WO2020181788A1

WO2020181788A1 - Method for manufacturing optical fiber preform based on sleeve method

Info

Publication number: WO2020181788A1
Application number: PCT/CN2019/114352
Authority: WO
Inventors: 莫思铭; 李凡; 眭立洪; 张国栋; 周莉; 李想
Original assignee: 江苏永鼎光纤科技有限公司
Priority date: 2019-03-11
Filing date: 2019-10-30
Publication date: 2020-09-17
Also published as: CN109942182B; CN109942182A

Abstract

Disclosed is a method for manufacturing an optical fiber preform based on a sleeve method, the method comprising the following steps: preparing an optical fiber mother core rod comprising a core layer and an inner cladding layer by using a VAD process, then heating and stretching the optical fiber mother core rod such that the curve degree of the stretched optical fiber core rod is less than 1 mm/m, then preparing a depressed layer by means of an OVD process, and finally, inserting the combined core rod into a quartz sleeve to form an optical fiber preform. The diameter of the prepared optical fiber preform may be up to 221 mm, the fiber pulling length of a single preform may be up to 2995 km, the attenuation coefficient of an optical fiber at a wavelength of 1310 nm is less than or equal to 0.305 dB/km, the attenuation coefficient of the optical fiber at a wavelength of 1383 nm is less than or equal to 0.275 dB/km, and the attenuation coefficient of the optical fiber at a wavelength of 1550 nm is less than or equal to 0.165 dB/km.

Description

Method for manufacturing optical fiber preform based on sleeve method

Technical field

The invention relates to a method for manufacturing an optical fiber preform based on a sleeve method, and belongs to the field of optical fiber preform manufacturing.

Background technique

At present, there are four main methods for producing optical fiber preforms: improved chemical vapor deposition (MCVD), microwave plasma chemical vapor deposition (PCVD), external vapor deposition (OVD) and axial vapor deposition (VAD), but only using the above method to manufacture large outer diameter optical fiber preforms has the following problems: In-tube deposition methods (MCVD and PCVD) are limited by the size of the liner tube, and it is impossible to directly manufacture large outer diameter optical fiber preforms. The deposition method (VAD and OVD) method directly manufactures mandrels with large outer diameters, and the cost is high, which cannot reflect the advantages of using the casing method to manufacture large-size preforms.

The tube method is to insert a core rod into a quartz tube to form an optical fiber preform. It is a better method for manufacturing large-size optical fiber preforms. However, when the tube method is used to prepare an optical fiber preform, strict control of the core rod and the tube is required. To ensure that the fiber has good core-wrap concentricity and optical performance, the fiber preform based on the tube method requires the bow and the uniformity of the diameter of the fiber core rod, and the current fiber preform prepared based on the tube method It is difficult to ensure the uniformity of bow and diameter of the core rod of the rod, resulting in large loss of the optical fiber preform prepared by the sleeve method.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for manufacturing an optical fiber preform based on the sleeve method to solve the technical problem that the core rod bow and diameter uniformity of the optical fiber preform prepared based on the sleeve method is difficult to ensure.

The technical solutions adopted by the present invention to solve its technical problems are:

A method for manufacturing an optical fiber preform based on the sleeve method, the steps are as follows:

Utilizing the VAD process to prepare the optical fiber core rod mother rod, the optical fiber core rod mother rod being a core layer and an inner cladding layer from the inside to the outside;

The fiber core rod mother rod is heated and stretched so that the bow of the fiber core rod after stretching is less than 1 mm/m; the stretching method is: the two ends of the fiber core rod mother rod are respectively connected to the drawing rod and Pull down the lead rod, and make the mother rod of the optical fiber core rod vertically pass through the drawing furnace, make the upper drawing lead rod and the lower drawing lead rod synchronously rotate at the same speed, and turn on the drawing furnace to set the mother rod of the optical fiber core rod. Heat from bottom to top and make the upper drawing rod move upward. The upward moving speed of the upper drawing rod depends on the required diameter of the mandrel after drawing, the speed at which the drawing furnace moves upward, and the fiber core of the drawn section The diameter of the rod mother rod is calculated in advance before stretching;

The OVD process is used to deposit the depressed layer loose body on the outside of the stretched optical fiber core rod, and then perform sintering treatment to obtain a synthetic core rod;

After the surface of the synthetic mandrel is corroded, cleaned and dried, it is inserted into the quartz sleeve to form an optical fiber preform.

