JP2009167029A - Method for manufacturing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical fiber by which characteristics of the glass fiber can be stabilized by suppressing the variation of a refractive index distribution in a longitudinal direction regardless of the change of the growth rate of glass particle deposits. <P>SOLUTION: The quantity of an additive to be supplied to adjust the refractive index is adjusted corresponding to the change of the growth rate of the glass particle deposits 14. As a result, the variation of the refractive index distribution ΔN of the manufactured glass particle deposits 14 in the longitudinal direction is suppressed to stabilize the characteristics of the optical fiber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical fiber manufacturing method, for example, an optical fiber manufacturing method for manufacturing an optical fiber by depositing glass particles by a VAD method.

Conventionally, a method of manufacturing an optical fiber preform by depositing glass particles by the VAD method is known (see, for example, Patent Documents 1 and 2).
In the method of manufacturing an optical fiber described in Patent Document 1, when manufacturing a porous preform having a first core and a second core, the first core portion shape is constant, The flame of the core burner is stabilized to produce a porous base material, and the longitudinal variation of the refractive index distribution is suppressed. At this time, in order to stabilize the second core shape, the second core shape is detected and any one of the burner position, the gas flow rate condition, and the porous base material position is controlled.

In addition, in the optical fiber manufacturing method described in Patent Document 2, the weight and growth rate of the glass particulate deposit are sequentially measured during the production of the porous preform, and the measured increased weight per unit length of the glass particulate deposit. The deviation of the target increase weight is fed back to any of the source gas, combustible gas, and auxiliary combustible gas, and the amount of accumulated glass particles in the radial direction is adjusted to stabilize the refractive index distribution in the longitudinal direction. .
JP-A-9-227147 JP 2004-307235 A

By the way, when forming a glass particle deposit by sooting the core in the optical fiber manufacturing process, the growth rate (rising speed) in the axial direction is usually controlled so that the outer diameter of the glass particle deposit is constant. As a result, the growth rate may fluctuate. On the other hand, in order to adjust the refractive index distribution (ΔN) of the sooted glass fine particle deposit to be constant, an additive (for example, GeCl ₄ ) that adjusts the refractive index during sooting depends on the growth rate. Instead, it is always added at a constant flow rate.
That is, in the optical fiber manufacturing method described in Patent Document 1 and Patent Document 2 described above, since the supply flow rate of the additive for adjusting the refractive index is constant, it is manufactured when the growth rate changes. There is a disadvantage that the refractive index distribution of the optical fiber fluctuates in the longitudinal direction and the characteristics of the optical fiber vary.

  The present invention has been made in view of the above-described problems, and its purpose is to stabilize the characteristics of the optical fiber by suppressing the fluctuation in the longitudinal direction of the refractive index distribution regardless of the change in the growth rate of the glass particulate deposit. An object of the present invention is to provide a method of manufacturing an optical fiber that can be realized.

  In order to achieve the above-mentioned object, the first feature of the optical fiber manufacturing method according to the present invention is a method of manufacturing an optical fiber in which a glass fine particle deposit is deposited by the VAD method. The supply flow rate of the agent is adjusted so as to increase or decrease in proportion to the growth rate in the axial direction of the glass fine particle deposit.

  In the optical fiber manufacturing method configured as described above, the supply flow rate of the additive for adjusting the refractive index is increased or decreased in proportion to the change in the growth rate of the glass particulate deposit, and for example, added when the growth rate is increased. By increasing the supply flow rate of the agent, fluctuations in the longitudinal direction of the refractive index distribution can be suppressed and the characteristics of the optical fiber can be stabilized.

  A second feature of the optical fiber manufacturing method according to the present invention is that, in the first feature of the present invention, the ratio of the supply flow rate of the additive to the growth rate in the axial direction is set within a predetermined range. There is.

  In the manufacturing method of the optical fiber configured as described above, the range of fluctuation of the refractive index distribution of the glass particulate deposit is controlled within a predetermined range by suppressing the supply flow rate of the additive to be changed according to the growth rate within the predetermined range. Can be suppressed within.

