JP5485003B2 - Optical fiber preform manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing an optical fiber preform, and more particularly to a technique that is useful when applied to a method for manufacturing an optical fiber preform using an external vapor deposition method.

  In general, optical fiber manufacturing methods include vapor phase axial deposition (VAD), external vapor deposition (OVD), and chemical vapor deposition (MCVD). There are known vapor phase synthesis methods such as Chemical Vapor Deposition) or a combination thereof.

As shown in FIG. 1, in the OVD method, a burner 10 supplies a raw material gas such as SiCl ₄ , a combustible gas H _2, and an auxiliary combustible gas O ₂ , and the raw material gas is supplied in an oxyhydrogen flame 101. Glass fine particles 102 are generated by a flame hydrolysis reaction. By rotating the burner 10 and the target rod 2 in the longitudinal direction while rotating the target rod 2 about the axis, glass fine particles (soot) 102 is deposited on the outer peripheral surface of the target rod 2 and the soot body 3 is formed. The
The soot body 3 thus formed is heated at a high temperature to be dehydrated and sintered, whereby the optical fiber preform 1 made into a transparent glass is manufactured. Moreover, an optical fiber is manufactured by drawing this optical fiber preform 1 by heating. For the target rod 2, a core base material manufactured by, for example, the VAD method is used.

As a burner used in the above-described OVD method, a raw material gas jet passage is arranged at the center of the combustible gas jet passage, and an auxiliary combustible gas is placed in the combustible gas outflow passage so as to surround the raw material gas jet passage. Burners (so-called multi-nozzle burners) in which an ejection channel is arranged in an annular shape have been proposed (for example, Patent Documents 1 to 4).
Patent Document 5 discloses a technique for arranging a plurality of burners in the longitudinal direction of a target rod when an optical fiber preform is manufactured using the OVD method.

JP 62-187135 A JP-A-5-323130 JP-A-6-247722 JP 2002-29759 A JP-A-3-228845

  By the way, in recent years, with the demand for optical fibers increasing dramatically, it is required to manufacture a larger-sized optical fiber preform in a shorter time and to reduce the cost. Furthermore, in consideration of the environment, it is desired to reduce as much raw materials as possible. However, the above-described method has a limit in improving both the deposition efficiency (the amount of deposited glass particles / the amount of glass particles generated from the supplied glass raw material) and the deposition rate without degrading the quality. In recent years, it has become difficult to meet the demand for further cost reduction and consideration for the environment.

  The present invention provides an optical fiber preform manufacturing method capable of efficiently forming a high-quality soot body in a short time by optimizing soot formation conditions (gas supply conditions) and reducing manufacturing costs. Objective.

In order to achieve the above object, the invention described in claim 1
A source gas ejection passage for ejecting source gas;
Composed of a plurality of small-diameter channels provided annularly so as to surround the raw material gas-ejecting channel, and an auxiliary-combustible gas-ejecting channel for ejecting auxiliary-combustible gas from these small-diameter channels;
Using a burner that is provided around the raw material gas ejection channel and the auxiliary combustible gas ejection channel, and includes a combustible gas ejection channel that ejects combustible gas,
The glass particles generated by injecting the combustible gas and the auxiliary combustible gas and supplying the raw material gas into a flame composed of the combustible gas and the auxiliary combustible gas are rotated about a cylindrical target rod as an axis. while, the burner and the target rod by causing relative movement in the longitudinal direction, to deposit the glass particles on the outer peripheral surface of the target rod, the steps that form a soot body,
A step of transparent vitrification by heating the formed soot body at a high temperature for dehydration and sintering;
In a method of manufacturing an optical fiber preform comprising:
The auxiliary combustion gas ejection flow path includes a first auxiliary combustion gas ejection flow path that is annularly disposed outside the raw material gas ejection flow path, and a second annular movement that is disposed outside the first auxiliary combustion gas ejection flow path. An auxiliary combustible gas ejection flow path, and
The flow rate of the auxiliary combustible gas from the first auxiliary combustible gas ejection flow path is expressed as Vis (m / s),
The flow rate of the combustible gas in the vicinity of the first auxiliary combustible gas ejection flow path is Vif (m / s),
The flow rate of the auxiliary combustion gas from the second auxiliary combustion gas ejection flow path is expressed as Vos (m / s),
When the flow rate of the combustible gas in the vicinity of the second auxiliary combustible gas ejection flow path is Vof (m / s),
| Vis-Vif |> | Vos-Vof |
Vis ≧ Vof
Vis ≦ 40 m / s
The flow rates of the auxiliary combustible gas and the combustible gas are controlled so as to satisfy the above condition.

According to a second aspect of the present invention, in the method for manufacturing an optical fiber preform according to the first aspect, the auxiliary combustion is performed so as to satisfy (V _is −V _if ) − (V _os −V _of )> 5 m / s. The flow rate of the combustible gas and the combustible gas is controlled.

The invention according to claim 3 is the method of manufacturing an optical fiber preform according to claim 1 or 2, wherein the auxiliary combustible gas and the combustible gas are set so as to satisfy (V _is −V _if ) ≧ 15 m / s. It is characterized by controlling the flow rate of gas.

According to a fourth aspect of the present invention, in the method of manufacturing an optical fiber preform according to any one of the first to third aspects, the auxiliary combustibility is set so as to satisfy (V _os −V _of ) ≦ 15 m / s. The flow rate of the gas and the combustible gas is controlled.

The invention according to claim 5 is the method of manufacturing an optical fiber preform according to any one of claims 1 to 4, wherein the auxiliary combustible gas and the combustible gas so as to satisfy V _if <V _of. It is characterized by controlling the flow rate of the gas.

The invention according to claim 6 is the method of manufacturing an optical fiber preform according to any one of claims 1 to 5, wherein the inner diameter of the small-diameter channel constituting the first auxiliary combustible gas ejection channel The V _is and V _os are controlled by making it smaller than the inside diameter of the small-diameter channel constituting the second auxiliary combustible gas ejection channel.

