JPH0247413B2 - GARASUBOZAISEIZOYOBAANANOICHIGIMEHOHO - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for positioning a burner for manufacturing a glass base material used in the vapor phase arranging method (VAD method).
In particular, the present invention relates to a burner that can be moved to a final setting position with good reproducibility while monitoring the end face shape and end face temperature of a porous base material.

[Conventional technology] VAD is one of the manufacturing methods for optical fiber base material.
A method is known, but to explain it simply, a starting member such as a quartz rod that is supported vertically and pulled upward while rotating the shaft at a constant speed is placed at the tip of a starting member such as a quartz rod. A frit gas is guided through a burner arranged at an inclined angle to grow oxide fine particles (soot),
A porous matrix is produced in the axial direction of the starting member.

By the way, the soot shape that grows at the tip of this starting material requires uniformity and symmetry in order to manufacture a high-quality optical fiber base material, and for this purpose, it is necessary to set the position of the burner with respect to the end face of the porous base material. becomes important. This is because the end face shape of the porous preform is determined by the position of the burner, and this end face shape greatly influences the uniformity and symmetry of the optical fiber preform.

Therefore, in the past, an operator arbitrarily moved the porous base material from an initial setting position to a final setting position where a predetermined end face shape was obtained while visually observing changes in the end face shape due to the initial growth of the porous base material.

[Problems to be Solved by the Invention] However, in the conventional burner positioning method described above, the operator arbitrarily moves the burner variably from the initial setting position to the final setting position, resulting in human error. In particular, it is difficult to reproduce the end face shape of the porous base material when repeatedly manufacturing the optical fiber base material, and when positioning the burner, the porous base material has a large effect on the refractive index distribution. Since the end surface temperature of the material was not measured, it was difficult to control the refractive index distribution with high precision.

[Object of the Invention] An object of the present invention is to solve the problems of the prior art described above and to obtain a method for positioning a burner for manufacturing a glass base material, which allows extremely accurate refractive index distribution control. be.

[Summary of the Invention] In order to achieve the above object, the present invention discloses that the final end face shape of a porous preform having uniformity and symmetry is influenced by the growth history up to that point, and that the final end shape of the porous preform having uniformity and symmetry is Based on the knowledge that the uniformity and symmetry of the material are also affected by the end face temperature of the porous base material, we quantitatively determined the end face shape and end face temperature of the porous base material that grows at the tip of the starting member. From the initial setting position of the burner, the central axis of the burner passes through a point on the end face of the porous base material that intersects with the vertical axis of the starting member, so that the shape and temperature finally reach the desired predetermined shape and temperature. , the burner is moved horizontally to the final setting position horizontally further away from this,
As a result, a porous base material having uniformity and symmetry is formed.

[Example] An example of the present invention will be described below based on FIGS. 1 to 6.

FIG. 4 is a schematic configuration diagram showing an example of an optical fiber base material manufacturing apparatus. In the figure, 1 is a concentric multilayer burner with its opening facing upward, and 2 is a support for horizontally movable burner 1. A burner supporting fine movement table, 3 is a porous base material grown by the burner 1, 4
is a glass container that houses the porous base material 3 and the burner 1. Further, 5 is a starting member such as a quartz rod located above the glass container 4, 6 is a rotating pulling device that pulls up the starting member 5 while rotating its axis, and 7 is an exhaust port provided on the side of the glass container 4. Reference numerals 8 and 9 are a television camera and a television display for observing the porous base material 3 growing on the tip of the starting member 5, and 10 is an infrared thermometer for detecting the end surface temperature of the porous base material 3.

In such a configuration, when frit and fuel gas are supplied to the burner 1 fixed upward, soot is generated by a hydrolysis reaction of the frit, and this soot is deposited on the tip of the starting member 5 located above. As a result, the porous base material 3 grows. In this case, the pulling speed of the starting member 5 is controlled so that the distance between the end face of the growing porous base material 3 and the burner 1 is always constant.

