CN102276145B - Manufacturing method of optical fiber perform with uniform optical waveguide axial direction - Google Patents
Manufacturing method of optical fiber perform with uniform optical waveguide axial direction Download PDFInfo
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- CN102276145B CN102276145B CN201110194275XA CN201110194275A CN102276145B CN 102276145 B CN102276145 B CN 102276145B CN 201110194275X A CN201110194275X A CN 201110194275XA CN 201110194275 A CN201110194275 A CN 201110194275A CN 102276145 B CN102276145 B CN 102276145B
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
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- 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]
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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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- C03B2203/00—Fibre product details, e.g. structure, shape
- C03B2203/10—Internal structure or shape details
- C03B2203/22—Radial profile of refractive index, composition or softening point
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- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2203/00—Fibre product details, e.g. structure, shape
- C03B2203/10—Internal structure or shape details
- C03B2203/22—Radial profile of refractive index, composition or softening point
- C03B2203/23—Double or multiple optical cladding profiles
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Abstract
Belonging to the optical communication technologies, the invention discloses a manufacturing method of an optical fiber perform with a uniform optical waveguide axial direction. With a process designed and controlled according to the normalized structure of optical fiber waveguides, the method comprises the steps of: first deposing a core and a coating layer within a quartz glass tube by a chemical vapor deposition method in the tube, making the normalization dimension and the refractive index of each layer consistent by means of axial control, with the normalization dimension as a proportionality factor of each layer to one layer therein, then conducting high temperature melting and shrinking so as to form a core rod; second, extending the core rod so as to form a deposition target rod; then preparing a SiO2 dust coating layer by an axial chemical vapor deposition method, and through axial control, depositing the SiO2 dust coating layer decided by the optical waveguide normalization dimension; finally, sintering the SiO2 dust coating layer into a transparent glass rod body, i.e. the optical fiber perform with uniform optical waveguides. The method of the invention is flexible and simple, and produces the perform with uniform optical waveguides. The method provided in the invention effectively utilizes the conical degrees of the two ends of the perform, increases the effective length, reduces the cost, and can be used for high speed production.
Description
Technical field
The invention belongs to the fiber manufacturing field, specifically a kind of method of using the interior chemical Vapor deposition process of pipe to make the axially uniform preform of fibre-optic waveguide to chemical Vapor deposition process in conjunction with external shaft.
Background technology
The optical fiber that is used for communications is to be made through wire drawing by prefabricated rods, and the making of preform is a core link in the optical fiber production, the structure of major decision optical fiber and optical property.The processing method that has had in the prior art several production preforms, pressing the manufacture method of Refractive Index Profile of Optical divides, can be divided into two large classes: sedimentation in the pipe comprises Plasma Enhanced Chemical Vapor Deposition (PECVD) (PCVD) and modified chemical vapor deposition process (MCVD) (MCVD); External deposition method comprises vapour phase axial deposition technique (VAD) and outside vapour deposition process (OVD).Wherein VAD method and OVD method can be made large prefabricated optical fiber bar with two-forty, but the outside chemical vapor deposition method is lower to the control accuracy of fibre-optic waveguide structure.PCVD method and MCVD method can be produced the waveguiding structure complexity and the high preform of precision, but owing to being subject to the restriction of parent tube diameter/wall thickness, exist the deficiencies such as production cost is high, sedimentation rate is lower when using separately, are difficult to make large prefabricated optical fiber bar.And be to improve optical fiber production speed comprehensively, reduce cost, strengthen the key of optical fiber production market competitiveness of enterprises to make at a high speed large prefabricated optical fiber bar, so preform all adopts " two-step approach " manufacturing process, the first step adopts a kind of manufacturing plug in aforementioned four kinds of techniques, form the refractive index profile (optical waveguides) of optical fiber, second step is made surrounding layer, main VAD, OVD or the tiretube process (RIT/RIC) of adopting, increase the length of string of single prefabricated rods, enhance productivity, reduce the optical fiber production cost.
Improved chemical vapour deposition (MCVD) technique and PCVD (PCVD) technique refractive index profile control are accurate, suitable manufacturing has the optical fiber of complex index of refraction section shape, such as non-zero dispersion displacement single mode optical fibre (G.655 and G.656 optical fiber).These two kinds belong to the techniques of method in the pipe, and two ends during deposition are owing to oppositely forming tapering, such as refractive index profile skewness (optical taper) vertically, or deposit thickness skewness (geometry tapering) vertically.The deposition taper effect affects the longitudinal uniformity of plug, has reduced the useful length of plug.Generally by modes such as Optimizing Process Parameters and improvement controls, can suitably suppress the ununiformity that taper effect causes.But, for G.655, for the G656 type optical fiber, the sandwich layer section adopts the design of multilayered structure, comparatively complicated, reducing taper effect needs more complicated parameter adjustment and process control technology, has increased technology difficulty, the utilization ratio of plug is difficult to improve, and affects the increase of prefabricated rods length.
