KR100251773B1 - Over cladding method of manufacturing optical fiber - Google Patents

Abstract

PURPOSE: An apparatus for manufacturing an optical fiber preform over cladding is provided to improve productivity in manufacturing an optical fiber preform, maintain concentricity of a preform section, manufacture an optical fiber having a high strength, make a collapse speed of a glass tube 5 times faster than before, conduct an over cladding irrespective of size of the optical fiber, and install a furnace on a carriage to heat or pre-heat the glass tube. CONSTITUTION: Chucks(20,30) maintain a glass tube(102) and an optical fiber preform in a vertical direction. A vertical lathe(10) includes the chucks(20,30). A carriage(60) is installed on the vertical lathe(10) and upwardly and downwardly moved. An oxygen/hydrogen burner(40) is installed on the carriage(60) and heats the optical fiber preform and the glass tube. A furnace(50) is installed on the carriage(60), positioned on a lower part of the burner(40), and heats or preheats the optical fiber perform and the glass tube. A vacuum pump is installed on one side end of the vertical lathe(10). A coupling connects the vacuum pump. A control part controls rotation of the glass tube which is maintained by the chuck(30), vertical motion speed of the carriage, flow rate control of the oxygen/hydrogen burner, and pressure of the vacuum pump. Additionally, a bus bar(53) supplies a power source to the furnace(50). A power source supplying part is connected to the bus bar(53) and a cable(55).

Description

Fiber Optic Substrate Overcladding Manufacturing Equipment

The present invention relates to an optical fiber base material manufacturing apparatus of an optical fiber manufacturing method, and more particularly to an optical fiber base material over cladding manufacturing apparatus using a furnace (furnace) of the optical fiber base material manufacturing method which is a step before the optical fiber manufacturing.

Typically, a method of manufacturing an optical fiber can be divided into two processes. The first step is to make an optical fiber preform, and the other step is to melt the made base material and draw it into an optical fiber having an outer diameter of 125 μm.

In the optical fiber base material manufacturing process, oxygen (O₂) is simultaneously supplied to a chemical gas such as gaseous SiCl 판 and other dopants, and hydrolyzed by a flame, and SiO2 particles called soot are deposited externally. Thereafter, the porous base material is placed in the blast furnace, and there are external deposition methods such as OVD and VAD to produce a transparent optical fiber base material by dehydration and sintering using Cl 2 and He.

In addition, after depositing several layers inside the quartz tube while simultaneously supplying SiCl₄ and other dopants with oxygen inside the quartz tube, the silica tube is supplied with Cl2 and He to the deposited quartz tube while heating and shrinking the quartz. There are internal deposition methods such as MCVD and CVD.

Among the internal vapor deposition manufacturing method MC V D and the method of V V D is a manufacturing method, it is difficult to produce a base material of more than about 25mm in diameter. Therefore, as a means of improving productivity, a method called over cladding is mainly used in which a large-diameter quartz tube is melted and pasted onto a base material prepared by the internal deposition method described above.

The OVD method and the VAD method have the advantage of making the base material large, but the MCVD method has difficulty in making the base material large.

In the optical fiber drawing process, the drawing method melts the base material and draws the fiber with a constant line speed from the molten base material with the outer diameter of 125 μm by the constant tensile load. In the drawing process, it is important to improve the productivity per unit time by increasing the speed of the ship.

Therefore, the method of making the optical fiber base material, which is the current pain point, is made by inserting a pre-made optical fiber base material into a large diameter glass tube and heating it with a burner to melt the optical fiber base material and the large diameter quartz tube to form a base material. There are methods such as the -Tube method, the Over Cladding method, and the Over Jacketing method, and since the methods listed above are well known techniques, detailed descriptions thereof will be omitted. In addition, this method is described in detail in Applicant Nos. 93-25712 (single mode primary over cladding method and apparatus) filed by the present inventors. It is also described in detail in US Pat. No. 4,820,322 (method and apparatus for overcladding a glass rod).

There is no problem in over cladding by inserting an optical fiber base material manufactured by the current MCVD method into a large diameter quartz tube having an outer diameter of 70 mm. However, as the diameter of the large diameter quartz tube increases or the thickness of the quartz tube increases, a large amount of heat required for over cladding is required, which causes a problem that the speed of the burner that supplies heat from the outside becomes slow.

