JP2007045680A - Method for manufacturing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a drawn optical fiber from getting into contact with a device such as a cooling apparatus when a drawing tower is vibrated by a factor such as the occurrence of an earthquake during manufacturing of the optical fiber by drawing. <P>SOLUTION: This method for manufacturing the optical fiber comprises a step of drawing a fiber preform G wherein an optical fiber preform G is inserted into a heating furnace 2 installed in the drawing tower 6, heated and melted in the heating furnace 2 and drawn to form an optical fiber. In this step, when a primary wave of an earthquake of a prescribed level or larger is detected by a seismometer 8 as an action-requiring vibration that will vibrate the drawing tower 6 at a level equal to or larger than a prescribed allowable vibration level, before the drawing tower 6 is vibrated at a level equal to or larger than the allowable vibration level, at least any one of the upper and lower shutters 12 and 13 of the cooling apparatus 11 and the main body of the cooling apparatus 11 is opened, or a gas is blown onto the optical fibers G1 and G2 located below the heating furnace 2 in the vertical direction to form fixed points at which a natural frequency is modified. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an optical fiber manufacturing method for manufacturing an optical fiber by drawing an optical fiber preform heated in a heating furnace.

  In general, an optical fiber is obtained by heating and melting an optical fiber preform made of a material such as quartz from the lower end side to reduce the diameter. The process of reducing the diameter of the optical fiber preform to form an optical fiber is called drawing.

  The drawn optical fiber is cooled by a cooling device and then coated with a resin, and then drawn to the downstream side of the pass line by take-up means such as a capstan roller and wound on a bobbin or the like.

  In this drawing process, in order to obtain a stable outer diameter and coating outer diameter of the optical fiber, it is important to hold the optical fiber preform and suppress vibrations of the drawing tower that fixes the heating furnace and the coating apparatus. . Then, the technique which can suppress the vibration of a drawing tower main body and can prevent the quality degradation, disconnection, etc. of an optical fiber is known (for example, refer patent document 1).

FIG. 3 shows a schematic diagram of an optical fiber manufacturing apparatus disclosed in Patent Document 1. As shown in FIG.
The drawing tower body 50 is built in a substantially vertical direction, and a heating furnace 52 is provided on the upper part of the drawing tower body 50. The optical fiber preform 53 is heated by the heating furnace 52 and the optical fiber 54 is drawn downward. After the coating is formed in the coating device 55, the optical fiber 54 is changed in direction by the pulley 56, taken up by a capstan (not shown), and then taken up by a winder (not shown). Further, in this optical fiber manufacturing apparatus, a vibration damping device 51 that actively prevents vibration is mounted on the uppermost part of the drawing tower main body 50. By suppressing the vibration of the drawing tower main body 50 by the vibration control device 51, the vibration of the gripped optical fiber preform 53 and the optical fiber 54 can be suppressed, and fluctuations in the outer diameter of the optical fiber 54 can be prevented. .

Japanese Patent Laid-Open No. 10-1324

  By the way, at the time of a drawing process, the optical fiber preform is usually inserted into the heating furnace with its upper end held. Therefore, it is difficult to completely suppress the vibration of the optical fiber preform against vibrations having irregular and wide vibration frequency bands such as earthquakes and vibrations including frequency components that resonate the drawing tower. . When the optical fiber preform vibrates, the drawn optical fiber also vibrates, and the optical fiber may come into contact with the outlet of the heating furnace, the cooling device, or the like. In particular, it was in a situation where it was easy to contact a cooling device located between the optical fiber preform and the device for coating the optical fiber.

  When the optical fiber before coating comes into contact with equipment such as a heating furnace or a cooling device, in addition to causing damage, the optical fiber may be broken in some cases. In the case of disconnection, a lot of time is required to redraw the optical fiber on the pass line and perform the drawing again. This reduces the manufacturing yield and increases the working time. This was a factor that reduced the production efficiency of the fiber.

  The present invention provides an optical fiber capable of preventing the drawn optical fiber from contacting a device such as a cooling device when the drawing tower vibrates due to an earthquake or the like when the optical fiber is manufactured by drawing. It aims at providing the manufacturing method of.

