CN114057388B - Optical fiber preform manufacturing method, optical fiber preform, and optical fiber - Google Patents
Optical fiber preform manufacturing method, optical fiber preform, and optical fiber Download PDFInfo
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- CN114057388B CN114057388B CN202010778158.7A CN202010778158A CN114057388B CN 114057388 B CN114057388 B CN 114057388B CN 202010778158 A CN202010778158 A CN 202010778158A CN 114057388 B CN114057388 B CN 114057388B
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
- C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
- C03B37/01815—Reactant deposition burners or deposition heating means
- C03B37/01823—Plasma deposition burners or heating means
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
- C03B37/01853—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
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Abstract
The manufacturing method of the optical fiber preform comprises the steps of carrying out deposition treatment on a target rod, and sequentially forming a core layer, a first inner cladding layer, a second inner cladding layer and a third inner cladding layer on the target rod to obtain a powder core rod; carrying out dehydroxylation and vitrification sintering on the powder core rod to obtain a glass rod; the glass rod is subjected to vapor deposition or quartz sleeve fusion shrinkage to obtain the optical fiber preform, the manufacturing method of the optical fiber preform, the optical fiber preform and the optical fiber, and when the optical fiber preform is manufactured, the design of the germanium-doped and fluorine-doped structure of the optical core layer and the cladding layer is completed at one time, so that the production difficulty is reduced, the use of the fluorine sleeve is avoided, the production cost is reduced, the mass production can be realized, and the optical fiber preform manufactured by the manufacturing method of the optical fiber preform and the optical fiber manufactured by the optical fiber preform are excellent in bending performance and low in attenuation.
Description
Technical Field
The present invention relates to the field of optical fiber manufacturing, and in particular, to a method for manufacturing an optical fiber preform, and an optical fiber.
Background
As broadband services start to reach home with optical fibers, the construction of communication networks from core networks to optical fiber access networks is important, so that the development of fiber to the home is advanced. In the construction of fiber to the home, because the optical cable is placed in a crowded pipeline or is fixed in a line receiving end in a narrow space such as a junction box and a socket after being bent for a plurality of times, the conventional g.652 optical fiber cannot completely meet the use requirement, so that optical fiber manufacturers are conducting researches on bending-resistant single-mode optical fibers. For fiber manufacturers, it is necessary to consider how to reduce bending loss within a range that ensures that the optical parameters (cut-off wavelength, mode field diameter, zero dispersion wavelength) of the fiber are controllable; while satisfying the bending loss of the optical fiber, consider how to realize simple and controllable manufacturing process and low-cost optical fiber manufacturing. It is well known that the attenuation, macrobend, optical parameter properties of an optical fiber depend on the properties of an optical fiber preform, and therefore, developing and manufacturing a bending-resistant optical fiber preform will be the core of an optical fiber manufacturer.
The ways of improving the bending performance of the optical fiber are three, namely: reducing the core diameter of the optical fiber to reduce the mode field diameter; increasing the refractive index difference between the fiber core and the cladding; the step-type refractive index distribution profile structure of the existing G.652 optical fiber is changed through special processes such as Photonic Crystal Fiber (PCF), hole Assisted Fiber (HAF) and the like. However, the existing bending loss insensitive single-mode fiber has complex fiber profile, the outer cladding is doped with germanium or chlorine, the difficulty of the production process is increased, the instability of the profile is aggravated, and the fiber is not suitable for mass production.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a method for manufacturing an optical fiber preform, and an optical fiber, which are low in production difficulty, suitable for mass production, and excellent in bending resistance.
In one embodiment of the present invention, there is provided a method for manufacturing an optical fiber preform, comprising the steps of:
carrying out deposition treatment on the target rod, and sequentially forming a core layer, a first inner cladding layer, a second inner cladding layer and a third inner cladding layer on the target rod to obtain a powder core rod;
carrying out dehydroxylation and vitrification sintering on the powder core rod to obtain a glass rod;
and carrying out vapor deposition or quartz sleeve fusion shrinkage on the glass rod to obtain the optical fiber preform.