Preferably, V ₁ =k×V ₂ ×V ₃ (D ₁ ² -D ₂ ² )/D ₁ ² is satisfied during the heating and drawing process of the mother rod of the optical fiber core rod, where V ₁ is the upper drawing rod Real-time moving speed, V ₂ is the rotation speed of the fiber core rod mother rod, V ₃ is the preset moving speed of the drawing furnace upwards, D ₁ is the diameter of the fiber core rod mother rod of the stretched section, D ₂ is the drawing after the required diameter of the mandrel, k is 0.1-0.15, V ₂ of 6-9mm / min, V ₃ of 30-40mm / min.

Preferably, the temperature at which the drawing furnace heats the mother rod of the optical fiber core rod is controlled at 1800-2300°C, and the heating area is filled with inert gas during heating.

Preferably, the sintering treatment method is as follows: pass inert gas and chlorine gas into the sintering furnace, first raise the sintering furnace to 1000-1200°C at a heating rate of 50-60°C/min, keep it for 2-3h, and then heat it for 20 The temperature rise rate of -30℃/min is increased to 1300-1500℃, and the temperature is kept for 5-6h.

Preferably, the sintered synthetic mandrel is heat-treated, and the heat treatment method is as follows: the synthetic mandrel, which has been kept at 1300-1500°C for 5-6h, is cooled to a temperature of <100°C with a coolant within 2 minutes, and then cooled The latter synthetic mandrel is heated to 600-800°C for 2 to 3 hours.

Preferably, the steps of using the VAD process to prepare the optical fiber core rod mother rod are: firstly deposit the powder core rod by the axial vapor deposition method, and then perform the dehydroxylation treatment, fluorine doping treatment and vitrification treatment on the powder core rod in the sintering furnace : During dehydroxylation treatment, pass Cl ₂ gas and inert gas into the sintering furnace, and the dehydroxylation temperature is 800-1000℃; during fluorine doping treatment, pass fluorine-containing gas and inert gas into the sintering furnace, and the sintering furnace temperature It is 1000～1300℃; during vitrification, only inert gas is introduced into the sintering furnace, and the glass transition temperature is 1400～1600℃.

Preferably, the core layer is a silica glass layer doped with P ₂ O ₅ , the relative refractive index Δn ₁ of the core layer is 0.35% to 0.5%, and the inner cladding layer and the depression layer are fluorine-doped silica For the glass layer, the relative refractive index Δn ₂ of the inner cladding layer is -0.05% to -0.01%, and the relative refractive index Δn ₃ of the depressed layer is -0.25% to -0.1%.

Preferably, the ratio b/a of the diameter b of the fiber core rod to the core diameter a after stretching is 3.0 to 5.0, and the ratio c/a of the diameter c of the composite core rod to the core diameter a is 7 to 9, and the optical fiber is prefabricated The ratio d/c of the effective diameter d of the rod to the diameter c of the composite core rod is 2.5 to 3.5.

The present invention also provides an optical fiber preform manufactured by the above method.

The present invention also provides an optical fiber, which is formed by drawing directly from the above-mentioned optical fiber preform, or formed by drawing after drawing.