The RIT/RIC method is that the plug of prefabricated rods is directly put into the high-purity quartz outer tube and is combined into prefabricated rods, or to the combination prefabricated rods carry out heat, the fusion of quartz socket tube and plug is made into integration preform, perhaps will make up prefabricated rods directly vacuumize wire drawing become optical fiber (as application number be 200510091570.7, publication number is CN1837868A; Application number is 20051009304.3, publication number is the Chinese invention patent application of CN1760150A; Application number is 09/515227, the patent No. is US6460378 B1; U.S.'s application for a patent for invention that application number is 09/581734, the patent No. is US6484540 B1 is described).On technique, tiretube process is comparatively simple, has been used for conventional production.But there is some defective in this method: the core of prefabricated rods/optical fiber of producing-covering concentricity is larger; The size of sleeve pipe must be according to the size match of plug; The high-purity quartz sleeve pipe is difficult to make, and the geometric accuracy that large-sized sleeve pipe requires is high, relies on outsourcing or import, and cost is relatively high.
Outside deposition OVD technique (as application number be 09/689389, the U.S. Patent application of patent No. US6546759 B1, application number is 10/188863, the U.S. Patent application of patent No. US6941772 B2; Application number is 200410057462.3, Granted publication number is the Chinese patent application of CN1275888C) and the VAD depositing operation (as application number be 10/142466, the patent No. is the U.S. Patent application of US6923024 B2, application number is that P2006-32686, publication number are the Japanese patent application of P2007-210817A), adopt SiCl
4Be raw material, by the loose porous SiO of flame hydrolysis deposition
2Then the dust surrounding layer forms transparent prefabricated rods with its dehydration densification.It is low that two kinds of methods all have material cost, and technique is easy to adjust flexibly, in theory size can be sufficiently large etc. advantage, be the method that is fit to prepare surrounding layer.
Utilize method (MCVD in the pipe, PCVD) make the specific refractory power complexity and the higher large prefabricated optical fiber bar of precision with two-forty, the documents and materials that had show, some combination process manufacture method that occurred, such as improved chemical vapour deposition and pipe outer vapour deposition combination process manufacture method (MCVD+OVD manufacture method), PCVD and tiretube process combination process manufacture method (PCVD+RIT/RIC manufacture method).But existing these combined technical methods all do not solve the homogeneity question that the plug tapering brings, thus the useful length of prefabricated rods and utilization ratio, the homogeneity of drawing optic fibre, and the production efficiency of optical fiber all is difficult to further improve.
Summary of the invention
The technical problem to be solved in the present invention is to overcome that above-mentioned prior art exists has the not high defective of homogeneity of the low and prefabricated rods drawing optic fibre that makes of tapering utilization ratio because of plug, provide interior method (MCVD or PCVD) the preparation plug of a kind of utilization pipe and VAD technique to prepare the combination prefabricated rods technique of surrounding layer, by the normalized control method of fibre-optic waveguide, make the fibre-optic waveguide uniformity of prefabricated rods, rather than geometric identity, thereby can effectively utilize deposition tapering part, increase the prefabricated rods useful length, namely increase drawing optical fiber length, improve the homogeneity of optical fiber and the axially uniform preform making method of optical waveguides of production efficiency.
For achieving the above object, the axially uniform preform making method of optical waveguides of the present invention may further comprise the steps:
Chemical gaseous phase depositing process prepares plug in A, the employing pipe, makes the normalization method size of each layer of plug consistent with specific refractory power through axially controlling;
B, plug extended make the target rod;
C, the axial chemical Vapor deposition process of employing prepare SiO at the target rod
2The dust surrounding layer is through the surrounding layer of axially control deposition by the normalization method size decision of fibre-optic waveguide, with loose SiO
2Dust surrounding layer sintering densification namely obtains the uniform prefabricated rods of fibre-optic waveguide;
Wherein, normalization method is of a size of each layer with respect to the scale-up factor of one deck wherein.
As the optimization technique measure, chemical gaseous phase depositing process is that unstripped gas is passed in the silica glass parent tube in the described pipe, under hot conditions, carry out chemical reaction and obtain dust deposit to the parent tube internal surface, after the covering of plug and sandwich layer deposition were complete, making the covering of parent tube, plug and sandwich layer be collapsed into a solid glass rod under higher temperature became plug.
As the optimization technique measure, set according to the shrinkage rates of the external diameter of target prefabricated rods and plug and to extend target and extend plug and make the target rod.
As the optimization technique measure, described axial chemical Vapor deposition process prepares SiO at the target rod
2The dust surrounding layer is reaction raw materials to be passed into delivery system send into deposit cavity, produces SiO with flame hydrolysis
2Dust, SiO
2Dust deposit forms loose SiO at the target rod
2The dust surrounding layer.