In some embodiments of the present invention, the step of depositing the core layer comprises using a core layer burner that is angled from horizontal at an angle of 30 DEG to 90 DEG to the horizontal, and introducing SiCl 4 、GeCl 4 、H 2 、O 2 Ar, wherein SiCl 4 The flow is controlled to be 2-5 g/min, geCl 4 The flow rate is controlled to be 50-300 cc/min, the flame temperature is 850-950 ℃, and the core layer is formed.
In some embodiments of the present invention, siCl is introduced while depositing the first inner cladding layer 4 Alkali metal dopant and fluoride、H 2 、O 2 Ar, wherein SiCl 4 Controlling the flow rate at 5-50 g/min, controlling the flow rate of the introduced fluoride at 50-400 cc/min, and controlling the flow rate of the introduced alkali metal dopant at 0-20 cc/min so as to form the first inner cladding layer on the surface of the core layer.
In some embodiments of the present invention, siCl is introduced while depositing the second inner cladding layer 4 、H 2 、O 2 Ar, wherein SiCl 4 The flow rate is controlled to be 5-20 g/min, and the flame temperature is 1250-1400 ℃ so as to form the second inner cladding on the surface of the first inner cladding.
In some embodiments of the present invention, siCl is introduced while depositing the third inner cladding layer 4 Fluoride, H 2 、O 2 Ar, wherein SiCl 4 Controlling the flow rate to be 10-50 g/min, controlling the flow rate of fluoride to be 500-1000 cc/min, and controlling the flame temperature to be 1250-1400 ℃ so as to form the third inner cladding on the surface of the second inner cladding.
In some embodiments of the invention, siCl is introduced 4 Fluoride, H 2 、O 2 Ar to increase and control the fluorine doping depth of the third inner cladding layer, wherein SiCl 4 The flow is controlled to be 0-5 g/min, the flow of fluoride is controlled to be 200-1000 cc/min, and the flame temperature is 1250-1400 ℃.
In some embodiments of the invention, the dehydroxylation temperature is controlled at 800-1000 ℃ during the sintering reaction, and 400-1000 cc/min of Cl is introduced 2 And 10-30L/min He, and simultaneously controlling the pressure to be 5-20 Pa by a pressure controller to improve the dehydroxylation effect.
In some embodiments of the invention, the temperature is raised to 1300-1600 ℃ at a temperature rise rate of 2-5 ℃/min after the end of the dehydroxylation during the sintering reaction, and the He is introduced for 10-30L/min.
In some embodiments of the invention, the bulk is sintered to a glass rod during the sintering reaction at a constant temperature between 1100 ℃ and 1400 ℃ for 3 to 6 hours while maintaining 10 to 30L/min of He.
In one embodiment of the present invention, an optical fiber preform is provided, which is prepared by the above-mentioned method for manufacturing an optical fiber preform.
In an embodiment of the present invention, an optical fiber is further provided, where the optical fiber is prepared from the optical fiber preform, and the optical fiber sequentially includes a core layer, a first inner cladding layer, a second inner cladding layer, a third inner cladding layer, and an outer cladding layer, where a refractive index difference of a cross-sectional center recess of the core layer is 0.00-0.03, a relative refractive index difference is 0.340-0.400, a relative refractive index difference of the first inner cladding layer is-0.030 to-0.060, and a relative refractive index difference of the third inner cladding layer is-0.100 to-0.200%.
According to the manufacturing method of the optical fiber preform, the optical fiber preform and the optical fiber, when the optical fiber preform is manufactured, the design of the germanium-doped and fluorine-doped structure of the optical core layer and the cladding layer is completed at one time, the production difficulty is reduced, the use of fluorine sleeves is avoided, the production cost is reduced, the mass production can be realized, and the optical fiber preform manufactured by the optical fiber preform manufacturing method and the optical fiber manufactured by the optical fiber preform have excellent bending performance and low attenuation.
Drawings
Fig. 1 is a flow chart illustrating a method for fabricating an optical fiber preform according to an embodiment of the present invention.
Fig. 2 is a schematic structural view of a deposition apparatus according to an embodiment of the present invention.
Fig. 3 is a schematic structural view of a sintering apparatus according to an embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view of an optical fiber according to an embodiment of the present invention.
FIG. 5 is a cross-sectional view of refractive index of an optical fiber according to an embodiment of the present invention.
Description of the main reference signs
The invention will be further described in the following detailed description in conjunction with the above-described figures.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
It will be understood that when an element is referred to as being "mounted" to another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present.
