CN1121053A - "Geometric Process" for prepn of special optical fibre - Google Patents

Abstract

The present technological process features that the whole work of preparing special optical fibre is based on several quartz glass cylinders containing circular symmetrical sediment material. The cylinders are first cut and ground according to geometric requirement and then compose required prefabricated rod, which is finally drawn out into fibre. The said process has wide suitability in preparing special optical fibre conforming original design.

Description

" geometric Process " of preparation special optical fiber

The present invention discloses preparation " special type " optical fiber, or claims the simple and easy processing method a kind of novelty, effective and applied widely of " unconventional " optical fiber.According to the characteristics of this kind method in technological process, be referred to as " geometric Process of special optical fiber " (GeometricalMethod of Special Fiber Fabrication).

Research and development from optical fiber technology, on the basis of conventional fiber research, carry out the research of special optical fiber, its topmost power be because, conventional fiber (its cross section structure circle symmetry) can not be realized stable polarization mode transmission, so many fibre systems (as coherent fiber communication, fiber optic gyro, light footpath between fields interferometer) require special optical fiber, make transmission luminous energy remain on the stable polarization mode.Usually so-called " single mode " optical fiber, it is conventional single-mode fiber, be actually " bimodulus " optical fiber, in optical fiber, exist two degeneracy polarization modes of mutually orthogonal, so any perturbation that actual fiber stood all can produce the conversion of power and conversion again between bimodulus, in other words, produce the variation of polarization state.Exist this inherent troublesome problem just because of conventional single-mode fiber, so the optical fiber investigator has to work hard, to seek various special optical fibers.

On technology, preparing various special optical fibers has difficulty in various degree than preparation conventional (circle symmetry) optical fiber.The MCVD that the optical fiber investigator knows (Modified Chemical Vapor Deposition) method is AT﹠amp; Mc doctor Chesney of TBell invents; Britain University of Southampton utilizes part (gas phase fluorine) etch on the basis of MCVD method, successfully made " knot " shape special optical fiber, is acknowledged as a very real accomplishment.In Japan, taked the technology approach of another kind of preparation special optical fiber, it is the blank pipe that gets out two cylinder body shapes in the single mode prefabricated rods that VAD (vapor axial deposition) method is made along axis, and (its geometric position is symmetrical in the axle center) is adjacent to two stress rods then and imbeds blank pipe; Special optical fiber with this method is made is called " panda " optical fiber, and is also very successful.In Japan, another kind of successful special optical fiber is (cylindrical) interior elliptical clad fiber, and its processing method is to introduce " rod is received in decompression " technology on the basis of MCVD method, and without the partial corrosion technology.In the U.S., what healthy and free from worry (Corning) company used is again a kind of processing method, its major technique is to insert plug in silica glass bushing pipe inside along axis, insert how much symmetric two stress rods on the plug both sides, and fill up glass stick in the blank parts of bushing pipe inside, can be used to stringy special optical fiber prefabricated rods thereby constitute.This processing method also is a kind of successful method, is called healthy and free from worry technology (CorningTechnique), the optical fiber that wire drawing is come out, and its structural shape is similar to panda optic fibre (stressed zone is generally not really round, but does not influence the performance that it keeps polarization state).In the U.S., another attracting invention is AT﹠amp; The oval inner cladding optical fiber of the flat of T Bell, its major advantage are to be easy to determine orientations of major; The processing method for preparing this kind optical fiber is that oval inner cladding prefabricated rods is flattened in the heating of the short-axis direction of ellipse, the prefabricated rods wire drawing at low temperatures of then this having been flattened.