As the optimization technique measure, to the pulling speed of target rod, be that the deposition weight of surrounding layer is divided by the merchant of sedimentation velocity gained to the pulling speed of target rod when setting the surrounding layer of needs and deposition surrounding layer according to the requirement of the specification data of target rod and fibre-optic waveguide normalization method size.
As the optimization technique measure, the pulling speed V=0.579W/ (G of target rod
i 2Ro
i 2-Ro
2), wherein W is SiO
2The sedimentation velocity of dust, G
iBe the normalization method structure coefficient of optical fiber external diameter to the i layer, Ro, Ro
iBe respectively the diameter of target rod and target rod i layer.
The core concept of this processing method is the normalization method structural parameter according to fibre-optic waveguide, adopts axial regulating and controlling technology to make.The first step of making, utilize method (MCVD in the pipe, PCVD) the advantage height of profile control accuracy prepared plug, not as previous technique, to adopt complicated control method to pursue simply geometrical dimension and the specific refractory power uniformity of each layer of plug, but adopt the axial adjustment control techniques, as the method for translational speed of regulating the oxyhydrogen flame of heating, make normalization method size and the specific refractory power uniformity of settled layer in the plug, simplified like this difficulty of making.In the second step of making, utilize the VAD method axially the surrounding layer deposition being controlled, preparation is the desired surrounding layer of fibre-optic waveguide accordingly, as adopt the method for regulating the barred body pulling speed, make every effort to fibre-optic waveguide uniformity in the prefabricated rods, rather than it is consistent to pursue simply the size uniform of surrounding layer as previous technique.Because fibre-optic waveguide uniformity in the prefabricated rods can guarantee to be drawn into the waveguiding structure uniformity of optical fiber, and effectively utilize plug deposition tapering part, increase prefabricated rods and can draw fiber lengths, improve homogeneity and the production efficiency of optical fiber.
Positively effect of the present invention is:
1, compares with the manufacture craft of prefabricated rods in the past, the present invention is based on the natural taper effect of method process deposits in the pipe and the characteristics of VAD sedimentation axial deposition, carry out technology controlling and process by normalized fibre-optic waveguide structure, complicated plug tapering problem is by simple axially regulating and controlling method, effectively solve, increase useful length and the utilization ratio of prefabricated rods, improved the homogeneity of drawing optic fibre, improved the production efficiency of optical fiber.
2, for the optical fiber of waveguiding structure complexity, the present invention can obtain the higher uniform light fiber wave guide structure of precision, has simplified technology difficulty.
3, because VAD surrounding layer deposition is take center symmetrical deposition as the axle center of plug, the core covering concentricity of prefabricated rods/optical fiber is less than tiretube process, and for large scale prefabricated rod, also exempted from the impact of conducting oneself with dignity in the OVD method lateral deposition, the polarization mode dispersion of optical fiber is low.
4, the surrounding layer deposition material by high purity silicon tetrachloride flame hydrolysis preparation is synthetic quartz glass, and based on very high purity can be improved the wire drawing strength characteristics of optical fiber.
5, the present invention is accurate to the Properties Control of optical fiber, and technology controlling and process has handiness, does not need to increase the investment of equipment.
Description of drawings
Fig. 1 is the refractive index profile schematic diagram of the embodiment of the invention 1 optical fiber.
Fig. 2 is the refractive index profile schematic diagram of the embodiment of the invention 2 optical fiber.
Fig. 3 is process flow diagram of the present invention.
Fig. 4 is the deposition schematic diagram of inner cladding, sandwich layer in the embodiment of the invention 1.
Fig. 5 is the silica tube schematic diagram of collapsing after the deposition in the embodiment of the invention 1.
Fig. 6 is VAD covering deposition schematic diagram in the embodiment of the invention 1.
Fig. 7 is the diameter distribution schematic diagram vertically of plug 1-4 layer in the embodiment of the invention 1.
Fig. 8 is the axial distribution schematic diagram of the normalization method structural parameter of plug take the first sandwich layer as reference in the embodiment of the invention 1.
Fig. 9 is the axial distribution schematic diagram of prefabricated rods external diameter and the 4th layer of diameter in the embodiment of the invention 1.
Figure 10 is the axial distribution schematic diagram of prefabricated rods external diameter and the 4th layer of diameter ratio in the embodiment of the invention 1.
Figure 11 is optical fiber property distribution schematic diagram in the embodiment of the invention 1.
Figure 12 is the diameter distribution schematic diagram vertically of plug 1-5 layer in the embodiment of the invention 2.
Figure 13 is the axial distribution schematic diagram of the normalization method structural parameter of plug take the first sandwich layer as reference in the embodiment of the invention 2.
Figure 14 is the axial distribution schematic diagram of prefabricated rods external diameter and the 5th layer of diameter in the embodiment of the invention 2.
Figure 15 is the axial distribution schematic diagram of prefabricated rods external diameter and the 5th layer of diameter ratio in the embodiment of the invention 2.
Figure 16 is optical fiber property distribution schematic diagram in the embodiment of the invention 2.