For ease of understanding, the following terms are defined: refractive index profile: the relationship between the refractive index of the glass of an optical fiber or optical fiber preform (including a core rod) and its radius;
difference in relative refractive index: Δni= (ni-n 0)/n 0, ni corresponds to the refractive index of each part of the optical fiber, and n0 is the refractive index of pure silica glass.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or/and" as used herein includes any and all combinations of one or more of the associated listed items.
An embodiment of the present invention provides a method for manufacturing an optical fiber preform, including the steps of:
sequentially depositing a first inner cladding layer, a second inner cladding layer and a third inner cladding layer on the surface of the core layer;
carrying out dehydroxylation and vitrification sintering on the formed core layer containing the first inner cladding, the second inner cladding and the third inner cladding to obtain a glass rod;
and forming an outer cladding layer on the surface of the glass rod by a vapor deposition method or a quartz sleeve in a fused way, thus obtaining the optical fiber preform.
An embodiment of the present application provides an optical fiber preform manufactured by the above-described method for manufacturing an optical fiber preform.
An embodiment of the present application further provides an optical fiber, which is prepared from the optical fiber preform, and the optical fiber sequentially includes a core layer, a first inner cladding layer, a second inner cladding layer, a third inner cladding layer, and an outer cladding layer, where a refractive index difference of a cross section center recess of the core layer is 0.00-0.03, a relative refractive index difference is 0.340-0.400, a relative refractive index difference of the first inner cladding layer is-0.030 to-0.060, and a relative refractive index difference of the third inner cladding layer is-0.100 to-0.200%.
According to the manufacturing method of the optical fiber preform, the optical fiber preform and the optical fiber, when the optical fiber preform is manufactured, the design of the germanium-doped and fluorine-doped structure of the optical core layer and the cladding layer is completed at one time, the production difficulty is reduced, the use of fluorine sleeves is avoided, the production cost is reduced, the mass production can be realized, and the optical fiber preform manufactured by the optical fiber preform manufacturing method and the optical fiber manufactured by the optical fiber preform have excellent bending performance and low attenuation.
Some embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Referring to fig. 2 and 3 together, an apparatus for use in the method for manufacturing an optical fiber preform according to an embodiment of the present invention will be described first, the apparatus including a deposition apparatus 10 and a sintering apparatus 20 for manufacturing an optical fiber preform, the deposition apparatus 10 being configured to deposit a target rod 200 to obtain a powder core rod 300, and the sintering apparatus 20 being configured to subject the powder core rod 300 to dehydroxylation and vitrification.
The deposition apparatus 10 includes a deposition chamber 11, a lifting assembly 12, a boom 13, and a torch assembly 15, wherein the deposition chamber 11 includes a deposition chamber 111, the lifting assembly 12 is mounted at one end of the deposition chamber 111, and the lifting assembly 12 can rotate around its own axis and move up and down along the length direction of the deposition chamber 11. One end of the boom 13 is fixed to the lifting assembly 12, and the other end is used for hanging the target rod 200. In one embodiment, a slot (shown in the figure) is provided on the boom 13 to cooperate with the target rod 200, and the target rod 200 moves up and down along the axial direction under the driving of the boom 13. In one embodiment, the deposition chamber 11 is generally hollow cylindrical. The torch assembly 15 is installed at one side of the deposition chamber 11, and one end of the torch assembly 15 faces the target rod 200 to deposit the target rod 200. In one embodiment, the torch assembly 15 includes a core torch 151, a first inner cladding torch 152, a second inner cladding torch 153, a third inner cladding torch 154, and a fourth inner cladding torch 155, which are sequentially disposed outside the deposition chamber 11, for depositing the target rod 200. The deposition apparatus 10 further includes a thermal infrared imager 16, where the thermal infrared imager 16 is connected to the deposition chamber 11, and is used for monitoring flame temperature of each layer of torch to control oxyhydrogen flow rate and set powder density, so as to achieve fluorine doping effect.
