WO2020248553A1

WO2020248553A1 - Optical fiber preform and method for fabricating ultra-low attenuation optical fiber, and optical fiber

Info

Publication number: WO2020248553A1
Application number: PCT/CN2019/124974
Authority: WO
Inventors: 罗文勇; 喻煌; 戚卫; 余志强; 伍淑坚; 柯一礼; 杜城; 朱侨; 曾凡球
Original assignee: 烽火通信科技股份有限公司; 锐光信通科技有限公司; 烽火藤仓光纤科技有限公司
Priority date: 2019-06-12
Filing date: 2019-12-13
Publication date: 2020-12-17
Also published as: BR112021008406A2; CN110357410B; MX2021006383A; CN110357410A; RU2768315C1

Abstract

Disclosed are an optical fiber preform and method used for fabricating an ultra-low attenuation optical fiber, and an optical fiber. The optical fiber preform comprises a core rod and a sleeve sleeved on the outside of the core rod; the core rod comprises a potassium-doped core layer and a potassium-fluorine co-doped core layer successively arranged from the inside to the outside; the sleeve comprises an inner sleeve and an outer sleeve successively arranged from the inside to the outside; the inner sleeve comprises a deep fluorine-doped layer and a shallow fluorine-doped layer successively arranged from the inside to the outside; and a gap between the core rod and the inner sleeve forms a first space. The present invention is capable of solving attenuation caused by high interface stress against an ultra-low attenuation optical fiber, and fabricating the ultra-low attenuation optical fiber.

Description

Optical fiber preform, method and optical fiber for manufacturing ultra-low attenuation optical fiber

Technical field

The invention relates to the technical field of optical fiber preforms, in particular to an optical fiber preform used for manufacturing ultra-low attenuation optical fibers, a method and an optical fiber.

Background technique

With the explosive growth of global informatization, the data traffic of communication systems has grown rapidly at a compound annual growth rate of 50% to 80% in recent years, which requires optical communication technology to develop in the direction of ultra-large capacity, ultra-long distance, and ultra-high speed. Optical communication technology is the physical basic layer of information communication, providing support for the entire mobile Internet, big data and other application layers. It is an indispensable basic field for the development of my country's 13th Five-Year Plan. It is under this background that the nerve of optical communication-the high-end manufacturing technology and industrialization of optical fiber is particularly important. With the development of high-speed communication technology, 100G technology has matured, 400G technology is rapidly commercialized, and traditional single-mode optical fiber media are increasingly unable to meet the requirements of high-speed communication.

Ultra-low attenuation optical fiber technology is the core basic material for large-capacity transmission and long-distance transmission systems. The core of the development of ultra-low attenuation fiber is to reduce the scattering loss in the fiber. Therefore, the ultra-low attenuation fiber is usually designed with a pure silica core. In order to form a fully reflective waveguide structure, when the core is a pure silicon core, the cladding material It cannot be a traditional pure silicon core material, so it is necessary to deposit a low refractive index material around the pure silica core, which is usually doped with fluorine to form the cladding. The quartz cladding is doped with fluorine in quartz glass to refract The rate is reduced, so compared with the core area of a pure silicon core, it can constitute a total reflection condition. However, when quartz glass is doped with fluorine, its viscosity will decrease, and the viscosity of the core and cladding is different at high temperatures. The manufacturing process of optical fibers is to first manufacture light rods and then melt and draw them into optical fibers at high temperature. In the process of manufacturing the light rod, both the core material and the cladding material go through a process of higher temperature melting and low temperature solidification. In this way, if the viscosity difference between the core layer and the cladding layer is large, during the manufacturing process, due to the mismatch of the viscosity, the thermal expansion and contraction in the high and low temperature are not matched during the manufacturing process, which will cause the difference between the core layer and the cladding layer. Therefore, there is a greater stress. These stresses act on the core layer and will cause the loss of light passing through the core layer to increase significantly.

Therefore, in the development of ultra-low attenuation optical fiber technology, the technology of reducing the core-package interface stress is a core technology.