  According to the present invention, by optimizing soot formation conditions (gas supply conditions), high-quality soot can be efficiently formed in a short time, and thus a large-sized optical fiber preform can be formed in a shorter time. Can be manufactured. Therefore, the manufacturing cost of the optical fiber preform can be significantly reduced.

It is a figure which shows the outline of the soot formation process by OVD method. It is a figure which shows an example of a burner. It is a figure which shows the relationship between the flow velocity difference (V _is -V _if ) of the flow velocity V _is of the auxiliary combustible gas and the flow velocity V _if of the combustible gas inside the burner, and the deposition efficiency. It is a diagram showing a burner of a difference in flow velocity of the flow velocity _{V of} the flow velocity _{V os} and combustible gas combustion supporting gas in the outer _(V os _{-V of)} the deposition efficiency relationship. The flow rate difference between the flow velocity V _is of the auxiliary combustion gas inside the burner and the flow velocity V _if of the combustible gas (V _is −V _if ) and the flow velocity V _os of the auxiliary combustion gas V _os and the flow velocity V _of the combustible gas outside the burner. It is a figure which shows the relationship between the difference _of ( _Vos- Vof), and deposition efficiency. It is a figure which shows another example (1st auxiliary | assistant combustible gas ejection flow path internal diameter <2nd auxiliary combustion gas ejection flow path internal diameter). It is a figure which shows another example (the auxiliary | assistant combustible gas ejection flow path of a triple ring structure) of a burner. It is a figure which shows another example (combustible gas ejection flow path of a double structure) of a burner. It is a figure which shows another example (combustible gas ejection flow path of a double structure) of a burner. It is a figure which shows another example (combustible gas ejection flow path of a double structure) of a burner.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, a soot body is formed on the outer peripheral surface of the target rod by the OVD method, and this is heated at a high temperature to be dehydrated and sintered, thereby forming a transparent glass to produce an optical fiber preform.

FIG. 1 is a diagram showing an outline of a soot forming process by the OVD method.
As shown in FIG. 1, in the OVD method, the burner 10 is disposed so as to be capable of reciprocating in the longitudinal direction of the target rod 2. The burner 10 supplies a raw material gas such as SiCl ₄ , a combustible gas (for example, H ₂ ), an auxiliary combustion gas (for example, O ₂ ), and a seal gas (for example, N ₂ ). Then, the raw material gas undergoes a flame hydrolysis reaction in a flame (for example, an oxyhydrogen flame) 101 composed of a combustible gas and an auxiliary combustible gas, thereby generating glass fine particles (soot) 102.
By rotating the burner 10 back and forth in the longitudinal direction while rotating the target rod 2 around the axis, the glass particulates 102 are deposited on the outer peripheral surface of the target rod 2 and the soot body 3 is formed. And the optical fiber preform 1 made into a transparent glass is manufactured by heating at high temperature and dehydrating and sintering. Moreover, an optical fiber is manufactured by drawing this optical fiber preform 1 by heating. For the target rod 2, a core base material manufactured by, for example, the VAD method is used.

FIG. 2 is a diagram illustrating an example of the burner 10. As shown in FIG. 2, the burner 10 includes a source gas ejection channel 11 that ejects a source gas, an auxiliary gas ejection channel 12 that ejects an auxiliary gas, and an inflammable gas ejection channel 13 that ejects an inflammable gas. It has.
At the center of the large-diameter combustible gas ejection channel 13, the source gas ejection channel 11 and the seal gas ejection channel 16 are concentrically arranged. Further, on the outside of the combustible gas ejection flow path 13, a seal gas ejection flow path 14 for ejecting seal gas and an auxiliary auxiliary combustion gas ejection flow path 15 for ejecting auxiliary combustion gas are arranged concentrically. For example, an inert gas such as Ar or N ₂ is generally used as the seal gas.
In addition, each ejection flow path 12-16 is comprised with material with high heat resistance, such as quartz glass and ceramics, for example. The same applies to burners 20 to 60 described later.

  The auxiliary combustion gas ejection channel 12 includes a first auxiliary combustion gas ejection channel 121 composed of six small-diameter channels annularly arranged outside the raw material gas ejection channel 11 at equal intervals, and the first auxiliary combustion gas. It has a double ring structure composed of second auxiliary combustible gas ejection channels 122 composed of eight small-diameter channels annularly arranged outside the ejection channel 121 at equal intervals. The first auxiliary combustible gas ejection channel 121 is disposed in the combustible gas ejection channel 13 so as to surround the raw material gas ejection channel 11 and the seal gas ejection channel 16, and the second auxiliary combustion gas ejection channel 122 is The first combustible gas ejection channel 121 is disposed in the combustible gas ejection channel 13 so as to surround the first auxiliary combustion gas ejection channel 121.

The six small-diameter channels constituting the first auxiliary combustible gas ejection channel 121 are focused at a point where the ejection gas is 180 mm from the gas ejection end, and the eight auxiliary combustion gas ejection channels 122 constitute the second auxiliary gas ejection channel 122. The small-diameter channel is configured such that the jet gas is focused at a point of 220 mm from the gas jet end as a distance greater than or equal to the first auxiliary combustible gas.
The inner diameters of the small-diameter channels constituting the first auxiliary combustion gas ejection channel 121 and the second auxiliary combustion gas ejection channel 122 are the same, and the first auxiliary combustion gas ejection channel 121 and the second auxiliary combustion gas ejection channel The auxiliary combustion gas is supplied to 122 through a separate supply path. Therefore, the flow rate of the auxiliary combustible gas to be ejected is individually controlled by adjusting each gas supply amount.

