JP2013112551A - Production method of optical fiber, control device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method by which the hole diameter of an optical fiber is adjusted to the desired value even when a preform varies in through hole formation position or preform diameter along the longitudinal direction of the preform.SOLUTION: An apparatus 100 for producing an optical fiber includes a pressure control device 200 which, when each portion of a preform 20 is melt-drawn, determines the pressure of a gas to be introduced into a through hole 20a in the preform 20 on the basis of at least any one of the outside diameter of the preform in the portion and the position of the through hole 20a in the portion.

Description

  The present invention relates to an optical fiber manufacturing method for manufacturing an optical fiber. The present invention also relates to a control device that controls an optical fiber manufacturing apparatus that manufactures an optical fiber, and a program for operating a computer as such a control device.

  In recent years, holey optical fibers have attracted attention. The holey optical fiber is formed by forming holes extending in the longitudinal direction of an optical fiber mainly composed of silica glass, and is also called a holey fiber. It is known that optical characteristics with holes can be obtained with optical characteristics that cannot be realized with conventional optical fibers.

  There are optical fibers with holes, one having a uniform refractive index of the base material and one having a refractive index of the base material different between the core and the clad. The latter optical fiber with holes is also referred to as a hole-assisted fiber, and a typical example is one in which a single hole group is formed in the cladding. It is known that the formation of holes in the cladding increases the light confinement effect and reduces the bending loss. For this reason, such a holey optical fiber has already been put into practical use for a home optical communication network that requires low bending loss.

  The optical fiber with holes includes (1) a preform manufacturing process for manufacturing a columnar base material made of silica glass (hereinafter referred to as “preform”), and (2) drilling a through hole that is a base of the hole. It is manufactured through a through-hole forming step formed in a preform by drilling or the like, and (3) a drawing step of melt-drawing the preform in which the through-hole is formed.

  In a holey optical fiber, the hole diameter (hereinafter referred to as “hole diameter”) and the position of the hole (hereinafter referred to as “hole position”) greatly affect the optical characteristics. For example, it is known that the bending loss changes greatly depending on the size of the hole diameter or the distance from the center axis of the hole. The hole position depends on the position of the through hole formed in the preform in the through hole forming step. The hole diameter depends on the diameter of the through hole formed in the preform in the through hole forming step (hereinafter referred to as “through hole diameter”).

  However, the hole diameter can be adjusted according to the conditions of the drawing process. A typical drawing condition that affects the hole diameter is the pressure of the gas introduced into the through hole (hereinafter referred to as “introduced gas pressure”) (the melting furnace temperature, drawing speed, etc. are also empty). May affect the pore size). Therefore, even if there is a slight deviation in the diameter of the through hole in the preform, this can be compensated for by appropriately controlling the introduced gas pressure.

  As a method for controlling the introduced gas pressure in the drawing process, feedback control is known in which the hole diameter of a holey optical fiber during drawing is measured and the introduced gas pressure is determined according to the measurement result. As a method for measuring the hole diameter in such feedback control, for example, those described in Patent Documents 1 to 3 are known.

Japanese Patent Laid-Open No. 5-264398 (published on October 12, 1993) Japanese Patent Laying-Open No. 2005-247621 (published on September 15, 2005) JP 2009-7201 A (released on January 15, 2009)

  However, it is not only the through hole diameter in the preform that affects the hole diameter in the optical fiber. For example, the position of the through hole in the preform (hereinafter referred to as “through hole position”) and the outer diameter of the preform (hereinafter referred to as “preform diameter”) are also factors that change the hole diameter of the optical fiber. .

  The closer to the surface of the preform, the higher the temperature during melt stretching and the lower the melt viscosity. For this reason, the through hole formed at a position closer to the surface of the preform is more easily crushed during melt drawing. This is why the hole diameter of the optical fiber depends on the position where the through hole is formed. Further, when the outer diameter of the preform changes, the proportion of the glass portion in the cross section of the preform changes. This is why the hole diameter of the optical fiber depends on the preform diameter. It should be noted that the fluctuation of the pore diameter accompanying the fluctuation of the preform diameter becomes larger as the preform diameter is larger and the through-hole diameter is smaller.

  And a through-hole position and a preform diameter may change along the longitudinal direction of a preform. That is, when the through-hole gradually approaches the inside or outside from one end to the other end, the preform may gradually become thicker or thinner from one end to the other end. In such a case, the conventional feedback control cannot make the hole diameter of the optical fiber a desired value. For this reason, the manufacturing yield deteriorates.

  For example, the feedback control described in Patent Document 3 measures the hole diameter of an optical fiber immediately before being wound by a winder, and controls the introduced gas pressure according to the measurement result. That is, the feedback control described in Patent Document 3 always involves a time delay. Therefore, when the through-hole position or the preform diameter changes along the longitudinal direction of the preform, the feedback control described in Patent Document 3 cannot make the hole diameter of the optical fiber a desired value.

  The present invention has been made in view of the above problems, and its purpose is to reduce the hole diameter of an optical fiber even when the through-hole formation position or the preform diameter changes along the longitudinal direction of the preform. An object of the present invention is to realize an optical fiber manufacturing method that can achieve a desired value.

  In order to solve the above-mentioned problems, an optical fiber manufacturing method according to the present invention is an optical fiber manufacturing method for manufacturing an optical fiber from a preform in which a through hole is formed, while introducing gas into the through hole. A drawing step of melt-drawing the preform, and a pressure of a gas introduced into the through-hole when the portions of the preform are melt-drawn in the drawing step. And a pressure determining step for determining based on at least one of the outer diameter and the position of the through hole in the portion measured in advance.