A third feature of the optical fiber manufacturing method according to the present invention is that, in the second feature of the present invention, the ratio of the supply flow rate of GeCl _{4 to} the axial growth rate is 0.002 to 0.005 SLM.・ To set in the range of h / mm.

  In the optical fiber manufacturing method configured as described above, the glass fine particle deposition is performed by suppressing the supply flow rate of the additive to be changed according to the growth rate within a predetermined range of 0.002 to 0.005 SLM · h / mm. The range of fluctuation in the longitudinal direction of the refractive index distribution of the body can be suppressed within a desired range.

A fourth feature of the optical fiber manufacturing method according to the present invention is that, in the second feature of the present invention, the ratio of the supply flow rate of GeCl _{4 to} the growth rate in the axial direction is ± 0.0005 SLM · h / It is to adjust within the range of mm.

In the manufacturing method of the optical fiber configured as above, the value of the supply flow rate of GeCl ₄ with respect to the growth rate in the axial direction is adjusted within a range of ± 0.0005 SLM · h / mm, whereby the length of the refractive index distribution is increased. It can be within a desired range without increasing the variation in direction.

  According to the present invention, since the supply flow rate of the additive for adjusting the refractive index is adjusted in accordance with the change in the growth rate of the glass fine particle deposit, the length of the refractive index distribution of the produced glass fine particle deposit is increased. It is possible to obtain an effect that the characteristics of the optical fiber can be stabilized while suppressing the variation in direction.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram showing an example of a manufacturing apparatus for carrying out an optical fiber manufacturing method according to the present invention, and FIG. 2 is a graph showing that the refractive index distribution changes when the ratio of the flow rate of the additive to the growth rate changes. FIG. 3 is a graph showing that the ratio of the flow rate of the additive to the growth rate is maintained at a predetermined value, and that the refractive index distribution maintains a predetermined value, and FIG. 4 is a supply flow rate of the additive corresponding to the growth rate. It is a graph which shows that refractive index distribution does not fluctuate by adjusting this even if a growth rate fluctuates.

  As shown in FIG. 1, in a manufacturing apparatus 10 for carrying out the optical fiber manufacturing method of the present invention, a support rod 12 is suspended from above a reaction vessel 11 and a dummy glass rod is placed below the support rod 12. 13 is attached. Glass particulates are deposited on the dummy glass rod 13 to form a glass particulate deposit 14. The upper end of the support bar 12 is held by the lifting device 15, and is rotated and lifted by the lifting device 15. The lifting device 15 is controlled to be pulled up by the control device 16.

A core burner 17 and a cladding burner 18 are provided below the inside of the reaction vessel 11. A gas supply device 19 controlled by the control device 16 supplies fuel gas, raw material gas, for example, to each burner 17, 18. A gas such as an additive that adjusts the refractive index, such as GeCl ₄ , is supplied by controlling the supply amount. An exhaust pipe 20 is attached to the central portion of the side wall of the reaction vessel 11.
A growth rate measuring device 21 for measuring the pulling rate that is the growth rate of the glass fine particle deposit 14 is provided. The growth rate measuring device 21 is provided with, for example, a laser oscillator 22 that emits laser light that is detection light, and a light receiving unit 23 that receives the laser light from the laser oscillator 22 and emits a signal to the control device 16.

Accordingly, the support rod 12 is attached to the elevating device 15, the glass rod 13 attached to the tip is placed in the reaction vessel 11, and the glass rod 13 is rotated by the elevating device 15, while the core burner 17 and the clad burner 18. Thus, glass fine particles are deposited on the surface of the glass rod 13. The glass fine particle deposit 14 is pulled up by the lifting device 15 so that the glass fine particle deposit 14 has a predetermined outer diameter, the pulling speed at this time is measured by the growth rate measuring device 21, and the signal is sent to the control device 16. Send. As will be described later, the control device 16 controls the supply flow rate of the additive (GeCl ₄ ) for adjusting the refractive index so that the refractive index distribution does not fluctuate in the longitudinal direction based on the measured growth rate.