When manufacturing ultra-low attenuation optical fibers in the industry, the core area is doped with potassium to reduce the viscosity, and at the same time, materials that do not bring too much additional absorption loss in the communication band, so as to achieve the viscosity matching of the core and cladding. However, with this method, there are still problems such as the viscosity imbalance caused by the diffusion of the potassium-doped interface and the fluorine-doped interface, and the stress interference between the fluorine-doped interface and the external pure silica interface, which causes the attenuation of the optical fiber to still not reach the ideal value.

Summary of the invention

In view of the defects in the prior art, the purpose of the present invention is to provide an optical fiber preform, method and optical fiber for manufacturing ultra-low attenuation optical fiber, which can solve the attenuation caused by the high interface stress faced by the ultra-low attenuation optical fiber, and achieve ultra-low attenuation fiber. Manufacturing of low-attenuation fiber.

In order to achieve the above objective, the technical solution adopted by the present invention is: an optical fiber preform for manufacturing ultra-low attenuation optical fiber, which includes a core rod and a sleeve sleeved outside the core rod;

The core rod includes a potassium-doped core layer and a potassium-fluorine co-doped core layer arranged sequentially from the inside to the outside;

The sleeve includes an inner sleeve and an outer sleeve arranged in sequence from the inside to the outside, and the inner sleeve includes a deep fluorine doped layer and a shallow fluorine doped layer arranged in sequence from the inside to the outside;

The gap between the core rod and the inner sleeve forms a first space.

Further, the optical fiber preform further includes a tail tube, and the tail tube includes:

Closed loop

A tail rod, one end of which is connected to the core rod and the other end to the closed ring;

The inner tail pipe is sleeved outside the tail rod, one end of the inner tail pipe is connected to the sleeve, and the other end is connected to the closed ring; at the same time,

The gap between the closed ring, the tail rod, and the inner tail pipe and the first space together form a first section, and the closed ring is provided with an inner suction hole communicating with the first section.

Further, the gap between the inner sleeve and the outer sleeve forms a second space.

Closed loop

An inner tail pipe sleeved outside the tail rod, one end of the inner tail pipe is connected to the inner sleeve, and the other end is connected to the closed ring;

The outer tail pipe is sleeved outside the inner tail pipe, one end of the outer tail pipe is connected to the outer sleeve, and the other end is connected to the closed ring; at the same time,

The gap between the closed ring, the tail rod, and the inner tail pipe and the first space jointly form a first section, and the closed ring is provided with an inner suction hole communicating with the first section;

The gap between the closed ring, the inner tail pipe, and the outer tail pipe and the second space together form a second section, and the closed ring is also provided with an outer exhaust hole communicating with the second section.

The present invention also provides a method for manufacturing an ultra-low attenuation optical fiber using the optical fiber preform as described above, which includes the following steps:

Provide drawing tower;

Fixing the optical fiber preform on the drawing tower;

The vacuum degree in the first space is adjusted to a first preset vacuum degree, and the optical fiber is drawn.

Closed loop

The method further includes: pumping air outward through the inner air extraction hole to adjust the vacuum degree in the first space to the first preset vacuum degree.

Provide drawing tower;

Fixing the optical fiber preform on the drawing tower;

Adjust the vacuum degree in the first space to a first preset vacuum degree, adjust the vacuum degree in the second space to a second preset vacuum degree, and perform fiber drawing, the second preset vacuum degree Less than the first preset vacuum degree.

Closed loop

The gap between the closed ring, the inner tail pipe, and the outer tail pipe and the second space together form a second section, and the closed ring is also provided with an outer exhaust hole communicating with the second section;

The method further includes: pumping air outward through the inner air extraction hole to adjust the vacuum degree in the first space to the first preset vacuum degree, and pumping air outward through the outer air extraction hole to adjust the vacuum. The vacuum degree in the second space reaches a second preset vacuum degree.

