δ1 _max , and the minimum relative refraction of the material of the inner cladding 20 The refractive index difference is △2 _min , and the relative refractive index difference of the deep recessed layer 31 material is △3; the maximum relative refractive index difference of the recessed platform layer 32 material is △4 _max , and the minimum relative refractive index is △4 _min , and the recessed platform layer The maximum relative refractive index difference of 33 materials is △5 _max , and the minimum relative refractive index is △5 _min ; △3＜△2 _min , △3＜△4 _min , and △3＜△5 _min ; r represents ultra-low loss The radial distance between a certain position in a large effective area fiber and the center of the fiber;

△1(r) represents the relative refractive index difference between a certain position in the core layer 10 and the center of the optical fiber. △1(r) and r satisfy the following relationship (1):

Among them, R ₀ represents the radius of the core layer 10, g represents the refractive index distribution parameter of the core layer 10, 2≤g≤6;

△2(r) represents the relative refractive index difference between a certain position in the inner cladding 20 and the center of the optical fiber. △2(r) and r satisfy the following relationship (2):

Among them, R ₁ represents the radial distance between the contact interface between the inner cladding 20 and the recessed cladding 30 and the center of the optical fiber, h represents the refractive index distribution parameter of the inner cladding 20, 3≤h≤10;

△4(r) represents the relative refractive index difference between a certain position in the recessed platform layer 32 and the center of the optical fiber. △4(r) and r satisfy the following relationship (3):

Among them, R ₂ represents the radial distance between the contact interface of the deep recessed layer 31 and the recessed platform layer 32 and the center of the optical fiber, R ₃ represents the radial distance between the contact interface of the recessed platform layer 32 and the recessed platform layer 33 and the center of the optical fiber, and m represents The refractive index distribution parameter of the concave stage layer 32 is 0.5≤m≤3;

△5(r) represents the relative refractive index difference between a certain position in the recessed platform layer 33 and the center of the optical fiber. △5(r) and r satisfy the following relationship (4):

Among them, R ₄ represents the radial distance between the contact interface of the recessed platform layer 33 and the outer cladding 40 from the center of the optical fiber, and n represents the refractive index distribution parameter of the recessed platform layer 33, 0.5≤n≤3;

The outer cladding 40 is a silicon dioxide layer, and the refractive index of the outer cladding 40 is 0.

It should be noted that the relative refractive index difference in this application refers to the difference between the refractive index of a certain layer in the ultra-low loss large effective area optical fiber and the refractive index of pure silica material.

By designing the recessed cladding 30 of the above-mentioned specific cladding structure, the relative refractive index difference Δ1(r) of the core layer 10 material, the relative refractive index difference Δ2(r) of the inner cladding 20 material, and the recessed platform layer 32 material are simultaneously designed. The change rules of the relative refractive index difference Δ4(r) and the relative refractive index difference Δ5(r) of the recessed platform layer 33 material respectively satisfy the relationships (1) to (4), and the relative refractive index difference of the deep recessed layer 31 material is The refractive index difference △3 is limited to the above range, which can effectively constrain the optical fiber guided wave transmission, improve the attenuation performance of the optical fiber, and make the optical fiber have high bending resistance and a cut-off wavelength of no more than 1520nm.

In short, the ultra-low loss large effective area optical fiber provided by this application with the above-mentioned specific refractive index profile structure (as shown in Figure 2) has good bending resistance, a cable cut-off wavelength of no more than 1520nm, and small macro-bending loss. , and the difference in attenuation coefficient between the short-wavelength C-band 1520nm~1565nm and the long-wavelength L-band 1565nm~1625nm is small, it can meet the G.654.E optical fiber standard and can be used for UHV power communications, submarine cables or land trunk ultra-high-speed communication lines medium.

In a preferred embodiment, Δ1 _max is 0.10~0.30%, Δ2 _min is -0.25~-0.35%, Δ3 is -0.45~-0.5%, Δ4 _max is -0.20~-0.25%, △4 _min is -0.25～-0.30%, △5 _max is -0.30～-0.35%, △5 _min is -0.35～-0.4%. △1 _max , △2 _min , △3, △4 _max , △4 _min , △5 _max and △5 _min respectively independently include but are not limited to the above ranges. Limiting them to the above ranges is beneficial to constraining optical fiber guided wave transmission. , which is conducive to improving the attenuation performance of the optical fiber, which is conducive to improving the bending resistance of the optical fiber, and is conducive to reducing the difference in the attenuation coefficient of the optical fiber from the short wavelength range to the long wavelength range.

In a preferred embodiment, R ₀ is 5 to 7 μm, the difference between R ₁ and R ₀ is 3.5 to 5 μm, the difference between R ₄ and R ₁ is 30 to 40 μm, and the distance between the outer surface of the outer cladding 40 and the optical fiber is The radial distance R ₅ between the centers is 50 to 65 μm. Compared with other ranges, limiting the radius or thickness of the core layer 10, the inner cladding layer 20, the recessed cladding layer 30 and the outer cladding layer 40 within the above range is beneficial to reducing the viscosity difference between the core layer 10 and each cladding layer, thereby achieving better results. It is beneficial to reduce the stress difference between the core layer 10 and each cladding layer, thereby reducing the impact of additional stress on the performance of the optical fiber; at the same time, it is also beneficial to reducing the attenuation of the optical fiber in the long wavelength band, and is beneficial to improving the bending resistance of the optical fiber.

In order to further control the cut-off wavelength of the optical fiber while reducing its macrobending loss, and maintain both properties at a better level, preferably, the ratio of R ₁ to R ₀ is (1.4~2.0):1.

In order to further improve the bending resistance and optical performance of the optical fiber, preferably, the difference between R ₂ and R ₁ is 4.5 to 5.5 μm, the difference between R ₃ and R ₂ is 6 to 18 μm, and the difference between R ₄ and R ₃ is 5.5～22μm.

In order to further improve the overall performance of the optical fiber, preferably, the radial distance between the outer surface of the outer cladding 40 and the center of the optical fiber is 62 to 63 μm.

The doping of Ge element and F element is beneficial to weakening the silicon-oxygen bond in the quartz material. The SiO ₂ chemical bond is more easily broken at high temperatures, which is beneficial to reducing the viscosity of glass at the same temperature. In a preferred embodiment, the core layer 10 is made of SiO ₂ doped with Ge element and F element, the inner cladding layer 20 is made of SiO ₂ doped with F element, and the recessed cladding layer 30 is made of SiO 2 doped with F element. Element SiO ₂ . Compared with other materials, using the quartz material doped with the above types of elements as the material of the core layer 10, the inner cladding layer 20 and the recessed cladding layer 30 is beneficial to adjusting the relative refractive index difference of the core layer 10 and each cladding layer to better Meet the above specific fiber refractive index profile design.