  According to said structure, the pressure of the gas introduced into the said through-hole when melt-extending each part of the said preform was measured in advance by the outer diameter of the said preform in this part, and measured beforehand It is determined based on at least one of the positions of the through holes in the portion. Therefore, even when the through-hole forming position or the preform diameter changes along the longitudinal direction of the preform, the hole diameter of the optical fiber can be set to a desired value.

  In the optical fiber manufacturing method, the pressure determining step includes a correlation between a change amount ΔD of the outer diameter of the preform and a change amount Δd of the hole diameter in the optical fiber determined in advance by an experiment, and an experiment performed in advance. The pressure of the gas introduced into the through hole is determined with reference to at least one of the correlations between the change amount ΔR of the position of the through hole and the change amount Δd of the hole diameter in the optical fiber determined by It is preferable.

  According to said structure, the hole diameter of an optical fiber can be made into a desired value easily and correctly.

  In the optical fiber manufacturing method, the method further includes a measurement step of measuring a hole diameter of the optical fiber melt-stretched in the drawing step, and the pressure determination step includes the pressure of the gas introduced into the through hole, In addition to at least one of the outer diameter of the preform and the position of the through hole, it is preferably determined based on the hole diameter of the optical fiber measured in the measurement step.

  According to the above configuration, the optical fiber is more accurately compared with the case where the pressure of the gas introduced into the through hole is determined based on at least one of the outer diameter of the preform and the position of the through hole. The hole diameter can be set to a desired value.

  The control device according to the present invention is a control device that controls an optical fiber manufacturing device that manufactures an optical fiber by melting and stretching the preform while introducing a gas into a through-hole formed in the preform. The pressure of the gas introduced into the through hole when each part of the preform is melt-drawn by the optical fiber manufacturing apparatus was measured in advance, and the preform outside diameter at the part was measured in advance. Pressure determining means for determining based on at least one of the positions of the through holes in the portion is provided.

  According to said structure, there can exist an effect similar to the manufacturing method of the said optical fiber.

  A program according to the present invention is a program for causing a computer to function as the control device, and causes the computer to function as the pressure determining means.

  According to the present invention, it is possible to achieve the same effect as the above-described optical fiber manufacturing method.

  According to the present invention, the hole diameter of the optical fiber can be set to a desired value even when the through hole forming position or the preform diameter changes along the longitudinal direction of the preform.

It is a figure showing a schematic structure of an optical fiber manufacturing system concerning an embodiment. It is sectional drawing of the preform 20 used for the optical fiber manufacturing system 10 which concerns on embodiment. It is a flowchart which shows the manufacture procedure of the optical fiber by the optical fiber manufacturing system which concerns on embodiment. It is a graph which shows the through-hole position in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus which concerns on embodiment. It is a graph which shows the outer diameter in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus which concerns on embodiment. It is a graph which shows the change of the pressure added to the preform in the optical fiber manufacturing apparatus concerning an embodiment. It is a graph which shows the hole position in each of several position of the longitudinal direction of the optical fiber manufactured by the optical fiber manufacturing apparatus which concerns on embodiment. It is a graph which shows the through-hole position in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus used by the comparative example 1. FIG. It is a graph which shows the outer diameter in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus used in the comparative example 1. It is a graph which shows the hole position in each of several position of the longitudinal direction of the optical fiber manufactured with the optical fiber manufacturing apparatus used in the comparative example 1. FIG. It is a graph which shows the through-hole position in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus which concerns on embodiment. It is a graph which shows the outer diameter in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus which concerns on embodiment. It is a graph which shows the hole position in each of several position of the longitudinal direction of the optical fiber manufactured by the optical fiber manufacturing apparatus which concerns on embodiment. It is a graph which shows the through-hole position in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus used in the comparative example 2. It is a graph which shows the outer diameter in each of the several position of the longitudinal direction of a preform measured by the measuring apparatus used in the comparative example 2. It is a graph which shows the hole position in each of several position of the longitudinal direction of the optical fiber manufactured by the optical fiber manufacturing apparatus used in the comparative example 2.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

(Configuration of optical fiber manufacturing system)
First, the configuration of the optical fiber manufacturing system 10 according to the embodiment will be described. FIG. 1 is a diagram illustrating a schematic configuration of an optical fiber manufacturing system 10 according to the embodiment. As shown in FIG. 1, the optical fiber manufacturing system 10 includes an optical fiber manufacturing apparatus 100, a measuring apparatus 150, and a pressure control apparatus 200.

  The optical fiber manufacturing system 10 is a system for manufacturing an optical fiber from the preform by drawing a cylindrical preform as an optical fiber preform in the longitudinal direction (axial direction). In particular, the optical fiber manufacturing system can manufacture the optical fiber 30 in which the holes 30a are formed from the preform 20 in which the through holes 20a are formed.

(Preform structure)
Next, the configuration of the preform 20 will be described. FIG. 2 is a cross-sectional view of the preform 20 used in the optical fiber manufacturing system 10 according to the embodiment. As shown in FIG. 2, the preform 20 includes a core portion 22 that is a central portion and a clad portion 24 that is a portion around the core portion.

  The refractive index of the core portion 22 is relatively high, and the refractive index of the cladding portion 24 is relatively low. The through hole 20 a is a through hole formed in the cladding portion 24 and penetrating between both end faces of the preform 20. In particular, the preform 20 has a plurality of through-holes 20a formed concentrically around the central axis. The through hole 20a is provided mainly for enhancing the light confinement effect in the core portion 22 and improving the bending characteristics.

  As the preform 20, for example, a material mainly composed of quartz glass is used. In addition, as the preform 20, a material containing germanium, fluorine or the like as a dopant may be used.

(Configuration of each device)
Next, the configuration of each device included in the optical fiber manufacturing system 10 will be described.