Further, the drawing tower includes:

A preheating heating element for preheating the optical fiber preform, and the preheating heating element has a preheating area for accommodating the optical fiber preform;

The fusion heating element is used to fuse the preheated optical fiber preform into a solid rod and form an ultra-low attenuation optical fiber, and the fusion heating element has a heat sink for accommodating the preheated optical fiber preform A melting zone, the melting zone is located below the preheating zone;

The heat preservation heating element is used to cool the ultra-low attenuation optical fiber at a first preset temperature to remove melting stress. The heat preservation heating element has a heat preservation area for accommodating the ultra-low attenuation optical fiber. The heat preservation zone is located below the melting zone;

The annealing furnace is used to anneal the ultra-low attenuation optical fiber from which the melting stress has been removed at a second preset temperature to remove interfacial stress, and the annealing furnace has an annealing furnace for accommodating the ultra-low attenuation optical fiber Zone, the annealing zone is located below the heat preservation zone;

A temperature detector is used to detect the temperature at which the ultra-low attenuation optical fiber after the melting stress has been removed enters and leaves the annealing furnace.

The present invention also provides an ultra-low attenuation optical fiber manufactured by using the optical fiber preform as described above, which includes a core layer and a cladding layer sheathed outside the core layer;

The core layer includes a potassium-doped core region and a potassium-fluorine co-doped core region arranged sequentially from the inside to the outside;

The cladding layer includes a deep fluorine-doped area, a shallow fluorine-doped area and a quartz area arranged in order from the inside to the outside;

At a working wavelength of 1550 nm, the attenuation of the ultra-low attenuation optical fiber is less than 0.150 dB/km.

Compared with the prior art, the advantages of the present invention are:

The present invention is based on the principle of viscosity matching to reduce the interfacial stress, and proposes the concept of combining a multi-layer core rod and a multi-layer sleeve. A potassium-fluorine co-doped core layer is arranged outside the potassium-doped core layer, and the inner sleeve is gradually transitioned. The inner layer of the tube is matched with a deep fluorine-doped layer to reduce the imbalance of the interface viscosity caused by the diffusion of the easily diffused fluorine ions to the core layer. At the same time, the outer layer of the inner sleeve gradually reduces the amount of fluorine doped to form The shallow fluorine-doped layer reduces the stress between the inner casing and the outer casing.

The end of the optical fiber preform of the present invention is equipped with a combined tail tube, so that the core rod and the inner sleeve, the inner sleeve and the outer sleeve can achieve good solid melting during the optical fiber drawing, and the first space during the optical fiber drawing The second space and the second space are separately evacuated to control the degree of vacuum, so as to achieve good solid melting of the core rod and the sleeve, the inner sleeve and the outer sleeve when the optical fiber is drawn.

Description of the drawings

Fig. 1 is a schematic diagram of an end face structure of an optical fiber preform provided by an embodiment of the present invention;

Figure 2 is a schematic diagram of drawing the optical fiber preform in Figure 1;

3 is a schematic diagram of the end face structure of an optical fiber preform provided by another embodiment of the present invention;

4 is a schematic diagram of drawing the optical fiber preform in FIG. 3;

Fig. 5 is a schematic diagram of an end face structure of an ultra-low attenuation optical fiber provided by an embodiment of the present invention.

In the figure: A, the first space; B, the second space; C, the first interval; D, the second interval; 1. the core rod; 10. the potassium-doped core layer; 11. the potassium-fluorine co-doped core layer; 2. Casing; 20. Inner casing; 200. Deep fluorine-doped layer; 201. Shallow fluorine-doped layer; 21. Outer tube; 3. Tail tube; 30. Closed ring; 31. Tail rod; 32. Inner tail tube; 33. Outer tail pipe; 34. Inner suction hole; 35. Outer suction hole; 4. Core layer; 40. Potassium-doped core area; 41. Potassium-fluorine co-doped core area; 5. Cladding; 50. Deep fluorine doped area; 51 , Shallow doped fluorine zone; 52, quartz zone; 6, drawing tower; 60, preheating heating element; 600, preheating zone; 61, melting heating element; 610, melting zone; 62, thermal insulation heating element; 620, thermal insulation zone ; 63. Annealing furnace; 630. Annealing zone; 64. Upper temperature detector; 65. Lower temperature detector; 7. Ultra-low attenuation fiber.

Detailed ways

The present invention will be further described in detail below in conjunction with the drawings and embodiments.