In a preferred embodiment, in the optical fiber, based on the total weight of the material of the core layer 10 , the doping amount of the Ge element is 1.0 to 4.0 wt%, and the doping amount of the F element is 0.01 to 0.3%. Compared with other doping amounts, limiting the doping amount of the Ge element in the core layer 10 to the above range is beneficial to reducing the influence of Rayleigh scattering caused by GeO ₂ , thereby helping to reduce fiber attenuation, and at the same time, the doping of the F element Limiting the amount within the above range is beneficial to reducing the relative refractive index difference of the core layer 10 and is beneficial to reducing the viscosity of the core layer 10 .

In a preferred embodiment, the doping amount of the F element in the optical fiber is 0.01 to 1.0% based on the total weight of the material of the inner cladding 20 . Compared with other doping amounts, limiting the doping amount of F element in the inner cladding layer 20 to the above range is beneficial to reducing the stress difference between the core layer 10 and the inner cladding layer 20 and between the inner cladding layer 20 and the recessed cladding layer 30 , thus helping to reduce additional losses caused by stress.

In a preferred embodiment, the doping amount of the F element in the optical fiber is 0.3 to 2.0 wt% based on the total weight of the material of the recessed cladding 30 . Compared with other doping amounts, limiting the doping amount of F element in the recessed cladding layer 30 to the above range is beneficial to realizing a relative refractive index depressed optical structure and achieving compatibility of comprehensive properties such as attenuation coefficient, cut-off wavelength, and bending loss. At the same time, it is beneficial to reduce the stress difference between the recessed layer and the core layer and reduce the occurrence of additional attenuation.

In a preferred embodiment, the compressive stress from the core layer 10 to the inner cladding layer 20 is 40 to 100 MPa. The compressive stress value in the range from the core layer 10 to the inner cladding layer 20 includes but is not limited to the above range. Limiting it within the above range is conducive to suppressing the expansion of internal micro-defects, conducive to reducing Rayleigh scattering, and thus conducive to reducing the fiber attenuation of the optical fiber. , and it is also helpful to improve the tension resistance of optical fiber.

In a preferred embodiment, within the radial range from the recessed platform layer 32 to the recessed platform layer 33, the radial viscosity change amplitude is no more than 2%/μm, and the stress difference is no more than 20%. Compared with other ranges, limiting the radial viscosity change amplitude and stress difference to the above range is beneficial to reducing sudden changes in stress in the optical fiber and reducing additional attenuation.

The setting of the coating is conducive to improving the flexibility and other comprehensive properties of the optical fiber. In a preferred embodiment, the outer surface of the outer cladding 40 is also covered with a first coating 51 and a second coating 52 in sequence. Preferably, the materials of the first coating 51 and the second coating 52 independently include but are not limited to one or more from the group consisting of acrylic resin, epoxy resin and silicone-modified acrylic resin.

In a preferred embodiment, the elastic modulus of the first coating 51 is 0.3-0.5MPa, the elastic modulus of the second coating 52 is 500-1000MPa, and the friction coefficient of the outer surface of the second coating 52 is 0.1～0.3. The elastic modulus of the first coating 51 and the second coating 52 each independently includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the flexibility of the optical fiber; Limiting the friction coefficient within the above range is beneficial to improving the wear resistance of the optical fiber to facilitate its application in the field of optical communications.

In a preferred embodiment, the mode field diameter of the optical fiber at the wavelength of 1550nm is 12-13 μm, and the effective area is 120-130 μm ² ; the attenuation coefficient of the optical fiber at the wavelength of 1550nm is ≤0.174dB/km; the attenuation coefficient of the optical fiber at 1520nm and The difference between the minimum attenuation coefficients in the wavelength range from 1520nm to 1625nm is Δα1520, Δα1520≤0.02dB/km, and the difference between the minimum attenuation coefficients at 1625nm and in the wavelength range from 1520nm to 1625nm is Δα1625, Δα1625≤0.02dB/ km, and the absolute value of the difference between Δα1520 and Δα1625 is not greater than 0.009dB/km. The above-mentioned optical fiber provided by this application has a large effective area and a small attenuation coefficient, and has excellent transmission performance. Moreover, the above-mentioned optical fiber has a small difference in attenuation coefficient from short wavelength range to long wavelength range, and the communication window of the optical fiber has excellent attenuation consistency. .

The second aspect of this application also provides a method for preparing an optical fiber. The method for preparing an optical fiber includes: preparing an optical fiber preform. The optical fiber preform includes, from the inside to the outside, a core layer 10 preliminary layer, an inner cladding 20 preliminary layer, and a recessed cladding layer. Layer 30 preparation layer and outer cladding 40 preparation layer; perform drawing and annealing treatment on the optical fiber preform, so that the core layer 10 preparation layer, the inner cladding 20 preparation layer, the recessed cladding 30 preparation layer and the outer cladding 40 preparation layer are sequentially transformed into this The core layer 10, the inner cladding 20, the recessed cladding 30 and the outer cladding 40 in the optical fiber provided by the application are used to obtain the optical fiber provided by the application.

An optical fiber preform is prepared according to the above-mentioned specific refractive index profile structure provided by this application. The preparation process includes deposition methods commonly used in this field. The optical fiber preform is subjected to drawing and annealing treatment to obtain the above-mentioned optical fiber provided by this application. The above-mentioned optical fiber produced by this application can meet the G.654.E optical fiber standard and can be used for ultra-high voltage power communications, submarine cables or land trunk ultra-high-speed communication lines, etc.

In a preferred embodiment, the material of the preliminary layer of the core layer 10 is SiO ₂ doped with Ge element and F element, the material of the preliminary layer of the inner cladding layer 20 is SiO ₂ doped with F element, and the material of the preparatory layer of the recessed cladding layer 30 is SiO 2 doped with the element F. The material is SiO ₂ doped with F element. Compared with other materials, using the quartz material doped with the above types of elements as the material for the core layer 10 preliminary layer, the inner cladding layer 20 preliminary layer and the recessed cladding 30 preliminary layer is beneficial to adjusting the core layer 10 and each cladding of the produced optical fiber. The relative refractive index difference of the layers to better meet the specific fiber refractive index profile design mentioned above.

In a preferred embodiment, based on the total weight of the material of the preliminary layer of the core layer 10, the doping amount of the Ge element is 1.0-4.0 wt%, and the doping amount of the F element is 0.01-0.3%. Compared with other doping amounts, limiting the doping amount of the Ge element in the preliminary layer of the core layer 10 to the above range is beneficial to reducing the influence of Rayleigh scattering caused by GeO ₂ , thereby helping to reduce fiber attenuation, and at the same time, reducing the amount of the F element. Limiting the doping amount within the above range is beneficial to reducing the relative refractive index difference of the core layer 10 produced, and is also beneficial to reducing the viscosity of the core layer 10 produced.

In a preferred embodiment, the doping amount of the F element is 0.01 to 1.0% based on the total weight of the material of the preliminary layer of the inner cladding layer 20 . Compared with other doping amounts, limiting the doping amount of the F element in the preliminary layer of the inner cladding layer 20 to the above range is beneficial to reducing the gap between the core layer 10 and the inner cladding layer 20 and the depression between the inner cladding layer 20 and the fabricated inner cladding layer 20 . The stress difference between the cladding layers 30 is beneficial to reducing the additional loss caused by stress in the manufactured optical fiber.