  As shown in FIG. 1, an optical fiber manufacturing apparatus 100 includes a pressurizing apparatus 102, a melting furnace 104, a primary coating layer forming apparatus 106, a primary coating layer curing apparatus 108, a secondary coating layer forming apparatus 110, and a secondary coating layer curing. A device 112 and a winding device 114 are provided.

  The pressurizing device 102 applies pressure to each through hole 20a by supplying gas to each through hole 20a. As the gas, an inert gas such as nitrogen gas, helium gas, or argon gas is used.

  The melting furnace 104 heat-melts the preform 20. The thermally melted portion of the preform 20 is drawn by the winding operation of the optical fiber 30 (the portion that has already been generated) by the winding device 114 to become the optical fiber 30 (bare wire). At this time, the through hole 20 a formed in the preform 20 becomes the hole 30 a formed in the optical fiber 30 as it is. The inner diameter of the hole 30a corresponds to the pressure in the hole 30a. That is, the higher the pressure in the hole 30a, the larger the inner diameter of the hole 30a.

  The primary coating layer forming apparatus 106 forms a primary coating layer on the surface of the optical fiber 30 (bare wire). The primary coating layer curing device 108 cures the primary coating layer formed on the surface of the optical fiber 30 (bare wire).

  A secondary coating layer is formed on the surface of the primary coating layer of the secondary coating layer forming apparatus 110 and the optical fiber 30. The secondary coating layer curing device 112 cures the secondary coating layer formed on the surface of the primary coating layer of the optical fiber 30.

  For example, an ultraviolet curable resin is used as the primary coating layer and the secondary coating layer. In this case, an ultraviolet lamp is used as the primary coating layer curing device 108 and the secondary coating layer curing device 112.

  The winding device 114 winds the optical fiber 30 on which the primary coating layer and the secondary coating layer are formed.

  The measuring device 150 measures the position of the through hole 20a and the outer diameter D of the preform 20 at each of a plurality of points in the longitudinal direction of the preform 20 where the through hole 20a is formed. In the present embodiment, the distance from the central axis of the preform 20 is used as the position of the through hole 20a.

  The pressure control device 200 is based on at least one of the position of the through hole 20a at each of the plurality of points and the outer diameter D at each of the plurality of points, which is measured by the measuring device 150. For each of the plurality of points, the pressure applied to the through hole 20a when the optical fiber manufacturing apparatus 100 manufactures the optical fiber 30 is controlled. By this control, the amount of gas supplied by the pressurizing device 102 is adjusted, whereby the optical fiber manufacturing apparatus 100 applies an appropriate pressure in the through hole 20a in order to make the hole diameter of the optical fiber 30 appropriate. It is possible to add.

(Feedback function)
The optical fiber manufacturing apparatus 100 further includes a hole diameter measuring device 116 and an outer diameter measuring device 118. The hole diameter measuring device 116 is an apparatus that measures the inner diameter of the hole 30 a formed in the optical fiber 30. The outer diameter measuring device 118 is a device that measures the outer diameter of the optical fiber 30.

  The inner diameter of the hole 30 a measured by the hole diameter measuring device 116 is fed back to the pressure control device 200. The pressure control device 200 can control the pressure applied to the through hole 20a based further on the hole diameter of the optical fiber 30 fed back. For example, when the hole diameter of the optical fiber 30 is smaller than the target value, the pressure control device 200 controls to increase the pressure applied to the through hole 20a according to the difference from the target value. On the contrary, when the hole diameter of the optical fiber 30 is larger than the target value, the pressure control device 200 performs control so as to reduce the pressure applied to the through hole 20a according to the difference from the target value. By this control, the optical fiber manufacturing apparatus 100 can apply a more appropriate pressure in the through hole 20a in order to make the hole diameter of the optical fiber 30 more appropriate.

(Optical fiber manufacturing procedure)
Next, the manufacturing procedure of the optical fiber 30 by the optical fiber manufacturing system 10 according to the embodiment will be described. FIG. 3 is a flowchart showing a manufacturing procedure of the optical fiber 30 by the optical fiber manufacturing system 10 according to the embodiment.

(Measurement process)
First, the user sets the preform 20 on the measuring device 150. And the measuring apparatus 150 measures the position of the through-hole 20a in each of the some point of the longitudinal direction of the preform 20 (step S302). At the same time, the measuring device 150 measures the outer diameter D at each of a plurality of points in the longitudinal direction of the preform 20 (step S304). Then, the measuring device 150 outputs measurement data indicating the measurement result of step S302 and the measurement result of step S304 (step S306).

(Pressure determination process)
Subsequently, the pressure control device 200 acquires the measurement data output in step S306 (step S308). The measurement data may be transferred from the measuring device 150 to the pressure control device 200 by communication or by some recording medium (for example, a floppy disk, a memory card, a CD-ROM, etc.).

  And the pressure control apparatus 200 determines the pressure added in the through-hole 20a based on the measurement data acquired by step S308 (step S310).

  Furthermore, the pressure control device 200 outputs control data for controlling the pressurizing device 102 so as to apply the pressure determined in step S310 into the through hole 20a to the optical fiber manufacturing device 100 (step S312).

(Pressurizing process, drawing process)
Subsequently, the optical fiber manufacturing apparatus 100 acquires the control data output in step S312 (step S314). The optical fiber manufacturing apparatus 100 applies the pressure determined in step S310 in the through hole 20a according to the control data (step S316). The transfer of control data from the pressure control device 200 to the optical fiber manufacturing device 100 may be by communication, or by some recording medium (for example, floppy disk, memory card, CD-ROM, etc.). Good.