The manufacturing technology of optical fiber can be divided into manufacturing technology of optical fiber preform and drawing technology of drawing optical fiber preform into optical fiber. Common optical fiber preform manufacturing technologies include PCVD (Plasma activated Chemical Vapor Deposition), MCVD (Modified Chemical Vapor Deposition), and VAD (Vapour phase Axial Deposition). Vapor deposition method), OVD (Outside Chemical Vapor Deposition, external chemical vapor deposition method) and other process methods. The above method usually requires the manufacture of the optical fiber core rod first, and then the manufacture of the fiber optic ferrule, and then the core rod and the ferrule are combined to form a finished fiber preform, and finally the fiber optic preform is placed on the drawing tower and drawn Make an optical fiber.

The invention adopts the PCVD or MCVD process to prepare the core rod, the PCVD process to prepare the inner sleeve, and the OVD process or other processes to prepare the outer sleeve.

As shown in Fig. 1, the first embodiment of the present invention provides an optical fiber preform for manufacturing ultra-low attenuation optical fibers. The optical fiber preform includes a core rod 1 and a sleeve 2 sheathed outside the core rod 1; The rod 1 includes a potassium-doped core layer 10 and a potassium-fluorine co-doped core layer 11 arranged in sequence from the inside to the outside; the sleeve 2 includes an inner sleeve 20 and an outer sleeve 21 arranged in sequence from the inside to the outside, and the outer sleeve 21 is made of pure quartz The inner sleeve 20 includes a deep fluorine-doped layer 200 and a shallow fluorine-doped layer 201 arranged in sequence from the inside to the outside; the gap between the core rod 1 and the inner sleeve 20 forms a first space A.

The present invention is based on the principle of viscosity matching to reduce the interfacial stress, and proposes the concept of combining a multi-layer core rod and a multi-layer sleeve. A potassium-fluorine co-doped core layer 11 is arranged outside the potassium-doped core layer 10, and through a gradual transition, The inner layer of the inner sleeve 20 is matched with a deep fluorine-doped layer 200 to reduce the imbalance of the interface viscosity caused by the diffusion of the easily diffused fluoride ions to the core layer. At the same time, the outer layer of the inner sleeve 20 will be doped with fluorine. The amount is gradually reduced to form a shallow fluorine-doped layer 201, thereby reducing the stress between the inner sleeve 20 and the outer sleeve 21.

In the present invention, the core rod 1 and the sleeve 2 can be directly placed on the drawing tower for wire drawing, and the core rod 1 and the sleeve 2 can be uniformly fused by adjusting the vacuum degree of the first space A. The core rod 1 and the sleeve 2 are preheated by the preheating heating element in the drawing tower, and then melted by the melting heating element, and then slowly annealed by the heat preservation heating element, and then under cold air conditions outside the high temperature furnace, Normal annealing is carried out in the annealing furnace to fully eliminate the closing stress between the mandrel 1 and the sleeve 2.

As shown in Figure 2, the optical fiber preform also includes a tail tube 3. The tail tube 3 includes a closed ring 30, a tail rod 31, and an inner tail tube 32; one end of the tail rod 31 is connected to the mandrel 1, and the other end is connected to the closed ring 30; the inner tail tube 32 It is sleeved outside the tail rod 31, one end of the inner tail tube 32 is connected to the sleeve 2, and the other end is connected to the closed ring 30; at the same time, the gap between the closed ring 30, the tail rod 31 and the inner tail tube 32 and the first space A together form a first In section C, the closed ring 30 is provided with an inner suction hole 34 communicating with the first section C.

The end of the optical fiber preform of the present invention is equipped with a combined tail tube 3, so that the core rod 1 and the sleeve 2 can achieve good solid melting during the fiber drawing, the first space A (or the first In section C), air is pumped to control the degree of vacuum, so as to achieve good solid melting of the core rod 1 and the sleeve 2 when the optical fiber is drawn.

The second embodiment of the present invention provides a method for manufacturing an ultra-low attenuation optical fiber using an optical fiber preform, which includes the following steps:

S1: Provide drawing tower 6;

S2: Fix the optical fiber preform on the drawing tower 6;

S3: Exhaust air through the inner air extraction hole 34 to adjust the vacuum degree in the first space A to a first preset vacuum degree, and perform fiber drawing.