The sintering equipment 20 comprises a furnace core tube 21, a heating body 22, a hanging rod 23, a lifting assembly 24, a heat insulation plate 25 and a pressure controller 26, wherein the heating body 22, the hanging rod 23, the lifting assembly 24, the heat insulation plate 25 and the pressure controller 26 are arranged around the furnace core tube 21, the lifting assembly 24 is installed at one end of the furnace core tube 21, and the lifting assembly 24 can rotate around the axis of the lifting assembly and move up and down along the length direction of the furnace core tube 21. One end of the boom 23 is fixed to the lifting assembly 24, and the other end is used for hanging the powder core rod 300. The heat insulation plate 25 is arranged in the furnace core tube 21 and sleeved on the suspender 23 to realize the heat insulation effect. The pressure controller 26 is connected to the furnace core tube 21 to control the pressure inside the furnace core tube 21. The furnace core tube 21 is provided with an air inlet hole 211 at one end far away from the lifting assembly 24, and the air inlet hole 211 is used for ventilation so as to realize sintering.
Referring to fig. 1, the method for manufacturing an optical fiber preform according to an embodiment of the present invention includes the following steps:
s11, carrying out deposition treatment on a target rod, and sequentially forming a core layer, a first inner cladding layer, a second inner cladding layer and a third inner cladding layer on the target rod to obtain a powder core rod;
specifically, in one embodiment, the target rod 200 is a quartz glass seed rod, the target rod 200 is suspended on the lifting assembly 12 by the suspension rod 13, and SiCl is introduced into the core layer torch 151 during the deposition reaction 4 、GeCl 4 、H 2 、O 2 、Ar，SiCl 4 The flow is controlled to be 2-5 g/min, geCl 4 Controlling the flow rate at 50-300 cc/min, and generating core powder SiO through high-temperature hydrolysis reaction 2 、GeO 2 Attached to the surface of the target rod 200 and gradually grown to form a core layer 101 as the target rod 200 is lifted upward, and simultaneously the flame temperature of the core layer torch 151 is monitored to be 850-950 ℃ during the deposition process to control GeO 2 Optimum reaction temperature, thereby reducing GeCl 4 When the core layer 101 is deposited, the core layer 101 with a concave structure is formed by setting the included angle between the core layer blowtorch 151 and the horizontal direction to be 30-90 degrees;
in one embodiment, siCl is introduced into the first inner cladding torch 152 while the first inner cladding 102 is deposited 4 Alkali metal dopant, fluoride, H 2 、O 2 Ar to form SiO with a certain thickness on the surface of the core layer 2 A layer, i.e. a first inner cladding layer 102, into which SiCl is introduced 4 Controlling the flow rate to be 5-50 g/min, controlling the flow rate of fluoride to be 50-400 cc/min, controlling the flow rate of alkali metal doping agent to be 0-20 cc/min, and controlling the powder density to be 0.3-0.7 g/cm 3 The resulting powder thickness of the first inner cladding 102 is 1.0 to 2.0 times the core rod diameter, wherein the alkali metal dopant may be any of the halides of Na, K, rb, cs, mg, ca. The alkali metal dopant acts to reduce cladding viscosity and reduce Rayleigh scattering loss due to structural non-uniformity.
In one embodiment, siCl is introduced into the second inner cladding torch 153 while depositing the second inner cladding 103 4 、H 2 、O 2 Ar to form SiO with a certain thickness on the surface of the first inner cladding 2 A layer, i.e. a second inner cladding layer, in which SiCl 4 The flow is controlled to be 5-20 g/min, and the powder density is controlled to be 0.7-1.0 g/cm 3 The thickness of the generated second inner cladding 103 powder is 0.5-1.0 times of the rod diameter of the core layer, and in the deposition process, the flame temperature is monitored to be 1250-1400 ℃, and the density of the second inner cladding 103 powder is controlled so as to reduce excessive fluorine penetrating into the core layer during deposition.
In one embodiment, the third inner cladding layer is deposited104, the third inner cladding torch 154 is fed with SiCl 4 Fluoride, H 2 、O 2 Ar to form fluorine-doped SiO with a certain thickness on the surface of the second inner cladding layer 103 2 A layer, i.e. a third inner cladding layer 104, into which SiCl is introduced 4 The flow rate is controlled to be 10-50 g/min, the flow rate of fluoride is controlled to be 500-1000 cc/min, and the powder density is controlled to be 0.2-0.6 g/cm 3 The thickness of the generated third inner cladding 104 powder is 1.5-2.5 times of the rod diameter of the core layer, and in the deposition process, the flame temperature is monitored to 1250-1400 ℃ to control the density of the third inner cladding powder, the expected fluorine doping depth is reached through fluoride doping, the use of a fluorine sleeve is reduced, and the deposition is stopped after the deposition reaches the set length. Specifically, the third burner is a fluorine-doped burner, and the end face of the raw material layer is 100-140 mm away from the sixth layer, wherein the raw material layer is SiCl 4 First layer O 2 And fluoride, second layer Ar, third layer H2, fourth layer Ar, fifth layer O 2 Specific layers are not described in detail herein.
