CN100334023C - Large scale optical fibre prefabricated rod preparation and optical fibre drawing method - Google Patents

Abstract

The present invention relates to a device and an optical fiber drawing method for preparing a large scale optical fiber prefabricated rod. The device uses an internal tube method or an external deposition method to prepare a core rod of the large scale optical fiber prefabricated rod. A plurality of core rods are welded together and are inserted into a cylinder so as to make the optical fiber prefabricated rod which is inserted into a drawing furnace for drawing after temperature rise. The drawing furnace is fed by the core rods and the cylinder according to respective motion rates. The feeding rate of each core rod is greater than that of the cylinder. The core rods are compressed in the process of drawing. Optical fibers which are pulled out are wound on a fiber receiving cylinder by a fiber receiving device. The present invention can reduce the production cost of the optical fibers, and can prepare the large scale optical fiber prefabricated rod by the existing production device conditions. Thereby, the present invention effectively improves the production capacity of the existing process. Besides, the continuous drawing length of the optical fiber drawing method of the present invention can exceed 1000 km.

Description

The preparation method of large-scale optical fiber prefabricating stick

Technical field

The present invention relates to a kind of preparation method of large-scale optical fiber prefabricating stick.

Background technology

In order to reduce the optical fiber production cost, the size of preform constantly increases, and length constantly increases, and the length of string of single prefabricated rods develops into thousands of kilometer from tens kilometers, has improved production efficiency.The diameter of large-scale optical fiber prefabricating stick generally all surpasses 100 millimeters now.

The manufacturing process of preform develops into and all adopts two step method now, promptly makes plug earlier, adopts different technology to make surrounding layer at mandrel outer then.

The plug manufacturing process generally is divided into intraductal deposition process and outside deposition technology two big classes, wherein, intraductal deposition process comprises improved chemical vapour deposition (MCVD) and nonthermal plasma chemistry vapour deposition (PCVD), and outside deposition technology comprises outside vapor deposition process (OVD) and axial vapor deposition (VAD).

Intraductal deposition process as MCVD and PCVD, is with SiCl ₄, GeCl ₄And in other reactant gases feeding quartz substrate pipe, under extra power effects such as oxyhydrogen flame, electrical heater or microwave, react then.The advantage of method is accurately to control optical fiber structure in the pipe, but the plug size is limited by substrate tube, thereby has limited final preform size.

Outside deposition technology as OVD and VAD, is with SiCl ₄, GeCl ₄And other reactant gas feeding flame, flame hydrolysis takes place, deposit at target rod outside surface.The advantage of external deposition method is the sedimentation rate height, is suitable for making the large size plug, and size is big more, and raw-material utilization ratio is high more, and sedimentation rate is also high more.But its control ratio to fibre profile is more coarse.

The surrounding layer manufacturing technology mainly contains tiretube process, external sediment method and plasma spraying process.Wherein tiretube process is plug to be inserted form preform in the quartz glass sleeve.

The sleeve pipe that optical fiber manufacturing is at present used mainly adopts the manufacturing of OVD method, deposits SiO on the target rod ₂Powder sinters glass then into, the target rod is taken away the back again and is formed cylindric Glass tubing.This cylinder (Cylinder) Glass tubing has very high geometric accuracy through mechanical workout.Quartz glass sleeve pulls into small size quartz glass tube (Tube) by this large size cylinder exactly, so tiretube process claims RIT (Rod In Tube) technology again.In recent years, make efficient and reduce production costs in order to improve optical fiber, tiretube process begins directly to adopt cylinder, has formed RlC (Rod In Cylinder) technology, and the simple optical fiber prefabricated stick drawn wire length of Zu Chenging can be above 1000 kilometers like this.

In order to give full play to the advantage of RIC technology, cylinder (Cylinder) needs 120 millimeters～200 millimeters major diameters and long length, and length can reach 3 meters, so gross weight is big.In order to bear such weight, target rod size can not be too small, and the internal diameter of final Glass tubing cylinder is subjected to certain restriction thus, generally all greater than 45 millimeters.