Then, the optical fiber manufacturing apparatus 100 heat-melts and draws the preform 20 with the pressure applied in the through hole 20a (step S318), and further generates and cures a primary coating layer and a secondary coating layer. By doing so (step S320), the optical fiber 30 is generated.
The optical fiber 30 generated in this way is wound up by the winding device 114 (step S322).

  According to the above procedure, the optical fiber manufacturing apparatus 100 applies a more appropriate pressure in the through hole 20a according to the position of the through hole of the preform 20 and the outer diameter D of the preform 20, and further increases the hole diameter of the optical fiber 30. It can be made appropriate.

  In the above procedure, the optical fiber manufacturing apparatus 100 responds to the position based on the measurement data every time the position where the preform 20 is drawn changes as the preform 20 is melted and drawn. Appropriate pressure is applied into the through hole 20a.

  Further, in the above procedure, when the process of measuring the hole diameter of the optical fiber 30 and the outer diameter of the optical fiber 30 and the process of feeding back these measured values to the pressure control apparatus 200 by the optical fiber manufacturing apparatus 100 are included. This process is performed between step S318 and step S320.

(Method of measuring through hole position and outer diameter)
Hereinafter, a method in which the measuring device 150 measures the through hole position and the outer diameter D of the preform 20 will be specifically described.

  The measuring device 150 measures the position of the through hole at each of a plurality of points in the longitudinal direction of the preform 20. For example, if the position of one end face in the longitudinal direction of the preform 20 is a reference position 0 and a certain measurement position is a position x (x is a distance from the reference position 0), the measuring apparatus 150 can have a plurality of positions x ( The through-hole position R (x) at each of the reference positions 0 is measured.

  As this measuring method, each end surface of the preform 20 is measured using an optical microscope, or is measured from the side of the preform 20 using an optical system (for example, International Publication No. 2011/052541). Any of various known measuring methods, such as the method disclosed in the Japanese Patent No. 3), may be used.

  The through hole position R (x) is represented by the distance from the center axis of the preform 20 to the center of the through hole 20a. Since the preform 20 has a plurality of through holes 20a, the measuring device 150 preferably measures the through hole position R (x) for each of the plurality of through holes 20a.

  The measuring device 150 measures the outer diameter D at each of a plurality of points in the longitudinal direction of the preform 20. Assuming that the position of one end face in the longitudinal direction of the preform 20 is a reference position 0 and a certain measurement position is a position x (x is a distance from the reference position 0), the measuring apparatus 150 is capable of measuring a plurality of positions x (reference positions). Measure the outer diameter D (x) at each of 0 (including 0). As this measuring method, any of various known measuring methods such as measurement using a general-purpose laser type outer diameter measuring device may be used.

(How to determine pressure)
Subsequently, a method for determining the pressure applied to the through hole 20a by the pressure control apparatus 200 will be specifically described.

  As already described, the pressure control device 200 acquires the measurement data indicating the through-hole position and the outer diameter D at each of the plurality of points in the longitudinal direction of the preform 20 from the measurement device 150, and uses the acquired measurement data as the acquired measurement data. Based on this, the pressure applied in the through hole 20a is determined.

  For example, it is assumed that the measurement data acquired from the measurement device 150 indicates the through-hole position R (x) and the outer diameter D (x) for each of the plurality of positions x in the longitudinal direction of the preform 20. In addition, it is assumed that the measurement data indicates the through-hole position R (0) and the outer diameter D (0) with respect to the reference position 0.

(Method of determining pressure according to changes in through-hole position)
In this case, the pressure control device 200 determines the pressure applied to the through hole 20a for each of the plurality of positions x based on the change of the through hole position R (x) from the through hole position R (0).

  First, the pressure control device 200 calculates the change amount Δd ′ of the hole diameter of the optical fiber 30 due to the change of the through hole position from the position 0 for each of the plurality of positions x by the following formula (1).

Δd ′ = (Δd / ΔR) × (R (x) −R (0)) (1)
In the above mathematical formula (1), Δd / ΔR is the change in the hole diameter of the optical fiber 30 (Δd) and the value obtained experimentally in advance using the preform 20 having different through-hole positions in the longitudinal direction. This represents the ratio to the change (ΔR) in the position of the through hole of the reform 20.

In this embodiment, a proportional relationship (Δd ′ = α ₁ ΔR) is provided as a correlation between the change amount ΔR = (R (x) −R (0)) of the through hole position and the change amount Δd ′ of the hole diameter. And adopting a configuration in which the hole diameter change amount Δd ′ is derived from the through hole position change amount ΔR with reference to a coefficient α ₁ = Δd / ΔR determined in advance by experiment. It is not limited to. For example, coefficients assuming _{Δd' = α 0 + α 1 ΔR} + α 2 ΔR 2 + ... + α N ΔR N, determined by experiment as correlation between the through-hole positions of the change amount [Delta] R and the hole diameter of the variation Derutad' alpha A configuration in which the hole diameter change amount Δd ′ is derived from the through hole position change amount ΔR with reference to _{0 to} α _N is also possible.

  Further, the pressure control device 200 calculates a difference ΔP ′ of the pressure applied to the through hole 20a according to the following formula (2) according to the calculated change amount Δd ′ of the hole diameter of the optical fiber 30.

ΔP ′ = Δd ′ ÷ (Δd / ΔP) (2)
In the above formula (2), Δd / ΔP is experimentally determined in advance as a change in the hole diameter of the optical fiber 30 (Δd) and a change in the pressure applied to the through hole 20a of the preform 20 (ΔP). It represents the ratio.

  Note that Δd / ΔP varies depending on various conditions (for example, the diameter of the through-hole of the preform 20 and the temperature in the melting furnace 104) when the preform 20 is drawn, and thus is the same as when the optical fiber 30 is manufactured. It is preferable to obtain it under conditions.