The smaller the inner diameter of the auxiliary combustible gas ejection flow path 12 (the small diameter flow path constituting the first auxiliary combustion gas ejection flow path 121 and the second auxiliary combustion gas ejection flow path 122), the faster the flow rate with a smaller gas supply amount. However, it is difficult to increase the flow rate as the inner diameter decreases. On the other hand, if the inner diameter of the auxiliary combustion gas ejection passage 12 is increased, a large amount of auxiliary combustion gas is required, which is uneconomical. Accordingly, the inner diameter of the auxiliary combustible gas ejection channel 12 is set to 0.5 to 3 mm, preferably 1 to 2 mm.
The inner diameter of the combustible gas ejection flow path 13 is preferably 25 to 55 mm when H ₂ is used as the combustible gas. This is for obtaining an appropriate flow rate difference between the combustible gas and the auxiliary combustible gas.

  The formation of the soot body 3 greatly depends on the temperature of the source gas and the temperature of the soot deposition surface. On the other hand, the auxiliary combustible gas and the combustible gas supplied from the separate ejection flow paths in the burner 10 burn at the interface. Therefore, by controlling these speed differences, the amount of combustion can be controlled by changing the amount of mixing at the gas interface. That is, by controlling the speed difference between the auxiliary combustible gas and the combustible gas, it is possible to appropriately maintain the temperature of the source gas and the temperature of the soot deposition surface.

In this embodiment, in the process of forming the soot body 3 using the burner 10 as shown in FIG. 2, the flow rates of the auxiliary combustible gas and the combustible gas are controlled so as to satisfy the following formulas (1) to (3). To do.
| V _is −V _if | >> | V _os −V _of | (1)
V _is ≧ V _os (2)
V _is ≦ 40 m / s (3)
Here, the flow rate of the auxiliary combustion gas from the first auxiliary combustion gas ejection channel 121 _is V _is , the flow rate of the combustible gas in the vicinity of the first auxiliary combustion gas ejection channel 121 is V _if , and the second auxiliary combustion gas ejection. The flow rate of the combustible gas from the flow path 122 is V _os , and the flow speed of the combustible gas in the vicinity of the second auxiliary combustible gas ejection flow path 122 is V _of .

V _is , V _if , V _os , and V _of are flow rates at the ejection ends of the ejection channels 121, 122, and 13, and are obtained from the gas supply amount / the sectional area of the ejection ends. In the burner 10 shown in FIG. 2, since combustible gas is supplied from one combustible gas ejection flow path 13, V _if and V _of are the same.

When the auxiliary combustible gas and the combustible gas are supplied so as to satisfy the above formulas (1) to (3), the combustion of the auxiliary combustible gas and the combustible gas inside the burner 10 is caused by the combustion of the auxiliary combustible gas and the combustible gas outside the burner 10. Combustion is faster than combustion. That is, combustion with the inner auxiliary combustible gas and the combustible gas contributes to making the raw material gas into glass particles immediately after being injected from the raw material gas injection flow path 11, and further combustion with the outer auxiliary combustible gas and the combustible gas is further performed. Contributes to glass particles and soot deposition.
As a result, the temperature of the source gas and the temperature of the soot deposition surface are appropriately maintained, so that a high-quality soot can be efficiently formed in a short time. Therefore, a large-sized optical fiber preform can be manufactured in a shorter time, and the manufacturing cost of the optical fiber preform can be significantly reduced.

[Example 1]
In Example 1, the burner 10 shown in FIG. 2 was arranged to face the 100 mmφ target rod 2 with a distance of 250 mm. Then, the raw material gas is SiCl ₄ , the combustible gas is H ₂ , and the auxiliary combustible gas is O _{2. The} burner 10 is reciprocated while rotating the target rod 2, and the glass particles 102 are deposited on the outer peripheral surface of the target rod 2. The soot body 3 was formed. At this time, the rotational speed of the target rod was 100 rpm, the traverse speed of the burner 10 was 2000 mm / min, the traverse length was 2000 mm, and the deposition time was 300 min.

In Example 1, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} flammable gas were controlled so as to satisfy all of the above formulas (1) to (3). And the soot body 3 was transparent vitrified by heating and dehydrating and sintering at high temperature, and the glass body which concerns on Example 1 was produced.

[Comparative Example 1]
In Comparative Example 1, in the soot formation step, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas are set so that at least one of the above formulas (1) to (3) is not satisfied. Controlled. Other soot formation conditions were the same as in Example 1. And the soot body 3 was transparent vitrified by heating and dehydrating and sintering at high temperature, and the glass body which concerns on the comparative example 1 was produced.

  Table 1 shows the results of evaluating the deposition rate (g / min), the deposition efficiency (%), and the outer diameter variation of the soot body for the glass bodies produced in Example 1 and Comparative Example 1. In addition, the outer diameter fluctuation | variation was measured using the laser in the glass body which made the soot body 3 transparent glass. In the optical fiber preform 1 that has been made into a transparent glass, the outer diameter fluctuates with a period of 0.2 to 0.5 m in the longitudinal direction of the preform, but the outer diameter fluctuation of this portion is within 3% of the average outer diameter. Is “◯” (no variation), 3 to 5% is “Δ” (some variation), and 5% or more is “×” (variation).

As shown in Table 1, in Examples 1-1 and 1-2, the flow rates V _is , V _os of the auxiliary combustible gas and the flow velocity V _{if of} the combustible gas so as to satisfy the above formulas (1) to (3). Since V _of was controlled, both a high deposition rate of 22 g / min or higher and a high deposition efficiency of 75% or higher could be achieved simultaneously. Moreover, the transparent vitrified glass body did not vary in outer diameter and was of good quality.
On the other hand, in Comparative Examples 1-1 and 1-2, there was no fluctuation in the outer diameter of the glass body, but because the above equations (1) and (2) were not satisfied, the deposition rate was 18 g / min. Later, the deposition efficiency was less than 70%. In Comparative Examples 1-3 and 1-4, both the deposition rate of 20 g / min or more and the deposition efficiency of 70% or more can be achieved at the same time. However, since the above formula (3) is not satisfied, Increased body outer diameter fluctuation.