In a preferred embodiment, the doping amount of the F element is 0.3 to 2.0 wt% based on the total weight of the material of the preparatory layer of the recessed cladding layer 30 . Compared with other doping amounts, limiting the doping amount of the F element in the preparatory layer of the recessed cladding layer 30 within the above range is beneficial to achieving a relative refractive index depressed optical structure and achieving comprehensive performance improvements such as attenuation coefficient, cut-off wavelength, and bending loss. The compatibility is also conducive to reducing the stress difference between the recessed layer and the core layer, and reducing the occurrence of additional attenuation.

In a preferred embodiment, the drawing annealing treatment is performed using an optical fiber drawing annealing device. As shown in Figure 3, the optical fiber drawing annealing device includes: an inner cavity heating section 100, a drawing annealing section 200 and an annealing tube 300. The inner cavity heating section 100 is used to heat the optical fiber preform; the inner cavity heating section 100 has an inner cavity, and according to the traveling direction of the optical fiber preform, at least one preheating component 110 and at least one The melting part 120, the preheating part 110 and the melting part 120 are each independently arranged around the circumferential direction of the inner cavity and parallel to each other; the wire drawing annealing section 200 includes a first annealing unit 210 and a second annealing unit 220. The first annealing unit 210 , the second annealing unit 220 is coaxially arranged with the inner cavity heating section 100, and the first annealing unit 210, the second annealing unit 220 and the inner cavity heating section 100 are provided with an annealing tube 300 penetrating in the coaxial direction, and the annealing tube 300 is used for Penetrate the optical fiber; the second annealing unit 220 is provided with an optical fiber annealing tube outlet 301 at one end away from the first annealing unit 210, and the temperature at the interface between the second annealing unit 220 and the first annealing unit 210 is higher than the optical fiber annealing tube outlet 301 temperature; during the wire drawing annealing process, the temperature of the preheating component 110 is set to T ₁ , the temperature of the melting component 120 is set to T ₂ , T ₂ is 1800 to 2000°C, the temperature of the first annealing unit 210 is set to T ₃ , The temperature of the second annealing unit 220 is T ₄ , T ₄ is 1150 to 1250°C, and T ₁ , T ₂ , T ₃ and T ₄ satisfy the following relationship: T ₂ >T ₃ >T _g >T ₁ >T ₄ , where T _g represents the glass transition temperature of the optical fiber preform; the difference between T ₃ and T _g is 50 to 100°C.

When the wire drawing annealing device is in working condition, put the optical fiber preform into the inner cavity. As the preheating component 110 and the melting component 120 preheat and melt the optical fiber preform, the heated and melted part of the optical fiber preform changes to flow. The state proceeds along the annealing tube 300 toward the first annealing unit 210 until entering the second annealing unit 220, and is finally pulled out from the fiber annealing tube outlet 301. For optical fiber preforms of a specific material (controlling Tg within the above range), limiting the temperature of the preheating component 110 and the melting component 120 to the above range is beneficial to improving the transformation of the optical fiber preform from a solid state to a fluid state compared to other ranges. The efficiency is conducive to obtaining optical fiber after drawing annealing treatment; at the same time, compared with other ranges, limiting the temperatures of the first annealing unit 210, the second annealing unit 220 and the fiber annealing tube outlet 301 to the above range is conducive to producing Optical fiber, reduce the occurrence of fiber breakage during the drawing process and reduce the residual stress between the layers in the fiber due to the drawing annealing process, while suppressing the concentration of residual stress somewhere in the fiber, and conducive to improving the attenuation performance of the fiber. Moreover, compared with other ranges, limiting the temperature of the fiber annealing tube outlet 301 to the above range is beneficial to suppressing surface turbulence and is beneficial to more precise control of the fiber diameter.

In short, using the above drawing annealing device to perform the above drawing annealing treatment on the optical fiber preform is beneficial to improving the communication window attenuation consistency of the optical fiber.

In a preferred embodiment, the inner cavity heating section 100 includes two preheating components 110, which are independently arranged around the circumferential direction of the inner cavity and parallel to each other, and the temperatures of the two preheating components 110 are arranged along the direction of the optical fiber preform. The direction of travel increases in sequence. Compared with a single preheating component 110, using two preheating components 110 and limiting their temperatures within the above range is beneficial to further reducing the temperature difference between various parts of the optical fiber preform during the drawing process, and is beneficial to further reducing The stress differences in each part are beneficial to further improving the attenuation consistency of the communication window of the optical fiber.

In a preferred embodiment, the inner cavity heating section 100 includes three melting parts 120, and the three melting parts 120 are independently arranged around the circumferential direction of the inner cavity and parallel to each other, and the temperatures of the three melting parts 120 are arranged along the path of the optical fiber preform. direction in order to decrease. Compared with a single melting part 120, using three melting parts 120 and limiting the temperatures of the three within the above range is beneficial to further reducing the temperature difference between various parts of the optical fiber preform during the drawing process, and is beneficial to further reducing the The stress difference in each part is beneficial to further improving the attenuation consistency of the communication window of the optical fiber.

In a preferred embodiment, the preheating component 110, the melting component 120, the first annealing unit 210 and the second annealing unit 220 in the optical fiber drawing annealing device each independently adopt graphite heating or coil heating, and the above Each component or each annealing unit has independent heating and temperature control, and is connected to the host remote industrial control system to adjust the temperature remotely.

In a preferred embodiment, the preheating component 110, the melting component 120, the first annealing unit 210 and the second annealing unit 220 in the optical fiber drawing annealing device are each independently provided with temperature detectors at corresponding positions. Monitor the temperature of the optical fiber at the corresponding location in real time. Preferably, the preheating component 110, the melting component 120, the first annealing unit 210 and the second annealing unit 220 are each independently provided with a thermal insulation component on their outer periphery, and a water circulation cooling component is disposed on the outer periphery of the thermal insulation component.

In a preferred embodiment, an inert gas is introduced into the inner cavity during the wire drawing annealing process. Preferably, the inert gas includes but is not limited to argon, or a mixture of argon and helium.

In a preferred embodiment, the inert gas introduction rate is 15-30L/min. The introduction rate of the inert gas includes but is not limited to the above range. Limiting it to the above range not only protects the heated graphite parts in the furnace, but also helps to stabilize the thermal field in the furnace, evenly discharge impurities into the furnace, and improve the strength and attenuation of the optical fiber. Uniformity.

In order to further reduce the temperature difference of various parts of the optical fiber preform during the drawing process, further reduce the stress difference of each part, and further improve the attenuation consistency of the communication window of the optical fiber, in a preferred embodiment, preheating The shortest distance between the component 110 and the molten component 120 is 200-500 mm, the length of the area where the annealing tube 300 is located in the first annealing unit 210 is 100-300 mm, and the length of the area where the annealing tube 300 is located in the second annealing unit 220 is 1000～2000mm.