Next, the manufacturing method of the optical fiber concerning this invention is demonstrated.
In the method for producing an optical fiber according to the present invention, the glass particulate deposit 14 is deposited by the VAD method. As described above, the supply flow rate of the additive for adjusting the refractive index is set to the glass particulate deposit 14. Increase or decrease in proportion to the growth rate in the axial direction.

As the adjustment of the flow rate of the additive GeCl _4, the flow rate of the additive can be increased when the axial growth rate is increased. Alternatively, when the growth rate decreases, the flow rate of the additive can be decreased. That is, based on the signal sent from the growth rate measuring device 21 to the control device 16, the control device 16 increases the supply flow rate of the additive to the gas supply device 19 when the growth rate is increasing. Command. When the growth rate is decreasing, the gas supply device 19 is commanded to decrease the supply flow rate of the additive.
Thereby, it becomes possible to adjust the supply flow rate of the additive corresponding to the growth rate.

In addition, it is desirable to set the ratio (a) of the supply flow rate of GeCl ₄ as an additive to a predetermined range with respect to the growth rate in the axial direction of the glass particulate deposit 14. In other words, when a = GeCl ₄ supply flow rate (SLM) / growth rate (mm / h), the predetermined range of a is desirably 0.002 to 0.005 SLM · h / mm.
Further, when the ratio (a) of the additive supply flow rate to the growth rate in the axial direction is kept within 0.002 to 0.005 SLM · h / mm, a is within the range of ± 0.0005 SLM · h / mm. It is desirable to adjust.
Thereby, the range of fluctuation of the refractive index distribution ΔN of the glass particulate deposit 14 can be suppressed within a predetermined range.

As described above, according to the optical fiber manufacturing method described above, the supply flow rate of GeCl ₄ which is an additive for adjusting the refractive index is increased or decreased in proportion to the change in the growth rate of the glass fine particle deposit 14. It is possible to stabilize the characteristics of the optical fiber by suppressing the fluctuation in the longitudinal direction of the refractive index distribution ΔN of the deposited glass fine particle body 14.

(Example)
FIG. 2 shows a state in which the refractive index distribution ΔN changes when the value of a (additive flow rate / growth rate) is changed. For example, when the value of a is 0.002 SLM · h / mm, the refractive index distribution ΔN = 0.33 (%), and when the value of a is 0.005 SLM · h / mm, the refractive index distribution ΔN = 0.4 (% ) That is, by controlling a to be within a predetermined range of 0.002 to 0.005 SLM · h / mm, ΔN can be within a range of 0.33 to 0.4 (%). From this relationship, for example, the value of a such that the refractive index distribution ΔN = 0.37 (%) is 0.003 SLM · h / mm as shown in FIG.
Therefore, in order to obtain a refractive index distribution ΔN = 0.37 (%), the flow rate of the additive is adjusted in accordance with the growth rate so that a is constant at 0.003 SLM · h / mm.

In FIG. 4, the supply flow rate of GeCl ₄ as an additive was controlled corresponding to the growth rate so that a was constant at 0.003 SLM · h / mm. As a result, even when the growth rate fluctuated in the longitudinal direction, the refractive index distribution ΔN showed a constant value (here 0.37 ± 0.001 (%)), and the fluctuation of the refractive index distribution ΔN could be suppressed. .

(Comparative example)
The case where the supply flow rate of the additive is not adjusted with respect to the growth rate is shown in FIGS. As shown in FIG. 5, when the supply flow rate of the additive is kept constant with respect to the growth rate, it can be seen that the refractive index distribution ΔN decreases as the growth rate increases. For example, if the additive supply flow rate is kept constant at 0.255 (SLM) when the growth rate is increased from 50 mm / h to 120 mm / h, ΔN is 0.4 (%) to 0.33 (%). It can be seen that it has fluctuated.