As described above, the soot deposition is achieved by controlling the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas so as to satisfy all of the above formulas (1) to (3). The speed and deposition efficiency can be improved. When the flow rates V _if and V _{of of} the combustible gas are the same as in the first embodiment, the flow velocity V _of the auxiliary combustible gas ejected from the first auxiliary combustible gas ejection channel 121 disposed inside. _The above formulas (1) to (3) can be easily satisfied by making is faster than the flow velocity V _os of the auxiliary combustible gas ejected from the second auxiliary combustible gas ejection channel 122 arranged on the outside. .
However, the deposition and the flow velocity V _IS is too fast (e.g., 40 m / s greater) rate, tend to either decrease the deposition efficiency, also increases the outer diameter fluctuation of the optical fiber preform after vitrification.

Furthermore, the relationship between the flow rate difference (V _is −V _if ) between the flow velocity V _is of the auxiliary combustible gas and the flow velocity V _if of the combustible gas inside the burner 10 and the deposition efficiency, the flow velocity V _os of the auxiliary combustion gas on the outer side and the flammability The relationship between the flow rate difference (V _os −V _of ) _of the gas flow rate V _of and the deposition efficiency was examined.
FIG. 3 is a diagram showing the relationship between the flow rate difference between the auxiliary combustible gas flow rate V _is and the combustible gas flow rate V _if and the deposition efficiency, and FIG. 4 shows the flow rate V _os of the auxiliary combustible gas and the flow rate V _{of the} combustible gas. It is a figure which shows the relationship between the flow velocity difference and deposition efficiency.
From FIG. 3, the deposition efficiency can be set to 70% or more by setting (V _is −V _if ) to 15 m / s or more. Further, from FIG. 4, by setting (V _os −V _of ) to 15 m / s or less, the deposition efficiency can be set to 70% or more.
Further, as shown in FIG. 5, the flow velocity difference (V _is −V _if ) between the flow velocity V _is of the auxiliary combustion gas inside the burner 10 and the flow velocity V _if of the combustible gas, and the flow velocity V _os of the auxiliary combustion gas on the outer side. By setting the difference in the flow rate difference (V _os −V _of ) _of the flow rate V _of the combustible gas to 5.0 m / s or more, the deposition efficiency can be set to 70% or more.

[Example 2]
FIG. 6 is a diagram illustrating another example of the burner. As shown in FIG. 6, the burner 20 includes a source gas ejection channel 21 that ejects a source gas, an auxiliary gas ejection channel 22 that ejects an auxiliary gas, and an inflammable gas ejection channel 23 that ejects an inflammable gas. It has.
At the center of the large-diameter combustible gas ejection channel 23, the source gas ejection channel 21 and the seal gas ejection channel 26 are concentrically arranged. Further, on the outside of the combustible gas ejection flow path 23, a seal gas ejection flow path 24 for ejecting seal gas and an auxiliary auxiliary combustion gas ejection flow path 25 for ejecting auxiliary combustion gas are arranged concentrically. As the sealing gas, for example, an inert gas such as Ar or N ₂ is generally used.

  The auxiliary combustion gas ejection flow path 22 includes a first auxiliary combustion gas ejection flow path 221 composed of six small-diameter flow paths arranged annularly at equal intervals outside the raw material gas ejection flow path 21, and the first auxiliary combustion gas. It has a double ring structure composed of second auxiliary combustible gas ejection channels 222 composed of eight small-diameter channels annularly arranged at equal intervals outside the ejection channel 221. The first auxiliary combustible gas ejection channel 221 is disposed in the combustible gas ejection channel 23 so as to surround the raw material gas ejection channel 21 and the seal gas ejection channel 26, and the second auxiliary combustion gas ejection channel 222 is The second auxiliary combustible gas ejection channel 121 is disposed in the combustible gas ejection channel 23 so as to surround it.

The six small-diameter channels constituting the first auxiliary combustible gas ejection channel 221 are focused on the point where the ejected gas is 180 mm from the gas ejection end, and constitute the second auxiliary gas ejection channel 222. The small-diameter channel is configured such that the jet gas is focused at a point of 220 mm from the gas jet end as a distance greater than or equal to the first auxiliary combustible gas.
The inner diameter of the small-diameter flow path constituting the first auxiliary combustible gas ejection flow path 221 is smaller than the inner diameter of the small-diameter flow path constituting the second auxiliary combustible gas ejection flow path 222 (for example, about 75%). The auxiliary gas is supplied to the gas ejection channel 121 and the second auxiliary combustion gas ejection channel 122 through a separate supply channel. Therefore, the flow rate of the auxiliary combustible gas to be ejected is individually controlled by adjusting each gas supply amount. Compared to the burner 10 of the first embodiment, the inner diameter of the small-diameter flow path constituting the first auxiliary combustible gas ejection flow path 221 is small, and therefore the flow velocity V of the auxiliary combustion gas ejected from the first auxiliary combustion gas ejection flow path 221. _{It is possible} to efficiently speed _is with a small gas supply amount.

In Example 2, the soot body 3 was formed in the same manner as in Example 1 by using the burner 20 shown in FIG. At this time, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so as to satisfy all of the above formulas (1) to (3). And the soot body 3 was transparent vitrified by heating and dehydrating and sintering at high temperature, and the glass body which concerns on Example 2 was produced.

[Comparative Example 2]
In Comparative Example 2, in the soot formation process, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so that the above equation (3) was not satisfied. Other soot formation conditions were the same as in Example 2. And the soot body 3 was made into transparent glass by heating at high temperature and dehydrating and sintering, and the glass body which concerns on the comparative example 2 was produced.

Table 2 shows the results of evaluating the deposition rate (g / min), the deposition efficiency (%), and the outer shape variation of the soot body for the glass bodies manufactured in Example 2 and Comparative Example 2.
As shown in Table 2, in Example 2, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so as to satisfy the above formulas (1) to (3). Both a deposition rate of 22 g / min or more and a deposition efficiency of 75% or more could be achieved simultaneously. Moreover, the optical fiber preform 1 that was made into a transparent glass had a good quality with no variation in outer diameter.
On the other hand, in Comparative Example 2, although both a deposition rate of 25 g / min or more and a deposition efficiency of 75% or more can be achieved at the same time, since the above formula (3) is not satisfied, the glass body The outer diameter fluctuation of became larger.