In order to further reduce the temperature difference of various parts of the optical fiber preform during the drawing process, further reduce the stress difference of each part, and further improve the attenuation consistency of the communication window of the optical fiber, in a preferred embodiment, when When the cavity heating section 100 includes two preheating components 110, the distance between two adjacent ones is 30 to 50 mm; and/or, when the cavity heating section 100 includes three melting components 120, the distance between two adjacent ones is The distance is 20~40mm.

In a preferred embodiment, during the drawing annealing process, the drawing tension is 50 to 180g, and the drawing tension and the drawing rate satisfy the following relationship (5):

Among them, F(v) represents the corresponding drawing tension when the drawing rate is v, F ₀ represents the minimum drawing tension, F ₁ represents the maximum drawing tension, and the units of F(v), F ₀ and F ₁ are all g, v ₂ represents the maximum wire drawing rate, the unit is 350~1200m/min, α represents the tension adjustment coefficient, and 0.5≤α≤4.

The drawing tension includes but is not limited to the above range. Limiting it within the above range is beneficial to improving the drawing annealing process to produce an optical fiber that meets the above refractive index profile structure of the present application, and at the same time, the relative refractive index difference of the core layer 10 material is Δ1(r ), changes in the relative refractive index difference Δ2(r) of the material of the inner cladding layer 20, the relative refractive index difference Δ4(r) of the material of the recessed platform layer 32, and the relative refractive index difference Δ5(r) of the material of the recessed platform layer 33 The laws satisfy the relationships (1) to (4) respectively, which is conducive to more precise control of the relative refractive index difference of each layer, which is conducive to improving the transmission performance of the optical fiber and reducing the attenuation of the optical fiber in the short wavelength range to the long wavelength range. The difference in coefficients is beneficial to improving the attenuation consistency of the optical fiber's communication window.

In a preferred embodiment, the drawing tension is monitored in real time using a non-contact tension testing device. The non-contact tension testing device can obtain the tension of the optical fiber by detecting the tiny vibrations of the optical fiber. During the monitoring process, the schematic diagram of the device structure used in the optical fiber preparation process is shown in Figure 4. On the basis of the optical fiber drawing annealing device, a non-contact tension testing device and a coating cup are further introduced. The coating cup refers to the first coating Container for coating 51 and second coating 52 . The non-contact tensiometer is set between the fiber annealing tube outlet 301 and the coating cup, preferably in an upper position. The distance between the non-contact tension testing device and the fiber annealing tube outlet 301 of the fiber drawing annealing device is H ₁ . The distance between the tension testing device and the coating cup is H ₂ , and preferably H ₂ /H ₁ is (2-3):1. Compared with other ranges, limiting the ratio of H ₂ to H ₁ within the above range is beneficial to improving the accuracy of the measured drawing tension.

In a preferred embodiment, the optical fiber preform is cylindrical or rod-shaped, and the diameter of the optical fiber preform is 60 to 200 mm. The shape and size of the optical fiber preform include but are not limited to the above range. Limiting it within the above range facilitates drawing and annealing processing, and is conducive to the production of optical fibers of specific shapes suitable for optical communication application scenarios, and is suitable for ultra-high voltage power. Communications, submarine cables or land trunk ultra-high-speed communication lines are medium.

In a preferred embodiment, when the diameter of the optical fiber preform is 60~80mm, the drawing tension is 50~100g; when the diameter of the optical fiber preform is 120~150mm, the drawing tension is 90~130g; when the optical fiber preform is 120~150mm in diameter, the drawing tension is 90~130g; When the diameter of the part is 160~200mm, the drawing tension is 130~180g. For optical fiber preforms with different diameters, using the above-mentioned preferred range of drawing tension is beneficial to more accurately control the distribution of doping elements within each preparation layer, which is conducive to more accurate control of the core layer 10 and 10 of the produced optical fiber. The relative refractive index difference of each cladding is beneficial to improving the transmission performance of the optical fiber, reducing the difference in attenuation coefficient of the optical fiber from the short wavelength range to the long wavelength range, and improving the attenuation consistency of the communication window of the optical fiber.

In a preferred embodiment, when T _g is 1360-1450°C, T ₁ is 1300-1350°C, T ₂ is 1800-2000°C, T ₃ is 1460-1500°C, and T ₄ is 1150-1250°C. , and the drawing tension is 60~130g; when T _g is 1310~1350℃, T ₁ is 1260~1300℃, T ₂ is 1800~2000℃, T ₃ is 1360~1450℃, and T ₄ is 1150~1250℃ , and the drawing tension is 50~120g; when T _g is 1460~1550℃, T ₁ is 1350~1450℃, T ₂ is 1900~2200℃, T ₃ is 1560~1650℃, and T ₄ is 1150~1250℃ , and the drawing tension is 80~180g.

For optical fiber preforms with different Tg or materials, using the above-mentioned preferred range of drawing tension is conducive to more precise control of the distribution of doping elements within each preparation layer, which is conducive to more precise control of the core layer of the produced optical fiber. 10 and the relative refractive index difference of each cladding, which is beneficial to improving the transmission performance of the optical fiber, reducing the difference in attenuation coefficient of the optical fiber from short wavelength range to long wavelength range, and improving the attenuation consistency of the communication window of the optical fiber.

In a preferred embodiment, after the wire drawing annealing treatment, a first coating treatment and a second coating treatment are performed in sequence, and the first coating treatment and the second coating treatment are performed using an ultraviolet curing coating method.

In a preferred embodiment, during the first coating process and the second coating process, the central wavelength range of the ultraviolet light source used is 365nm ~ 405nm, and it is a line light source in the parallel direction along the traveling direction of the optical fiber. The effective light source The length is above 800mm. The distance between the light source and the optical fiber is set to 30~80mm, and the light source output power is steplessly adjusted from 10~100%, and increases with the increase of the drawing speed, ensuring that the ultraviolet irradiation energy obtained by the inner and outer layers reaches 400~600mJ/ cm ² to ensure uniform curing of the inner and outer layers. The optical fiber curing channel is protected by nitrogen and compressed air is introduced. The preferred flow ratio of nitrogen to compressed air is (15~20):1, and the total air intake flow is 15~30L/min. Exhaust gas to discharge oil fume volatiles. The ratio of protective gas inlet flow and exhaust flow is (3~5):1.

During the above-mentioned first coating process and second coating process, the introduction of nitrogen is helpful to reduce the inhibition of oxygen on the resin curing reaction and increase the curing rate; the introduction of compressed air is beneficial to promote the ablation of oil fume volatiles on the one hand, On the other hand, it is beneficial to improve the friction performance of the outer surface of the second coating 52, thereby facilitating the adhesion of the subsequent colored layer.

In a preferred embodiment, the curing degree of the first coating process is 90-92%, and the curing degree of the second coating process is 90-95%. The curing degrees of the first coating process and the second coating process respectively include but are not limited to the above ranges. Limiting them within the above ranges is beneficial to reducing the micro-bending additional loss of the optical fiber, thereby improving the bending resistance of the optical fiber.