  By adding ΔP ′ thus calculated to the pressure applied to the through hole 20a when drawing the reference position 0, the pressure applied to the through hole 20a when drawing the position x is obtained.

(Method of determining pressure according to changes in outer diameter)
Moreover, the pressure control apparatus 200 determines the pressure applied in the through-hole 20a based on the change from the outer diameter D (0) of the outer diameter D (x) for each of the plurality of positions x.

  First, the pressure control device 200 calculates the amount of change Δd ″ of the hole diameter of the optical fiber 30 due to the change of the outer diameter from the position 0 for each of the plurality of positions x by the following formula (3).

Δd ″ = (Δd / ΔD) × (D (x) −D (0)) (3)
In the above formula (1), Δd / ΔD is a change in the hole diameter (Δd) of the optical fiber 30 and the preform, which have been experimentally obtained in advance using the preform 20 having different outer diameters in the longitudinal direction. This represents a ratio with a change in outer diameter (ΔD) of 20.

In the present embodiment, a proportional relationship (Δd ″ = β ₁ ΔD) is provided as a correlation between the through hole diameter variation ΔD = (D (x) −D (0)) and the hole diameter variation Δd ″. ) And a configuration in which the hole diameter change amount Δd ″ is derived from the through hole diameter change amount ΔD with reference to a coefficient β ₁ = Δd / ΔD determined in advance by experiment. It is not limited to this. For example, assuming _{Δd'' = β 0 + β 1 ΔD} + β 2 ΔD 2 + ... + β N ΔD N as correlation between the change amount Derutad'' variation [Delta] D and the hole diameter of the through hole diameter, determined by experiment coefficient A configuration in which the hole diameter change amount Δd ″ is derived from the through hole diameter change amount ΔD with reference to β _{0 to} β _N is also possible.

  Further, the pressure control device 200 calculates the difference ΔP ″ of the pressure applied to the through hole 20a according to the following formula (4) according to the calculated change amount Δd ″ of the hole diameter of the optical fiber 30.

ΔP ″ = Δd ″ ÷ (Δd / ΔP) (4)
By adding ΔP ″ calculated in this way to the pressure applied to the through hole 20a when drawing the reference position 0, the pressure applied to the through hole 20a when drawing the position x is obtained. .

  As described above, by further applying the pressure ΔP ′ determined for each position x, an appropriate pressure corresponding to the position of the through hole of the preform 20 at that position x can be applied to the through hole 20a. The hole diameter of the optical fiber 30 can be made appropriate.

  Further, by further applying the pressure ΔP ″ obtained for each position x, an appropriate pressure corresponding to the outer diameter of the preform 20 at the position x can be applied to the through hole 20a, and the optical fiber A hole diameter of 30 can be made appropriate.

  Therefore, by adding both the pressure ΔP ′ and the pressure ΔP ″ obtained for each position x, an appropriate pressure corresponding to both the through-hole position and the outer diameter of the preform 20 at the position x is applied. It can be added into the through hole 20a, and the hole diameter of the optical fiber 30 can be made appropriate.

(Method of feedback of hole diameter and outer diameter)
Further, the pressure control device 200 can determine the pressure to pressurize the through hole 20a of the preform 20 according to the hole diameter of the optical fiber 30 fed back from the hole diameter measuring device 116.

  For example, when the hole diameter of the optical fiber 30 fed back from the hole diameter measuring device 116 is dm, and the desired hole diameter is dt, the pressure control device 200 calculates the pressure difference ΔP ′ ″ applied to the through hole 20a. Is calculated by the following formula (5).

ΔP ″ ″ = (dt−dm) ÷ (Δd / ΔP) (5)
Then, the pressure control device 200 can apply an appropriate pressure in accordance with the hole diameter of the optical fiber 30 to the inside of the through hole 20a by further applying the obtained pressure ΔP ′ ″. The pore diameter can be made more appropriate.

  As a method of measuring the hole diameter of the optical fiber 30 by the hole diameter measuring device 116, among various known measuring methods (for example, methods disclosed in Japanese Patent Application Laid-Open No. 2010-145288, International Publication No. 2010/116762). Any of these may be used.

  The optical fiber manufacturing apparatus 100 applies pressure to the preform 20 in the through-hole 20a each time the drawing position of the preform 20 changes as drawing of the preform 20 proceeds according to the pressure determined by the pressure control device 200. However, the appropriate timing depends on various conditions during drawing (drawing speed, speed at which the preform 20 is fed into the melting furnace 104, temperature in the melting furnace 104, outer diameter of the preform 20, light Since it varies depending on the outer diameter of the fiber 30), it is preferable to set the timing according to various conditions that are actually applied at the time of drawing.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. Of course, the present invention is not limited to the following examples, and various modes are possible for details.

[Example 1]
First, Example 1 will be described.

(Implementation procedure)
In Example 1, the optical fiber 30 was manufactured by the following procedure to which the present invention was applied, and the effectiveness of the present invention was confirmed.

  (1) A preform 20 having an outer diameter of 100 mm and a length of 900 mm was prepared. As shown in FIG. 2, eight through holes 20 a were formed concentrically on the preform 20 by drilling. In addition, the through-hole diameter of each through-hole 20a was 4 mm, and the through-hole position was 10 mm.

  (2) The position of the through hole at each of a plurality of positions in the longitudinal direction of the preform 20 was measured by the measuring device 150. As the measuring method, the method disclosed in International Publication No. 2011/052541 was used. The measurement results are as shown in FIG.

  (3) The outer diameter of the preform 20 at each of a plurality of positions in the longitudinal direction of the preform 20 was measured by the measuring device 150. As the measuring device 150, a laser type outer diameter measuring device was used. The measurement results are as shown in FIG.