As described above, the soot deposition is achieved by controlling the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas so as to satisfy all of the above formulas (1) to (3). The speed and deposition efficiency can be improved. At this time, by making the inner diameter of the first auxiliary combustible gas ejection flow path 221 disposed on the inner side smaller than the inner diameter of the second auxiliary combustion gas ejection flow path 222 disposed on the outer side, the above formula (1 ) To (3) can be satisfied.
Further, it is possible to obtain a desired flow rate V _IS without excessively supplied supporting gas from the first supporting gas injection passage 221. Therefore, when the auxiliary combustion gas and the combustible gas are mixed and burned on the deposition surface, the soot deposition efficiency can be prevented from being lowered due to the extremely different supply amounts of the two.

[Example 3]
FIG. 7 is a diagram illustrating another example of the burner. As shown in FIG. 7, the burner 30 includes a source gas ejection channel 31 that ejects a source gas, an auxiliary gas ejection channel 32 that ejects an auxiliary gas, and an inflammable gas ejection channel 33 that ejects an inflammable gas. It has.
At the center of the large-diameter combustible gas ejection channel 33, the source gas ejection channel 31 and the seal gas ejection channel 36 are concentrically arranged. Further, outside the combustible gas ejection flow path 33, a seal gas ejection flow path 34 for ejecting seal gas and an auxiliary auxiliary combustion gas ejection flow path 35 for ejecting auxiliary combustion gas are concentrically arranged. As the sealing gas, for example, an inert gas such as Ar or N ₂ is generally used.

  The auxiliary combustion gas ejection channel 32 includes a first auxiliary combustion gas ejection channel 321 composed of six small-diameter channels annularly arranged outside the raw material gas ejection channel 31 at equal intervals, and the first auxiliary combustion gas. A second auxiliary combustible gas ejection channel 322 composed of eight small-diameter channels annularly arranged outside the ejection channel 321 at equal intervals, and further annular at equal intervals outside the second auxiliary combustion gas ejection channel 322 It has a triple ring structure composed of third auxiliary combustible gas ejection channels 323 composed of twelve small-diameter channels arranged.

  The first auxiliary combustible gas ejection channel 321 is disposed in the combustible gas ejection channel 33 so as to surround the raw material gas ejection channel 31 and the seal gas ejection channel 36, and the second auxiliary combustion gas ejection channel 322 is The first auxiliary combustible gas jet passage 321 is disposed in the combustible gas jet passage 33 so as to surround the first auxiliary combustible gas jet passage 321, and the third auxiliary combustible gas jet passage 323 surrounds the second auxiliary combustible gas jet passage 322. It arrange | positions in the combustible gas ejection flow path 33. FIG.

The six small-diameter channels constituting the first auxiliary combustible gas ejection flow path 321 are focused on the point where the ejected gas is 180 mm from the gas ejection end, and the eight auxiliary combustible gas ejection flow paths 322 are configured. The small-diameter channel is focused at a point where the ejected gas is at a distance of 220 mm or more from the gas ejection end to the first combustible gas, and the twelve small-diameter channels constituting the third combustible gas ejecting channel 323 are ejected. The gas is focused at a point of 240 mm as a distance greater than the second auxiliary gas from the gas ejection end.
The first flammable gas ejection channel 321, the second flammable gas ejection channel 322, and the third flammable gas ejection channel 323 have the same diameter, and the first flammable gas ejection channel 323 has the same diameter. 321, the second auxiliary combustion gas ejection channel 322 and the third auxiliary combustion gas ejection channel 323 are supplied with the auxiliary combustion gas through a separate supply channel. Therefore, the flow rate of the auxiliary combustible gas to be ejected is individually controlled by adjusting each gas supply amount.

Here, as shown in FIG. 7, when the auxiliary combustion gas ejection flow path 32 has a triple ring structure, the third auxiliary combustion gas ejection flow path 323 is also the same as the second auxiliary combustion gas ejection flow path 322. It can be seen that the first auxiliary combustible gas ejection flow path 321 is disposed so as to surround the first auxiliary combustible gas ejection flow path 321. Therefore, the flow velocity of combustion assisting gas from the second supporting gas injection passages 322 V _os1, V _of1 the flow rate of the flammable gas in the vicinity of the second supporting gas injection passage _322, the third supporting gas injection flow If the flow rate of the combustible gas from the passage 323 is V _os2 , and the flow rate of the combustible gas in the vicinity of the third auxiliary combustible gas ejection flow path 322 is V _of2 , the above equation (1) is expressed by the following equations (4), ( 5), and the above equation (2) is represented by the following equations (6) and (7).
| V _is −V _if | >> | V _os1 −V _of1 | (4)
| V _is −V _if | >> | V _os2 −V _of2 | (5)
V _is ≧ V _os1 (6)
V _is ≧ V _os2 (7)
In the burner 30 shown in FIG. 7, since the combustible gas is supplied from one combustible gas ejection flow path 33, V _if , V _of1 and V _of2 are the same.

In Example 3, the soot body 3 was formed in the same manner as in Example 1 by using the burner 30 shown in FIG. At this time, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so as to satisfy all of the above formulas (3) and (4) to (7). And the soot body 3 was transparent vitrified by heating and dehydrating and sintering at high temperature, and the glass body which concerns on Example 3 was produced.

[Comparative Example 3]
In Comparative Example 3, in the soot formation step, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so that the above equations (4) to (7) were not satisfied. Other soot formation conditions were the same as in Example 3. And the soot body 3 was made into transparent glass by heating at high temperature and dehydrating and sintering, and the glass body which concerns on the comparative example 3 was produced.