In one embodiment, siCl is introduced into the fourth inner cladding torch 155 4 Fluoride, H 2 、O 2 Ar for increasing the fluorine doping depth of the third inner cladding 104; wherein SiCl 4 Controlling the flow rate to be 0-5 g/min, controlling the flow rate of fluoride to be 200-1000 cc/min, and monitoring the flame temperature to be 1250-1400 ℃ in the deposition process, wherein the fluoride is used for further increasing and controlling the fluorine doping depth of the third inner cladding 104, so that the fluorine doping depth in the third inner cladding 104 is-0.15 to-0.20%, and the fluorine doping powder density is controlled to be 0.2-0.6 g/cm 3 After the deposition process is completed, the target rod 200 forms a powder core rod, and it is understood that the target rod 200 moves back and forth along an axis and continuously rotates in the deposition chamber 11 during the deposition reaction.
S12: carrying out dehydroxylation and vitrification sintering on the powder core rod to obtain a glass rod;
specifically, the deposition is completed, the obtained powder core rod 300 is connected to the hanger rod 23 and suspended in the furnace core tube 21, and the powder core rod 300 is set by the lifting assembly 24In a predetermined position. The heating body 22 is heated according to a predetermined temperature profile to achieve the dehydroxylation. Specifically, in the first stage, the dehydroxylation temperature is controlled to be 800-1000 ℃, and Cl of 400-1000 cc/min is introduced from the bottom of the middle furnace core tube 2 He with the volume of 10-30L/min is introduced, and the pressure is controlled to be 5-20 pa by a pressure controller so as to improve the dehydroxylation effect; the second stage, after the dehydroxylation is finished, raising the temperature to 1300-1600 ℃ according to the heating rate of 2-5 ℃/min, and keeping the He introduced into the reactor for 10-30L/min; and in the third stage, the temperature is kept between 1100 ℃ and 1400 ℃ for 3 to 6 hours, and meanwhile, 10 to 30L/min of He is introduced, and the powder core rod 300 is sintered into a glass rod.
S13: and forming an outer cladding 105 on the surface of the glass rod to obtain the optical fiber preform.
Specifically, the outer cladding 105 is prepared using an outside vapor deposition process (OVD), or a pure silicon sleeve is fused. Wherein the external vapor deposition process is to deposit the finished glass rod on an OVD machine, deposit according to the designed outer diameter or the target weight, and pass through Cl after the deposition is finished 2 And (5) dehydroxylating and sintering to finish the bending loss insensitive optical fiber preform.
And finally, drawing the optical fiber preform at a certain drawing speed and tension to obtain the bending loss insensitive optical fiber. In one embodiment, the wire drawing speed is 1000-1800 m/min and the tension is 1-3N.
Referring to fig. 4 and 5, the present invention further provides a bend insensitive optical fiber, which sequentially includes a core layer 101, a first inner cladding layer 102, a second inner cladding layer 103, a third inner cladding layer 104, and an outer cladding layer 105. The refractive index difference of the cross section center concave of the core layer is 0.00-0.03, and the relative refractive index difference delta n 1=0.340-0.400%, r 1=3.5-5.0 μm; the first inner cladding layer r2=8-10 μm, and the relative refractive index difference delta n2= -0.030 to-0.060; a second inner cladding region r3=10 to 13 μm; the third inner cladding r4=18-20 μm, and the relative refractive index difference Δn3= -0.100 to-0.200%. It can be seen that the refractive index tends to decrease.