Referring to Fig. 3, the third embodiment of the present invention provides an optical fiber preform for manufacturing ultra-low attenuation optical fiber. The optical fiber preform includes a core rod 1 and a sleeve 2 sheathed outside the core rod 1; The rod 1 includes a potassium-doped core layer 10 and a potassium-fluorine co-doped core layer 11 arranged in sequence from the inside to the outside; the sleeve 2 includes an inner sleeve 20 and an outer sleeve 21 arranged in sequence from the inside to the outside, and the inner sleeve 20 includes The deep fluorine-doped layer 200 and the shallow fluorine-doped layer 201 are arranged in sequence from the inside to the outside; the gap between the core rod 1 and the inner sleeve 20 forms the first space A, and the gap between the inner sleeve 20 and the outer sleeve 21 forms the second Two space B.

The present invention can directly place the mandrel 1 and the sleeve 2 on the drawing tower for wire drawing, adjust the vacuum degree of the first space A to make the mandrel 1 and the inner sleeve 20 uniformly fuse, and adjust the vacuum degree of the second space B The inner sleeve 20 and the outer sleeve 21 are evenly fused. The core rod 1 and the sleeve 2 are preheated by the preheating heating element in the drawing tower, and then melted by the melting heating element, and then slowly annealed by the heat preservation heating element, and then under cold air conditions outside the high temperature furnace, Normal annealing is carried out in the annealing furnace, thereby fully eliminating the closing stress between the core rod 1 and the inner sleeve 20, and the inner sleeve 20 and the outer sleeve 21.

4, the optical fiber preform also includes a tail tube 3. The tail tube 3 includes a closed ring 30, a tail rod 31, an inner tail tube 32, and an outer tail tube 33; one end of the tail rod 31 is connected to the core rod 1, and the other end is connected to the closed ring 30; the inner tail pipe 32 is sleeved outside the tail rod 31, one end of the inner tail pipe 32 is connected to the inner sleeve 20, and the other end is connected to the closed ring 30; the outer tail pipe 33 is sleeved outside the inner tail pipe 32, and one end of the outer tail pipe 33 is connected to the outer sleeve 21. The other end is connected to the closed ring 30; at the same time, the gap between the closed ring 30, the tail rod 31, and the inner tail pipe 32 and the first space A together form a first section C, and the closed ring 30 is provided with the first section C connected The inner exhaust hole 34; the gap between the closed ring 30, the inner tail pipe 32, the outer tail pipe 33 and the second space B together form a second section D, and the closed ring 30 is also provided with an outer pump connected to the second section D Stoma 35.

The end of the optical fiber preform of the present invention is provided with a combined tail tube 3, so that the core rod 1 and the inner sleeve 20, the inner sleeve 20 and the outer sleeve 21 can achieve good solid melting during the fiber drawing, and the fiber is drawn In the first space A (or the first interval C) and the second space B (or the second interval D) respectively for vacuum control, so as to realize the core rod 1 and the sleeve 2 during the fiber drawing. Good solid melting of sleeve 20 and outer sleeve 21.

The fourth embodiment of the present invention provides a method for manufacturing an ultra-low attenuation optical fiber using an optical fiber preform, which includes the following steps:

S1: Provide drawing tower 6;

S2: Fix the optical fiber preform on the drawing tower 6;

S3: Exhaust air through the inner exhaust hole 34 to adjust the vacuum degree in the first space A to the first preset vacuum degree, and extract air outward through the outer exhaust hole 35 to adjust the vacuum degree in the second space B to the first Second, the vacuum degree is preset and the fiber is drawn; since the first space A is far from the hot zone and the heat is small, and the second space B is closer to the hot zone and the heat is large, therefore, the second preset vacuum degree The vacuum is smaller than the first preset vacuum degree, so as to ensure that the core rod 1 and the sleeve 2, the inner sleeve 20 and the outer sleeve 21 can achieve uniform and good solid melting.