Adopt external deposition method (OVD and VAD) can prepare the plug of large-size, but because the characteristics of technology have determined that its core/bag is bigger than requiring, if directly preparation can be inserted the plug of cylinder, do not bring into play the advantage of external deposition method on the one hand, Shi Ji length of string is restricted on the other hand.Therefore be preparation large size plug in the actual production, be drawn into the small size plug then and use.As United States Patent (USP) 6,131, the large size plug of introducing in 415 with the VAD preparation is drawn into the small size plug.But handled stretching process separately so then many, needing increases stretcher, and the optical fiber production cost is increased.

The plug that adopts method (MCVD and PCVD) preparation in the pipe is owing to be subjected to the restriction of substrate tube size, and its diameter is generally all less than 40 millimeters.If plug is inserted directly wire drawing in the cylinder, then the excessive clearance between plug and the cylinder is understood the geometric parameter that influence optical fiber, as fibre cladding circularity and sandwich layer/covering concentricity etc. in drawing process.

In order to address this problem, can between plug and cylinder, increase one or more gaps sleeve pipe, reducing the gap between plug and the cylinder, thereby improve the geometrical performance of optical fiber.United States Patent (USP) 6,460,378 B1 and U.S. Patent application 2005/0064188 A1 have introduced this method.But the gap telescopic makes technology be tending towards complicated, and has increased an interface newly, makes the cleaning at interface and drying become strict more, is unfavorable for optical fiber quality control.

Another thinking of dealing with problems is to adopt plug " compression " technology to increase the size of plug.So-called compression process is a notion relative with drawing process, promptly plug is applied external mechanical force and makes it to be compressed, thereby obtain larger-diameter plug.European patent EP 1156018 A1 and U.S. Pat 6,553,790 B1 disclose so a kind of technology, and heating makes it softening to plug, apply drawing force or pressure then to obtain the plug of different diameter.Chinese invention patent application 200310102706.0 introduced MCVD is molten shorten solid bar into after, along y direction compression plug, it is short but the bigger plug of diameter places the sleeve pipe wire drawing to such plug then to make length.Chinese invention patent application 03124114.X discloses similar techniques, adjusts drawing force or force of compression according to the diameter Distribution of prefabricated rods, to improve the homogeneity of prefabricated rods diameter.But the technology that these methods are introduced all is an independently technological process, has increased the manufacturing process of preform, is unfavorable for reducing the optical fiber production cost.

Summary of the invention

One object of the present invention is in order to reduce the optical fiber production cost, a kind of method for preparing large-scale optical fiber prefabricating stick that solves is provided, adopt this method can use the existing equipment condition, prepare large-scale optical fiber prefabricating stick, thereby effectively improve the production capacity of existing technology.

Another object of the present invention provides a kind of drawing process of large-scale optical fiber prefabricating stick, adopts the continuous length of string of this method above 1000 kilometers.

The present invention mainly may further comprise the steps:

(1) adopt interior method of pipe or external deposition method to prepare the plug of preform;

(2) many plugs are welded together and insert form preform in the cylinder;

(3) preform is inserted in the fiber drawing furnace, the back wire drawing heats up; Plug and cylinder are pressed movement rate feeding in fiber drawing furnace separately, and the plug input speed is compressed plug greater than the cylinder input speed in drawing process; The optical fiber of pulling out is wrapped on the wire drawing tube by receiving silk device.Compression ratio is a length and compression back length ratio before the plug compression, and compression ratio is greater than 1.0, less than 9.0.Described plug with respect to the input speed of cylinder greater than zero, less than 8.0m/min.

Core of the present invention is in the drawing process, controls the input speed of plug and cylinder respectively, and the softening plug of the heat that utilizes fiber drawing furnace to provide makes it to be compressed under external force, thereby reduces the gap between plug and the cylinder, and reaches the matching size that needs.