The processing method of the preparation special optical fiber of Cai Yonging is not above-mentioned several outward in the world.Except that these representational, basic processing methodes, also also have some meliorative processing methodes, for example, in Australia, will part " weak " corrosion the two combines with " decompression receive excellent ", the maintenance polarization state special optical fiber that utilizes the MCVD method to make to be better than common oval inner cladding optical fiber.At home, foreign imitation development " knot " " oval inner cladding " also carried out a lot of years with the work of " bear is retouched " optical fiber.About adding that with the MCVD method partial corrosion technology prepares tie fiber, one of existing technical problem is a circularity that cannot say for sure to demonstrate,prove fibre core, this be because, this method in receiving rod motion since the stressed zone from both sides to the fuse stress application, and fuse is in hot melting state, so be easy to become elliptical shape in various degree.About the manufacturing of panda optic fibre, require primary single mode rod thicker, be beneficial to boring.External report is holed with ultrasonic technique, this kind technical qualification still have any problem at home (domestic ultrasonic drilling is generally dark inadequately, and precision also is difficult for reaching requirement).About the healthy and free from worry technology of preparation class panda optic fibre, because of Corning Incorporated holds in close confidence, still fail in the native land to grasp, also do not see the report that this respect real work is arranged.This technology is also uncomplicated from the principle, but then difficult in practice, because plug and the stress rods position in sleeve pipe needs the strict sight alignment that keeps through whole drawing process, two stress rods need strict symmetry with respect to fibre core, the filling glass rod need be close to mutually, or the like.Above-mentioned several representational Technology, the rod that draws that wherein prepares tie fiber and the used prefabricated rods of oval inner cladding optical fiber is the solid glass rod, the prefabricated rods of panda optic fibre and healthy and free from worry casing fiber optic is drawn rod then need use hollow glass tube, and have venting hole on the tube wall, so that in the heating drawing process, get rid of the bubble in the air gap between inner each binding face of prefabricated rods.

About AT﹠amp; T Bell makes the technology of flat ellipse optical fiber with pressure sintering, domesticly grasps as yet so far.It is very simple that the method for hot pressing prefabricated rods is imagined, but in fact difficulty is very big.On physical conception, the softening temperature of boron-doping stressor layers and fluxing point are lower than germnium doped core.Lower than quartzy surrounding layer, so, adding in the hot procedure, the boron-doping inner cladding is softening at first, so fuse can move in the stressed zone, its final position is decided by that temperature and pressure applies situation.Temperature, pressure are not high enough, then prefabricated rods press not flat, and temperature, pressure go beyond the limit or its when distributing imbalance, the fuse of then pulling out optical fiber is not placed in the middle, even whole optical fiber structure wrecks.

The object of the present invention is to provide the processing method of the preparation special optical fiber of a kind of novelty and practicality.

The processing method of this preparation special optical fiber, be called " geometric Process ", it is characterized in that, used starting materials and structure thereof are the symmetrical doped-glass cylinders of several circles, geometrical shape according to special optical fiber is reprocessed these cylinders, thereby is put together required prefabricated rods geometrical shape, then with an end of this subassembly with draw excellent welding mutually, the other end is melt into cone shape, becomes fine for wire drawing.Compare with above-mentioned various processing methodes, it both had been different from the MCVD method for preparing tie fiber and had added gas phase partial corrosion technology, be different from the MCVD method for preparing oval inner cladding optical fiber and add the excellent technology of decompression receipts, " the stress post embedment method " and " tiretube process " that also are different from preparation panda optic fibre and healthy and free from worry polarization maintaining optical fibre, and " hot pressing prefabricated rods " method of preparation flat optical fiber.According to the characteristics of the inventive method, for the sake of simplicity, be referred to as " geometric Process " of special optical fiber.

The novelty of the inventive method or its projecting point have two.One of characteristics are: prepare special optical fiber with the inventive method, only need the symmetric identical or different doped-glass cylinder of several circles, and need not other any material; Its easy-to-use conventional MCVD method or other method make this kind doped column because it justifies symmetry (not containing the symmetrical body of any non-circle).The investigator who participated in optical fiber fabrication technology is familiar with, and with the symmetrical doped-glass column structure of MCVD manufactured circle, non-round symmetrical structure is much simple and easy than making, and only need deposit, receive excellent operation and get final product.With the symmetrical doped-glass cylinder of two or more circles is starting materials or " part ", reprocess according to the geometry of required special optical fiber, thus the geometrical body of the special optical fiber prefabricated rods that is put together.

Two of the characteristics of the inventive method are all need not glue together or heat fusion between contained each the amalgamation face of above-mentioned prefabricated rods body.For making the precast segment structure firmly firm, only need with the two ends of this unit construction in addition heat fusion get final product (it is constant that the main part former state in amalgamation face gap is left in the centre); One of these two ends end is melt into taper, so that wire drawing, its other end then draws excellent welding mutually with solid glass.Keep the space between amalgamation face in the combination prefabricated rods, when wire drawing, play a part to get rid of bubble.