The beneficial effects of the present invention are:

The present invention uses the VAD process to prepare an optical fiber core rod mother rod including a core layer and an inner cladding layer, and then heats and stretches the optical fiber core rod mother rod to make the bow of the optical fiber core rod less than 1 mm/m after drawing, and then passes through OVD The process prepares the sink layer, and finally inserts the synthetic core rod into the quartz sleeve to form an optical fiber preform, where:

(1) After the VAD process step, the fiber core rod mother rod is stretched vertically upwards. At the same time, the diameter of each position of the mother rod is scanned in advance to calculate the upper stretching guide during the stretching process. The upward moving speed of the rod controls the coaxiality of the mandrel after stretching and ensures the bow and diameter uniformity of the mandrel after stretching; further, after the powder mandrel is prepared by the VAD method, a reasonable The dehydroxylation, fluorine doping and vitrification process can not only effectively remove the hydroxyl groups, but also optimize the viscosity matching of the core and cladding, reduce the Rayleigh scattering of the drawn fiber, and achieve the purpose of low loss;

(2) The reasonable sintering process after the OVD process steps, plus the heat treatment of the sintered synthetic core rod, not only effectively removes the hydroxyl group, but also makes the sunken layer have a reasonable structure, which can effectively block the metal in the quartz sleeve Impurities and hydroxyls diffuse into the core layer, which effectively reduces the loss of the drawn fiber, and the diameter of the synthetic mandrel prepared by the OVD process is uniform, and finally the diameter of the synthetic mandrel can be accurately controlled, and the gap between the quartz sleeve and the synthetic mandrel can be reduced. Gap to reduce the concentricity error of the fiber core/package;

(3) The dopant, refractive index and diameter of the core layer, inner cladding layer and sink layer are reasonably limited, which can ensure the fiber length of the optical fiber preform and reduce the attenuation coefficient of the optical fiber. The quartz sleeve is used as the optical fiber preform. The outer cladding material can effectively reduce the manufacturing cost of optical fiber preform;

Finally, the diameter of the optical fiber preform prepared by the present invention can reach 221mm, the drawing length of a single preform can reach 2995km, the fiber attenuation at 1310nm wavelength is ≤0.305dB/km, and the attenuation coefficient at 1383nm wavelength is ≤0.275dB/km , The attenuation coefficient at 1550nm wavelength is ≤0.165dB/km.

detailed description

The present invention will now be described in further detail.

Example 1

This embodiment provides a method for manufacturing an optical fiber preform based on the sleeve method, and the steps are as follows:

The optical fiber core rod mother rod is prepared by the VAD process. The optical fiber core rod mother rod has a core layer and an inner cladding layer from the inside to the outside. The core layer is a silica glass layer doped with P ₂ O ₅ , and the core layer is The relative refractive index Δn ₁ is 0.35%, the inner cladding layer is a fluorine-doped silica glass layer, and the relative refractive index Δn ₂ of the inner cladding layer is -0.05%; the specific steps for preparing the optical fiber core rod mother rod are: first use the shaft The powder core rod is deposited by the vapor deposition method, and then the powder core rod is subjected to dehydroxylation treatment, fluorine doping treatment and vitrification treatment in the sintering furnace: during the dehydroxylation treatment, Cl ₂ gas and helium gas are passed into the sintering furnace, The dehydroxylation temperature is 800℃; during fluorine doping treatment, fluorine-containing gas and helium gas are introduced into the sintering furnace, and the temperature of the sintering furnace is 1000℃; during vitrification, only helium gas is introduced into the sintering furnace for vitrification The temperature is 1400℃;

The fiber core rod mother rod is heated and stretched so that the bow of the fiber core rod after stretching is less than 1mm/m, and the ratio b/a of the fiber core rod diameter b to the core layer diameter a after stretching is 3.0; The stretching method is as follows: connect the two ends of the optical fiber core rod mother rod to the upper and lower drawing lead rods respectively, and make the optical fiber core rod mother rod vertically pass through the drawing furnace, so that the upper drawing lead rod and The lower drawing rod rotates synchronously at the same speed, the drawing furnace is turned on to heat the fiber core rod mother rod from bottom to top, and the upper drawing rod is moved upward, and the upward moving speed of the upper drawing rod is according to After stretching, the required diameter of the core rod, the upward moving speed of the stretching furnace, and the diameter of the fiber core rod mother rod of the stretched section are calculated in advance before stretching. During the heating and stretching process of the optical fiber core rod mother rod, V ₁ = k×V ₂ ×V ₃ (D ₁ ² -D ₂ ² )/D ₁ ² , where V ₁ is the real-time moving speed of the upper drawing rod, and V ₂ is the rotation speed of the optical fiber core rod mother rod, V ₃ is the preset upward moving speed of the stretching furnace, D ₁ is the diameter of the fiber core rod mother rod of the stretched section, and D ₂ is the required diameter of the core rod after stretching, the k is 0.1, the V ₂ is 9 mm/min, the V ₃ is 30 mm/min, the temperature at which the drawing furnace heats the optical fiber core rod mother rod is controlled at 1800°C, and helium is filled in the heating area during heating;