The present application will be described in further detail below with reference to specific examples. These examples shall not be construed as limiting the scope of protection claimed by the present application.

Example 1

A method for preparing optical fibers, including:

(1) Preparation of optical fiber preforms: In the reactor, the basic gas and doping gas are deposited using the MCVD deposition method. The basic gases SiCl ₄ , H ₂ and O ₂ are introduced, and the inert gas Ar or He is used as the carrier. The gas is introduced into the reaction chamber, and GeCl ₄ gas and CF ₄ are introduced. The temperature of the deposition process is 1450°C. After 24 hours of deposition and sintering at 1550°C for 4 hours, the optical fiber preform is obtained; the optical fiber preform is cylindrical and has a diameter of 155mm. The glass transition temperature Tg is 1360°C;

(2) Drawing annealing process: Use an optical fiber drawing annealing device as shown in Figure 3 to perform drawing annealing. The inner cavity heating section 100 includes two adjacent preheating components 110, and both are independently arranged around The circumferential direction of the inner cavity is parallel to each other, and the distance between the two is 40mm. The temperatures of the two preheating components 110 along the traveling direction of the optical fiber preform are set to 1310°C and 1340°C in sequence; the inner cavity heating section 100 includes three The melting parts 120 are independently arranged around the circumferential direction of the inner cavity and parallel to each other. The distance between two adjacent ones is 30 mm. The temperatures of the three melting parts 120 are set sequentially along the traveling direction of the optical fiber preform. are 1800°C, 1850°C and 1900°C; the temperature T ₃ of the first annealing unit 210 is set to 1480°C, and the temperature T ₄ of the second annealing unit 220 is set to 1250°C; wire drawing annealing is performed under the above temperature conditions. During the process, the optical fiber travels downward from the annealing tube 300 due to the effect of gravity, and is finally pulled out from the fiber annealing tube outlet 301;

In this process, a non-contact tension testing device is used to monitor the drawing tension in real time (as shown in Figure 4). The drawing tension is controlled to 130g and the drawing speed is 800m/min. Finally, the outer surface of the outer cladding 40 is coated in sequence. After the first coating layer 51 and the second coating layer 52 are cured by ultraviolet light of 365 nm to 395 nm, they are pulled and wound into a coil to obtain an optical fiber. Among them, the first coating layer 51 is an acrylic resin layer, and the second coating layer 52 is an acrylic resin layer.

A schematic cross-sectional view of the structure of the optical fiber prepared in Example 1 is shown in Figure 1. The optical fiber includes a core layer 10, an inner cladding 20, a recessed cladding 30 and an outer cladding 40 from the inside to the outside. The recessed cladding 30 includes a deep The recessed layer 31 , the recessed mesa layer 32 and the recessed mesa layer 33 . Among them, the material of the core layer 10 is SiO ₂ doped with Ge element and F element, and based on the total weight of the material of the core layer 10 , the doping amount of the Ge element is 2.1wt%, and the doping amount of the F element is 2.1wt%. 0.1wt%; the material of the inner cladding layer 20 is SiO ₂ doped with F element, and based on the total weight of the material of the inner cladding layer 20, the doping amount of the F element is 0.45wt%; the material of the recessed cladding layer 30 is doped with SiO 2 . SiO ₂ doped with F element, and the doping amount of F element is 1.2 wt% based on the total weight of the material of the recessed cladding layer 30 .

The cross-sectional view of the refractive index structure of the optical fiber prepared in Example 1 is shown in Figure 2, in which the relative refractive index difference Δ1(r) of the core layer 10 material and the relative refractive index difference Δ2(r) of the inner cladding 20 material ), the relative refractive index difference △4(r) of the material of the recessed platform layer 32 and the relative refractive index difference △5(r) of the material of the recessed platform layer 33 respectively satisfy the relational expressions (1) to (4) defined above. . Parameters such as the radius and relative refractive index difference of each layer in the optical fiber are shown in Table 1. As shown in Table 1, the maximum relative refractive index difference Δ1 _max of the material of the core layer 10 in the relationship formula (1) is 0.2%, the radius R ₀ of the core layer 10 is 6.2 μm, and the refractive index distribution parameter g of the core layer 10 is 4; In the relationship equation (2), the minimum relative refractive index difference Δ2 _min of the inner cladding layer 20 material is -0.32%, R ₁ is 11.16 μm, and the refractive index distribution parameter h of the inner cladding layer 20 is 4; in the relationship equation (3) The maximum relative refractive index difference Δ4 _max of the material of the concave platform layer 32 is -0.20%, the minimum relative refractive index Δ4 _min is -0.30%, _R2 is 16.16μm, _R3 is 26.56μm, the refractive index of the concave platform layer 32 The distribution parameter m is 2; in the relation (4), the maximum relative refractive index difference Δ5 _max of the recessed platform layer 33 material is -0.30%, and the minimum relative refractive index Δ5 _min is -0.35%, and R ₄ is 44.16 μm. The refractive index distribution parameter n of the recessed platform layer 33 is 2.

Example 2

The difference from Embodiment 1 is that in step (1), the doping amount in each layer is changed so that the relative refractive index difference is the value shown in Table 1, where the material of the core layer 10 is doped with Ge element and F element. Of SiO ₂ , based on the total weight of the material that accounts for the core layer 10 , the doping amount of the Ge element is 3.2wt%, and the doping amount of the F element is 0.2wt%; based on the total weight of the material that accounts for the inner cladding layer 20 , The doping amount of the F element is 0.65wt%; based on the total weight of the material of the recessed cladding 30, the doping amount of the F element is 2.0wt%; in step (2), the drawing tension is controlled to 120g, and the drawing speed is 650m /min for drawing.

Example 3

The difference from Embodiment 1 is that in step (1), the doping amount in each layer is changed so that the relative refractive index difference is the value shown in Table 1, where the material of the core layer 10 is doped with Ge element and F element. Of SiO ₂ , based on the total weight of the material that accounts for the core layer 10 , the doping amount of the Ge element is 2.6wt%, and the doping amount of the F element is 0.15wt%; based on the total weight of the material that accounts for the inner cladding layer 20 , The doping amount of F element is 0.65wt%; based on the total weight of the material of the recessed cladding 30, the doping amount of F element is 1.2wt%; in step (2), the drawing tension is controlled to 142g, and the drawing rate is 1000m /min for drawing.

Example 4

Step (1) is the same as Example 1. The difference from Example 1 is that the drawing tension in step (2) is 50g and the drawing speed is 350m/min.

Example 5

Step (1) is the same as Example 1. The difference from Example 1 is that the drawing tension in step (2) is 180g and the drawing speed is 1200m/min.

Example 6

Step (1) is the same as Example 1. The difference from Example 1 is that the drawing tension in step (2) is 200g and the drawing speed is 1500m/min.