  (4) The preform 20 was set in the optical fiber manufacturing apparatus 100 of the present embodiment. Further, the pressurizing pressure at the start of drawing was set to 0.5 kpa for the optical fiber manufacturing apparatus 100. Further, the outer diameter of the target optical fiber 30 was set to 125 μm, and the hole diameter of the target optical fiber 30 was set to 5 μm.

  (5) The optical fiber 30 was manufactured from the preform 20 by the optical fiber manufacturing apparatus 100 of the present embodiment. At this time, in the optical fiber manufacturing apparatus 100, the pressure applied to the preform 20 was dynamically changed as shown in FIG.

  (6) The generated optical fiber 30 was cut at each of a plurality of drawing positions, and the hole diameter of the hole 30a was measured for each of the cut positions. The measurement results are as shown in FIG.

(Measurement results, etc.)
FIG. 4 is a graph showing through-hole positions at each of a plurality of positions in the longitudinal direction of the preform 20 measured by the measuring apparatus 150 according to the embodiment. FIG. 5 is a graph showing the outer diameter at each of a plurality of positions in the longitudinal direction of the preform 20 measured by the measuring device 150 according to the embodiment. FIG. 6 is a graph showing a change in pressure applied to the preform 20 in the optical fiber manufacturing apparatus 100 according to the embodiment. FIG. 7 is a graph showing the hole positions at each of a plurality of positions in the longitudinal direction of the optical fiber 30 manufactured by the optical fiber manufacturing apparatus 100 according to the embodiment.

  From the graphs shown in FIGS. 4 and 5, there is an error in the through hole position of the through hole 20 a and the outer diameter of the preform 20 in the longitudinal direction of the preform 20 used when manufacturing the optical fiber 30. I understand.

  Accordingly, as shown in FIG. 6, an appropriate pressure corresponding to the error is applied to the preform 20 in the optical fiber manufacturing apparatus 100. As a result, as shown in FIG. It can be seen that the apparatus 100 has produced an optical fiber 30 having a substantially uniform hole diameter in the longitudinal direction. In particular, it can be seen from the graph shown in FIG. 7 that the hole diameter error in the longitudinal direction of the optical fiber 30 is only about ± 0.1 μm. From these measurement results, it was confirmed that it was very effective to apply the present invention when manufacturing an optical fiber.

[Comparative Example 1]
Next, Comparative Example 1 will be described. The present comparative example 1 is a comparative example of the first embodiment. In Example 1, the pressure applied to the preform is determined based on the position of the preform through hole, the outer diameter of the preform, and the hole diameter of the optical fiber. The applied pressure is determined based on only the hole diameter of the optical fiber.

(Implementation procedure)
In this comparative example 1, an optical fiber was manufactured by the following procedure not applying the present invention, and the effectiveness of the present invention was confirmed.

  (1) As in Example 1, a preform having an outer diameter of 100 mm and a length of 900 mm was prepared. As shown in FIG. 2, eight through holes 20 a were concentrically formed by drilling. Formed into a shape. In addition, the through-hole diameter of each through-hole 20a was 4 mm, and the through-hole position was 10 mm.

  (2) In the same manner as in Example 1, the through-hole positions at each of a plurality of positions in the longitudinal direction of the preform were measured by a measuring device. As the measuring method, the method disclosed in International Publication No. 2011/052541 was used. The measurement results are as shown in FIG.

  (3) In the same manner as in Example 1, the outer diameter of the preform at each of a plurality of positions in the longitudinal direction of the preform was measured by a measuring device. As this measuring apparatus, a laser type outer diameter measuring device was used. The measurement results are as shown in FIG.

  (4) The preform was set in an optical fiber manufacturing apparatus. Moreover, the pressurization pressure at the time of a drawing start was set to 0.5 kpa with respect to the optical fiber manufacturing apparatus. Further, the outer diameter of the target optical fiber was 125 μm, and the hole diameter of the target optical fiber was 5 μm. The optical fiber manufacturing apparatus used here has the same configuration as that of the optical fiber manufacturing apparatus 100 of the first embodiment, and has the same configuration in which the pressure to which the hole diameter of the optical fiber is fed back is applied to the preform. This is different from the optical fiber manufacturing apparatus 100 of Example 1 in that the pressure corresponding to the through hole position and the outer diameter is not applied to the preform.

  (5) An optical fiber was manufactured from this preform using an optical fiber manufacturing apparatus.

  (6) The produced | generated optical fiber was cut | disconnected in each of several drawing position, and the hole diameter was measured about each. The measurement result was as shown in FIG.

(Measurement results, etc.)
FIG. 8 is a graph showing through-hole positions at each of a plurality of positions in the longitudinal direction of the preform, measured by the measuring apparatus used in Comparative Example 1. FIG. 9 is a graph showing the outer diameter at each of a plurality of positions in the longitudinal direction of the preform, measured by the measuring apparatus used in Comparative Example 1. FIG. 10 is a graph showing the hole positions at each of a plurality of positions in the longitudinal direction of the optical fiber manufactured by the optical fiber manufacturing apparatus used in Comparative Example 1.

  From the graphs shown in FIGS. 8 and 9, it can be seen that, as in Example 1, there is an error in the through-hole position and the outer diameter in the longitudinal direction of the preform used when manufacturing the optical fiber.

  The optical fiber manufacturing apparatus used in Comparative Example 1 cannot apply pressure corresponding to these errors to the preform 20, and as a result, as shown in FIG. It can be seen that an optical fiber having a non-uniform hole diameter was manufactured. In particular, it can be seen from the graph shown in FIG. 10 that the hole diameter error in the longitudinal direction of the optical fiber is about ± 0.4 μm. From these measurement results, it was confirmed that it was very effective to apply the present invention when manufacturing an optical fiber.