First characteristics of the invention described above method are considered from intuition, are understood that; And second characteristic then at first glance generally is difficult for being accepted by the optical fiber fabrication technology investigator.Be in dispersion state because the intermediate host of precast segment partly is actually, do not glued together or fuse.Yet,, just can understand through more careful thinking, this is considered to unreasonable point easily and is reasonably in fact, suits, because the silica glass component two ends are fused respectively, its intensity has been enough to cause a firm firm prefabricated rods, stands straight line or rotation wire drawing.Become in the fine process in whole wire drawing, move on the taper fused portion is continuous, but remain its fusion state.In fact, think that instinctively whole amalgamation faces need to be glued together or fuse, not all right on the contrary, because, so, in the drawing process there be not deflated mechanism, and the introducing of glueing material also may influence the characteristic that wire drawing becomes fibre, and fusion processing is difficult for getting rid of all bubbles in the amalgamation prefabricated rods, and easily makes structural distortion.Our a large amount of process practice has fully confirmed above-mentioned argument.

In the present invention, all justify the reprocessing of symmetrical doped-glass cylinders, generally only require the grinding process of cutting of plane or circular arc, need not to carry out the processing of abnormity geometry, so very simple and easy on Technology.Draw rod and get final product, need not with the open tube that has venting hole (amalgamation face keeps the space in the prefabricated rods, plays a part nature and get rid of bubble in wire drawing) with the solid glass rod.The used combination prefabricated rods of this Process does not add sleeve pipe, thereby the geometry and the positioning requirements of prefabricated rods have further been simplified, and simplified the design of special optical fiber, this be because, the originally influence of all not reprocessed according to designed fiber size of single mode condition and core size etc.

In sum, the inventive method is compared with MCVD gas phase partial corrosion method, and multiple working procedure that must be required after having avoided (deposition boron or aluminium → to burning partial corrosion → deposit Germanium → receipts rod.Conventional operations such as deposition buffer layer not very); Compare with the technology of the oval inner cladding optical fiber of preparation, need not to use decompression to receive the special technique of rod; " stress post embedment method " compared, and avoided the desired ultrasonic drilling technology of the latter; " tiretube process " compared, and avoided in desired geometry location of the latter and the pipe many glass sticks to be close to mutually and uses exhaust to draw rod etc.In addition, existing various successful processing method, it is effective being used for preparing how much regular special optical fibers (as tie fiber, panda optic fibre, oval inner cladding optical fiber, healthy and free from worry optical fiber), but be used for preparing special more special optical fiber, then must on the basis of maturation method, introduce various special technical skill.From the various embodiments of the following stated as seen, the inventive method has very extensive applicability for the preparation special optical fiber.

Below in conjunction with accompanying drawing and relevant embodiment, be that " geometric Process " described in detail to the inventive method.

Fig. 1 shows the processing sequence of usefulness " geometric Process " preparation spiral optical fiber.

Fig. 2 shows that " geometric Process prepares the processing sequence of twin-core fiber to usefulness.

Fig. 3 shows the processing sequence of usefulness " geometric Process " preparation three core fibres.

Fig. 4 shows the processing sequence of usefulness " geometric Process " preparation flat high birefringence optical fiber.

Fig. 5 shows that usefulness " geometric Process " preparation circular polarization state keeps the processing sequence of optical fiber.

Fig. 6 shows the processing sequence of usefulness " geometric Process " preparation superelevation linear birefringence (superpower polarization maintaining optical fibre).

One of embodiment of the present invention's " geometric Process ": the preparation of spiral optical fiber.

Spiral optical fiber is that the mid-80 is invented by the Englishman.Domestic someone once attempts trying every possible means on the MCVD method fuse made and departs from the center, but does not succeed.Very easily make this kind special optical fiber with " geometric Process " of the present invention.

Whole technology manufactured materials of required usefulness only are a conventional single mode rod, add a quartz glass bar and get final product that (according to the requirement on how much, latter's diameter need slightly be coarser than the former, as shown in Figure 1).