Wherein:
Among Fig. 1, i represents the from inside to outside structural sheet of optical fiber, and Ri is the diameter of each layer, and Δ i is that the specific refractory power of each layer is with respect to the relative refractive index of the specific refractory power of outermost layer 5,6, i=1～5.
Among Fig. 2, i represents the from inside to outside structural sheet of optical fiber, and Ri is the diameter of each layer, and Δ i is that the specific refractory power of each layer is with respect to the relative refractive index of the specific refractory power of outermost layer 5,6, i=1～6.
Among Fig. 4, a represents the quartz glass deposition parent tube, and b represents oxygen-hydrogen torch, the glass coating of c representative deposition, and the dust glass of d representative deposition, e represents the gas technology raw material that mixes, the chemical reaction in the f representative pipe, g represents the waste gas eliminating and processes.
Among Fig. 5, b represents oxygen-hydrogen torch, the plug that the h representative is collapsed and finished, and the part that the i representative is not collapsed, g represents the waste gas eliminating and processes.
Among Fig. 6, h ' represents the deposition targets rod, and j represents SiO
2The dust surrounding layer, the quartzy blowtorch of k representative deposition, V represents the barred body pulling speed, and X represents turning axle.
Among Fig. 7,12, ordinate zou R is each layer of plug diameter (mm of unit), and X-coordinate P is that check point is apart from the position (mm of unit) at plug head tip.
Among Fig. 8,13, ordinate zou G is each layer of plug diameter to the 1st layer ratio, and X-coordinate P is that check point is apart from the position (mm of unit) at plug head tip.
Among Fig. 9,14, ordinate zou R is diameter (mm of unit), and X-coordinate P is that check point is apart from the position (mm of unit) at prefabricated rods head tip.
Among Figure 10,15, ordinate zou G is the prefabricated rods diameter to the 5th layer ratio, and X-coordinate P is that check point is apart from the position (mm of unit) at prefabricated rods head tip.
Among Figure 11,16, ordinate zou: D is dispersion (ps/nm/km of unit), and Ds0 is zero-dispersion slop (ps/nm2/km of unit), and λ is wavelength (nm of unit), and MFD is mode field diameter (um of unit); X-coordinate L is fiber lengths, and the km of unit, λ c are cutoff wavelength, and λ 0 is zero-dispersion wavelength.
Embodiment
The present invention will be further described below in conjunction with Figure of description.
The axially uniform preform making method of optical waveguides of the present invention may further comprise the steps:
Chemical gaseous phase depositing process prepares plug in A, the employing pipe, makes the normalization method size of each layer of plug consistent with specific refractory power through axially controlling;
B, plug extended make the target rod;
C, the axial chemical Vapor deposition process of employing prepare SiO at the target rod
2The dust surrounding layer is through the surrounding layer of axially control deposition by the normalization method size decision of fibre-optic waveguide, with loose SiO
2Dust surrounding layer sintering densification namely obtains the uniform prefabricated rods of fibre-optic waveguide;
Wherein, normalization method is of a size of each layer with respect to the scale-up factor of one deck wherein.
As the optimization technique measure, chemical gaseous phase depositing process is that unstripped gas is passed in the silica glass parent tube in the described pipe, under hot conditions, carry out chemical reaction and obtain dust deposit to the parent tube internal surface, after the covering of plug and sandwich layer deposition were complete, making the covering of parent tube, plug and sandwich layer be collapsed into a solid glass rod under higher temperature became plug.
As the optimization technique measure, set according to the shrinkage rates of the external diameter of target prefabricated rods and plug and to extend target and extend plug and make the target rod.
As the optimization technique measure, described axial chemical Vapor deposition process prepares SiO at the target rod
2The dust surrounding layer is reaction raw materials to be passed into delivery system send into deposit cavity, produces SiO with flame hydrolysis
2Dust, SiO
2Dust deposit forms loose SiO at the target rod
2The dust surrounding layer.
As the optimization technique measure, to the pulling speed of target rod, be that the deposition weight of surrounding layer is divided by the merchant of sedimentation velocity gained to the pulling speed of target rod when setting the surrounding layer of needs and deposition surrounding layer according to the requirement of the specification data of target rod and fibre-optic waveguide normalization method size.
As the optimization technique measure, the pulling speed V=0.579W/ (G of target rod
i 2Ro
i 2-Ro
2), wherein W is SiO
2[sedimentation velocity W determines by deposition process conditions (factors such as equipment, processing parameter) is comprehensive the sedimentation velocity of dust, generally by the interior SiO that deposits of repeated measurement unit time
2The weight of dust and obtaining, unit is g/min; With regard to an equipment, determine can obtain sedimentation velocity by repeated measurement after its processing parameter, the statistical average value of this sedimentation velocity can be used as this and determines technique constant under the processing condition], G
iBe the normalization method structure coefficient of optical fiber external diameter to the i layer, Ro, Ro
iBe respectively the diameter of target rod and target rod i layer.