For convenience of description, do to give a definition and to suppose:

Term definition:

Plug: manage interior method deposition after melt the solid bar that contracts and form, comprise the sandwich layer and the part covering of optical fiber.

Cylinder: by the OVD prepared, through the cylindric quartz glass tube of the large size of mechanical workout, high geometric accuracy.

CSA: sectional area, Cross-Section Area writes a Chinese character in simplified form.

Deposition: by the sedimentary quantity of material of method in the pipe what, represent in the reflection optical fiber with its diameter in cross section of optic fibre.

Compression ratio: length and compression back length ratio before the plug compression.

Suppose:

1., the compression before plug 4 center core layer 3 diameters be a, diameter of mandrel is c, useful length is 1 ₀ Cylinder 5 internal diameters are D ₀, external diameter is D ₁, length is L; Optical fiber 2 center core layer 1 diameter is s ₀, external diameter is s ₁

2., plug 6 relative cylinder 5 speed are v ₁The input speed of cylinder 5 relative fiber drawing furnaces 10 is v ₂The drawing speed of optical fiber 11 is v ₃

3., the process deposits amount is b; Compression ratio y.

On the basis of above definition and hypothesis, describe technological process of the present invention below in detail.

1, plug preparation;

Before the relative dimensions of calculating plug, need to determine the deposition b that estimates, the compression ratio y that hope reaches earlier, and, utilize known data to determine the size of plug center core layer, i.e. a value according to the geometric relationship between optical fiber shown in Figure 1, plug and the cylinder.Carry out program setting on this basis, the preparation plug.

Calculation formula is as follows:

Compression back plug center core layer diameter is: $a^{\′}=a\×\sqrt{y}$

Then compression back plug settled layer diameter is: $b^{\′}=\frac{b}{s_0}\×a^{\′}$

Calculate the sectional area of compression back plug in view of the above: ${\mathrm{CSA}}_{\mathrm{core}-\mathrm{rod}}^{\′}={\mathrm{CSA}}_{s.t.}\×y+\frac{\mathrm{\π}}{4}\×b^{\′2}$

The cylinder section that then needs is long-pending to be: ${\mathrm{CSA}}_{\mathrm{cylinder}}=\frac{\mathrm{\π}}{4}\×\frac{a^{{\′}^2}\×{s_1}^2}{{s_0}^2}-{\mathrm{CSA}}_{\mathrm{core}-\mathrm{rod}}^{\′}$

CSA wherein _CylinderAnd CSA _S.t.Be respectively the sectional area of cylinder and bushing pipe, can calculate and get by external diameter in it.Because s ₀, s ₁, b, y, CSA _Cylinder, CSA _S.t.Equivalence is all known, therefore can calculate a value.

Aforementioned calculation can be undertaken by computer program, and can set flexibly optical fiber structure, to make different sorts, the different fibre-optical mandrel that requires.

2, preform preparation;

The plug useful length of the rapid preparation of previous step is I ₀, the plug total length I ' that can calculate actual needs by the length and the compression ratio of cylinder, that is:

1’=L×y， $n=\frac{1^{\′}}{1_0}$

According to this length requirement, n root plug is welded together, insert then in the cylinder, form preform.N can be for arbitrarily greater than 1 value in principle, but gets 0.5 integral multiple from production efficiency n, and greater than 1.

Welding can adopt oxyhydrogen flame to carry out as thermal source, because the optical fiber water peak that oxyhydrogen flame causes increases, can also adopt electrical heater or plasma body to carry out welding as thermal source in order to reduce.

Long plug 6 after the welding connects and prolongs rod 8, by normal procedure clean, drying.

As shown in Figure 2, cylinder 5 is connected prolongation pipe 7, then long plug 6 is fitted in the cylinder, will prolong the seal of tube and fixed plug with plug 9.

3, wire drawing;

Preform is fixed with chuck, its bottom is placed in the fiber drawing furnace 10.Raise then furnace temperature to 2000～2200 ℃, the tapering 12 that makes prefabricated rods is softening and be pumped into bare fibre 11.