Example 7

Step (1) is the same as Embodiment 1. The difference from Embodiment 1 is that the inner cavity heating section 100 includes two preheating components 110, the distance between two adjacent ones is 30 mm, and the temperatures are set to 1330°C and 110°C respectively. 1350°C; the inner cavity heating section 100 includes three melting parts 120, and the three melting parts 120 are independently arranged around the circumferential direction of the inner cavity and parallel to each other. The distance between two adjacent ones is 20mm, and the temperature is set in sequence. 1900°C, 1950°C and 2000°C; the temperature T ₃ of the first annealing unit 210 is set to 1480°C, and the temperature T ₄ of the second annealing unit 220 is set to 1250°C.

Example 8

Step (1) is the same as Embodiment 1. The difference from Embodiment 1 is that the inner cavity heating section 100 includes two preheating components 110, the distance between two adjacent ones is 50 mm, and the temperatures are set to 1300°C and 1100°C respectively. 1320°C; the inner cavity heating section 100 includes three melting parts 120, and the three are independently arranged around the circumferential direction of the inner cavity and parallel to each other, the distance between two adjacent ones is 40mm, and the temperature is set in sequence. 1800°C, 1850°C and 1900°C; the temperature T ₃ of the first annealing unit 210 is set to 1480°C, and the temperature T ₄ of the second annealing unit 220 is set to 1250°C.

Example 9

Step (1) is the same as Embodiment 1. The difference from Embodiment 1 is that the inner cavity heating section 100 includes two preheating components 110, the distance between two adjacent ones is 70 mm, and the temperatures are set to 1200°C and 1250°C in sequence. ° C; the inner cavity heating section 100 includes three melting parts 120, and the three are independently arranged around the circumferential direction of the inner cavity and parallel to each other. The distance between two adjacent ones is 60 mm, and the temperature is set to 1750 in turn. ℃, 1800℃ and 1850℃; set the temperature _T3 of the first annealing unit 210 to 1480℃, and set the temperature _T4 of the second annealing unit 220 to 1250℃.

Comparative example 1

The difference from Embodiment 1 is that the optical fiber preform does not include the concave cladding 30 preliminary layer, and the prepared optical fiber includes the core layer 10, the inner cladding 20 and the outer cladding 40 in order from the inside to the outside. The core layer 10 preliminary layer, the inner cladding layer 20 preliminary layer, and the outer cladding 40 preliminary layer are the same as those in Embodiment 1 respectively.

Comparative example 2

The difference from Embodiment 1 is that the optical fiber preform does not include the concave platform layer 32 preliminary layer and the concave platform layer 33 preliminary layer. The prepared optical fiber includes a core layer 10, an inner cladding layer 20, and a deep concave layer 31 from the inside to the outside. and outer cladding 40. The core layer 10 preliminary layer, the inner cladding layer 20 preliminary layer, the deep recessed layer 31 preliminary layer, and the outer cladding 40 preliminary layer are the same as those in Embodiment 1 respectively.

Comparative example 3

The difference from Embodiment 1 is that the doping amount of the F element in the preliminary layer material of the deep recessed layer 31 in step (1) is changed so that the relative refractive index difference Δ3 of the deep recessed layer 31 material in the prepared optical fiber is - 0.55%. The materials of the core layer 10 preliminary layer, the inner cladding layer 20 preliminary layer, the recessed platform layer 32 preliminary layer, the depressed platform layer 33 preliminary layer and the outer cladding 40 preliminary layer are the same as those in Embodiment 1 respectively.

Parameters such as the radius and relative refractive index difference of each layer in the ultra-low loss large effective area optical fiber produced in all the above embodiments of the application are shown in Table 1, and the performance test results are shown in Table 2 and Table 3 respectively.

Table 1

Table 2

table 3

Comparative number 1 2 3 Mode field diameter@1550nm/μm 13.8 12.9 12.6 22m optical cable cut-off wavelength/nm 1580 1532 1544 Attenuation coefficient@1550nm, dB/km 0.192 0.178 0.173 Absolute value of the difference between Δα1520 and Δα1625, dB/km 0.015 0.013 0.011

From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects:

Comparing Example 1 and Comparative Examples 1 to 3, it can be seen that the optical fiber cable cut-off wavelength of the optical fiber prepared in Comparative Examples 1 to 3 is greater than 1520 nm, and the attenuation coefficient of the optical fiber prepared in Comparative Examples 1 to 3 is greater than that of Example 1. The absolute values of the differences between Δα1520 and Δα1625 are also larger than those in Example 1. It can be seen from this that by designing the recessed cladding 30 of the specific cladding structure of this application, the relative refractive index difference Δ1(r) of the core layer 10 material, the relative refractive index difference Δ2(r) of the inner cladding 20 material, and The changing rules of the relative refractive index difference Δ4(r) of the material of the recessed platform layer 32 and the relative refractive index difference Δ5(r) of the material of the recessed platform layer 33 respectively satisfy the above relational expressions (1) to (4) provided by this application. , and limiting the relative refractive index difference △3 of the material of the deep recessed layer 31 within the scope of the present application, it can effectively constrain the optical fiber waveguide transmission, improve the attenuation performance of the optical fiber, and make the optical fiber have high bending resistance and optical cables of no more than 1520nm. Cutoff wavelength.

Comparing Examples 1, 4 to 6, it can be seen that during the drawing annealing process, the compressive stress values from the core layer 10 to the inner cladding 20 were adjusted by changing the drawing tension and the drawing rate. Under the action of the drawing tension, the outer cladding remains stretched. The stress then acts on the inner cladding to form compressive stress. The compressive stress can prevent the expansion of micro-cracks and reduce Rayleigh scattering loss. However, excessive drawing tension will cause the radial stress variation from the inner cladding to the recessed cladding to increase, which is not conducive to the uniformity control of the attenuation coefficient. Moreover, the optical fiber cable cut-off wavelengths of the optical fibers prepared in Examples 1, 4 to 6 are all less than 1520 nm, and the attenuation coefficient at 1550 nm and the absolute value of the difference between Δα1520 and Δα1625 of the optical fiber prepared in Example 6 are respectively greater than those of Example 1 , 4 and 5. It can be seen from this that, compared with other ranges, limiting the drawing tension within the preferred range of this application is beneficial to controlling the radial stress change amplitude, which is beneficial to improving the transmission performance of the optical fiber, and is beneficial to reducing the stress of the optical fiber from the short wavelength range to the long wavelength range. The difference in segment attenuation coefficient is beneficial to improving the attenuation consistency of the optical fiber communication window.