Embodiment 1:
Shown in Figure 1 is a kind of G655 fibre-optic waveguide refractive index distribution curve of the embodiment of the invention 1, and fibre profile adopts five hierarchial design, and its Jie structure Can is Shuoed ⊿
i(%) and R
i(um) be respectively: layer 1,0.52,5.2; Layer 2 ,-0.08,10.2; Layer 3,0.29,15; Layer 4 ,-0.08,20; Layer 5,0,125.In order to embody the geometric properties of fibre-optic waveguide structure, make things convenient for process calculation and control, make normalized, i.e. each layer normalization method diameter R by the diameter (R1) of layer 1
i'=R
i/ R
1(i=1～5) obtain the normalization method size: 1,1.96,2.88,3.58,24.04.
Fig. 3 is process flow diagram of the present invention.The G655 optical fiber for preparing the embodiment of the invention 1 according to Fig. 3.Fig. 4 and Fig. 5 adopt the MCVD legal system to make the process of plug in the embodiment of the invention 1.In Fig. 4 MCVD method plug is made, adopt external diameter 33 mm, wall thickness 2 mm, the import synthetic quartz pipe of length 1100 mm is parent tube, pass into the mixed airflow of a certain proportion of silicon tetrachloride vapor, phosphorus oxychloride steam, germanium tetrachloride steam and high purity oxygen gas in from an end of pipe to pipe, the other end of pipe joins with rotation seal joint and reaction end gas treatment system.Keep pressure-fired 10-20mm water column in the pipe.Hydrogen-oxygen flame blowtorch heating quartz glass tube, 1800-1900 ℃ of temperature, initiating chamical reaction, and form the settled layer of silica glass film at the silica glass pipe internal surface, the reaction product that not have to deposit is rejected to exhaust treatment system.Deposit first covering, deposit sandwich layer again, covering from outside to inside deposits respectively 3,5,4,3 layers to sandwich layer.As shown in Figure 5, collapse by high temperature (2000-2200 ℃), internal surface has been deposited the parent tube of covering and sandwich layer is molten to shorten a solid glass rod into, be plug.G.655 the plug external diameter of preparation is 19.95mm, and useful length is 950mm approximately.
Based on the natural taper effect of MCVD process deposits, in the situation that other processing parameter maintenance is identical, control the from inside to outside gauge of 1-4 layer by the translational speed of regulating hydrogen-oxygen flame blowtorch, make normalization method be of a size of 1,1.96,2.88,3.58.Namely in the optical fiber designs scope, each layer specific refractory power and normalization method size are consistent vertically.After prefabricated rods analyser test passes, obtain its cross-section structure parameter of test of plug.Shown in Figure 7 is the diameter distribution vertically of 1-4 layer in the embodiment of the invention 1 plug, although there is obvious tapering in plug, the variation tendency of 1-4 layer diameter is identical.Shown in Figure 8 is the distribution axial distribution of the embodiment of the invention 1 plug normalization method size, in the control accuracy scope of technique license, plug normalization method size uniform is consistent, and the specific refractory power parameter meets design and fluctuation is less, and the waveguiding structure that proves plug 1-4 layer is identical vertically.
Because plug deposition SiO
2Sinter into behind the dust surrounding layer in the process of transparent prefabricated rods, produce axial shortening and radially increase thick variation, the control of the actual core covering ratio of prefabricated rods behind the sintering must be considered the impact of shrinking effect.Plug contraction ratio η is the length and initial length ratio behind the sintering.Through repeatedly test, the value of the η of plug is 0.8, and (described calculating is that to establish the prefabricated rods external diameter be R to calculate thus prefabricated rods external diameter and surrounding layer curve
P, prefabricated rods surrounding layer thickness is R
C, the diameter that extends the 4th layer of plug is R
04, the external diameter that extends plug is R
0, the prefabricated rods external diameter is G to the 4th layer normalization coefficient
4According to the physical significance of contraction ratio and the relation of normalization method waveguide coefficient, prefabricated rods R
P=η
-1/2G
4R
04, the relational expression that this extends for plug; Prefabricated rods surrounding layer thickness is the external diameter that the external diameter of prefabricated rods deducts plug, according to the physical significance of contraction ratio, and the external diameter=η of plug
-1/2R
0, R
C=η
-1/2G
4R
04-η
-1/2R
0=η
-1/2(G
4R
04-R
0), with above-mentioned two relational expressions of the data substitution of each position, obtain prefabricated rods external diameter and surrounding layer curve).Plug is extended, its mean outside diameter 17.84mm, length is about 1180mm.Measure the external diameter Ro of extension plug and the 4th layer diameter Ro