The depressed layer loose body is deposited on the outside of the stretched fiber core rod by the OVD process, and then sintering and heat treatment are sequentially performed to obtain a synthetic core rod. The depressed layer is a fluorine-doped silica glass layer, and the relative refraction of the depressed layer The ratio Δn ₃ is -0.25%, and the ratio c/a of the diameter c of the synthetic core rod to the diameter a of the core layer is 7; the sintering method is: inert gas and chlorine gas are introduced into the sintering furnace, and the sintering furnace is first The heating rate of 50°C/min is increased to 1000°C and the temperature is kept for 3 hours, and then the temperature rise rate of 20°C/min is raised to 1300°C and the temperature is kept for 6 hours; the heat treatment method is: the synthetic mandrel is heated at 1300°C for 6 hours Use cooling liquid to cool to a temperature of <100°C within 2 minutes, and then heat the cooled synthetic mandrel to 600°C for 3 hours;

The surface of the synthetic mandrel is etched with a mixture of hydrofluoric acid and nitric acid at a molar ratio of 1:1, and the corrosion depth is not less than 0.6mm. Then the corroded synthetic mandrel is cleaned and dried, and then the synthetic mandrel is inserted into the quartz sleeve The tube is assembled into an optical fiber preform, and the ratio d/c of the effective diameter d of the optical fiber preform to the composite core rod diameter c is 2.5.

After testing, the diameter of the optical fiber preform reaches 203mm, and the prepared optical fiber preform is drawn on-line. The length of a single rod can reach 2865km. After drawing, the fiber attenuation at 1310nm is 0.302dB/km, and the attenuation at 1383nm It is 0.271dB/km, and the attenuation at 1550nm is 0.163dB/km.

Example 2

The optical fiber core rod mother rod is prepared by the VAD process. The optical fiber core rod mother rod has a core layer and an inner cladding layer from the inside to the outside. The core layer is a silica glass layer doped with P ₂ O ₅ , and the core layer is The relative refractive index Δn ₁ is 0.5%, the inner cladding layer is a fluorine-doped silica glass layer, and the relative refractive index Δn ₂ of the inner cladding layer is -0.01%; the specific steps for preparing the optical fiber core rod mother rod are: The powder core rod is deposited by the vapor deposition method, and then the powder core rod is subjected to dehydroxylation treatment, fluorine doping treatment and vitrification treatment in the sintering furnace: during the dehydroxylation treatment, Cl ₂ gas and helium gas are passed into the sintering furnace, The dehydroxylation temperature is 1000°C; during fluorine doping treatment, fluorine-containing gas and helium gas are passed into the sintering furnace, and the temperature of the sintering furnace is 1300°C; during vitrification, only helium gas is passed into the sintering furnace to vitrify The temperature is 1600℃;