  The optical fiber manufacturing method of the present invention that can achieve the above object is to insert an optical fiber preform into a heating furnace provided in a drawing tower, heat and melt the optical fiber preform, and draw the optical fiber. In a drawing process of forming a fiber and passing the optical fiber through a cooling device, vibration information around the drawing tower is obtained, and the drawing tower is expected to vibrate so as to adversely affect the drawing of the optical fiber. In some cases, at least one of the upper shutter, the lower shutter, and the cooling device of the cooling device is opened or located in the drawing tower before the drawing tower gives harmful vibrations to the optical fiber. A fixed point for changing the natural frequency is formed in the optical fiber.

  In the optical fiber manufacturing method according to the present invention, the obtained vibration information is a seismic longitudinal wave having a predetermined level or more, or a frequency component n times (n is a positive integer) the natural frequency of the drawing tower. In the case of vibrations that include a level or more, it is preferable to determine that the drawing of the optical fiber is adversely affected.

  In the optical fiber manufacturing method of the present invention, when the cooling device is opened, it is preferable that the degree of opening is adjusted so as not to contact the optical fiber.

  In the optical fiber manufacturing method of the present invention, it is preferable that when the cooling device is opened, a space for cooling the optical fiber is substantially shielded from the outside.

  In the optical fiber manufacturing method of the present invention, when the obtained vibration information is vibration including a frequency component that is n times (n is a positive integer) the natural frequency of the drawing tower, the drawing tower. It is preferable to apply a gas from the surroundings to the optical fiber located inside to change the natural frequency of the optical fiber.

  In the optical fiber manufacturing method of the present invention, when at least one of the upper shutter, the lower shutter, and the cooling device of the cooling device is opened, the longitudinal position of the optical fiber that has passed through the cooling device is determined. It is preferable to record.

  According to the optical fiber manufacturing method of the present invention, when it is predicted that the drawing tower vibrates so as to adversely affect the drawing of the optical fiber according to the obtained vibration information, the upper shutter and the lower Opening at least one of the shutter and the cooling device, or forming a fixing point for changing the natural frequency in the optical fiber positioned vertically below the heating furnace, the cooling device is changed from the vibrating optical fiber. By keeping away or decreasing the amplitude of the optical fiber, the drawn optical fiber can be prevented from coming into contact with the cooling device, and disconnection of the optical fiber can be prevented. Therefore, since the optical fiber can be manufactured without causing the interruption of the drawing due to vibration, the manufacturing efficiency of the optical fiber can be kept good.

Embodiments of an optical fiber manufacturing method according to the present invention will be described below.
FIG. 1 is a schematic configuration diagram of an apparatus capable of performing the optical fiber manufacturing method of the present embodiment.
As shown in FIG. 1, an optical fiber manufacturing apparatus 1 includes a drawing tower 6 erected in a substantially vertical direction, and a vertical heating furnace 2 provided on an upper portion of the drawing tower 6 for heating an optical fiber preform G. An outer diameter measuring device 10 for measuring the outer diameter of the drawn optical fiber G1, a cooling device 11 for cooling the optical fiber G1, a coating application device 14 for applying a resin coating around the optical fiber G1, and ultraviolet irradiation The apparatus 15 includes a capstan 19 that takes up the coated optical fiber G2, and a take-up bobbin 26 that takes up the optical fiber G2.

  The drawing tower 6 is fixed in a state in which various devices such as the heating furnace 2, the outer diameter measuring device 10, the cooling device 11, the coating application device 14, and the ultraviolet irradiation device 15 are arranged in the vertical direction along the drawing pass line. is doing. In addition, it is desirable that the drawing tower 6 is independently built on the foundation without being connected to a building or the like surrounding the drawing tower 6.