4The 1160mm that extends rod is made VAD deposition targets rod carry out the surrounding layer making.Shown in Figure 6 is that the embodiment of the invention 1 adopts the VAD legal system to do the signal of surrounding layer.Silicon tetrachloride vapor passes into blowtorch with fuel gas with different pipelines, mixes at the nozzle of blowtorch, and hydrogen-oxygen flame makes silicon tetrachloride vapor generation hydrolysis reaction generate the SiO of white
2Dust.In the deposition process, the target rod is around its axle center rotation and lifting.Flame burner generation hydrolysis reaction generates SiO
2Dust accumulation becomes the SiO of porosity and looseness on target rod surface
2Surrounding layer.SiO
2The sedimentation velocity of dust surrounding layer is 18 g/min, SiO as required
2Surrounding layer is set VAD pulling speed V, V=10.422/ (45.16Ro
4 2-Ro
2), the cm/min of unit.Deposit the SiO of the q.s that needs by pulling speed control
2Surrounding layer.After deposition is finished, vertically insert in the special-purpose dehydration-sintering oven forming Porous base rod, pass into oxygen and chlorine in the stove, drive away moisture and other various impurity; Then, will dewater-sintering oven is warmed up to about 1600 ℃, and Porous base rod makes loose Porous base rod change transparent preform into through high temperature sintering.Detect through the prefabricated rods analyser, mean outside diameter is about 73.9mm, and length is 900mm approximately, and each stratum proportion remains unchanged in the plug, and the structure of prefabricated rods can represent with external diameter with the 4th layer simply.Shown in Figure 9 is the prefabricated rods of the embodiment of the invention 1 and the 4th layer diameter axial distribution, and shown in Figure 10 is that the prefabricated rods external diameter is to the ratio of the 4th layer of diameter.As can be seen from Figure 9, the tapering of prefabricated rods external diameter still exists, but its normalization method size optical texture is uniformly as can be seen from Figure 10, mean pull into 125um optical fiber after, the optical property of its optical fiber will be uniform.Prefabricated rods is total to approximately 300km of drawing optic fibre, is divided into 28 coiled optical fibers and tests.The indices of optical fiber all satisfies product requirement, main performance index: 1530,1550,1565, dispersion (Dispersion, the D) average of 1625nm is respectively 2.20,4.06,5.42,10.71 ps/nm/km, zero-dispersion slop (Zero Dispersion Slop, D
S0) be 0.080ps/nm
2/ km, zero-dispersion wavelength (Zero Dispersion Wavelength, λ 0) be 1506nm, fiber cut off wavelength (Cutoff wavelength, λ c) be 1334nm, cable cut-off wavelength (Cable cutoff wavelength, λ cc) is 1284nm, mode field diameter (Mode Field Diameter, MFD) is 9.92um.Shown in Figure 11 is MFD, the λ of the embodiment of the invention 1 optical fiber that draws
0, λ c, S
0With the distribution of D, the corresponding fiber lengths of X-coordinate.As seen the performance uniformity of optical fiber is high, owing to effectively having utilized tapering part, the length of prefabricated rods to increase approximately 15%, the production efficiency of optical fiber has increased nearly 16%.
Embodiment 2:
Shown in Figure 2 is a kind of G656 fibre-optic waveguide refractive index distribution curve of the embodiment of the invention 2, and fibre profile adopts six hierarchial design, and its Jie structure Can is Shuoed ⊿
i(%) and R
i(um) be respectively: layer 1,0.46,5.8; Layer 2,0.25,6.8; Layer 3 ,-0.09,11.8; Layer 4,0.25,16.8; Layer 5 ,-0.16,19.8; Layer 6,0,125.In order to embody the geometric properties of fibre-optic waveguide structure, make things convenient for process calculation and control, make normalized, i.e. each layer normalization method diameter R by the diameter (R1) of layer 1
i'=R
i/ R
1(i=1～6) obtain the normalization method size: 1,1.17,2.03,2.9,3.41,21.55.
Fig. 3 is process flow diagram of the present invention.The G656 optical fiber for preparing the embodiment of the invention 2 according to Fig. 2.Fig. 4 and Fig. 5 adopt the MCVD legal system to make the process of plug in the embodiment of the invention 2.In Fig. 4 MCVD method plug is made, adopt external diameter 33 mm, wall thickness 2 mm, the import synthetic quartz pipe of length 1100 mm is parent tube, pass into the mixed airflow of a certain proportion of silicon tetrachloride vapor, phosphorus oxychloride steam, germanium tetrachloride steam and high purity oxygen gas in from an end of pipe to pipe, the other end of pipe joins with rotation seal joint and reaction end gas treatment system.Keep pressure-fired 10-20mm water column in the pipe.Hydrogen-oxygen flame blowtorch heating quartz glass tube, temperature 1800-1900 ℃, initiating chamical reaction, and form the settled layer of silica glass film at the silica glass pipe internal surface, the reaction product that not have to deposit is rejected to exhaust treatment system.Deposit first covering, deposit sandwich layer again, covering from outside to inside deposits respectively 3,5,4,1 to sandwich layer, 2 layers.As shown in Figure 5, collapse by high temperature (2000-2200 ℃), internal surface has been deposited the parent tube of covering and sandwich layer is molten to shorten a solid glass rod into, be plug.G.656 the plug mean outside diameter of preparation is about 20mm, and useful length is 970mm approximately.