[Example 2]
Next, Example 2 will be described. The second embodiment is a modification of the first embodiment. In the first embodiment, the pressure applied to the preform is determined based on the position of the through hole of the preform, the outer diameter of the preform, and the hole diameter of the optical fiber. In the second embodiment, the pressure of the preform is determined. The structure is determined based on the position of the through hole and the outer diameter of the preform. That is, the hole diameter of the optical fiber is not fed back to the pressure.

(Implementation procedure)
In Example 2, the optical fiber 30 was manufactured by the following procedure to which the present invention was applied, and the effectiveness of the present invention was confirmed.

  (1) As in Example 1, a preform 20 having an outer diameter of 100 mm and a length of 900 mm is prepared. As shown in FIG. 2, eight through holes 20 a are drilled into the preform 20. To form concentric circles. In addition, the through-hole diameter of each through-hole 20a was 4 mm, and the through-hole position was 10 mm.

  (2) In the same manner as in Example 1, the through-hole positions at each of a plurality of positions in the longitudinal direction of the preform 20 were measured by the measuring device 150. As the measuring method, the method disclosed in International Publication No. 2011/052541 was used. The measurement result was as shown in FIG.

  (3) In the same manner as in Example 1, the outer diameter of the preform 20 at each of a plurality of positions in the longitudinal direction of the preform 20 was measured by the measuring device 150. As the measuring device 150, a laser type outer diameter measuring device was used. The measurement result was as shown in FIG.

  (4) As in Example 1, the preform 20 was set in the optical fiber manufacturing apparatus 100 of the present embodiment. Further, the pressurizing pressure at the start of drawing was set to 0.5 kpa for the optical fiber manufacturing apparatus 100. Further, the outer diameter of the target optical fiber 30 was set to 125 μm, and the hole diameter of the target optical fiber 30 was set to 5 μm.

  (5) In the same manner as in Example 1, the optical fiber 30 was manufactured from the preform 20 by the optical fiber manufacturing apparatus 100 of the present embodiment.

  (6) In the same manner as in Example 1, the generated optical fiber 30 was cut at each of a plurality of drawing positions, and the hole diameter of the hole 30a was measured for each of them. The measurement result was as shown in FIG.

(Measurement results, etc.)
FIG. 11 is a graph showing through-hole positions at each of a plurality of positions in the longitudinal direction of the preform 20 measured by the measuring apparatus 150 according to the embodiment. FIG. 12 is a graph showing the outer diameter at each of a plurality of positions in the longitudinal direction of the preform 20 measured by the measuring device 150 according to the embodiment. FIG. 13 is a graph showing the hole positions at each of a plurality of positions in the longitudinal direction of the optical fiber 30 manufactured by the optical fiber manufacturing apparatus 100 according to the embodiment.

  From the graphs shown in FIGS. 12 and 13, there is an error in the through hole position of the through hole 20 a and the outer diameter of the preform 20 in the longitudinal direction of the preform 20 used when manufacturing the optical fiber 30. I understand.

  Accordingly, an appropriate pressure corresponding to the above error is applied to the preform 20 in the optical fiber manufacturing apparatus 100. As a result, as shown in FIG. It can be seen that the optical fiber 30 having a substantially uniform hole diameter is manufactured. In particular, it can be seen from the graph shown in FIG. 14 that the error of the hole diameter in the longitudinal direction of the optical fiber 30 is only about ± 0.2 μm. From these measurement results, it was confirmed that it was very effective to apply the present invention when manufacturing an optical fiber.

[Comparative Example 2]
Next, Comparative Example 2 will be described. The present comparative example 2 is a comparative example of the second embodiment. In Example 2, the pressure applied to the preform is determined based on the position of the through-hole of the preform and the outer diameter of the preform. However, in Comparative Example 2, the pressure applied to the preform is determined as follows. The configuration is determined based on neither.

(Implementation procedure)
In Comparative Example 2, an optical fiber was manufactured by the following procedure not applying the present invention, and the effectiveness of the present invention was confirmed.

  (1) As in Example 2, a preform having an outer diameter of 100 mm and a length of 900 mm was prepared. As shown in FIG. 2, eight through holes 20 a were concentrically formed by drilling. Formed into a shape. In addition, the through-hole diameter of each through-hole 20a was 4 mm, and the through-hole position was 10 mm.

  (2) In the same manner as in Example 2, the position of the through hole at each of a plurality of positions in the longitudinal direction of the preform was measured by a measuring device. As the measuring method, the method disclosed in International Publication No. 2011/052541 was used. The measurement results are as shown in FIG.

  (3) In the same manner as in Example 2, the outer diameter of the preform at each of a plurality of positions in the longitudinal direction of the preform was measured by a measuring device. As this measuring apparatus, a laser type outer diameter measuring device was used. The measurement results are as shown in FIG.

  (4) The preform was set in an optical fiber manufacturing apparatus. Moreover, the pressurization pressure at the time of a drawing start was set to 0.5 kpa with respect to the optical fiber manufacturing apparatus. Further, the outer diameter of the target optical fiber was 125 μm, and the hole diameter of the target optical fiber was 5 μm. The optical fiber manufacturing apparatus used here has the same configuration as that of the optical fiber manufacturing apparatus 100 of Example 1, but does not apply pressure to which the hole diameter of the optical fiber is fed back to the preform. It differs from the optical fiber manufacturing apparatus 100 of Example 1 in that the pressure corresponding to the hole position and the outer diameter is not applied to the preform.

  (5) An optical fiber was manufactured from this preform using an optical fiber manufacturing apparatus.

  (6) The produced | generated optical fiber was cut | disconnected in each of several drawing position, and the hole diameter was measured about each. The measurement results are as shown in FIG.