Table 3 shows the results of evaluating the deposition rate (g / min), the deposition efficiency (%), and the soot body external shape variation of the optical fiber preform 1 manufactured in Example 3 and Comparative Example 3.
As shown in Table 3, in Examples 3-1 and 3-2, the flow rates V _is and V _os of the auxiliary combustible gas and the combustible gas so as to satisfy the above formulas (3) and (4) to (7). Since the flow rates V _if and V _of were controlled, it was possible to simultaneously achieve both a deposition rate of 25 g / min or more and a deposition efficiency of 80% or more. Moreover, the transparent vitrified glass body did not vary in outer diameter and was of good quality.
In contrast, in Comparative Example 3, there was no fluctuation in the outer diameter of the optical fiber preform 1, but since the above equations (4) to (7) are not satisfied, the deposition rate is about 20 g / min. The deposition efficiency was low and less than 60%.

Thus, even when the auxiliary combustion gas ejection flow path 32 has a triple ring structure, the flow rates V _is and V _os1 of the auxiliary combustion gas so as to satisfy all of the above formulas (3) and (4) to (7). , V _os2, and the flow rate of combustible gas V _if , V _of1 , V _of2 , the deposition rate and the deposition efficiency can be improved. When the flow rates V _if , V _of1 , and V _of2 of the combustible gas are the same as in the third embodiment, the auxiliary combustible gas ejected from the first auxiliary combustible gas ejection channel 321 disposed inside. _Is made faster than the flow rates V _os1 and V _{os2 of the} auxiliary combustion gas ejected from the second auxiliary combustion gas ejection channel 322 and the third auxiliary combustion gas ejection channel 323 arranged outside. The above formulas (3) and (4) to (7) can be easily satisfied.
Further, from Examples 3-1 and 3-2, in order to improve the deposition rate and the deposition efficiency, the auxiliary combustion gas and the combustible gas ejected from the third auxiliary combustion gas ejection flow path 323 arranged on the outside are used. It is desirable to reduce the gas flow rate difference (V _os2 −V _of2 ).

[Example 4]
FIG. 8 is a diagram illustrating another example of the burner. As shown in FIG. 8, the burner 40 includes a source gas ejection channel 41 that ejects a source gas, an auxiliary gas ejection channel 42 that ejects an auxiliary gas, and an inflammable gas ejection channel 43 that ejects an inflammable gas. It has.
The combustible gas ejection flow path 43 has a double structure in which the first combustible gas ejection flow path 431 and the second auxiliary combustible gas ejection flow path 432 are arranged concentrically, and the flow of combustible gas The road is divided.
The inner diameter of the first combustible gas ejection channel 431 is approximately twice the inner diameter of the second combustible gas ejection channel 432, and the first combustible gas ejection channel 431 and the second combustible gas ejection channel 432. Is supplied with combustible gas through a separate supply path. Therefore, the flow rate of the combustible gas to be ejected is individually controlled by adjusting each gas supply amount.

At the center of the first combustible gas ejection channel 431, a raw material gas ejection channel 41 and a seal gas ejection channel 46 are concentrically arranged. Further, outside the second combustible gas ejection channel 432, a seal gas ejection channel 44 for ejecting seal gas and an auxiliary auxiliary combustion gas ejection channel 45 for ejecting auxiliary combustion gas are concentrically arranged. . As the sealing gas, for example, an inert gas such as Ar or N ₂ is generally used.

  The auxiliary combustion gas ejection channel 42 includes a first auxiliary combustion gas ejection channel 421 including six small-diameter channels annularly arranged outside the raw material gas ejection channel 41 at equal intervals, and the first auxiliary combustion gas. It has a double ring structure composed of second auxiliary combustible gas ejection channels 422 composed of eight small-diameter channels annularly arranged at equal intervals outside the ejection channel 421. The first auxiliary combustible gas ejection channel 421 is disposed in the first combustible gas ejection channel 431 so as to surround the raw material gas ejection channel 41 and the seal gas ejection channel 46, and the second auxiliary combustion gas ejection channel 421. 422 is disposed in the second combustible gas ejection flow path 432.

The six small-diameter channels constituting the first auxiliary combustible gas ejection channel 421 focus on the point where the ejection gas is 180 mm from the gas ejection end, and constitute the second auxiliary combustion gas ejection channel 422. The small-diameter channel is configured such that the jet gas is focused at a point of 220 mm from the gas jet end as a distance greater than or equal to the first auxiliary combustible gas.
The inner diameters of the small-diameter channels constituting the first auxiliary combustion gas ejection channel 421 and the second auxiliary combustion gas ejection channel 422 are the same, and the first auxiliary combustion gas ejection channel 421 and the second auxiliary combustion gas ejection channel 421 are the same. The auxiliary combustion gas is supplied to 422 through a separate supply path. Therefore, the flow rate of the auxiliary combustible gas to be ejected is individually controlled by adjusting each gas supply amount.

In Example 4, the soot body 3 was formed in the same manner as in Example 1 by using the burner 40 shown in FIG. At this time, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so as to satisfy all of the above formulas (1) to (3). And the soot body 3 was made into transparent glass by heating at high temperature and dehydrating and sintering, and the glass body which concerns on Example 4 was produced.

[Comparative Example 4]
In Comparative Example 4, in the soot formation process, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so that the above formula (1) was not satisfied. Other soot formation conditions were the same as in Example 4. And the soot body 3 was transparent vitrified by heating at high temperature and dehydrating and sintering, and the glass body which concerns on the comparative example 4 was produced.

Table 4 shows the results of evaluating the deposition rate (g / min), the deposition efficiency (%), and the outer shape variation of the soot body for the optical fiber preform 1 manufactured in Example 4 and Comparative Example 4.
As shown in Table 4, in Example 4, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so as to satisfy the above formulas (1) to (3). Both a high deposition rate of 25 g / min or more and a deposition efficiency of about 80% could be achieved at the same time. Moreover, the optical fiber preform 1 that was made into a transparent glass had a good quality with no variation in outer diameter.
In contrast, in Comparative Example 4, there was no fluctuation in the outer diameter of the optical fiber preform 1, but since the above equation (1) is not satisfied, the deposition rate is about 20 g / min, and the deposition efficiency is Less than 60%.