Natural taper effect based on the MCVD process deposits, in the situation that other processing parameter maintenance is identical, control the from inside to outside gauge of 1-5 layer by the translational speed of regulating hydrogen-oxygen flame blowtorch, make normalization method be of a size of 1,1.17,2.03,2.9,3.41 namely in the optical fiber designs scope, each layer specific refractory power and normalization method size are consistent vertically.After prefabricated rods analyser test passes, obtain its cross-section structure parameter of test of plug.Shown in Figure 12 is the diameter distribution vertically of 1-5 layer in the embodiment of the invention 2 plugs, although there is obvious tapering in plug, the variation tendency of 1-5 layer diameter is identical.Shown in Figure 13 is the distribution axial distribution of the embodiment of the invention 2 plug normalization method sizes, in the control accuracy scope of technique license, plug normalization method size uniform is consistent, and the specific refractory power parameter meets design and fluctuation is less, and the waveguiding structure that proves plug 1-5 layer is identical vertically.
Because plug deposition SiO
2Sinter into behind the dust surrounding layer in the process of transparent prefabricated rods, produce axial shortening and radially increase thick variation, the control of the actual core covering ratio of prefabricated rods behind the sintering must be considered the impact of shrinking effect.Plug contraction ratio η is the length and initial length ratio behind the sintering.Through repeatedly test, the η experimental value of plug is 0.80, and (described calculating is that to establish the prefabricated rods external diameter be R to calculate thus prefabricated rods external diameter and surrounding layer curve
P, prefabricated rods surrounding layer thickness is R
C, the diameter that extends the 5th layer of plug is R
05, the external diameter that extends plug is R
0, the prefabricated rods external diameter is G to the 5th layer normalization coefficient
5According to the physical significance of contraction ratio and the relation of normalization method waveguide coefficient, prefabricated rods R
P=η
-1/2G
4R
05, the relational expression that this extends for plug; Prefabricated rods surrounding layer thickness is the external diameter that the external diameter of prefabricated rods deducts plug, according to the physical significance of contraction ratio, and the external diameter=η of plug
-1/2R
0, R
C=η
-1/2G
5R
05-η
-1/2R
0=η
-1/2(G
5R
05-R
0), with above-mentioned two relational expressions of the data substitution of each position, obtain prefabricated rods external diameter and surrounding layer curve).Plug is extended, its mean outside diameter 17.94mm, length is 1200mm approximately, measures the external diameter Ro of extension plug and the diameter Ro of layer 5
5The 1180mm that extends rod is made VAD deposition targets rod carry out the surrounding layer making.Shown in Figure 5 is that the embodiment of the invention 1 adopts the VAD legal system to do the signal of surrounding layer.Silicon tetrachloride vapor passes into blowtorch with fuel gas with different pipelines, mixes at the nozzle of blowtorch, and hydrogen-oxygen flame makes silicon tetrachloride vapor generation hydrolysis reaction generate the SiO of white
2Dust.In the deposition process, the target rod is around its axle center rotation and lifting.Flame burner generation hydrolysis reaction generates SiO
2Dust accumulation becomes the SiO of porosity and looseness on target rod surface
2Surrounding layer.SiO
2The sedimentation velocity of dust surrounding layer is 20g/min, SiO as required
2Surrounding layer is set VAD pulling speed V, V=11.58/ (39.94Ro
5 2-Ro
2), the cm/min of unit.Deposit the SiO of the q.s that needs by pulling speed control
2Surrounding layer.After deposition is finished, vertically insert in the special-purpose dehydration-sintering oven forming Porous base rod, pass into oxygen and chlorine in the stove, drive away moisture and other various impurity; Then, will dewater-sintering oven is warmed up to about 1600 ℃, and Porous base rod makes loose Porous base rod change transparent preform into through high temperature sintering.Detect through the prefabricated rods analyser, mean outside diameter is 71.89mm, and length is 910mm approximately, and each stratum proportion remains unchanged in the plug, and the structure of prefabricated rods can represent with external diameter with the 5th layer simply.Shown in Figure 14 is the prefabricated rods of the embodiment of the invention 2 and the 5th layer diameter axial distribution, and shown in Figure 15 is that the prefabricated rods external diameter is to the ratio of the 5th layer of diameter.As can be seen from Figure 14, the tapering of prefabricated rods external diameter still exists, but its normalization method size optical texture is uniformly as can be seen from Figure 15, mean pull into 125um optical fiber after, the optical property of its optical fiber will be uniform.Prefabricated rods is drawing optic fibre 300km altogether, is divided into 28 coiled optical fibers and tests.The indices of optical fiber all satisfies product requirement, main performance index: 1460,1530,1550,1565, dispersion (Dispersion, the D) average of 1625nm is respectively 1.18,5.90,7.23,8.25,11.0 4ps/nm/km, zero-dispersion slop (Zero Dispersion Slop, D
S0) be 0.064 ps/nm
2/ km, zero-dispersion wavelength (Zero Dispersion Wavelength, λ 0) be 1443nm, fiber cut off wavelength (Cutoff wavelength, λ c) be 1333nm, cable cut-off wavelength (Cable cutoff wavelength, λ cc) is 1236nm, mode field diameter (Mode Field Diameter, MFD) is 9.55um.Shown in Figure 16 is MFD, the λ of the embodiment of the invention 2 optical fiber that draws
0, λ c, S
0With the distribution of D, the corresponding fiber lengths of X-coordinate.As seen the performance uniformity of optical fiber is high, owing to effectively having utilized tapering part, the length of prefabricated rods to increase approximately 14%, the production efficiency of optical fiber has increased nearly 15%.