(Measurement results, etc.)
FIG. 14 is a graph showing through-hole positions at each of a plurality of positions in the longitudinal direction of the preform, measured by the measuring apparatus used in Comparative Example 2. FIG. 15 is a graph showing the outer diameter at each of a plurality of positions in the longitudinal direction of the preform, measured by the measuring device used in Comparative Example 2. FIG. 16 is a graph showing the hole positions at each of a plurality of positions in the longitudinal direction of the optical fiber manufactured by the optical fiber manufacturing apparatus used in Comparative Example 2.

  From the graphs shown in FIGS. 14 and 15, as in Example 2, it can be seen that there is an error in the position of the through hole and the outer diameter in the longitudinal direction of the preform used in manufacturing the optical fiber.

  The optical fiber manufacturing apparatus used in Comparative Example 2 cannot apply pressure according to these errors to the preform 20, and as a result, as shown in FIG. It can be seen that an optical fiber having a non-uniform hole diameter was manufactured. In particular, it can be seen from the graph shown in FIG. 16 that the hole diameter error in the longitudinal direction of the optical fiber is about ± 0.5 μm. From these measurement results, it was confirmed that it was very effective to apply the present invention when manufacturing an optical fiber.

(Program, storage medium)
Each function of the pressure control device 200 described in each of the above embodiments may be realized by hardware by a logic circuit formed on an integrated circuit (IC chip), or using a CPU (Central Processing Unit). It may be realized by software.

  For example, the pressure control device 200 includes a CPU that executes instructions of a program that realizes each function, a ROM that stores the program, a RAM that expands the program, and various storage devices (recording media) that store the program and various data. It has. Each function of the pressure control device 200 can be realized by the CPU reading out the programs stored in the various storage devices and executing the programs.

  Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, and disks including optical disks such as CD-ROM / MO / MD / DVD / CD-R. IC cards (including memory cards) / optical cards, semiconductor memories such as mask ROM / EPROM / EEPROM / flash ROM, PLD (Programmable logic device), FPGA (Field Programmable Gate Array), etc. Logic circuits or the like can be used.

  Note that the program may be supplied to the pressure control apparatus 200 via a communication network. The communication network only needs to be able to transmit at least the program to the pressure control device 200, and may be of any type. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication network, etc. can be used as the communication network. is there.

  Further, any kind of transmission medium for supplying the program to the pressure control device 200 may be used. For example, a wired medium such as IEEE1394, USB, power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital Subscriber Line) line may be used as the transmission medium. As transmission media, infrared rays such as IrDA and remote control, Bluetooth (registered trademark), IEEE80211 wireless, HDR (High Data Rate), NFC (Near Field Communication), DLNA, cellular phone network, satellite line, terrestrial digital network You may use the thing by radio | wireless.

(Supplementary explanation)
The present invention is not limited to the above-described embodiments and examples, and various modifications can be made within the scope shown in the claims, and embodiments and implementation methods obtained by appropriately combining the disclosed technical means. Is also included in the technical scope of the present invention.

  The optical fiber manufacturing method, the optical fiber manufacturing system, the pressure control device, and the program according to the present invention are any optical fiber (holey fiber) in which at least holes are formed, such as hole assist fibers and photonic band gap fibers. It can be suitably used for manufacturing any optical fiber.

DESCRIPTION OF SYMBOLS 10 Optical fiber manufacturing system 20 Preform 20a Through-hole 22 Core part 24 Clad part 30 Optical fiber 30a Air hole 100 Optical fiber manufacturing apparatus 102 Pressurization apparatus 104 Melting furnace 106 Primary coating layer forming apparatus 108 Primary coating layer hardening apparatus 110 Secondary Coating layer forming device 112 Secondary coating layer curing device 114 Winding device 150 Measuring device 200 Pressure control device (control device)

Claims (5)

In an optical fiber manufacturing method for manufacturing an optical fiber from a preform in which a through hole is formed,
A drawing step of melting and stretching the preform while introducing gas into the through-hole;
The outer diameter of the preform in the portion measured in advance and the portion measured in advance when the pressure of the gas introduced into the through hole when each portion of the preform is melt-drawn in the drawing step. And a pressure determining step for determining based on at least one of the positions of the through holes in
An optical fiber manufacturing method characterized by the above. The pressure determination step includes
The correlation between the change amount ΔD of the outer diameter of the preform determined in advance by experiment and the change amount Δd of hole diameter in the optical fiber, and the change amount ΔR of the position of the through hole determined in advance by experiment The pressure of the gas introduced into the through hole is determined with reference to at least one of the correlations with the change amount Δd of the hole diameter in the optical fiber.
The method of manufacturing an optical fiber according to claim 1. A measurement step of measuring a hole diameter of the optical fiber melt-drawn in the drawing step,
In the pressure determination step, the pressure of the gas introduced into the through hole is applied to at least one of the outer diameter of the preform and the position of the through hole, and the hole diameter of the optical fiber measured in the measurement step Is to be determined based on the
An optical fiber manufacturing method according to claim 1 or 2. In a control device for controlling an optical fiber manufacturing apparatus that manufactures an optical fiber from a preform in which a through hole is formed,
The optical fiber manufacturing apparatus melts and stretches the preform while introducing gas into the through-hole,
The control device is configured to measure the pressure of the gas introduced into the through hole when each part of the preform is melt-stretched by the optical fiber manufacturing apparatus, the outer diameter of the preform at the part measured in advance, and Pressure determining means for determining based on at least one of the positions of the through holes in the portion measured in advance,
A control device characterized by that. A program for causing a computer to operate as the control device according to claim 4, wherein the computer functions as the pressure determining means.
A program characterized by that.

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