In addition, the pressure of the vacuum applied to the boundary between the optical fiber base material and the large-diameter quartz tube may be further lowered, but the problem of deterioration of the concentricity and specific ratio of the geometry may be deteriorated by a very large negative pressure.

On the other hand, in order to increase the amount of external heat, it is simply solved by increasing the supply flow rate of the acid and hydrogen burners currently used. However, in the over cladding process, the surface of the large-diameter quartz tube is softened and the viscosity drops. Therefore, since the internal diameter of the base fiber of the optical fiber is less softened to maintain a constant viscosity, the supply flow rate of the acid and hydrogen burners increases, and the surface of the large-diameter quartz tube is crushed due to the pressure (flame force). In addition, problems such as impurity particles from burners stick to the surface of large diameter quartz tubes.

In addition, acid and hydrogen burners are relatively short in length of hot zones, so they cannot deliver sufficient heat to the surface of large-diameter quartz tubes (because the burners are ring-shaped), causing temperature imbalances (temperature gradients occur). do. Therefore, geometrical unevenness (ovality, cross-sectional area, etc.) is generated, and the viscosity of the optical fiber cross-sectional area must be uniform, but when manufacturing burners, the microbending loss increases due to the difference in viscosity. Moreover, the current manufacturing time takes about 1.5 to 2 hours, so it is necessary to improve productivity.

The present invention has been made to solve the above-mentioned conventional problems, an object of the present invention is to provide an optical fiber base material over cladding manufacturing apparatus in pursuit of improving the optical fiber base material production productivity in the optical fiber base material manufacturing process.

Another object of the present invention is to narrow the hot zone of the narrow base material by the furnace in the manufacturing process of the optical fiber base material to transmit a sufficient amount of heat to prevent temperature imbalance (temperature gradient), stable by the pressure of acid, hydrogen Collapsing is possible to provide an optical fiber base material over cladding manufacturing apparatus that maintains the concentricity of the base material cross section.

It is another object of the present invention to provide an optical fiber base material over cladding manufacturing apparatus capable of producing a high strength optical fiber by protecting the base material surface from impurities by using a small flow rate of acid and hydrogen in the optical fiber base material manufacturing process.

It is still another object of the present invention to provide an optical fiber base material over cladding manufacturing apparatus capable of increasing the collapsing speed of large diameter quartz tubes up to 5 times as the total amount of heat supplied in the optical fiber base material manufacturing process is large.

Still another object of the present invention is to provide an optical fiber base material over cladding manufacturing apparatus capable of over cladding regardless of the size of the optical fiber base material.

In order to achieve the above objects, the present invention is characterized in that a furnace for preheating or heating the quartz tube to coat the quartz tube on the optical fiber base material during the over cladding of the optical fiber base material is installed in the carriage.

1 is a perspective view showing an over cladding manufacturing apparatus equipped with a furnace in an optical fiber base material manufacturing process according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawing

10: Vertical lathe 20, 30: Chuck

40: Burner 50: Furnace

60: carriage 100; optical fiber base material over cladding manufacturing apparatus

Hereinafter, with reference to the accompanying drawings will be described in detail the most preferred embodiment of the present invention. First, in describing each of the drawings, only the same components have the same reference numerals as much as possible even if shown on different drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a perspective view showing an over cladding manufacturing apparatus equipped with a furnace in an optical fiber base material manufacturing process according to an embodiment of the present invention. Referring to the drawings, the configuration is roughly as follows.

A vertical lathe 10 including a glass tube and chucks 20 and 30 that vertically hold an optical fiber preform and the shelf 10. A carriage (60) mounted on the carriage and vertically moved up and down, an acid and hydrogen burner 40 mounted on the carriage 60 to heat the base material and the quartz tube, and a burner mounted on the carriage 60. (40) A coupling located between the vacuum pump installed at one end of both ends of the furnace (50: furnace) for heating or preheating the base material and the quartz tube, and the vertical shelf (10) And a control unit for controlling rotation of the quartz tube caught by the chuck 30, vertical movement speed of the carriage, flow rate control of acid and hydrogen burners, pressure of a vacuum pump, and the like. In addition, a bus bar 53 for supplying power to the furnace 50 and a power supply connected with a cable 55 are configured.

The components are described in detail as follows.