In addition, as shown in FIG. 6, when the supply flow rate of the additive is kept constant with respect to the longitudinal position, that is, the growth length, the refractive index distribution ΔN is the growth length as in the case of the change in the growth rate described above. It can be seen that it decreases as the value increases. For example, if the supply flow rate of the additive is kept constant at 0.255 (SLM) when the growth length grows from 100 mm to 800 mm, ΔN varies from 0.4 (%) to 0.33 (%). You can see that
Thus, when the supply flow rate of the additive is not adjusted, the refractive index distribution ΔN will fluctuate in the longitudinal direction when the growth rate or growth length becomes long, and the characteristics of the optical fiber will not be stable. become.

In addition, the manufacturing method of the optical fiber of this invention is not limited to embodiment mentioned above, A suitable deformation | transformation, improvement, etc. are possible.
For example, in the above-described embodiment, the growth rate measuring device 21 is provided and the flow rate of the additive is adjusted with respect to the growth rate detected by the growth rate measuring device 21. It is also possible to adjust the additive by detecting the growth rate from the rotational speed of a drive motor or gear device. In this case, it is not necessary to provide the growth rate measuring device 21.

  In the above-described embodiment, as shown in FIG. 4, the case where the flow rate of the additive is directly adjusted with respect to the growth rate has been described. However, as shown in FIG. It is also possible to adjust the flow rate of the additive with respect to the longitudinal position, ie the growth length. In this case, there is a certain relationship between the growth length and the growth rate.

  As described above, the optical fiber manufacturing method according to the present invention is manufactured because the supply flow rate of the additive for adjusting the refractive index is adjusted in accordance with the change in the growth rate of the glass particulate deposit. This has the effect of suppressing the fluctuation in the longitudinal direction of the refractive index distribution of the glass fine particle deposited body and stabilizing the characteristics of the optical fiber. For example, light for producing an optical fiber by depositing glass fine particles by the VAD method. It is useful as a fiber manufacturing method.

It is a block diagram which shows an example of the manufacturing apparatus which enforces the manufacturing method of the optical fiber which concerns on this invention. It is a graph which shows that a refractive index distribution will also fluctuate if the ratio of the supply flow rate of the additive to a growth rate fluctuates. It is a graph which shows that refractive index distribution hold | maintains a predetermined value by maintaining the ratio of the supply flow rate of the additive with respect to a growth rate at a predetermined value. It is a graph which shows that a refractive index distribution does not fluctuate even if a growth rate fluctuates by adjusting supply flow rate of an additive corresponding to a growth rate, and shows the effect of the present invention. It is a graph which shows that refractive index distribution fluctuates when the supply flow rate of an additive is kept constant with respect to fluctuations in growth rate. It is a graph which shows that a refractive index distribution fluctuates in the longitudinal direction when the supply flow rate of the additive is kept constant with respect to the longitudinal direction position of the glass particulate deposit. It is a graph which shows that a refractive index distribution does not fluctuate | regulate regardless of a longitudinal direction position by adjusting the supply flow rate of an additive corresponding to the longitudinal direction position of a glass particulate deposit.

Explanation of symbols

  14 Glass particulate deposits

Claims (4)

An optical fiber manufacturing method for depositing a glass particulate deposit by a VAD method,
A method of manufacturing an optical fiber, wherein the flow rate of an additive for adjusting the refractive index is adjusted to increase or decrease in proportion to the growth rate in the axial direction of the glass fine particle deposit.   The method of manufacturing an optical fiber according to claim 1, wherein a ratio of a supply flow rate of the additive to the growth rate in the axial direction is set within a predetermined range. The method of manufacturing an optical fiber according to claim 2, wherein the ratio of the supply flow rate of GeCl _{4 to} the growth rate in the axial direction is set in a range of 0.002 to 0.005 SLM · h / mm. The method of manufacturing an optical fiber according to claim 2, wherein a ratio of a supply flow rate of GeCl _{4 to} the growth rate in the axial direction is adjusted within a range of ± 0.0005 SLM · h / mm.

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