Example 1
1) The temperature of the flame of the core layer is controlled between 850 and 950 ℃;
2) SiCl is introduced into the core layer blowtorch 4 Flow 3g/min, geCl 4 Flow rate 250cc/min; the included angle between the core layer blowtorch and the horizontal is 40 degrees;
3) The first inner cladding blowlamp is filled with SiCl 4 Flow 20g/min, CF 4 A flow rate of 200cc/min, a flow rate of KCl of 5cc/min; the second inner cladding blowtorch is led into SiCl 4 The flow rate is 5g/min; the third inner cladding blowtorch is led into SiCl 4 The flow rate is 25g/min, and CF is introduced 4 Is 600cc/min; siCl is introduced into the fourth inner cladding blowtorch 4 Flow 1g/min, CF 4 The flow rate of the flame is 200cc/min, and the temperature of the flame is controlled between 1250 ℃ and 1400 ℃.
4) In the first stage, the dehydroxylation temperature is set at 1000 ℃, and Cl of 500cc/min is introduced from the bottom of the central furnace core tube 2 Introducing 20L/min He, and controlling the pressure at 10pa; in the second stage, after the dehydroxylation is finished, the temperature is raised to 1300 ℃ at a heating rate of 3 ℃/min, and 20L/min of He is introduced; thirdly, keeping the temperature constant for 3.5 hours at 1300 ℃, sintering the loose body into a transparent glass rod, and keeping the He introduced into the transparent glass rod at 20L/min;
according to the flow setting, the refractive index difference of the central depression of the formed core section is between 0 and 0.03, the relative refractive index difference delta n1 of the core layer is between 0.340 and 0.400 percent, the relative refractive index difference delta n2 of the first inner cladding layer is between-0.03 and-0.06 percent, the relative refractive index difference delta n3 of the third inner cladding layer is between-0.15 and-0.20 percent, the third inner cladding layer adopts an OVD deposition process, the transparent glass rod is extended to the length 1800mm with the diameter of 55mm, the OVD deposition is carried out, and the through Cl is carried out after the deposition is finished 2 And (3) dehydroxylating and sintering to finally form the bending loss insensitive optical fiber preform, and drawing the optical fiber preform to obtain the bending loss insensitive optical fiber.
Example 2
1) The temperature of the flame of the core layer is controlled between 850 and 950 ℃;
2) SiCl is introduced into the core layer blowtorch 4 Flow 3g/min, geCl 4 Flow 240cc/min; the included angle between the core layer blowtorch and the horizontal is 38 degrees;
3) The first inner cladding blowlamp is filled with SiCl 4 Flow 20g/min, CF 4 A flow rate of 400cc/min, a flow rate of KCl of 5cc/min; the second inner cladding blowtorch is led into SiCl 4 The flow rate is 5g/min; third inner partThe cladding blowlamp is filled with SiCl 4 The flow rate is 25g/min, and CF is introduced 4 Is a flow rate of 500cc/min; siCl is introduced into the fourth inner cladding blowtorch 4 Flow 1g/min, CF 4 The flow rate of the flame is 300cc/min, and the temperature of the flame is controlled between 1250 and 1400 ℃.
4) In the first stage, the dehydroxylation temperature is set at 1000 ℃, and Cl of 500cc/min is introduced from the bottom of the central furnace core tube 2 Introducing 20L/min He, and controlling the pressure at 10pa; in the second stage, after the dehydroxylation is finished, the temperature is raised to 1300 ℃ at a heating rate of 3 ℃/min, and 20L/min of He is introduced; thirdly, keeping the temperature constant for 3.5 hours at 1300 ℃, sintering the loose body into a transparent glass rod, and keeping the He introduced into the transparent glass rod at 20L/min;
according to the flow setting, the refractive index difference of the cross section center concave forming the core layer is between 0 and 0.03, the relative refractive index difference delta n1 of the core layer is between 0.340 and 0.400 percent, the relative refractive index difference delta n2 of the first inner cladding layer is between-0.03 and-0.06 percent, the relative refractive index difference delta n3 of the third inner cladding layer is between-0.15 and-0.20 percent,
and the third inner cladding adopts an OVD deposition process, a transparent glass rod is extended to a diameter of 55mm and a length of 1800mm, the OVD deposition is carried out, the Cl2 dehydroxylation sintering is carried out after the deposition is finished, and finally, the bending loss insensitive optical fiber preform is formed, and the bending loss insensitive optical fiber is obtained by the optical fiber preform through drawing.