By the way, as shown in FIG. 3, the two detection systems comprising the television camera 8, television display 9, and infrared thermometer 10 constituting the optical fiber base material manufacturing apparatus are equipped with a recorder 11,
It has 12. That is, the end face temperature of the porous base material 3 at an arbitrary burner setting position is detected by the infrared thermometer 10, and the detection result is sent to the recorder 1.
Recorded in 2. In addition, the end face shape of the porous base material 3 is detected by the television camera 8 and outputted to the television display 9, and the bottom face shape of the porous base material 3 output here is set at an arbitrarily set reference line L. The distance D is calculated from the bottom of the porous base material specified from
is configured to be recorded.

Next, the operation of the configuration of the present embodiment as described above will be explained. In this embodiment, the central axis of the burner 1 is θ is _the angle _formed between When the distance from the tip of the burner 1 is l ₀ , the conditions for these θ and l ₀ and the burner conditions are as follows. Note that a in the figure is a horizontal line passing through the intersection _X0 .

θ = 30°, l ₀ = 50 mm, burner 1 has a 4-layer structure, and the first layer in the center is filled with SiCl ₄ at 100 c.c./min.
GeCl ₄ was supplied at a flow rate of 10 c.c./min and Ar gas was supplied at a flow rate of 500 c.c./min. Ar gas was supplied to the second layer at a flow rate of 500 c.c./min, and the third layer was _H2 gas 2900
cc/min, and O ₂ gas was supplied to the fourth layer at a flow rate of 7000 c.c./min. Now, in order to grow the porous base material 3 on the tip of the starting member 5 under the above conditions, instead of suddenly bringing the burner ₁ to the final setting position After setting the burner 1 to X ₀ , move the burner 1 horizontally in steps until it reaches the final setting position X _o shown in Figure 1B.
I also try to keep up with it. That is, the area from the initial setting position X ₀ on the horizontal line a corresponding to the horizontal movement distance of the burner 1 to the final setting position X _o is arbitrarily divided into a plurality of intermediate setting positions X ₂ , X ₃ , X ₄ . . . As shown in FIGS. 5 and 6, the porous base material 3
The burner 1 is moved in steps to the next intermediate setting position when the end face temperature T and end face shape D ₁ are stable and have sufficiently settled down to the values determined by each intermediate setting position, rather than during transient times when the end face temperature T and end face shape D 1 are still unstable. do. The point X _o (n = ₀ to n) on the curve in the same figure is the time at which a sufficiently stable end face temperature and end face shape can be obtained, and only when stable end face temperature and end face shape are obtained at the same time. The burner 1 is moved at a predetermined speed and this step movement is repeated until it reaches the final setting position _Xo . Here, this step movement is performed by an operator who is observing the recorder recording results shown in FIGS. 5 and 6.
It can also be automated by computer processing. Thus, at the final set position _Xo , the end surface of the porous base material 3 forms a smooth circular arc symmetrical with respect to the vertical axis of the starting member 5, as shown in FIG. 1B, and this shape forms a final predetermined shape. In addition, a stable end face temperature at the final setting position X _o becomes a predetermined temperature that controls the refractive index distribution of the base material to a desired value. In this way, the burner 1 is moved stepwise and positioned while creating a stable temperature and shape each time, and after this positioning is completed, continuous production of the glass base material is carried out.

By the way, the burner movement until this burner positioning is completed is an intermediate process for obtaining a predetermined end surface temperature and end surface shape for the porous base material 3 at the final setting position X _o , so the final predetermined temperature and predetermined In order to obtain the desired shape, the end face shape and end face temperature of the porous base material 3 at the intermediate stage of growth also affect the final value, so it is necessary to maintain their uniformity and symmetry. requires careful management. This means that the burner 1
With the initial spherical porous base material 3 formed at the initial setting position X ₀ as the core, a predetermined amount of skirt is formed at each setting position X ₁ , X ₂ ...X _o , just like the skin of an onion. As the particles adhere, not only the initial shape (temperature) but also the intermediate shape become asymmetrical (non-uniform), and the shape of the porous base material 3 at the final setting position X _o becomes asymmetrical, like a distorted onion. This can be understood from the fact that it becomes

However, until the positioning is completed, the burner 1 moves stepwise to the next intermediate setting position after the end face shape and temperature of the porous base material 3 have sufficiently settled to the values determined by each intermediate setting position.
Uniformity and symmetry of the end face shape and end face temperature of the porous base material 3 are ensured even during the growth process, and the same predetermined shape and predetermined temperature without any artificial errors are ultimately obtained.