  The upper part of the optical fiber preform G is gripped by the grip portion 5. The gripping part 5 is connected to a drive part 7 provided above the heating furnace 2 in the drawing tower 6 and is movable in the vertical direction. The optical fiber preform G is sent into the heating furnace 2 by driving the drive unit 7. As described above, the lower end side of the optical fiber preform G supplied into the heating furnace 2 is heated and melted, and is drawn downward to be reduced in diameter, so that a glass body optical fiber G1 is formed.

  At the outlet located at the lower end of the heating furnace 2, a heating furnace shutter 9 that can be opened and closed is provided. The heating furnace shutter 9 is closed during drawing to prevent outside air from entering the heating furnace 2. Further, the heating furnace shutter 9 is closed so that a small-diameter hole is formed in the center thereof. The small-diameter hole has a slightly larger diameter than the drawn optical fiber G1. The optical fiber G1 passes through the small-diameter hole while maintaining a slight clearance with the heating furnace shutter 9.

  Below the heating furnace 2, for example, a laser beam type outer diameter measuring device 10 is provided, and the outer diameter of the optical fiber G1 exiting the heating furnace 2 is measured by the outer diameter measuring device 10. In addition, it is preferable to measure the outer diameter here in each of the orthogonal axis (X axis and Y axis) directions on a plane in a direction orthogonal to the axis of the optical fiber G1. At the time of drawing, the drive of the capstan 19 is feedback-controlled so that the outer diameter value measured by the outer diameter measuring instrument 10 falls within a predetermined range, and the linear velocity of the optical fiber G1 is controlled.

  The outer diameter measuring instrument 10 has a measurement detection range in which the optical fiber G1 can be measured, for example, about 2 mm in a direction orthogonal to the axis of the optical fiber G1. If the position of the optical fiber G1 is out of the measurement detection range, it becomes impossible to perform measurement, and an error signal is detected or the measurement value is detected as 0 μm. At that time, since it can be determined that the optical fiber G1 is out of the normal pass line, the outer diameter measuring instrument 10 can also be used as a position sensor that can determine whether the drawn optical fiber G1 is present on the pass line. Function.

  A cooling device 11 is provided below the outer diameter measuring instrument 10. The main body of the cooling device 11 is configured to be able to be opened and closed by being divided into two in a direction away from the pass line of the optical fiber G1, and is usually used in a state of being joined together and integrated when drawing. The cooling device 11 has an insertion hole through which the optical fiber G1 is passed in the longitudinal direction at a central position where two members constituting the main body are closed. Cooling gas is fed into the insertion hole, and the optical fiber G1 inserted through the insertion hole is cooled. Further, the main body of the cooling device 11 has a cooling channel formed therein along the longitudinal direction, and the cooling fluid circulates inside the cooling channel. The cooling gas in the insertion hole is cooled by the cooling fluid, and the optical fiber G1 passes through the cooling gas atmosphere, so that the optical fiber G1 after drawing can be cooled to an appropriate temperature. Thereby, the shape of the optical fiber G1 is stabilized.

An upper shutter 12 that can open and close the entrance of the insertion hole is provided at the upper end of the cooling device 11. A lower shutter 13 that can open and close the outlet of the insertion hole is provided at the lower end of the cooling device 11. These upper shutter 12 and lower shutter 13 are closed at the time of drawing to increase the cooling efficiency of the cooling device 11. The upper shutter 12 and the lower shutter 13 are closed so that a small diameter hole is formed at the center thereof. The small-diameter hole has a slightly larger diameter than the drawn optical fiber G1. The optical fiber G1 passes through the small diameter hole while maintaining a slight clearance with the upper shutter 12 and the lower shutter 13 respectively.
A plurality of cooling devices 11 may be provided on the pass line.

  Below the cooling device 11, a coating application device 14 for applying an ultraviolet curable resin to the optical fiber G1 and an ultraviolet irradiation device 15 for curing the applied ultraviolet curable resin are provided. The ultraviolet irradiation device 15 irradiates the optical fiber G2 coated with resin with, for example, a multi-lamp UV lamp to cure the ultraviolet curable resin. The optical fiber G1 was coated with an ultraviolet curable resin on the outer periphery by the coating application device 14, and then the ultraviolet curable resin was cured by the ultraviolet irradiation device 15, whereby a coating layer of the ultraviolet curable resin was formed. It becomes the optical fiber G2.

