JPH08188439A - Apparatus for drawing optical fiber and drawing - Google Patents

Abstract

PURPOSE: To obtain an optical fiber, having a small noncircularity ratio and hardly causing a connection loss by controlling the operation of a chuck based on the information from both the chuck holding an optical fiber preform and an apparatus for measuring the optical fiber. CONSTITUTION: This apparatus for drawing an optical fiber is obtained by installing an apparatus 28 for measuring the position in the horizontal uni- or biaxial directions of the optical fiber 26 between a drawing furnace 25 and a coating device 29 for coating a protecting resin, providing an XY-moving part 232 capable of moving an optical fiber preform 21 in the horizontal biaxial directions and a rotating part 231 capable of rotating the optical fiber preform 21 in a chuck 23 for holding the optical fiber preform 21, sending the rotation information or rotation command information and horizontal biaxial positional information or positional command information of the optical fiber preform 21 and the horizontal uni- or biaxial positional information of the optical fiber 26 to a computing unit 35, carrying out the computing and changing the rotation and horizontal biaxial movement command of the optical fiber preform 21 based on the results of the computing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drawing device and a drawing method for drawing an optical fiber preform into an optical fiber, and more particularly to an optical fiber having a small non-circularity. The present invention relates to a wire drawing apparatus and a wire drawing method.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a conventional optical fiber drawing apparatus. This drawing apparatus is disclosed in JP-A-54-281.
No. 56.

In FIG. 3, reference numeral 3 indicates an optical fiber preform. The optical fiber preform 3
Is gripped by the chuck 1 and inserted into the drawing furnace 4. The lower end of the optical fiber preform 3 is heated and melted by the drawing furnace 4 and drawn to form the optical fiber 14. The drawn optical fiber 14 has its outer diameter measured by the outer diameter measuring device 8, is drawn by the capstan 6 so that the outer diameter is constant, and is wound by a winding device (not shown). At this time, the optical fiber 14 is coated with the protective resin by the coating device 7 and then taken up by the capstan 6. When the wire drawing is continued in this way, the preform 3 gradually shortens, but the preform 3 is sent downward by the lifting mechanism 2 by the shortened amount.

In JP-A-54-28156, the fine movement stage 13 of the chuck is moved by using the function of measuring the fiber positions X and Y of the outer diameter measuring device 8 so that the optical fiber 14 is constantly moved in the XY directions. It is characterized in that the position of the preform 3 is controlled so as to come to the center of the outer diameter measuring instrument 8. The center of the optical fiber 14 is displaced (i)
Mechanical accuracy of the lifting device for the optical fiber preform 3, (i
i) This is because the preform 3 is bent or bent. Therefore, (a) if the center of the furnace 4 and the neutral point of the outer diameter measuring device 8 are centered, the optical fiber 14 is placed at the center of the outer diameter measuring device 8.
By controlling the preform 3 so that the preform 3 is positioned, the tip of the preform is positioned in the center of the furnace, which enables the drawing of the optical fiber having a uniform circumferential direction. As a result, (b) The effect is that uneven thickness at the time of resin coating can be small.

Further, the outer diameter is measured at substantially the same portion of the outer diameter measuring device 8, whereby the optical fiber diameter can be measured at the most accurate portion of the outer diameter measuring device 8. Therefore, there is an effect that the fluctuation of the optical fiber diameter is stabilized.

In FIG. 3, 9X and 9Y are loop controllers in the X and Y directions, respectively.
10Y is a motor controller in the X and Y directions, 11X and 11Y are servomotors or stepping motors that move the preform in the X and Y directions, and 12X and 12Y are gears.

[0007]

There is a parameter called non-circularity as a structural parameter of an optical fiber. This is defined by measuring the major axis and minor axis of the optical fiber cross section and the ratio of the difference between the major axis and the minor axis to the average diameter, that is, (major axis-minor axis) / average diameter.

In recent years, there has been a strong demand for connecting optical fibers with low loss. If the optical fiber has a non-circular shape, the hole diameter of the ferrule used to position the connector must be increased.However, if the hole diameter of the ferrule is increased, misalignment between the optical fiber and ferrule hole will occur, resulting in a large connection loss. Become.

Also, in the mechanical splice in which the optical fiber is abutted in the V groove, if the optical fiber has a non-circle, the radius of the optical fiber at the portion in contact with the V groove varies, and the optical fiber axis shifts, This will increase the connection loss of the optical fiber.

As described above, the presence of the non-circle in the optical fiber causes a great problem in connecting the connector of the optical fiber.
Therefore, there is a strong demand for improvement of the non-circularity of optical fibers.

In the conventional method, as described above, by aligning the lower end of the optical fiber preform with the center of the drawing furnace, the optical fiber is uniformly heated in the circumferential direction and the non-circle of the optical fiber becomes relatively small. Is being considered by.