The fiber core rod mother rod is heated and stretched so that the bow of the fiber core rod after stretching is less than 1 mm/m, and the ratio b/a of the fiber core rod diameter b to the core layer diameter a after stretching is 5.0; The stretching method is as follows: connect the two ends of the optical fiber core rod mother rod to the upper and lower drawing lead rods respectively, and make the optical fiber core rod mother rod vertically pass through the drawing furnace, so that the upper drawing lead rod and The lower drawing rod rotates synchronously at the same speed, the drawing furnace is turned on to heat the fiber core rod mother rod from bottom to top, and the upper drawing rod is moved upward, and the upward moving speed of the upper drawing rod is according to After stretching, the required diameter of the core rod, the upward moving speed of the stretching furnace, and the diameter of the fiber core rod mother rod of the stretched section are calculated in advance before stretching. During the heating and stretching process of the optical fiber core rod mother rod, V ₁ = k×V ₂ ×V ₃ (D ₁ ² -D ₂ ² )/D ₁ ² , where V ₁ is the real-time moving speed of the upper drawing rod, and V ₂ is the rotation speed of the optical fiber core rod mother rod, V ₃ is the preset upward moving speed of the stretching furnace, D ₁ is the diameter of the fiber core rod mother rod of the stretched section, and D ₂ is the required diameter of the core rod after stretching, the k is 0.15, the V ₂ is 6 mm/min, and the V ₃ is 40 mm/min. The temperature of the fiber core rod mother rod heated by the drawing furnace is controlled at 2300°C, and helium is filled in the heating area during heating;

The depressed layer loose body is deposited on the outside of the stretched fiber core rod by the OVD process, and then sintering and heat treatment are sequentially performed to obtain a synthetic core rod. The depressed layer is a fluorine-doped silica glass layer, and the relative refraction of the depressed layer The rate Δn ₃ is -0.1%, and the ratio c/a of the diameter c of the synthetic core rod to the diameter a of the core layer is 9; the sintering method is: inert gas and chlorine gas are introduced into the sintering furnace, and the sintering furnace is first The temperature rise rate of 60°C/min is increased to 1200°C and the temperature is kept for 2 hours, and then the temperature rise rate is 30°C/min to 1500°C and the temperature is kept for 5 hours; the heat treatment method is: the synthetic core rod after being kept at 1500°C for 5 hours Use cooling liquid to cool to a temperature of <100°C within 2 minutes, and then heat the cooled synthetic mandrel to 800°C for 2 hours;

The surface of the synthetic mandrel is etched with a mixture of hydrofluoric acid and nitric acid at a molar ratio of 1:1, and the corrosion depth is not less than 0.6mm. Then the corroded synthetic mandrel is cleaned and dried, and then the synthetic mandrel is inserted into the quartz sleeve In the tube, the optical fiber preform is assembled, and the ratio d/c of the effective diameter d of the optical fiber preform to the composite core rod diameter c is 3.5.

After testing, the diameter of the optical fiber preform reaches 221mm. The prepared optical fiber preform is drawn into the optical fiber online. The length of a single rod can reach 2995km. After the drawing, the fiber attenuation at 1310nm is 0.305dB/km, and the attenuation at 1383nm. It is 0.275dB/km, and the attenuation at 1550nm is 0.165dB/km.

Example 3

The optical fiber core rod mother rod is prepared by the VAD process. The optical fiber core rod mother rod has a core layer and an inner cladding layer from the inside to the outside. The core layer is a silica glass layer doped with P ₂ O ₅ , and the core layer is The relative refractive index Δn ₁ is 0.4%, the inner cladding layer is a fluorine-doped silica glass layer, and the relative refractive index Δn ₂ of the inner cladding layer is -0.08%; the specific steps for preparing the optical fiber core rod mother rod are: The powder core rod is deposited by the vapor deposition method, and then the powder core rod is subjected to dehydroxylation treatment, fluorine doping treatment and vitrification treatment in the sintering furnace: during the dehydroxylation treatment, Cl ₂ gas and helium gas are passed into the sintering furnace, The dehydroxylation temperature is 900°C; during fluorine doping treatment, fluorine-containing gas and helium gas are passed into the sintering furnace, and the temperature of the sintering furnace is 1100°C; during vitrification, only helium gas is passed into the sintering furnace to vitrify The temperature is 1500℃;