An outer diameter measuring device 16 is provided below the ultraviolet irradiation device 15, and the outer diameter of the optical fiber G2 on which the coating layer is formed is measured.
The outer diameter measuring device 16 can be the same as the outer diameter measuring device 10 described above. In addition, an ultraviolet curable resin is apply | coated with the coating application apparatus 14 so that the outer diameter of the optical fiber G2 measured here may become a predetermined value.

  The optical fiber G <b> 2 that has passed through the outer diameter measuring device 16 is drawn into the capstan 19 through the guide rollers 17 and 18, and a predetermined tension is applied by the capstan 19. The capstan 19 includes a capstan belt 21 wound around a plurality of rollers 20, and a capstan roller 22 to which the capstan belt 21 is in close contact, and the capstan belt 21 and the capstan roller 22. The optical fiber G2 is sandwiched between and pulled. The capstan 19 pulls the optical fiber G2 further downstream.

On the downstream side of the capstan 19, the optical fiber G <b> 2 is sent to the take-up bobbin 26 via the dancer rollers 24 and 25, and is taken up by the take-up bobbin 26.
With the configuration described above, an optical fiber G2 as a product can be manufactured by drawing the optical fiber preform G.

In addition, a seismometer 8 is installed on the foundation on which the drawing tower 6 is built, and an acceleration sensor or a velocity sensor for detecting vibration is built in the seismometer 8, and the foundation due to the earthquake. And vibrations of the foundation caused by surrounding traffic conditions can be detected. Further, the frequency component of the vibration can be known by performing Fourier transform on the detected vibration wave.
When an earthquake occurs, two waves, a longitudinal wave (P wave) and a transverse wave (S wave), are generated simultaneously from the epicenter and travel through the ground. Longitudinal waves arrive at, causing initial tremors. Later, depending on the distance from the epicenter to the observation site (seismic meter 8), the transverse waves are transmitted with a delay and main motion occurs. This main movement causes the drawing tower 6 to roll.
Further, when the vibration generated by the surrounding traffic condition includes a frequency component that is n times the natural frequency of the drawing tower 6 (n is a positive integer), the drawing tower 6 rolls due to resonance. To do.

Thus, when the drawing tower 6 vibrates due to an earthquake or the like, the optical fiber preform G vibrates, and thereby the optical fiber G1 vibrates. The optical fiber G1 comes into contact with a device such as a cooling device due to vibration when the drawing tower 6 vibrates at a predetermined allowable vibration level or higher, and the required vibration that causes the drawing tower 6 to vibrate at or above the allowable vibration level. When it is detected that the drawing tower 6 vibrates so as to adversely affect the drawing of the optical fiber, the uncoated optical fiber G1 is prevented from coming into contact with the heating furnace 2, the cooling device 11, and the like. To respond as soon as possible.
In the case of an earthquake, the vibration level of the main movement caused by the subsequent transverse wave can be roughly estimated from the vibration level of the initial fine movement caused by the longitudinal wave. Therefore, a longitudinal wave of a predetermined level or more is detected as the corresponding vibration. Alternatively, in the case of a vibration other than an earthquake, a vibration including a frequency component that is n times (n is a positive integer) the natural frequency of the drawing tower 6 is detected as a required vibration.