Example 3
1) The temperature of the flame of the core layer is controlled between 850 and 950 ℃;
2) SiCl is introduced into the core layer blowtorch 4 Flow 3g/min, geCl 4 Flow rate 260cc/min; the included angle between the core layer blowtorch and the horizontal is 42 degrees;
3) The first inner cladding blowlamp is filled with SiCl 4 Flow 20g/min, CF 4 A flow rate of 150cc/min, a flow rate of KCl of 5cc/min; the second inner cladding blowtorch is led into SiCl 4 The flow rate is 5g/min; the third inner cladding blowtorch is led into SiCl 4 The flow rate is 25g/min, and CF is introduced 4 Flow rate of 700cc/min; siCl is introduced into the fourth inner cladding blowtorch 4 Flow 1g/min, CF 4 The flow rate of the flame is 300cc/min, and the temperature of the flame is controlled between 1250 and 1400 ℃.
4) First stage, take offSetting the temperature of the hydroxyl at 1000 ℃, and introducing 500cc/min of Cl from the bottom of the central furnace core tube 2 Introducing 20L/min He, and controlling the pressure at 10pa; in the second stage, after the dehydroxylation is finished, the temperature is raised to 1300 ℃ at a heating rate of 3 ℃/min, and 20L/min of He is introduced; thirdly, keeping the temperature constant for 3.5 hours at 1300 ℃, sintering the loose body into a transparent glass rod, and keeping the He introduced into the transparent glass rod at 20L/min;
according to the flow setting, the refractive index difference of the cross section center concave of the formed core layer is between 0 and 0.03, n1 is between 0.340 and 0.400 percent, n2 is between-0.03 and-0.06 percent, n3 is between-0.15 and-0.20 percent, the third inner cladding layer adopts an OVD (over-the-counter (OVD) deposition process, a transparent glass rod is extended to the length 1800mm with the diameter of 55mm, the OVD deposition is carried out, and the through Cl is carried out after the deposition is finished 2 And (3) dehydroxylating and sintering to finally form the bending loss insensitive optical fiber preform, and drawing the optical fiber preform to obtain the bending loss insensitive optical fiber.
The relevant parameters of the optical fiber obtained by the above three examples are as follows:
referring to fig. 3, parameters of the fiber profile: wherein H is a refractive index difference of a central depression of the profile, Δn is a relative refractive index difference, r is an optical fiber radius, Δn1 is a core relative refractive index difference, Δn2 is a first inner cladding relative refractive index difference, Δn3 is a third inner cladding relative refractive index difference, r1 is a core radius, r2 is a first inner cladding radius, r3 is a second inner cladding radius, and r4 is a third inner cladding radius, and specifically, the refractive index profile can use a VAD deposition process or a PCVD deposition process.
| Parameters (parameters) | Unit (B) | Numerical value | Example 1 | Example 2 | Example 3 |
| H | \ | 0.00～0.03 | 0.015 | 0.013 | 0.018 |
| Δn1 | ％ | 0.340～0.400 | 0.358 | 0.352 | 0.362 |
| Δn2 | ％ | -0.030～-0.060 | -0.030 | -0.040 | -0.035 |
| Δn3 | ％ | -0.100～-0.200 | -0.150 | -0.150 | -0.180 |
| r1 | mm | 3.5～5.0 | 4.0 | 3.9 | 4.2 |
| r2 | mm | 8～10 | 9 | 9 | 9 |
| r3 | mm | 10～13 | 11 | 11 | 11 |
| r4 | mm | 18～20 | 19 | 19 | 19 |
Optical fiber test performance parameters:
according to the manufacturing method of the optical fiber preform, the optical fiber preform and the optical fiber, the temperature is monitored by the thermal infrared imager for preparing the optical fiber preform, the ratio of oxyhydrogen gas in each layer is optimized, the powder density is controlled, and a basis is provided for fluorine doping effect; simultaneously, alkali metal and fluoride are introduced into the first inner cladding, so that the viscosity of the cladding is reduced, the network structure of the preform is uniform, and the Rayleigh scattering loss caused by structural non-uniformity is further reduced; meanwhile, by controlling the powder density of each inner cladding and the design of fluorine-doped structure, the bending performance of the manufactured optical fiber is ensured, the attenuation is improved, and the optical fiber is suitable for mass production.