The vertical shelf 10 is provided with a conveying means and a guide rod 11 not shown in the figure for moving the carriage 60, and the top chuck 20 and the bottom chuck 30 are respectively installed at both ends of the vertical shelf. It is. One saw chuck 20 is fixed to the optical fiber base material (inserted in the quartz tube in Figure 1), and serves to rotate the base material, another bottom chuck 30 to fix the quartz tube 102 , To rotate the quartz tube.

The shelf 10 is equipped with a burner 40, the carriage 60 is vertically moved around the guide rod 11 with the center axis, and the furnace 50 is mounted below the burner 40. In addition, the upper portion of the burner 40 is provided with a ventilation duct 42 capable of stretching and contracting. That is, the duct 42, the burner 40, and the furnace 50 have a structure provided to be stacked in the carriage 60. Therefore, the burner 40, the furnace 50, and the duct 42 are integrally mounted to the carriage 60 to be controlled by the control unit for vertical movement.

The furnace 50 is composed of a heating element called graphite (graphite), and receives the power from the power supply to generate heat. The temperature that can supply a high heat of about 2000 ~ 2500 ℃ is maintained, this heat is transferred to the quartz tube and the base material by the radiation phenomenon to form a hot zone in the base material or quartz tube. In addition, the operation unit 54 is installed in the lateral direction of the furnace 50 and is configured to be easily operated by the user.

The furnace 50 used in the optical fiber base material cladding manufacturing apparatus has a longer heating portion (a shape extending further in the up and down direction) than the furnace used in the optical fiber drawing process, and has a thickness to maximize the transfer effect of radiant heat. Make it thinner. This is to thin a portion of the thickness of the liner material that is not shown in the figure located inside.

As a heating element of the furnace 50 used in the optical fiber base material manufacturing process, graphite of an electrically resistent type is mainly used, and induction type zirconia (ZrO₂) is also used. .

At this time, the furnace is connected to a plurality of tubes 58 to the body for injecting helium (He), argon (Ar) or a mixed gas of helium and argon (He + Ar), the upper and lower centering around the body Cover flanges 52 and conductor flanges 51a and 51b are assembled, respectively. Conductor flanges 51a and 51b positioned at upper and lower sides are provided with a plurality of bus bars 53, which are connected to a power supply by a power cable 55 to receive power. The flanges 51a and 51b are cornered by a tie bar 56 so as to be firm and fixed.

The helium or argon gas injected into the furnace 50 is an inert gas (inert gas), and is injected into a high temperature furnace to prevent oxidation of graphite occurring on the outer circumferential surface of the base metal or quartz tube. Good thermal conductivity plays a role of uniformizing the temperature distribution in the outer peripheral surface of the optical fiber base material or quartz tube (102).

The furnace body detects the internal temperature by installing a pyrometer (57: built-in temperature sensor). In addition, a cooling line not shown in the drawing is installed to cool the hot furnace. That is, it functions to cool the fever.

In the place of installation of the above-mentioned optical fiber base material manufacturing apparatus (external environment), when the power is turned off, the temperature should be maintained within 0 to 40 ° C, and the humidity should not exceed 50%.

According to the above-described configuration, the pre-prepared optical fiber base material is clamped to the top chuck 20 using a handle road, and the optical fiber base material is leveled so that the optical fiber base material is in a vertical state. Subsequently, one end of the large diameter quartz tube is connected to a dummy tube, and the dummy tube is leveled so that the dummy tube is fixed to a bottom chuck 30 so as to be vertical.

After the leveling is completed, the optical fiber base material fixed to the tub chuck 20 using the controller is lowered to be inserted coaxially into the large-diameter quartz tube 102.

Thereafter, the carriage 60 is moved by using the controller so that the hot zone portion of the furnace is located at the portion where the block portion of the optical fiber base material and the large-diameter quartz tube are combined.

Then, using the controller to drive the chuck (20, 30) to maintain the combined optical fiber base material and large-diameter quartz tube at 20 ~ 30RPM, supply the inert gas and power to the furnace 50 so that the connection is preheated Hold for 10 to 30 minutes. At this time, the acid, hydrogen burner 40 at the top of the furnace is lit with the first gas flow rate.