By default compression interrelated geometrical parameters when, can be by drawing speed v ₃Calculate the input speed of plug and cylinder.

Wherein, the input speed of the relative fiber drawing furnace of cylinder is:

$v_2=\frac{{\mathrm{CSA}}_{\mathrm{fiber}}}{{\mathrm{CSA}}_{\mathrm{cylinder}}+{\mathrm{CSA}}_{\mathrm{core}-\mathrm{rod}}^{\′}}\×v_3$

And plug with respect to the movement velocity of cylinder is:

$v_1=\frac{{\mathrm{CSA}}_{\mathrm{fiber}}\×v_3-{\mathrm{CSA}}_{\mathrm{cylinder}}\×v_2-{\mathrm{CSA}}_{\mathrm{core}-\mathrm{rod}}\×v_2}{{\mathrm{CSA}}_{\mathrm{core}-\mathrm{rod}}}$

Wherein, CSA _Core-rodBe the plug sectional area before compressing, CSA _Core-rod=CSA ' _Core-rod/ y, CSA _FiberBe the sectional area of optical fiber, can be directly calculate by the external diameter of optical fiber.

By servo control mechanism plug is applied power F, make plug with respect to cylinder v ₁The speed charging.Plug is heated 13 and is compressed after the deliquescing, increases at 13 position diameter of mandrel.Cylinder is then under the transmission rig effect, with speed v ₂Charging.

The bare fibre 11 that draws passes applicator and solidified cell then successively by monitoring equipment control diameter, is wrapped on the wire drawing tube at last.

Those of ordinary skill in the art knows, can do various improvement and variation to the present invention under conditions without departing from the scope of the present invention.For example plug can also can be made by external deposition method by method preparation in the pipe.Therefore, the present invention will comprise these improvement and variation, as long as they are in claims scope and content of equal value thereof.

As mentioned above, the present invention can prepare large-scale optical fiber prefabricating stick, and a kind of method of continuous drawing large-scale optical fiber prefabricating stick is provided.

The present invention can reduce the optical fiber production cost, can use the existing equipment condition, prepare the large-scale optical fiber prefabricating stick that diameter surpasses 100 millimeters, thereby effectively improve the throughput of existing method, and the continuous length of string of method for drawing optical fibers of the present invention is above 1000 kilometers.

Description of drawings

Fig. 1 a is the cross section of optic fibre structural representation.

Fig. 1 b plug cross-sectional structure synoptic diagram.

Fig. 1 c cylinder cross-sectional structure synoptic diagram.

Fig. 2 is the preform synoptic diagram that the present invention assembles.

Fig. 3 is a view before the wire drawing of the present invention.

Fig. 4 is a drawing process synoptic diagram of the present invention.

Embodiment

Embodiment 1

The employing internal diameter is 50mm, and external diameter is 150mm, and useful length is that the cylinder of 3000mm is produced G.652.B single-mode fiber.The core diameter of optical fiber is 8.6um, and external diameter is 125um.The deposition of 20um is adopted in design, and compression ratio is decided to be 2.0.Then can calculate according to formula:

a＝7.05mm，c＝22.38mm。Total rod of actual needs is long: I '=6000mm

Prepare plug by aforementioned parameters, the useful length of plug is 1000mm, therefore 6 plugs is welded together with oxyhydrogen flame, forms new long plug.After cleaning and drying, will be assembled into preform in this plug insertion cylinder.