In this way, by controlling the flow rates V _is , V _os of the auxiliary combustible gas and the flow rates V _if , V _{of of the} combustible gas so as to satisfy all of the above formulas (1) to (3), the deposition rate and The deposition efficiency can be improved. When the combustible gas ejection flow path is divided as in the fourth embodiment, the flow rate V _{of the} combustible gas ejected in the vicinity of the second auxiliary combustible gas ejection flow path 422 is set to the first auxiliary combustible gas ejection flow. By making it faster than the flow velocity V _if of the combustible gas ejected in the vicinity of the path 421, the above equations (1) to (3) can be easily satisfied.

[Example 5]
FIG. 9 is a diagram illustrating another example of the burner. As shown in FIG. 9, the burner 50 includes a source gas ejection channel 51 that ejects a source gas, an auxiliary gas ejection channel 52 that ejects an auxiliary gas, and an inflammable gas ejection channel 53 that ejects an inflammable gas. It has.
The combustible gas ejection channel 53 includes a first combustible gas ejection channel 531 and a second combustible gas ejection channel 532. The second combustible gas ejection channel 532 is configured by blocking a part of the opening of a large-diameter combustible gas ejection channel (for example, the second combustible gas ejection channel 432 in FIG. 8) with a baffle plate 532a. Thus, the combustible gas is ejected only around the second auxiliary combustible gas ejection channel 522 described later. The baffle plate 532a is, for example, a quartz plate in which a hole slightly larger than the outer diameter of the second auxiliary combustible gas ejection flow path 522 is formed at a position corresponding to the second auxiliary combustible gas ejection flow path 522. It has a thickness of 20 mm that can rectify the property gas.
The combustible gas is supplied to the first combustible gas ejection channel 531 and the second combustible gas ejection channel 532 through a separate supply channel. Therefore, the flow rate of the combustible gas to be ejected is individually controlled by adjusting each gas supply amount.

In the center of the first combustible gas ejection channel 531, the source gas ejection channel 51 and the seal gas ejection channel 56 are concentrically arranged. Further, outside the second combustible gas ejection channel 532, a seal gas ejection channel 54 for ejecting seal gas and an auxiliary auxiliary combustion gas ejection channel 55 for ejecting auxiliary combustion gas are arranged concentrically. . As the sealing gas, for example, an inert gas such as Ar or N ₂ is generally used.

  The auxiliary combustion gas ejection channel 52 includes a first auxiliary combustion gas ejection channel 521 composed of six small-diameter channels annularly arranged outside the raw material gas ejection channel 51 at equal intervals, and the first auxiliary combustion gas. It has a double ring structure composed of second auxiliary combustible gas ejection channels 522 consisting of eight small-diameter channels annularly arranged at equal intervals outside the ejection channel 521. The first auxiliary combustible gas ejection channel 521 is disposed in the first combustible gas ejection channel 531 so as to surround the raw material gas ejection channel 51 and the seal gas ejection channel 56, and the second auxiliary combustion gas ejection channel 521. 522 is disposed in the second combustible gas ejection flow path 532.

The six small-diameter channels constituting the first auxiliary combustible gas ejection channel 521 are focused at a point where the ejection gas is 180 mm from the gas ejection end, and constitute the second auxiliary combustion gas ejection channel 522. The small-diameter channel is configured such that the jet gas is focused at a point of 220 mm from the gas jet end as a distance greater than or equal to the first auxiliary combustible gas.
The inner diameters of the small-diameter channels constituting the first auxiliary combustion gas ejection channel 521 and the second auxiliary combustion gas ejection channel 522 are the same, and the first auxiliary combustion gas ejection channel 521 and the second auxiliary combustion gas ejection channel 521 are the same. The auxiliary combustion gas is supplied to 522 through a separate supply path. Therefore, the flow rate of the auxiliary combustible gas to be ejected is individually controlled by adjusting each gas supply amount.

In Example 5, the soot body 3 was formed similarly to Example 1 using the burner 50 shown in FIG. At this time, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so as to satisfy all of the above formulas (1) to (3). And the soot body 3 was transparent vitrified by heating at high temperature and dehydrating and sintering, and the glass body which concerns on Example 5 was produced.

[Comparative Example 5]
In Comparative Example 5, in the soot formation process, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so that the above formula (1) was not satisfied. Other soot formation conditions were the same as in Example 5. And the soot body 3 was made into transparent glass by heating at high temperature and dehydrating and sintering, and the glass body which concerns on the comparative example 5 was produced.

Table 5 shows the results of evaluating the deposition rate (g / min), the deposition efficiency (%), and the outer shape variation of the soot body for the optical fiber preform 1 manufactured in Example 5 and Comparative Example 5.
As shown in Table 5, in Example 5, the flow rates V _is and V _os of the auxiliary combustible gas and the flow rates V _if and V _{of the} combustible gas were controlled so as to satisfy the above formulas (1) to (3). Both a deposition rate of 25 g / min or more and a deposition efficiency of 75% or more could be achieved simultaneously. Moreover, the optical fiber preform 1 that was made into a transparent glass had a good quality with no variation in outer diameter.
In contrast, in Comparative Example 5, there was no fluctuation in the outer diameter of the optical fiber preform 1, but since the above equation (1) is not satisfied, the deposition rate is slower than 20 g / min, and the deposition efficiency is 60. %.