The definition of term among the present invention:
The refractive index contrast Δ
iDefined by following equation:
The refractive index contrast Δ
i=(
n i 2-
n 0 2)/2
n i 2(1)
Wherein
n i Be the maximum value of the optical fibre refractivity of i layer,
n 0 Be the specific refractory power of outermost covering (pure silicon dioxide glass part), it is the specific refractory power of layer 6 in this application, as the reference specific refractory power.
Fibre-optic waveguide structure normalization method scantlings of the structure diameter R
i' be defined as i structural sheet diameter R
iTo the first layer diameter R
1Ratio:
R
i'=R
i/ R
1, i is the structural sheet code name.
Axially controlling in the VAD covering deposition is the gordian technique that realizes prefabricated rods surrounding layer coupling.According to the fibre-optic waveguide structure, the optical fiber external diameter is to i layer diameter R
iNormalization method structure coefficient G
iDefinition:
G
i=125/R
i,
Plug external diameter after the extension is Ro, corresponding i layer diameter Ro
i, the theoretical external diameter of prefabricated rods is made as D, and D=G is then arranged
iRo
i
If VAD technique SiO
2The sedimentation velocity of dust is W (g/min), and the barred body pulling speed is V (cm/min), and the density of the pure silica glass of surrounding layer is 2.2g/cm in theory
2, can obtain the control formula V=of barred body pulling speed
f(W, Ro, Ro
i),
V=0.579W/(?G
i 2·Ro
i 2-?Ro
2)
Plug contraction ratio η is defined as
η=L
1/L
0，
Wherein, L
0Be plug initial length ratio, L
1Be SiO
2Length behind the dust surrounding layer sintering.
Claims (4)
1. the axial uniform preform making method of an optical waveguides is characterized in that may further comprise the steps:
Chemical gaseous phase depositing process prepares plug in A, the employing pipe, makes the normalization method size of each layer of plug consistent with specific refractory power through axially controlling;
B, plug extended make the target rod;
C, when setting the surrounding layer of needs and deposition surrounding layer according to the requirement of the specification data of target rod and fibre-optic waveguide normalization method size to the pulling speed of target rod; Pulling speed V=0.579W/ (G to the target rod
i 2Ro
i 2-Ro
2), wherein W is SiO
2The sedimentation velocity of dust, G
iBe the normalization method structure coefficient of optical fiber external diameter to the i layer, Ro, Ro
iBe respectively the diameter of target rod and target rod i layer; Adopt axial chemical Vapor deposition process to prepare SiO at the target rod
2The dust surrounding layer is through the surrounding layer of axially control deposition by the normalization method size decision of fibre-optic waveguide, with loose SiO
2Dust surrounding layer sintering densification namely obtains the uniform prefabricated rods of fibre-optic waveguide;
Wherein, normalization method is of a size of each layer with respect to the scale-up factor of one deck wherein.
2. the axial uniformly preform making method of optical waveguides according to claim 1, it is characterized in that: chemical gaseous phase depositing process is that unstripped gas is passed in the silica glass parent tube in the described pipe, under hot conditions, carry out chemical reaction and obtain dust deposit to the parent tube internal surface, after the covering of plug and sandwich layer deposition were complete, making the covering of parent tube, plug and sandwich layer be collapsed into a solid glass rod under higher temperature became plug.
3. the axial uniformly preform making method of optical waveguides according to claim 1 is characterized in that: set according to the shrinkage rates of the external diameter of target prefabricated rods and plug and extend target and extend plug and make the target rod.
4. the axial uniformly preform making method of optical waveguides according to claim 1, it is characterized in that: described axial chemical Vapor deposition process prepares SiO at the target rod
2The dust surrounding layer is reaction raw materials to be passed into delivery system send into deposit cavity, produces SiO with flame hydrolysis
2Dust, SiO
2Dust deposit forms loose SiO at the target rod
2The dust surrounding layer.
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