Preform is entered in the fiber drawing furnace, and heating up by setup program makes the end of preform be subjected to thermal softening.According to actual drawing speed, advance plug and cylinder according to following set(ting)value.

v 3(m/min)	v 2(mm/min)	v 1(mm/min)	v 3(m/min)	v 2(mm/min)	v 1(mm/min)
						200	0.15	0.15	900	0.67	0.67
300	0.22	0.22	1000	0.74	0.74
						400	0.30	0.30	1100	0.82	0.82
500	0.37	0.37	1200	0.89	0.89
						600	0.45	0.45	1300	0.97	0.97
700	0.52	0.52	1400	1.04	1.04
						800	0.60	0.60	1500	1.12	1.12

Last stabilized fiber fixes on the drawing speed of 1500m/min, and the optical fiber total length of drawing is 8000km, and every performance meets the requirement of ITU-TG.652.B sonet standard, and the significant parameter of optical fiber is as follows:

Optical parametric
			Decay 1310nm 1550nm	0.332	dB/km
0.188	dB/km
		Chromatic dispersion 1310nm 1550nm		-0.334	ps/(nm.km)
16.45	ps/(nm.km)
			Mode field diameter 1310nm	9.20	um
Polarization mode dispersion	0.036	ps/√km
			Geometric parameter
Cladding diameter	124.8	um
			Sandwich layer/covering concentricity	0.21	um
Non-circularity of cladding	0.38	％
			Coating diameter	245.5	um
Coating/covering concentricity	2.8	um

Embodiment 2

The employing internal diameter is 46mm, and external diameter is 120mm, and length is produced G.652.D single-mode fiber for the cylinder of 1500m.The core diameter of this optical fiber is 8.6um, and external diameter is 125um.Adopt the deposition of 22um, compression ratio is decided to be 2.67.Then can calculate: a=4.86mm, c=19.66mm according to formula.Total rod of actual needs is long: I '=4000mm.

Prepare plug by aforementioned parameters, the useful length of plug is 1000mm, and 4 plugs are welded together with flame passes, forms new long plug.After cleaning and drying, will be assembled into preform in this plug insertion cylinder.

The same operation is according to actual drawing speed, by following setting control plug and cylinder input speed.

v 3(m/min)	v 2(mm/min)	v 1(mm/min)	v 3(m/min)	v 2(mm/min)	v 1(mm/min)
						200	0.23	0.39	700	0.82	1.37
300	0.35	0.59	800	0.94	1.56
						400	0.47	0.78	900	1.06	1.76
500	0.59	0.98	1000	1.17	1.96
						600	0.70	1.17	1200	1.41	2.35

Last drawing speed is stabilized in 1200m/min, and the optical fiber total length of drawing is 3400km, and every index all meets the G.652.D requirement of sonet standard of ITU-T.Significant parameter is as follows:

Optical parametric
			Decay 1310nm 1383nm (the aging back of hydrogen)	0.336	dB/km
0.297	dB/km
		1550nm		0.192	dB/km
Chromatic dispersion 1310nm 1550nm	-0.215		ps/(nm.km)
		16.36		ps/(nm.km)
	Mode field diameter 1310nm		9.16		um
Polarization mode dispersion		0.024		ps/√km
	Geometric parameter
Cladding diameter				125.4	um
	Sandwich layer/covering concentricity	0.33	um
Non-circularity of cladding				0.28	％
	Coating diameter	245.3	um
Coating/covering concentricity				4.8	um

The embodiment that more than provides is for this patent is described, rather than to the restriction of this patent.The described method of this patent is not only applicable to G.652 single-mode fiber, is applicable to other various optical fiber yet.

Claims (3)

1, the preparation method of large-scale optical fiber prefabricating stick adopts method in the pipe or external deposition method to prepare the plug of large-scale optical fiber prefabricating stick, and the plug of n root large-scale optical fiber prefabricating stick is welded together, and inserts in the cylinder and make large-scale optical fiber prefabricating stick, $n=\frac{l^{\′}}{l_0},$ L wherein ₀Be the plug useful length, l '=L * y, wherein L is the length of cylinder, and y is a compression ratio, and compression ratio is a length and compression back length ratio before the plug compression.

2, method according to claim 1 is characterized in that described plug welding employing oxyhydrogen flame, electrical heater or plasma body carry out welding as thermal source.

3, method according to claim 1 is characterized in that: compression ratio is greater than 1.0, less than 9.0.

Images