Comparing Examples 1, 7 to 9, it can be seen that the compressive stress values from the core layer 10 to the inner cladding 20 of the optical fiber prepared in Example 9 are significantly greater than those in Examples 1, 7 and 8, which shows that the optical fiber prepared in Example 9 has Tension resistance is even worse. It can be seen from this that the compressive stress value in the range from the core layer 10 to the inner cladding layer 20 includes but is not limited to the scope of the present application. Limiting it within this range is beneficial to reducing the fiber attenuation of the optical fiber, and is also beneficial to improving the tension resistance of the optical fiber. Moreover, the attenuation coefficient at 1550 nm and the absolute value of the difference between Δα1520 and Δα1625 of the optical fiber produced in Example 9 are larger than those in Examples 1, 7 and 8 respectively. It can be seen from this that, compared with other ranges, the temperature T ₃ of the first annealing unit 210 , the temperature T ₄ of the second annealing unit 220 , the distance between two adjacent preheating components 110 in the cavity heating section 100 and The temperature of each component, the distance between two adjacent melting components 120 and the temperature of each component are limited to the preferred range of this application, which is conducive to further reducing the temperature difference between various parts of the optical fiber preform during the drawing process, and more This further reduces the stress difference in each part and further improves the attenuation consistency of the optical fiber's communication window.

It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It is to be understood that the terms so used are interchangeable under appropriate circumstances so that the embodiments of the application described herein can, for example, be practiced in sequences other than those described herein.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (19)