In this way, by controlling the flow rates V _is , V _os of the auxiliary combustible gas and the flow rates V _if , V _{of of the} combustible gas so as to satisfy all of the above formulas (1) to (3), the deposition rate and The deposition efficiency can be improved. When the combustible gas ejection flow path is divided as in the fifth embodiment, the flow velocity V _{of the} combustible gas ejected in the vicinity of the second auxiliary combustible gas ejection flow path 522 is set to the first auxiliary combustible gas ejection flow. By making it faster than the flow velocity V _if of the combustible gas ejected in the vicinity of the path 521, the above equations (1) to (3) can be easily satisfied.
In addition, the desired flow velocity V _of can be achieved without excessively supplying the combustible gas from the second combustible gas ejection channel 532. For example, the supply amount of the combustible gas from the second combustible gas ejection channel 532 in the fifth embodiment is smaller than the supply amount of the combustible gas from the second combustible gas ejection channel 432 in the fourth embodiment. Since the cross-sectional area of the ejection channel is small, the flow velocity V _{of the} combustible gas is the same. Therefore, when the auxiliary combustion gas and the combustible gas are mixed and burned on the deposition surface, the soot deposition efficiency can be prevented from being lowered due to the extremely different supply amounts of the two. This is effective when it is desired to increase the flow velocity V _{of the} combustible gas ejected from the second combustible gas ejection flow path 532.

  As mentioned above, although the invention made by this inventor was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.

For example, the burner to which the present invention can be applied is not limited to the one shown in the embodiment, and the auxiliary combustible gas jet passage is arranged in a multi-ring structure around the raw material gas jet passage, and this auxiliary combustible gas jet passage What is necessary is just the burner by which the combustible gas ejection flow path is arrange | positioned around.
For example, in the embodiment, the case where the auxiliary combustible gas ejection flow path has a double ring structure or a triple ring structure has been described, but more multiple ring structures can be formed. In this case, as in the case of the triple ring structure (Example 3), the flow rate difference between the auxiliary combustible gas and the combustible gas on the outside of the burner is smaller than the speed difference between the auxiliary combustible gas and the combustible gas on the innermost side. What should I do.

  Further, in Example 5 (see FIG. 9), a part of the large-diameter combustible gas ejection channel is closed with the baffle plate 532a, so that the ejection channel is placed around the second auxiliary combustible gas ejection channel 522. Although the restricted second combustible gas ejection flow path 532 is formed, as shown in FIG. 10, the second combustible gas ejection flow path 632 corresponds to the second auxiliary combustible gas ejection flow path 622. May be provided. In this case, the second combustible gas ejection channel 632 is disposed in the seal gas ejection channel 64, and the second auxiliary combustible gas ejection channel 622 is disposed in the second combustible gas ejection channel 632. Become.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Optical fiber base material 2 Target rod 3 Soot body 10 Burner 11 Raw material gas ejection flow path 12 Auxiliary combustion gas ejection flow path 121 The 1st combustion combustion gas ejection flow path 122 The 2nd combustion combustion gas ejection flow path 13 A combustible gas ejection flow Path 14 Seal gas ejection flow path 15 Auxiliary auxiliary gas 16 Seal gas ejection flow path

Claims (6)

A source gas ejection passage for ejecting source gas;
Composed of a plurality of small-diameter channels provided annularly so as to surround the raw material gas-ejecting channel, and an auxiliary-combustible gas-ejecting channel for ejecting auxiliary-combustible gas from these small-diameter channels;
Using a burner that is provided around the raw material gas ejection channel and the auxiliary combustible gas ejection channel, and includes a combustible gas ejection channel that ejects combustible gas,
The glass particles generated by injecting the combustible gas and the auxiliary combustible gas and supplying the raw material gas into a flame composed of the combustible gas and the auxiliary combustible gas are rotated about a cylindrical target rod as an axis. while, the burner and the target rod by causing relative movement in the longitudinal direction, to deposit the glass particles on the outer peripheral surface of the target rod, the steps that form a soot body,
A step of transparent vitrification by heating the formed soot body at a high temperature for dehydration and sintering,
In a method of manufacturing an optical fiber preform comprising:
The auxiliary combustion gas ejection flow path includes a first auxiliary combustion gas ejection flow path that is annularly disposed outside the raw material gas ejection flow path, and a second annular movement that is disposed outside the first auxiliary combustion gas ejection flow path. An auxiliary combustible gas ejection flow path, and
The flow rate of the auxiliary combustible gas from the first auxiliary combustible gas ejection flow path is expressed as Vis (m / s),
The flow rate of the combustible gas in the vicinity of the first auxiliary combustible gas ejection flow path is Vif (m / s),
The flow rate of the auxiliary combustion gas from the second auxiliary combustion gas ejection flow path is expressed as Vos (m / s),
When the flow rate of the combustible gas in the vicinity of the second auxiliary combustible gas ejection flow path is Vof (m / s),
| Vis-Vif |> | Vos-Vof |
Vis ≧ Vof
Vis ≦ 40 m / s
The method of manufacturing an optical fiber preform, wherein flow rates of the auxiliary combustible gas and the combustible gas are controlled so as to satisfy the above.   2. The optical fiber preform according to claim 1, wherein flow rates of the auxiliary combustible gas and the combustible gas are controlled so as to satisfy (Vis−Vif) − (Vos−Vof)> 5 m / s. Production method.   3. The method of manufacturing an optical fiber preform according to claim 1, wherein flow rates of the auxiliary combustible gas and the combustible gas are controlled so as to satisfy (Vis−Vif) ≧ 15 m / s.   4. The optical fiber preform according to claim 1, wherein flow rates of the auxiliary combustible gas and the combustible gas are controlled so as to satisfy (Vos−Vof) ≦ 15 m / s. 5. Manufacturing method.   5. The method of manufacturing an optical fiber preform according to claim 1, wherein flow rates of the auxiliary combustible gas and the combustible gas are controlled so as to satisfy Vif <Vof.   The Vis and Vos are controlled by making the inside diameter of the small-diameter channel constituting the first auxiliary combustible gas ejection channel smaller than the inside diameter of the small-diameter channel constituting the second auxiliary combustion gas ejection channel. The method for producing an optical fiber preform according to any one of claims 1 to 5.

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