The fiber core rod mother rod is heated and stretched so that the bow of the fiber core rod after stretching is less than 1mm/m, and the ratio b/a of the fiber core rod diameter b to the core layer diameter a after stretching is 4.0; The stretching method is as follows: connect the two ends of the optical fiber core rod mother rod to the upper and lower drawing lead rods respectively, and make the optical fiber core rod mother rod vertically pass through the drawing furnace, so that the upper drawing lead rod and The lower drawing rod rotates synchronously at the same speed, the drawing furnace is turned on to heat the fiber core rod mother rod from bottom to top, and the upper drawing rod is moved upward, and the upward moving speed of the upper drawing rod is according to After stretching, the required diameter of the core rod, the upward moving speed of the stretching furnace, and the diameter of the fiber core rod mother rod of the stretched section are calculated in advance before stretching. During the heating and stretching process of the optical fiber core rod mother rod, V ₁ = k×V ₂ ×V ₃ (D ₁ ² -D ₂ ² )/D ₁ ² , where V ₁ is the real-time moving speed of the upper drawing rod, and V ₂ is the rotation speed of the optical fiber core rod mother rod, V ₃ is the preset moving speed of the stretching furnace upward, D ₁ is the diameter of the fiber core rod mother rod of the stretched section, D ₂ is the required diameter of the core rod after stretching, the k is 0.12, the V ₂ is 8 mm/min, the V ₃ is 35 mm/min, the temperature at which the drawing furnace heats the optical fiber core rod mother rod is controlled at 2000° C., and helium is filled in the heating area during heating;

The depressed layer loose body is deposited on the outside of the stretched fiber core rod by the OVD process, and then sintering and heat treatment are sequentially performed to obtain a synthetic core rod. The depressed layer is a fluorine-doped silica glass layer, and the relative refraction of the depressed layer The ratio Δn ₃ is -0.2%, and the ratio c/a of the diameter c of the synthetic core rod to the diameter a of the core layer is 8; the sintering method is: inert gas and chlorine gas are introduced into the sintering furnace, and the sintering furnace is first The temperature rise rate of 55°C/min is increased to 1100°C and the temperature is kept for 2h, and then the temperature rise rate is 25°C/min to 1400°C and the temperature is kept for 5.5h; the heat treatment method is: the synthesis after being kept at 1400°C for 5.5h The core rod is cooled to a temperature of <100°C with the cooling liquid within 2 minutes, and then the cooled synthetic core rod is heated to 700°C for 2.5 hours;

The surface of the synthetic mandrel is etched with a mixture of hydrofluoric acid and nitric acid at a molar ratio of 1:1, and the corrosion depth is not less than 0.6mm. Then the corroded synthetic mandrel is cleaned and dried, and then the synthetic mandrel is inserted into the quartz sleeve The tube is assembled into an optical fiber preform, and the ratio d/c of the effective diameter d of the optical fiber preform to the composite core rod diameter c is 3.

After testing, the diameter of the optical fiber preform reaches 215mm, and the prepared optical fiber preform is drawn on-line. The length of a single rod can reach 2905km. After drawing, the fiber attenuation at 1310nm is 0.303dB/km, and the attenuation at 1383nm It is 0.273dB/km, and the attenuation at 1550nm is 0.160dB/km.

Taking the above-mentioned ideal embodiment according to the present invention as enlightenment, through the above-mentioned description content, relevant workers can make various changes and modifications without departing from the scope of the technical idea of the present invention. The technical scope of the present invention is not limited to the content of the description, and its technical scope must be determined according to the scope of the claims.

Claims

A method for manufacturing an optical fiber preform based on a ferrule method is characterized in that the steps are as follows: the optical fiber core rod mother rod is prepared by a VAD process, and the optical fiber core rod mother rod is a core layer and an inner cladding layer from the inside to the outside;

The fiber core rod mother rod is heated and stretched so that the bow of the fiber core rod after stretching is less than 1 mm/m; the stretching method is: the two ends of the fiber core rod mother rod are respectively connected to the drawing rod and Pull down the lead rod, and make the mother rod of the optical fiber core rod vertically pass through the drawing furnace, make the upper drawing lead rod and the lower drawing lead rod synchronously rotate at the same speed, and turn on the drawing furnace to set the mother rod of the optical fiber core rod. Heat from bottom to top and make the upper drawing rod move upward. The upward moving speed of the upper drawing rod depends on the required diameter of the mandrel after drawing, the speed at which the drawing furnace moves upward, and the fiber core of the drawn section The diameter of the rod mother rod is calculated in advance before stretching;