When the preheated joint is less viscous and the joint is softened, a vacuum pump is used with the controller to suck the interface between the fiber optic substrate and the quartz tube to ensure a complete seal. At this time, SiCl₄ and O₂ are flowed to the interface between the optical fiber base material and the quartz tube, and contact agent deposition such as POCl 석영, which is a quartz forming material, is possible, thereby preventing stresses generated at the interface. Then, the carriage 60 is moved downwards, and the flow rate of the acid and hydrogen burners is increased to 75 LPM of oxygen and 150 LPM of hydrogen.

The carriage speed gradually increases at 1 CPM and moves downward at 3 to 5 CPM. Therefore, the large-diameter quartz tube and the optical fiber base material rotating at a constant circumference are collapsed to the entire length to form a body. When the entire length is collapsed, the furnace is turned off, and the connection portion between the large-diameter quartz tube and the dummy tube Fix the acid and hydrogen burner 40, and hold it for 3 to 5 minutes with 75 LPM of oxygen and 150 LPM of hydrogen until it softens to this part, and when softened, the top chuck 20 is gradually moved upward at a speed of 1 to 3 mm / minute. Move to make the connection thinner.

When the outer diameter of the large-diameter base material is about 2/3 of the original diameter, it is quickly moved upward by the manual operation panel to completely boil the dummy tube and the collapsed base material. The finished substrate is removed from the chuck and allowed to cool in the rack to cool for a period of time. This completes the overcladding process of the optical fiber base material.

On the other hand, in the detailed description of the present invention has been described with respect to specific embodiments, it will be apparent to those skilled in the art that various modifications are possible without departing from the scope of the present invention.

As described above, the present invention achieves many effects as follows.

First, since a narrow hot zone, which is a problem of acid and hydrogen burners shown in the related art, is enlarged by a furnace, the hot zone is increased, so that sufficient heat is transmitted to prevent temperature imbalance, and constant and stable collapsing is possible.

Secondly, since the mutual contact surface (interface) of the optical fiber base material and the large diameter quartz tube becomes equal in viscosity by sufficient heat amount, the micro bending loss is reduced.

Thirdly, the substrate surface may be contaminated by impurities in the acid and hydrogen burners during the process by the acid and hydrogen burners. However, since the acid and hydrogen flow rates are used at a low flow rate, the substrate surface can be protected from impurities. Optical fiber manufacturing is possible.

Fourth, the surface of the large-diameter quartz tube is heated with a furnace, and collapsing is carried out at the pressure of acid and hydrogen, so that the optical fiber base material can be manufactured while maintaining the concentration of the exact base material section with the uniform temperature distribution inside the furnace. .

Fifth, the heat supply amount of heat is larger than that of the related art, and the collapsing speed of the large-diameter quartz tube can be up to 5 times faster, and the process can be automatically controlled.

Sixth, over cladding of any size is possible regardless of the size of the optical fiber base material.

Seventhly, when the present invention is applied to an optical fiber drawing process, if the manufacturing method of the present invention is applied to a portion where the optical fiber base material is mounted in the drawing facility, continuous drawing of the optical fiber is possible.

Eighth, the collapsing using vacuum pump not only facilitates collapsing, but also allows the deposition of SiCl₄ and O₂ on the interface between the optical fiber base material and the large-diameter quartz tube, and the deposition of contact agents such as POCl₃, a glass forming material. It can reduce the stress generated in the

Claims (4)

Chuck is installed at both ends of the vertical shelf, the carriage is provided with vertical movement between both ends of the shelf, the carriage is equipped with a ring-shaped acid, hydrogen burner, the vacuum pump and the vacuum pump at either end of the chuck In the optical fiber base material over cladding manufacturing apparatus for coating a quartz tube on the optical fiber base material is installed, the control unit for controlling the vertical movement of the carriage, the flow rate of the acid, hydrogen burner and the rotation of the chuck is installed outside. An optical fiber base material over cladding manufacturing apparatus characterized by installing a furnace for preheating or heating a quartz tube in the carriage to coat a quartz tube on the optical fiber base material when the optical fiber base material over cladding. The apparatus of claim 1, wherein the furnace is installed under a burner mounted on a carriage. The apparatus of claim 1, wherein the furnace is supplied with power from a power supply and the heating element is graphite. The apparatus of claim 1, wherein the furnace prevents oxidation of the base metal and the quartz tube using an inert gas such as helium, argon, helium + argon, or nitrogen.

Images