With quartz glass bar (Fig. 1 a) cuts along straight dashed line, remove the small semicircle crescent moon need not, only use the large semicircle crescent moon.One edge straight dashed line of conventional single mode rod fibre core is cut (Fig. 1 b), straight dashed line equal in length among this straight dashed line and Fig. 1 a; Simultaneously, conventional single mode rod fibre core the other side is ground off imaginary circle camber line part in addition.Will cut two planar side (i.e. two straight dashed lines) phase amalgamation of mill back two cylinders, then an end and (solid) of amalgamation assembly are drawn excellent welding, the other end is melt into cone, thereby constitutes required special optical fiber prefabricated rods, be rotated wire drawing spiral optical fiber.As previously mentioned, two plane amalgamation faces of prefabricated rods intermediate host part neither glue together, and also do not fuse, and are beneficial to get rid of in the wire drawing bubble.Among Fig. 1, label 1 shows the quartz glass bar cylindrical; Label 2 shows single mode rod cylindrical, and label 3 shows fuse, and label 5 shows rifle bar or spiral optical fiber cylindrical.

In Fig. 1, a, b, c, be the barred body of cutting mill processing; The special optical fiber of d for pulling out, originally excellent intravital amalgamation interface (i.e. straight dashed line among the figure) fuse naturally through adding hot wire drawing, so inside of optical fibre does not contain gapped interface (that is not having straight dashed line among the figure d).

Two of the embodiment of the inventive method: the preparation of twin-core fiber.

This kind optical fiber is hopeful to be used for optical fibre devices such as fiber switch, coupling mechanism, modulator, wavelength division multiplexer, wave filter.This research is abroad carried out for many years; Not long ago, Australia once obtained considerable investment because of developing this research.

Prepare twin-core fiber with the inventive method, very simple and easy.Material therefor is two conventional single mode rods.According to distance and geometric layout thereof between desired twin-core, the every straight dotted line in single mode rod fuse one edge is cut a small semicircle; The fuse the other side is ground off a thin crescent moon along the circular arc dotted line (see Fig. 2 a, b).Barred body after two processing in both sides planar section (i.e. straight dotted line among the figure) phase amalgamation, is become the combination rod (Fig. 2 c) that contains twin-core, and its two ends are fused.After the straight line wire drawing twin-core fiber (Fig. 2 d).As be rotated wire drawing, then become duplex optical fiber.Among Fig. 2, label 7 is represented twin-core rod or twin-core fiber cylindrical, and label 3 is represented plug or fuse.

The preparation of three: three core fibres of the embodiment of the inventive method.

Three core fibres are newer research projects in the world.This kind special optical fiber is hopeful with being 3 * 3 coupling mechanisms, even is used for the full optical fibre top system.

Prepare three core fibres and prepare the technology of above-mentioned twin-core fiber similar with the inventive method, also do not bother.Material therefor be three single mode rods (Fig. 3 a, b, c).Wherein single mode rod all cuts along straight dotted line on the fuse both sides, and removing the narrowing toward each end semi-circular portions need not (Fig. 3 b).In addition the processing of two single modes then is similar to the situation of twin-core fiber single mode rod processing, one side every excellent fuse cut a small half of circle, the other side is worn into circular arc (Fig. 3 a, the circular arc dotted line among the 3c).According to in twos between fuse the geometric layout of the requirement of distance and three fuses process, three single mode rods after very easily will processing, paste and in addition amalgamation with its planar side two two-phases, promptly constitute required extraordinary prefabricated rods thereby constitute this barred body two ends fusion of combination barred body (Fig. 3 d) that includes three cores.Three core fibres that wire drawing forms are shown in Fig. 3 e.9 is three plugs or three core fibre cylindricals among Fig. 3, and the meaning of all the other labels is identical with the front.

Four of the embodiment of the inventive method: flat birefringence fiber.

This type of special optical fiber is U.S. AT﹠amp; T Bell invents, and its advantage is the main shaft that is easy to determine linear birefringence optical fiber, and is easy to optical fiber on cylinder.AT﹠amp; T makes this kind optical fiber with the Process that prefabricated rods is flattened in heating, and difficulty is very big, some technical problem AT﹠amp; T oneself is also still unresolved.Utilize the present invention's " geometric Process " preparation flat optical fiber, then avoid or reduced to a great extent the technical difficulty of " pressure sintering ".

Required starting materials be a conventional single mode rod and two round stress symmetric rods (Fig. 4 a, b, c).Number in the figure 13 is stressed zones, the 15th, and flat prefabricated rods outer rim, the 17th, flat optical fiber outer rim.All the other label implications are with preceding identical.Three barred bodies are cut mill processing by dotted line among the figure respectively.The planar side part of back three cylinders of processing is pasted mutually and amalgamation becomes the combination barred body.To make up barred body two ends fusions, required extraordinary prefabricated rods.Add hot wire drawing flat linear birefringence optical fiber (Fig. 4 e).