2 or 4, the fifth embodiment of the present invention provides a drawing tower 6, the drawing tower 6 includes a preheating heating element 60, a melting heating element 61, a heat preservation heating element 62, an annealing furnace 63, and a temperature detector; among them,

The preheating heating element 60 is used for preheating the optical fiber preform, and the preheating heating element 60 has a preheating zone 600 for accommodating the optical fiber preform;

The fusion heating element 61 is used to fuse the preheated optical fiber preform into a solid rod to form an ultra-low attenuation optical fiber 7. The fusion heating element 61 has a fusion zone 610 for accommodating the preheated optical fiber preform. Zone 610 is located below the preheating zone 600;

The heat preservation heating element 62 is used to slowly cool the ultra-low attenuation optical fiber 7 at a first preset temperature (usually about 2000°C) to remove the melting stress. The heat preservation heating element 62 has a heat preservation element for accommodating the ultra-low attenuation optical fiber 7 The heat preservation zone 620, the heat preservation zone 620 is located below the melting zone 610;

The annealing furnace 63 is used to normally anneal the ultra-low attenuation optical fiber 7 from which the melting stress has been removed at a second preset temperature (far less than the first preset temperature, usually room temperature, such as about 25°C) to remove the interface stress. The annealing furnace 63 has an annealing zone 630 for accommodating the ultra-low attenuation optical fiber 7, and the annealing zone 630 is located below the holding zone 620;

The temperature detector includes an upper temperature detector 64 and a lower temperature detector 65. The upper temperature detector 64 is used to detect the temperature at which the ultra-low attenuation fiber 7 from which the melting stress has been removed enters the annealing furnace 63, and the lower temperature detector 65 is used to detect The temperature at which the ultra-low attenuation optical fiber 7 from which the melting stress is removed leaves the annealing furnace 63.

By detecting the temperature at which the ultra-low attenuation optical fiber 7 enters the annealing furnace 63 and the temperature at which it leaves the annealing furnace 63, the temperature of the heat-retaining heating element 62 is adjusted so that the temperature of the ultra-low attenuation optical fiber 7 entering the annealing furnace 63 meets the predetermined requirements. The temperature of the annealing furnace 63 is adjusted so that the temperature of the ultra-low attenuation optical fiber 7 when it leaves the annealing furnace 63 meets the predetermined requirements, so as to meet the stress removal requirements.

Referring to FIG. 5, the sixth embodiment of the present invention provides an ultra-low attenuation optical fiber manufactured by using the optical fiber preform of the first embodiment, which includes a core layer 4 and a cladding layer 5 sheathed outside the core layer 4; The core layer 4 includes a potassium-doped core region 40 and a potassium-fluorine co-doped core region 41 arranged in order from the inside to the outside; the cladding layer 5 includes a deep fluorine doped area 50, a shallow fluorine doped area 51 and a quartz area arranged in order from the inside to the outside. 52; Under the working wavelength of 1550nm, the attenuation of the ultra-low attenuation fiber is less than 0.150dB/km.

The diameter of the potassium-doped core region 40 and the diameter of the potassium-fluorine co-doped core region 41 are D ₄₀ and D ₄₁ , respectively, the thickness of the deep fluorine-doped region 50 and the thickness of the shallow fluorine-doped region 51 are H ₅₀ and H ₅₁ , respectively, and 1.1 ≤D ₄₁ /D ₄₀ ≤1.5, 3≤H ₅₀ /D ₄₀ ≤5, 0.05≤H ₅₁ /H ₅₀ ≤0.2.

Three specific examples are given below:

Table 1 Optical fiber 1～3 parameters

The diameter of the optical fiber preform of the above-mentioned embodiment 1 reaches 150mm, the drawing speed reaches 2000m/min, and the drawn fiber 1-3 has an attenuation of 0.150dB/km at 1550nm. The bending performance of the fiber with a smaller core diameter is better. some.

Referring to FIG. 5, a seventh embodiment of the present invention provides an ultra-low attenuation optical fiber manufactured by using the optical fiber preform of the third embodiment, which includes a core layer 4 and a cladding layer 5 sheathed outside the core layer 4; The core layer 4 includes a potassium-doped core region 40 and a potassium-fluorine co-doped core region 41 arranged in order from the inside to the outside; the cladding layer 5 includes a deep fluorine doped area 50, a shallow fluorine doped area 51 and a quartz area arranged in order from the inside to the outside. 52; Under the working wavelength of 1550nm, the attenuation of the ultra-low attenuation fiber is less than 0.150dB/km.