It will be appreciated by persons skilled in the art that the above embodiments have been provided for the purpose of illustrating the invention and are not to be construed as limiting the invention, and that suitable modifications and variations of the above embodiments are within the scope of the invention as claimed.
Claims (6)
1. A method of manufacturing an optical fiber preform, comprising the steps of:
carrying out deposition treatment on the target rod, and sequentially forming a core layer, a first inner cladding layer, a second inner cladding layer, a third inner cladding layer and a fourth inner cladding layer on the target rod to obtain a powder core rod;
the step of depositing the core layer comprises the steps of using a core layer blowtorch, wherein the included angle between the core layer blowtorch and the horizontal direction is 30-90 degrees, and introducing SiCl 4 、GeCl 4 、H 2 、O 2 Ar, wherein SiCl 4 The flow is controlled to be 2-5 g/min, geCl 4 Controlling the flow rate at 50-300 cc/min and the flame temperature at 850-950 ℃ to form a core layer;
during the deposition of the first inner cladding, siCl is introduced 4 Alkali metal dopant, fluoride, H 2 、O 2 Ar, wherein SiCl 4 Controlling the flow rate to be 5-50 g/min, controlling the flow rate of the introduced fluoride to be 50-400 cc/min, and controlling the flow rate of the introduced alkali metal dopant to be 0-20 cc/min so as to form the first inner cladding on the surface of the core layer;
during the deposition of the second inner cladding, siCl is introduced 4 、H 2 、O 2 Ar, wherein SiCl 4 Controlling the flow to be 5-20 g/min and the flame temperature to be 1250-1400 ℃ so as to form the second inner cladding on the surface of the first inner cladding;
when the third inner cladding is deposited, siCl is introduced 4 Fluoride, H 2 、O 2 Ar, wherein SiCl 4 Controlling the flow rate to be 10-50 g/min, controlling the flow rate of fluoride to be 500-1000 cc/min, and controlling the flame temperature to be 1250-1400 ℃ so as to form the third inner cladding on the surface of the second inner cladding;
when the fourth inner cladding is deposited, siCl is introduced 4 Fluoride, H 2 、O 2 Ar to increase and control the fluorine doping depth of the third inner cladding layer, wherein SiCl 4 Controlling the flow rate to be more than 0 and less than or equal to 5g/min, controlling the flow rate of fluoride to be 200-1000 cc/min, and controlling the flame temperature to be 1250-1400 ℃;
carrying out dehydroxylation and vitrification sintering on the powder core rod to obtain a glass rod;
and carrying out vapor deposition or quartz sleeve fusion shrinkage on the glass rod to obtain the optical fiber preform.
2. The method of manufacturing an optical fiber preform according to claim 1, wherein: during sintering reaction, the dehydroxylation temperature is controlled at 800-1000 ℃, and 400-1000 cc/min of Cl is introduced 2 And 10-30L/min of He, and simultaneously controlling the pressure to be 5-20 Pa by a pressure controller to improve the dehydroxylation effect.
3. The method of manufacturing an optical fiber preform according to claim 1, wherein: and during sintering reaction, after the dehydroxylation is finished, the temperature is increased to 1300-1600 ℃ according to the heating rate of 2-5 ℃/min, and 10-30L/min of He is introduced.
4. The method of manufacturing an optical fiber preform according to claim 1, wherein: during sintering reaction, the temperature is kept constant for 3-6 hours at 1100-1400 ℃, meanwhile, 10-30L/min of He is introduced, and the loose body is sintered into a glass rod.
5. An optical fiber preform, characterized in that the optical fiber preform is produced by the method for producing an optical fiber preform according to any one of the preceding claims 1 to 4.
6. An optical fiber prepared from the optical fiber preform of claim 5, wherein: the optical fiber sequentially comprises a core layer, a first inner cladding layer, a second inner cladding layer, a third inner cladding layer, a fourth inner cladding layer and an outer cladding layer, wherein the refractive index difference of the section center pits of the core layer is 0.00-0.03, the relative refractive index difference is 0.340-0.400%, the relative refractive index difference of the first inner cladding layer is-0.030-0.060%, and the relative refractive index difference of the third inner cladding layer is-0.100-0.200%.
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