Adopting the low temperature wire drawing, still is flat with the optical fiber outer rim that keeps pulling out.As for making up four corner angle that barred body outer rim straight line and circular arc join, even then adopt the low temperature wire drawing, can become circular shape (shown in label 17 among Fig. 4 e) by the stress when adding hot wire drawing, but this result does not influence originally to the desired superiority of flat linear birefringence optical fiber yet.In addition, even add hot wire drawing at low temperatures, because the special geometry of flat preform and corresponding stress distribution thereof, two stress solids become fine through adding hot wire drawing, can cannot not become roundly yet, but still be symmetrical in fibre core, so do not influence the linear birefringence performance of flat optical fiber yet.

Five of the embodiment of the inventive method: circular polarization state keeps optical fiber.

This special optical fiber is the Chinese patent CN108894A patent that awaits the reply, belong to same contriver with this patent application, by its shape and structure, this circular polarization state keeps optical fiber to be called screw optical fiber (Screw fiber), to be different from existing spiral optical fiber (heliacl fiber), spin fiber (spun fiber), twisted fiber (twist fiber) etc.The processing method of suggested several preparation screw optical fiber all is sophisticated common process method in prospectus CN1088894A, as " stress post imbed single mode rod method " (or be called for short " lock pin method "), " extra heavy pipe cover plug and stress post method " (or be called for short " tiretube process ") etc., and do not comprise " geometric Process " of the present invention.

Facts have proved, with " geometric Process " of the present invention preparation screw optical fiber, than much simple and easy with common process method or its improving technology.Material requested is a conventional single mode rod and the round stress symmetric rod that summary is thick.(Fig. 5 a) cuts a small semicircle along straight dotted line among the figure with the single mode rod.To justify stress symmetric rod (Fig. 5 b) and be cut into small semicircle therewith with just as big but be surrounded by the small semicircle shape of stressed zone, shown in dotted line among Fig. 5 b.Barred body after these two processing pastes and amalgamation becomes a combination barred body (Fig. 5 c) mutually with its two planar side (being straight dotted line), and this barred body promptly constitutes required extraordinary prefabricated rods after two ends fusions.Rotation after the wire drawing required screw optical fiber (Fig. 5 d).Among Fig. 5, on behalf of circular polarization state, 19 keep the prefabricated rods cylindrical, and on behalf of circular polarization state, 2 keep the optical fiber cylindrical, and all the other label implications as hereinbefore.

Six of the embodiment of the inventive method: superpower line polarization maintaining optical fibre.

This special optical fiber is the China patent 93112381X that awaits the reply, and belongs to same contriver with this patent application.By its structural shape, this optical fiber can be described as " cruciform " optical fiber (crossfiber), but this title does not reflect the physical mechanism that produces the superelevation linear birefringence, and two knots or two panda optic fibre (wherein two counter stress district same materials) that Yi Yuyi discussed are in theory obscured mutually.So should be according to the physical mechanism of superpower linear birefringence generations, renaming as this kind optical fiber be saddle optical fiber (saddle fiber), emphasizing the wherein material of two counter stress faunas employing different heat expansion coefficient, is one to push away one and draw to the stress that fibre core applied.In the patent 933112381X that awaits the reply, the processing method of this kind of preparation saddle optical fiber of being considered is not outer to be several sophisticated common process methods, as deposition and the each post-depositional gas phase partial corrosion (twice corrosion region limit is at orthogonal space) that on the basis of MCVD method, adds the different stress materials of twice, and " lock pin method " and " tiretube process " etc., and do not comprise " geometric Process " of the present invention.

In patent application of the present invention, be that embodiment narrates " geometric Process " superior on using with preparation saddle optical fiber, be good at saying something.Material requested is a single mode rod and two pairs of stress rods that dopant material is different.With two pairs of round stress symmetric rods all cut the mill form fan-shaped, as Fig. 6 a, shown in the c.With two to (four) fan-shaped amalgamation in addition, the intermediary roundlet is the cylinder (Fig. 6 b) that contains plug then.Fusion back, this subassembly (Fig. 6 d) two ends required extraordinary prefabricated rods, after the wire drawing saddle optical fiber (Fig. 6 e).Number in the figure 23 is represented saddle preform cylindrical, and 25 represent saddle optical fiber cylindrical, and 13 and 14 represent the different stressed zone of thermal expansivity respectively.Fig. 6 a and 6c are following to be annotated * and this stress rods represented in 2 printed words, and each needs two meaning.When actual process is made,, can make the barred body of one two double-length earlier, be divided into two then for the characteristics such as geometry, material composition and concentration that make two barred bodies in every counter stress rod are all identical as far as possible.