Three specific examples are given below:

Table 2 Optical fiber 4～6 parameters

The diameter of the optical fiber preform used in the third embodiment above can reach 150mm, the drawing speed can reach 2200m/min, and the drawn fiber 4～6, its 1550nm attenuation can reach 0.150dB/km, and the fiber with a smaller core diameter has better bending performance Some of them, the splicing loss of fiber 6 and conventional G.652D fiber can be controlled at 0.1dB.

The present invention is not limited to the above-mentioned embodiments. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also regarded as the protection of the present invention. Within range. The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims

An optical fiber preform for manufacturing ultra-low attenuation optical fibers, characterized in that it comprises a core rod (1) and a sleeve (2) sheathed outside the core rod (1);

The core rod (1) includes a potassium-doped core layer (10) and a potassium-fluorine co-doped core layer (11) arranged sequentially from the inside to the outside;

The sleeve (2) includes an inner sleeve (20) and an outer sleeve (21) arranged in order from the inside to the outside, and the inner sleeve (20) includes a deep fluorine-doped layer (200) arranged in order from the inside to the outside. ) And a shallow fluorine-doped layer (201);

The gap between the core rod (1) and the inner sleeve (20) forms a first space (A).
The optical fiber preform for manufacturing ultra-low attenuation optical fiber according to claim 1, wherein the optical fiber preform further comprises a tail tube (3), and the tail tube (3) comprises:

Closed ring (30);

A tail rod (31), one end of which is connected to the core rod (1), and the other end is connected to the closed ring (30);

The inner tail pipe (32) is sleeved outside the tail rod (31), one end of the inner tail pipe (32) is connected to the sleeve (2), and the other end is connected to the closed ring (30); at the same time,

The gap between the closed ring (30), the tail rod (31), and the inner tail pipe (32) and the first space (A) together form a first interval (C), and the closed ring (30) is provided with There is an inner suction hole (34) communicating with the first section (C).
The optical fiber preform for manufacturing ultra-low attenuation optical fiber according to claim 1, wherein the gap between the inner sleeve (20) and the outer sleeve (21) forms a second space (B) .
The optical fiber preform for manufacturing ultra-low attenuation optical fiber according to claim 3, wherein the optical fiber preform further comprises a tail tube (3), and the tail tube (3) comprises:

Closed ring (30);

A tail rod (31), one end of which is connected to the core rod (1), and the other end is connected to the closed ring (30);

The inner tail pipe (32) is sleeved outside the tail rod (31), one end of the inner tail pipe (32) is connected to the inner sleeve (20), and the other end is connected to the closed ring (30);

The outer tail pipe (33) is sleeved outside the inner tail pipe (32), one end of the outer tail pipe (33) is connected to the outer sleeve (21), and the other end is connected to the closed ring (30); ,

The gap between the closed ring (30), the tail rod (31), and the inner tail pipe (32) and the first space (A) together form a first interval (C), and the closed ring (30) is provided with There is an inner suction hole (34) communicating with the first section (C);

The gap between the closed ring (30), the inner tail pipe (32), and the outer tail pipe (33) and the second space (B) together form a second interval (D), on the closed ring (30) An external suction hole (35) communicating with the second section (D) is also provided.
A method for manufacturing ultra-low attenuation optical fiber using the optical fiber preform according to claim 1, characterized in that it comprises the following steps:

Provide drawing tower (6);

Fixing the optical fiber preform on the drawing tower (6);

The vacuum degree in the first space (A) is adjusted to a first preset vacuum degree, and the optical fiber is drawn.
The method according to claim 5, wherein the optical fiber preform further comprises a tail pipe (3), and the tail pipe (3) comprises:

Closed ring (30);

A tail rod (31), one end of which is connected to the core rod (1), and the other end is connected to the closed ring (30);