In the optical fiber manufacturing method of the present invention, when the drawing is performed by the apparatus as shown in FIG. 1, the seismometer 8 detects the necessary vibration that causes the drawing tower 6 to vibrate at a predetermined allowable vibration level or higher. In this case, the drawing tower 6 is predicted to vibrate so as to adversely affect the drawing of the optical fiber, so that the optical fiber G1 before coating does not come into contact with equipment such as the heating furnace 2 and the cooling device 11. Therefore, the optical fiber manufacturing apparatus 1 includes a control unit that can control the opening and closing operations of the upper shutter 12 and the lower shutter 13 of the cooling device 11, the main body of the cooling device 11, and the heating furnace shutter 9 at the lower end of the heating furnace 2. 27 is provided. The control unit 27 monitors the output value of the speed sensor or the acceleration sensor and detects the occurrence of the required vibration. When the required vibration is detected, the upper shutter 12, the lower shutter 13, and the cooling device 11 of the cooling device 11 are detected. Is set to open at least one of the main bodies. This opening operation is performed immediately after detecting the required vibration, and before the drawing tower 6 vibrates to the above allowable vibration level, that is, before the drawing tower 6 gives harmful vibration to the optical fiber G1. In this way, at the time of detecting vibrations requiring response, the optical fiber G1 can be brought into contact with the equipment such as the cooling device 11 by quickly moving the equipment such as the cooling device 11 to which the optical fiber G1 is approaching from the optical fiber G1. Can be prevented.
Further, preferably, the upper shutter 12, the lower shutter 13 and the main body of the cooling device 11 are set to be opened.

  Furthermore, it is preferable that the heating furnace shutter 9 is also set to open at the time of detection of a vibration requiring response, in which case the optical fiber G1 immediately after drawing is prevented from coming into contact with the outlet of the heating furnace 2. Alternatively, after detecting the transverse wave, the heating furnace shutter 9 and other devices may be opened according to the magnitude of the transverse wave.

  Since the permissible vibration level varies depending on the size of the drawing tower 6 and the state of the installation floor surface, an appropriate value is set in accordance with the value of the required vibration that is set as a threshold value when opening the cooling device or the like. However, it can be set as a vibration corresponding to an earthquake with a seismic intensity of 1, for example.

  In addition, the control unit 27 detects that the corresponding vibration is detected from the seismometer 8, and opens at least one of the upper shutter 12, the lower shutter 13, and the main body of the cooling device 11 of the cooling device 11. After that, after confirming that the vibration is suppressed, after waiting for a predetermined time to elapse, the opened device is closed again. The predetermined time is preferably in the range of 2 to 60 seconds.

  If the measured value of the speed sensor or the acceleration sensor becomes less than a predetermined value and 2 seconds or more pass, or if the optical fiber G1 returns to the measurement detection range of the outer diameter measuring instrument 10 and 2 seconds or more pass, the optical fiber G1 Returns to the normal pass line again. In addition, the vibration of the optical fiber preform G is sufficiently attenuated within 60 seconds after the vibration becomes equal to or less than a predetermined value, and the drawing can be performed so as to have a predetermined diameter.

  Further, if the main body and shutter of the cooling device 11 are left open, the optical fiber G1 cannot be sufficiently cooled. If the resin is applied while the optical fiber G1 is at a high temperature, the coating becomes thin and a desired outer diameter cannot be obtained. For example, when the outer diameter of the optical fiber G2 coated before detecting the required vibration is 245 μm, if the main body of the cooling device 11 and the shutters 12 and 13 are open, the outer diameter is reduced to about 230 μm. When the main body, upper and lower shutters 12 and 13 of the apparatus 11 are closed, the outer diameter of the optical fiber G2 returns to a predetermined value again. Thus, the location where the outer diameter becomes small is defective as a product. Therefore, it is preferable to close the main body and the shutter of the cooling device 11 as soon as possible. For example, when an earthquake with a seismic intensity of 1 occurs, the predetermined time may be about 30 seconds.

Moreover, the cooling device 11 can adjust the degree of opening thereof. For example, the degree of opening is at least according to the amplitude detected by the seismometer 8 and the amplitude of the optical fiber G1 detected by the outer diameter measuring instrument 10. By preventing the air from contacting the optical fiber G1, it is possible to prevent the cold air from escaping to the outside as much as possible.
Further, as shown in FIG. 2, when the cooling device 11 is opened, a shielding plate 11a that substantially shields the space inside (that is, the space for cooling the optical fiber G1) from the outside is provided, and the cold air escapes to the outside. It may be prevented.

  Note that vibration information around the drawing tower 6 that vibrates the drawing tower 6 may be obtained by means other than the seismometer 8. For example, the detection of longitudinal waves due to an earthquake may be based on earthquake occurrence information provided by an external information provider without depending on the seismometer 8.