Present patent application has disclosed " geometric Process " of the special optical fiber of being invented and has adopted this method to prepare the embodiment of varied special optical fiber.These embodiment only give an example for ease of the some of illustration method.Several the inventive method is used to prepare other special optical fiber, or basic inventive concept and may be obvious that the reasoning that obtains, claim scope of the present invention also belonged to.

Claims (7)

1. processing method for preparing special optical fiber, be called " geometric Process ", it is characterized in that, used starting materials and structure thereof are the symmetrical doped-glass cylinders of several circles, geometrical shape according to special optical fiber is reprocessed these cylinders, thereby is put together required prefabricated rods geometrical shape, then with an end of this subassembly with draw excellent welding mutually, the other end is melt into cone shape, becomes fine for wire drawing.

2. the spiral optical fiber that is prepared from according to claim 1 described " geometric Process ", its technology characteristics is, the starting materials structure contains two cylinders, and one is quartz glass bar, and one is slightly thin conventional single mode prefabricated rods, press the desired degree of eccentricity of spiral optical fiber and how much, two rods are cut mill, be about to the former and cut a crescent moon, the latter is cut into the crescent moon that contains fuse, carry out amalgamation then and form the prefabricated rods of core shift, will be rotated wire drawing behind its two ends heat fusion.

3. the twin-core fiber that is prepared from according to claim 1 described " geometric Process ", its technology characteristics is, the starting materials structure contains two conventional single mode prefabricated rods, press between the desired twin-core of twin-core fiber distance and how much, every rod is cut a small semicircle crescent moon respectively, carry out amalgamation then and form the prefabricated rods that contains twin-core, will carry out wire drawing behind its two ends heat fusion.

4. three core fibres that are prepared from according to claim 1 described " geometric Process ", its technology characteristics is, the starting materials structure contains three single mode prefabricated rods, by distance between the desired core of three core fibres and how much, preform core both sides are all cut crescent moon, other two prefabricated rods are cut mill form the crescent moon that contains fibre core, carry out amalgamation then and form the prefabricated rods that contains three cores, will carry out wire drawing behind its two ends heat fusion.

5. the flat linear polarization that is prepared from according to claim 1 described " geometric Process " keeps optical fiber, its technology characteristics is, the starting materials structure contains the glass stick that a conventional single mode prefabricated rods and two round symmetries are mixed stress material (boron or aluminium), last rod is cut into rectangle, back two rods are cut into the straight geometrical shape in circle three limits on one side, carry out amalgamation then and form the flat preform, will carry out wire drawing behind its two ends heat fusion.

6. the circular polarization state that is prepared from according to claim 1 described " geometric Process " keeps optical fiber, its technology characteristics is, the starting materials structure contains the glass stick that a conventional single mode prefabricated rods and thick round symmetry of summary are mixed stress material (boron or aluminium), the former is cut the crescent moon that is slightly less than semicircle that does not contain fuse, the latter is cut into the crescent moon that contains the stressed zone, carry out amalgamation then and form asymmetrical double refraction prefabricated rods, will be rotated wire drawing behind its two ends heat fusion.

7. the superpower line polarization maintaining optical fibre that is prepared from according to claim 1 described " geometric Process ", its technology characteristics is, the starting materials structure contains a conventional single mode prefabricated rods and two pairs of round symmetries and mixes the quartz glass cylinder of different stress materials and (wherein a pair ofly mix the material that thermal expansivity is higher than silica glass, as boron or aluminium; Another is to mixing the material that thermal expansivity is lower than silica glass, as titanium), with these two pairs of cylinders be symmetrical in respectively fuse cut the mill form fan-shaped, place big four circular quadrants, the intermediate portion is the right cylinder that contains fuse, contain the extraordinary single-mode fiber prefabricated rods of two pairs of different stress solids thereby be put together one, will carry out wire drawing after its two ends fusion.

Images