We manufactured 20 optical fiber base materials using this burner positioning method, and were able to reproduce the same refractive index distribution within all measurement errors.

In the above embodiment, the burner 1 is moved in steps, but it is also possible to move the burner 1 continuously by adjusting the speed of its movement, and in this case, the same effect can be obtained. be able to.

Also, in order to know the end face shape of the porous base material 3,
Although the straight line distance from the simplest reference line L to one point on the end face of the porous base material 3 is detected, the distance or plane between multiple points may be detected.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

(1) The end face shape and end face temperature of the porous base material are detected, and the burner is moved horizontally with good reproducibility so that these shapes and temperatures finally reach the predetermined shape and temperature, so the end face shape can be simply visually observed. Compared to conventional methods that do not detect the end face temperature, which has a significant effect on the refractive index distribution, porous base materials with excellent uniformity and symmetry can be manufactured with good reproducibility, and high precision Refractive index distribution control can be performed.

(2) Therefore, the yield of broadband optical fibers can be significantly improved.

[Brief explanation of the drawing]

The figures show an embodiment according to the method of the present invention, in which Fig. 1A is an explanatory diagram of initial burner settings, Fig. 1B is an explanatory diagram of final burner settings, and Fig. 2 is a porous base material for each burner setting position. An explanatory diagram of the end face shape, Figure 3 is a configuration diagram of the end face shape of the porous base material and the temperature detection device, Figure 4 is a configuration diagram of the optical fiber base material manufacturing equipment, and Figure 5 is a diagram of the burner from X ₀ to X. Figure 6 is a characteristic curve diagram of the porous base material end surface _temperature T and time t when the burner is moved in steps from X ₀ to X _o .
FIG. 4 is a characteristic curve diagram of distance D and time t representing the shape of the end face of the porous base material when the porous base material is moved in a stepwise manner until the end of the porous base material. In the figure, 1 is a burner, 3 is a porous base material, 5 is a starting member, 8 and 9 are a television camera and a television display that detect the end face shape of the porous base material, and 10 is the end face temperature of the porous base material. An infrared thermometer that detects , l ₀ is the distance between the end face of the porous base material and the burner tip, X ₀ is the initial setting position of the burner, and X _o is the final setting position of the burner.

Claims (1)

[Claims] 1. A porous base material is formed by spraying soot generated by an oxyhydrogen flame from a burner arranged diagonally downward at the tip of a starting member arranged vertically and rotating on its axis,
When growing the porous base material in the axial direction by pulling the starting member upward while maintaining a constant distance between the end face of the porous base material and the tip of the burner, the shape of the end face of the porous base material and In order to quantitatively detect the end surface temperature and make the shape and temperature finally reach a predetermined shape and temperature, the center axis of the burner is set at a point on the end surface of the porous base material that intersects with the vertical axis of the starting member. A method for positioning a burner for manufacturing a glass base material, characterized by horizontally moving the burner from an initial setting position of the burner passing through to a final setting position horizontally distant from the initial setting position. 2. The first aspect of the present invention is characterized in that the end face shape of the porous base material is detected by detecting the distance from a reference line drawn horizontally at an arbitrary position below the end face to the end face. Method for positioning a burner for producing glass base material as described in Section 1. 3. The method for positioning a burner for producing a glass base material according to claim 1 or 2, wherein the horizontal movement of the burner is performed in steps. 4 A theory of the porous base material in which the step-like horizontal movement of the burner is determined by each intermediate setting position at a plurality of intermediate setting positions arbitrarily divided between the initial setting position and the final setting position of the burner. A method for positioning a burner for manufacturing a glass base material according to claim 1, 2, or 3, characterized in that the burner is moved to the next intermediate setting position each time the surface shape and end surface temperature are settled. .