The inner tail pipe (32) is sleeved outside the tail rod (31), one end of the inner tail pipe (32) is connected to the sleeve (2), and the other end is connected to the closed ring (30); at the same time,

The gap between the closed ring (30), the tail rod (31), and the inner tail pipe (32) and the first space (A) together form a first interval (C), and the closed ring (30) is provided with There is an inner suction hole (34) communicating with the first section (C);

The method further includes: pumping air outward through the inner air extraction hole (34) to adjust the vacuum degree in the first space (A) to the first preset vacuum degree.
A method for manufacturing ultra-low attenuation optical fiber using the optical fiber preform according to claim 3, characterized in that it comprises the following steps:

Provide drawing tower (6);

Fixing the optical fiber preform on the drawing tower (6);

Adjust the vacuum degree in the first space (A) to a first preset vacuum degree, adjust the vacuum degree in the second space (B) to a second preset vacuum degree, and perform fiber drawing, the The second preset vacuum degree is less than the first preset vacuum degree.
The method according to claim 7, wherein the optical fiber preform further comprises a tail tube (3), and the tail tube (3) comprises:

Closed ring (30);

A tail rod (31), one end of which is connected to the core rod (1), and the other end is connected to the closed ring (30);

The inner tail pipe (32) is sleeved outside the tail rod (31), one end of the inner tail pipe (32) is connected to the inner sleeve (20), and the other end is connected to the closed ring (30);

The outer tail pipe (33) is sleeved outside the inner tail pipe (32), one end of the outer tail pipe (33) is connected to the outer sleeve (21), and the other end is connected to the closed ring (30); ,

The gap between the closed ring (30), the tail rod (31), and the inner tail pipe (32) and the first space (A) together form a first interval (C), and the closed ring (30) is provided with There is an inner suction hole (34) communicating with the first section (C);

The gap between the closed ring (30), the inner tail pipe (32), and the outer tail pipe (33) and the second space (B) together form a second interval (D), on the closed ring (30) There is also an external exhaust hole (35) communicating with the second section (D);

The method further includes: pumping air outward through the inner suction hole (34) to adjust the degree of vacuum in the first space (A) to the first preset vacuum degree, and passing through the outer suction hole ( 35) Exhaust air to adjust the vacuum degree in the second space (B) to a second preset vacuum degree.
The method according to any one of claims 5 to 8, wherein the drawing tower (6) comprises:

A preheating heating element (60), which is used to preheat the optical fiber preform, and the preheating heating element (60) has a preheating area (600) for accommodating the optical fiber preform;

The fusion heating element (61) is used to melt the preheated optical fiber preform into a solid rod and form an ultra-low attenuation optical fiber (7). The fusion heating element (61) has an The heated melting zone (610) of the optical fiber preform, where the melting zone (610) is located below the preheating zone (600);

Heat preservation heating element (62), which is used to cool the ultra-low attenuation optical fiber (7) at a first preset temperature to remove melting stress. The heat preservation heating element (62) has a The heat preservation zone (620) of the ultra-low attenuation optical fiber (7), the heat preservation zone (620) is located below the melting zone (610);

The annealing furnace (63) is used to anneal the ultra-low attenuation optical fiber (7) from which the melting stress has been removed at a second preset temperature to remove the interface stress. The annealing furnace (63) has a An annealing zone (630) for accommodating the ultra-low attenuation optical fiber (7), the annealing zone (630) is located below the heat preservation zone (620);

A temperature detector is used to detect the temperature of the ultra-low attenuation optical fiber (7) after the melting stress has been removed entering and leaving the annealing furnace (63).
An ultra-low attenuation optical fiber manufactured by using the optical fiber preform according to any one of claims 1 to 4, characterized in that it comprises a core layer (4) and a cladding layer sheathed outside the core layer (4) (5);

The core layer (4) includes a potassium-doped core region (40) and a potassium-fluorine co-doped core region (41) arranged sequentially from the inside to the outside;

The cladding (5) includes a deep fluorine-doped region (50), a shallow fluorine-doped region (51) and a quartz region (52) arranged in order from the inside to the outside;

At a working wavelength of 1550 nm, the attenuation of the ultra-low attenuation optical fiber is less than 0.150 dB/km.