The OVD process is used to deposit the depressed layer loose body on the outside of the stretched optical fiber core rod, and then perform sintering treatment to obtain a synthetic core rod;

After the surface of the synthetic mandrel is corroded, cleaned and dried, it is inserted into the quartz sleeve to form an optical fiber preform.
The method for manufacturing an optical fiber preform based on the ferrule method according to claim 1, characterized in that, during the heating and drawing process of the mother rod of the optical fiber core rod, it satisfies V 1 =k×V 2 ×V 3 (D 1 2 -D 2 2 )/D 1 2 , where V 1 is the real-time moving speed of the upper drawing rod, V 2 is the rotation speed of the optical fiber core rod mother rod, V 3 is the preset moving speed of the drawing furnace up, D 1 is the diameter of the fiber core rod mother rod of the stretched section, D 2 is the required diameter of the core rod after stretching, k is 0.1-0.15, V 2 is 6-9mm/min, V 3 is 30-40mm/min .
The method for manufacturing an optical fiber preform based on the ferrule method according to claim 1 or 2, wherein the temperature at which the drawing furnace heats the optical fiber core rod mother rod is controlled at 1800-2300°C, and the heating area is filled during heating. Inert gas.
The method for manufacturing an optical fiber preform based on the ferrule method according to any one of claims 1-3, wherein the sintering treatment method is: inert gas and chlorine gas are introduced into the sintering furnace, and the sintering furnace is first The temperature rise rate of 50-60°C/min is increased to 1000-1200°C and the temperature is kept for 2-3 hours, and then the temperature rise rate is 20-30°C/min to 1300-1500°C and the temperature is kept for 5-6 hours.
The method for manufacturing an optical fiber preform based on the sleeve method according to any one of claims 1 to 4, wherein the sintered synthetic core rod is heat treated, and the heat treatment method is: heat preservation at 1300-1500°C The synthetic core rod after 5-6h is cooled to a temperature of <100°C within 2 minutes with a cooling liquid, and then the cooled synthetic core rod is heated to 600-800°C for 2 to 3 hours.
The method for manufacturing an optical fiber preform based on the sleeve method according to any one of claims 1 to 5, wherein the step of preparing the optical fiber core rod mother rod by the VAD process is: firstly depositing the powder core by the axial vapor deposition method Then, the powder core rod is subjected to dehydroxylation treatment, fluorine doping treatment and vitrification treatment in the sintering furnace: during the dehydroxylation treatment, pass Cl 2 gas and inert gas into the sintering furnace, and the dehydroxylation temperature is 800～1000 ℃; during fluorine doping treatment, fluorine-containing gas and inert gas are introduced into the sintering furnace, the temperature of the sintering furnace is 1000～1300℃; during vitrification, only inert gas is introduced into the sintering furnace, and the glass transition temperature is 1400 ～1600℃.
The method for manufacturing an optical fiber preform based on the sleeve method according to any one of claims 1-6, wherein the core layer is a silica glass layer doped with P 2 O 5 , and the relative refraction of the core layer is The rate Δn 1 is 0.35% to 0.5%, the inner cladding layer and the sink layer are fluorine-doped silica glass layers, the relative refractive index of the inner cladding layer Δn 2 is -0.05% to -0.01%, and the relative refractive index of the sink layer Δn 3 is -0.25% to -0.1%.
The method for manufacturing an optical fiber preform based on the ferrule method according to any one of claims 1-7, wherein the ratio b/a of the diameter b of the optical fiber core rod to the core diameter a after stretching is 3.0-5.0 , The ratio c/a of the diameter c of the composite core rod to the diameter a of the core layer is 7-9, and the ratio d/c of the effective diameter d of the optical fiber preform to the diameter c of the composite core rod is 2.5-3.5.
An optical fiber preform manufactured by the method of any one of claims 1-8.
An optical fiber, characterized in that the optical fiber is formed by directly drawing the optical fiber preform according to claim 9, or drawing after drawing.