  Further, in the present invention, after detecting the required vibration, the shaking of the optical fibers G1 and G2 in the drawing tower 6 can be positively suppressed. For example, the optical fiber G1 can be held on the pass line by blowing a gas (clean air or the like) from the surroundings to the traveling optical fiber G1 with a good balance. Further, a fixed point (so-called vibration mode node portion) is formed by blowing gas from the surroundings intensively to a portion having a large amplitude when the traveling optical fiber G1 vibrates (so-called antinode portion of the vibration mode). ) To reduce the amplitude and change the natural frequency to prevent the vibration mode from being formed. In particular, when the obtained vibration information is vibration including a frequency component that is n times the natural frequency of the drawing tower 6 at a predetermined level or more, it is effective to change the natural frequency of the optical fibers G1 and G2.

  Further, the optical fiber G1 that has passed through the cooling device 11 when at least one of the upper shutter 12, the lower shutter 13, and the main body of the cooling device 11 is opened becomes a defective product. Therefore, the position information in the longitudinal direction of the optical fiber G1 of the abnormal part that has passed through the cooling device 11 when any of the upper shutter 12, the lower shutter 13, and the main body of the cooling device 11 is opened is the control unit 27. It is possible to recognize and remove the abnormal part corresponding to the position from the optical fiber G2 wound around the take-up bobbin 26 separately from other normal parts that are drawn normally. Therefore, it is possible to prevent the non-defective part and the abnormal part from being mixed in the drawn optical fiber G2.

It is a schematic block diagram which shows the apparatus which can implement the manufacturing method of the optical fiber which concerns on this invention. It is a top view which shows the structural example of the cooling device shown in FIG. It is a schematic block diagram which shows the manufacturing apparatus of the conventional optical fiber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber manufacturing apparatus 2 Heating furnace 5 Grasping part 6 Drawing tower 7 Drive part 10,16 Outer diameter measuring device 11 Cooling device 12 Upper shutter 13 Lower shutter 14 Coating coating device 15 Ultraviolet irradiation device 19 Capstan 26 Winding bobbin 27 Control unit G Optical fiber preform G1, G2 Optical fiber

Claims (6)

In a drawing step of inserting an optical fiber preform into a heating furnace provided in a drawing tower, heating and melting the optical fiber preform, forming an optical fiber by drawing, and passing the optical fiber into a cooling device ,
If vibration information around the drawing tower is obtained and the drawing tower is expected to vibrate so as to adversely affect the drawing of the optical fiber, before the drawing tower gives harmful vibration to the optical fiber, At least one of an upper shutter, a lower shutter, and the cooling device of the cooling device is opened, or a fixed point for changing the natural frequency is formed in the optical fiber located in the drawing tower. An optical fiber manufacturing method.   When the obtained vibration information is a longitudinal wave of an earthquake of a predetermined level or higher, or a vibration including a frequency component of n times (n is a positive integer) the natural frequency of the drawing tower or higher, a predetermined level or more. 2. The method of manufacturing an optical fiber according to claim 1, wherein it is determined that the drawing of the fiber is adversely affected.   3. The method of manufacturing an optical fiber according to claim 1, wherein when the cooling device is opened, an opening degree is adjusted so as not to contact the optical fiber.   4. The method of manufacturing an optical fiber according to claim 1, wherein when the cooling device is opened, a space for cooling the optical fiber is substantially shielded from the outside. 5.   When the obtained vibration information is vibration that includes a frequency component that is n times (n is a positive integer) the natural frequency of the drawing tower at a predetermined level or more, the optical fiber located in the drawing tower is moved from the surroundings to the optical fiber. The method for producing an optical fiber according to any one of claims 1 to 4, wherein a natural frequency of the optical fiber is changed by applying a gas.   The longitudinal position of the optical fiber that has passed through the cooling device is recorded when at least one of the upper shutter, the lower shutter, and the cooling device of the cooling device is opened. 6. The method for producing an optical fiber according to any one of items 1 to 5.

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