1. An ultra-low loss large effective area optical fiber, characterized in that the ultra-low loss large effective area optical fiber includes a core layer (10), an inner cladding layer (20), a recessed cladding layer (30) and a Outer cladding (40); the recessed cladding (30) includes a deep recessed layer (31), a recessed platform layer (32) and a recessed platform layer (33); the maximum relative refractive index difference of the material of the core layer (10) is Δ1 _max , the minimum relative refractive index difference of the inner cladding layer (20) material is Δ2 _min , and the relative refractive index difference of the deep recessed layer (31) material is Δ3; the recessed platform layer (32) The maximum relative refractive index difference of the material is △4 _max , and the minimum relative refractive index is △4 _min . The maximum relative refractive index difference of the material of the recessed platform layer (33) is △5 _max , and the minimum relative refractive index is △5 _min ; △3＜△2 _min , △3＜△4 _min , and △3＜△5 _min ; r represents the radial distance from a certain position in the ultra-low loss large effective area optical fiber to the center of the optical fiber; △1(r) represents the relative refractive index difference between a certain position in the core layer (10) and the material from the center of the optical fiber. The △1(r) and the r satisfy the following relationship (1): Wherein, R ₀ represents the radius of the core layer (10), g represents the refractive index distribution parameter of the core layer (10), 2≤g≤6; △2(r) represents the relative refractive index difference between a certain position in the inner cladding (20) and the material from the center of the optical fiber. The △2(r) and the r satisfy the following relationship (2): Wherein, R ₁ represents the radial distance between the contact interface between the inner cladding (20) and the recessed cladding (30) and the center of the optical fiber, h represents the refractive index distribution parameter of the inner cladding (20), 3 ≤h≤10; △4(r) represents the relative refractive index difference between a certain position in the recessed platform layer (32) and the material from the center of the optical fiber. The △4(r) and the r satisfy the following relationship (3): Wherein, R ₂ represents the radial distance between the contact interface between the deep recessed layer (31) and the recessed platform layer (32) and the center of the optical fiber, and R ₃ represents the radial distance between the recessed platform layer (32) and the recessed platform layer (32). The radial distance between the contact interface of the platform layer (33) and the center of the optical fiber, m represents the refractive index distribution parameter of the recessed platform layer (32), 0.5≤m≤3; △5(r) represents the relative refractive index difference between a certain position in the recessed platform layer (33) and the material from the center of the optical fiber. The △5(r) and the r satisfy the following relationship (4): Wherein, _R4 represents the radial distance between the contact interface between the recessed platform layer (33) and the outer cladding (40) and the center of the optical fiber, and n represents the refractive index distribution parameter of the recessed platform layer (33), 0.5≤n≤3; The outer cladding (40) is a silicon dioxide layer, and the refractive index of the outer cladding (40) is 0. 2. The ultra-low loss large effective area optical fiber according to claim 1, characterized in that the Δ1 _max is 0.10~0.30%, the Δ2 _min is -0.25~-0.35%, and the Δ3 is -0.45～-0.5%, the △4 _max is -0.20～-0.25%, the △4 _min is -0.25～-0.30%, the △5 _max is -0.30～-0.35%, the △5 _min is -0.35～-0.4%. 3. The ultra-low loss large effective area optical fiber according to claim 1, characterized in that the R ₀ is 5-7 μm; the difference between the R ₁ and the R ₀ is 3.5-5 μm, preferably the The ratio of R ₁ to R ₀ is (1.4-2.0):1; the difference between R ₄ and R ₁ is 30-40 μm, preferably the difference between R ₂ and R ₁ is 4.5 ~5.5 μm, preferably the difference between R ₃ and R ₂ is 6 ~ 18 μm, preferably the difference between R ₄ and R ₃ is 5.5 ~ 22 μm; the outer surface of the outer cladding (40) The radial distance R ₅ from the center of the optical fiber is 50 to 65 μm, preferably 62 to 63 μm. 4. The ultra-low loss large effective area optical fiber according to any one of claims 1 to 3, characterized in that the material of the core layer (10) is SiO ₂ doped with Ge element and F element, and the The material of the inner cladding layer (20) is _SiO2 doped with F element, and the material of the recessed cladding layer (30) is _SiO2 doped with F element. 5. The ultra-low loss large effective area optical fiber according to claim 4, characterized in that, in the ultra-low loss large effective area optical fiber, based on the total weight of the material accounting for the core layer (10), the Ge element The doping amount of F element is 1.0~4.0wt%, and the doping amount of F element is 0.01~0.3%; and/or, Based on the total weight of the material of the inner cladding layer (20), the doping amount of the F element is 0.01 to 1.0%; and/or, Based on the total weight of the material of the recessed cladding layer (30), the doping amount of the F element is 0.3 to 2.0 wt%. 6. The ultra-low loss large effective area optical fiber according to any one of claims 1 to 5, characterized in that the compressive stress from the core layer (10) to the inner cladding layer (20) is 40-100MPa; And/or, within the radial range from the recessed platform layer (32) to the recessed platform layer (33), the radial viscosity change amplitude is not greater than 2%/μm, and the stress difference is not greater than 20%. 7. The ultra-low loss large effective area optical fiber according to claim 6, characterized in that the outer surface of the outer cladding (40) is also coated with a first coating (51) and a second coating (52) in sequence. ), the elastic modulus of the first coating (51) is 0.3~0.5MPa, the elastic modulus of the second coating (52) is 500~1000MPa, and the outer surface of the second coating (52) The friction coefficient of the surface is 0.1~0.3. 8. The ultra-low loss large effective area optical fiber according to any one of claims 1 to 7, characterized in that the mode field diameter of the ultra-low loss large effective area optical fiber at a wavelength of 1550 nm is 12-13 μm, and the effective area is 12-13 μm. The area is 120~130μm ² ; and/or, The attenuation coefficient of the ultra-low loss large effective area optical fiber at the wavelength of 1550nm is ≤0.174dB/km; and/or, The difference between the minimum attenuation coefficients of the ultra-low loss large effective area optical fiber at 1520nm and in the wavelength range from 1520nm to 1625nm is △α1520, △α1520≤0.02dB/km, at 1625nm and in the wavelength range from 1520nm to 1625nm. The difference in the minimum attenuation coefficient is △α1625, △α1625≤0.02dB/km, and the absolute value of the difference between the △α1520 and the △α1625 is not greater than 0.009dB/km. 9. A method for preparing ultra-low loss large effective area optical fiber, characterized in that the preparation method includes: Preparing an optical fiber preform, which includes a core preparation layer, an inner cladding preparation layer, a recessed cladding preparation layer and an outer cladding preparation layer in order from the inside to the outside; The optical fiber preform is subjected to drawing annealing treatment, so that the core preparation layer, the inner cladding preparation layer, the recessed cladding preparation layer and the outer cladding preparation layer are sequentially transformed into the core in claim 1 layer (10), inner cladding (20), recessed cladding (30) and outer cladding (40), thereby obtaining the ultra-low loss large effective area optical fiber. 10. The preparation method of ultra-low loss large effective area optical fiber according to claim 9, characterized in that the material of the core layer preparation layer is SiO ₂ doped with Ge element and F element, and the inner cladding preparation layer The material is SiO ₂ doped with F element, and the material of the recessed cladding preparation layer is SiO ₂ doped with F element. 11. The preparation method of ultra-low loss large effective area optical fiber according to claim 10, characterized in that, based on the total weight of the material of the core layer preparation layer, the doping amount of the Ge element is 1.0 to 4.0 wt. %, the doping amount of F element is 0.01~0.3%; and/or, The doping amount of the F element is 0.01 to 1.0% based on the total weight of the material of the inner cladding preliminary layer; and/or, Based on the total weight of the material of the recessed cladding preliminary layer, the doping amount of the F element is 0.3 to 2.0 wt%. 12. The method for preparing ultra-low loss large effective area optical fiber according to any one of claims 9 to 11, characterized in that the drawing annealing treatment is carried out using an optical fiber drawing annealing device, and the optical fiber drawing annealing device includes: The inner cavity heating section (100) is used to heat the optical fiber preform; the inner cavity heating section (100) has an inner cavity, and according to the traveling direction of the optical fiber preform, the inner cavity has At least one preheating component (110) and at least one melting component (120) are arranged in sequence, and the preheating component (110) and the melting component (120) are independently arranged around the circumference of the inner cavity. direction and parallel to each other; Drawing annealing section (200), the drawing annealing section (200) includes a first annealing unit (210) and a second annealing unit (220), the first annealing unit (210), the second annealing unit (220) ) is coaxially arranged with the inner cavity heating section (100), and the first annealing unit (210), the second annealing unit (220) and the inner cavity heating section (100) are in the coaxial direction An annealing tube (300) is provided throughout, and the annealing tube (300) is used to penetrate the optical fiber; the second annealing unit (220) is provided with an optical fiber annealing tube outlet (220) at one end away from the first annealing unit (210). 301), and the temperature at the interface between the second annealing unit (220) and the first annealing unit (210) is higher than the temperature of the fiber annealing tube outlet (301); During the wire drawing annealing process, the temperature of the preheating component (110) is set to T ₁ , the temperature of the melting component (120) is set to T ₂ , and the T ₂ is 1800 to 2200°C. The temperature of the first annealing unit (210) is T ₃ , the temperature of the second annealing unit (220) is T ₄ , the T ₄ is 1150˜1250°C, and the T ₁ , the T ₂ , the T ₃ and T ₄ satisfy the following relationship: T ₂ >T ₃ >T _g >T ₁ >T ₄ , where T _g represents the glass transition temperature of the optical fiber preform; T ₃ and T _g The difference is 50~100℃. 13. The method for preparing ultra-low loss large effective area optical fiber according to claim 12, characterized in that the inner cavity heating section (100) includes two preheating components (110), and both are independent and/or, The inner cavity heating section (100) includes three melting parts (120), and the three melting parts (120) are independently arranged around the circumferential direction of the inner cavity and parallel to each other, and the temperatures of the three are predetermined along the optical fiber. The direction of travel of the pieces decreases in sequence. 14. The method for preparing ultra-low loss large effective area optical fiber according to claim 12, characterized in that the shortest distance between the preheating component (110) and the melting component (120) is 200~500mm, The length of the area where the annealing tube (300) is located in the first annealing unit (210) is 100-300 mm, and the length of the area where the annealing tube (300) is located in the second annealing unit (220) is 1000～2000mm. 15. The method for preparing ultra-low loss large effective area optical fiber according to claim 13, characterized in that when the inner cavity heating section (100) includes two preheating components (110), two adjacent ones The distance between them is 30~50mm; and/or, When the inner cavity heating section (100) includes three of the melting parts (120), the distance between two adjacent ones is 20 to 40 mm. 16. The preparation method of ultra-low loss large effective area optical fiber according to any one of claims 12 to 15, characterized in that, during the drawing annealing process, the drawing tension is 50 to 180g, and the drawing Tension and drawing rate satisfy the following relationship (5): Wherein, F(v) represents the corresponding drawing tension when the drawing rate is v, F ₀ represents the minimum drawing tension, and F ₁ represents the maximum drawing tension. The F (v), the F ₀ and the F ₁ The units are g, v ₂ represents the maximum wire drawing rate, the unit is 350~1200m/min, α represents the tension adjustment coefficient, and 0.5≤α≤4; Preferably, the drawing tension is monitored in real time using a non-contact tension testing device. 17. The method for preparing ultra-low loss large effective area optical fiber according to claim 16, characterized in that the optical fiber preform is cylindrical or rod-shaped, and the diameter of the optical fiber preform is 60 to 200 mm; Preferably, when the diameter of the optical fiber preform is 60-80mm, the drawing tension is 50-100g; when the diameter of the optical fiber preform is 120-150mm, the drawing tension is 90-130g; When the diameter of the optical fiber preform is 160-200mm, the drawing tension is 130-180g. 18. The method for preparing ultra-low loss large effective area optical fiber according to claim 16, characterized in that when the _Tg is 1360~1450°C, the _T1 is 1300~1350°C, and the _T2 The temperature is 1800-2000°C, the T ₃ is 1460-1500°C, the T ₄ is 1150-1250°C, and the drawing tension is 60-130g; When the _Tg is 1310~1350℃, the _T1 is 1260~1300℃, the _T2 is 1800~2000℃, the _T3 is 1360~1450℃, and the _T4 is 1150~1250 ℃, and the drawing tension is 50~120g; When the T _g is 1460 to 1550°C, the T ₁ is 1350 to 1450°C, the T ₂ is 1900 to 2200°C, the T ₃ is 1560 to 1650°C, and the T ₄ is 1150 to 1250 ℃, and the drawing tension is 80-180g. 19. The method for preparing an ultra-low loss large effective area optical fiber according to any one of claims 9 to 11, characterized in that, after the drawing annealing treatment, the method further includes sequentially performing a first coating treatment and a second coating. Processing, the first coating process and the second coating process are performed using a UV curing coating method.