However, in recent years, as the cost of the optical fiber has been reduced, the diameter of the optical fiber preform has been increased and the drawing speed has been increased. Moreover, in the drawing furnace itself, some circumferential temperature non-uniformity is unavoidable due to the non-uniformity of the heater and the heat insulating material. Such slight temperature non-uniformity in the circumferential direction is more likely to occur due to the larger diameter of the optical fiber preform (a) than in the case where the diameter is small, as compared with the case where the diameter is small. (B) Since the optical fiber preform has a higher drawing speed than the conventional one, the passing time of the neck-down portion (preform fusion reduced diameter portion) where the temperature becomes more uniform becomes shorter, and it is difficult to eliminate the temperature unevenness. As a result, temperature unevenness is more likely to remain than in the past, and it is easy to increase the non-circularity. Furthermore, as mentioned above, the requirements for non-circles themselves are becoming stricter.

If there is a change in the diameter reduction, it also leads to a connection loss when connecting the connector or the mechanical splice. Therefore, improvement of non-circularity should not be accompanied by worsening of wire diameter fluctuation.

An object of the present invention is to provide an optical fiber drawing apparatus and a drawing method capable of reducing the non-circularity of the optical fiber and reducing the connection loss of the optical fiber even in the various situations described above. To do.

[0015]

In order to solve the above-mentioned problems, an optical fiber drawing apparatus according to the present invention comprises a chuck for holding an optical fiber preform and a vertical movement of the optical fiber preform via this chuck. An elevating device having a function, a drawing furnace for heating and melting the lower part of the optical fiber preform to draw an optical fiber, and a coating located under the drawing furnace for applying a protective resin to the optical fiber A drawing apparatus having an apparatus and a winding apparatus having a function of drawing and winding the drawn and coated optical fiber, wherein a horizontal axis 1 to 2 of the optical fiber is provided between the drawing furnace and the covering apparatus. A measuring device for measuring a position in the axial direction is provided, and the chuck has an XY moving part for moving the optical fiber preform in two horizontal axis directions and a rotating part for rotating the optical fiber preform, The optical phi The rotation information or rotation command information of the base material and the horizontal two-axis position information or the position command information and the horizontal one-axis or two-axis position information of the optical fiber are taken in, all the information is calculated, and the optical fiber base material It is characterized by having an arithmetic unit having a function of changing rotation and horizontal two-axis movement commands.

In the optical fiber drawing method of the present invention, the optical fiber preform is inserted into a drawing furnace by an elevating device having a chuck, the preform is fed downward, and the lower part thereof is heated and melted. In an optical fiber drawing method of drawing an optical fiber, covering a drawn optical fiber with a protective resin, and drawing and winding the optical fiber base material, while performing rotational movement of the optical fiber base material with a chuck, the drawing is performed. Characterize.

In the drawing method, the rotation cycle and the revolution cycle may be matched in the command value before the correction signal is applied.

Here, the positional information of the drawn optical fiber on the horizontal plane is measured, and the locus thereof is subjected to arithmetic processing so as to be fitted to the circular orbit of the rotation cycle, and the radius and phase of the obtained circular orbit are calculated. The radius and phase of revolution of the chuck may be corrected based on the numerical values calculated from the radius and phase of revolution of the chuck.

Here, the radius of the circular orbit of the locus of the optical fiber may be controlled to be a fixed value or less.

[0020]

In the structure of the present invention, by rotating the optical fiber preform, the entire circumference of the preform is evenly opposed to the entire circumference of the drawing furnace. Therefore, even if there is some heat generation unevenness in the drawing furnace, temperature unevenness does not occur in the cross-sectional direction of the preform, leading to improvement in non-circularity. The rotation speed of the preform should be determined by the drawing speed of the optical fiber and the preform diameter. For example, if the drawing speed is 500 m / min and the preform diameter is φ80, the preform is rotated at 2 rpm. Since the preform feed is 0.61 mm per rotation, it is possible to avoid temperature unevenness and prevent non-circle generation due to temperature unevenness.

By the way, a method of simply rotating a preform is known from the publication of International Publication No. WO83 / 00232 (Applicant: CENTRAL ELECTRICITY GENERATING BOARD, International filing date: July 7, 1982). WO8
3/00232 aims to reduce polarization dispersion, and rotates at a rate of 1 rotation at a drawing speed of 2 to 10 cm (5000 to 25000 rpm at a drawing speed of 500 m / min). In this case, if the preform has a large diameter and a long length, it will come off from the outer diameter measuring device, or will come off from the center even if it does not reach there. Since it is necessary to perform measurement at the same position in order to perform highly accurate measurement, the outer diameter measurement accuracy deteriorates and the wire diameter fluctuation of the optical fiber deteriorates. This does not reduce the splice loss even if the non-circle is improved. This is because the preform melting lower end is not located on the chuck shaft in the case of a large diameter and long base material. That is, (1) since the preform is long, even if there is a slight bend in the preform, a considerable amount of misalignment occurs at the lower end. (2) Because of the large diameter, the neck-down shape is likely to be non-axially symmetric, and this slight non-axial symmetry causes a large axial misalignment of the optical fiber.

Even a simple combination of preform rotation, biaxial fiber position measurement, and biaxial preform chuck position control cannot reduce splice loss. Further, the large-diameter and long preform is in contact with the airtight plate for gas sealing in the upper part of the drawing furnace, which causes irregular vibration in the preform. Moreover, this also vibrates the drawn optical fiber.

Therefore, the central control is not stable only by the above measures, and if the control is performed too finely, the air flow is disturbed in the drawing furnace. All of these are factors that worsen the fluctuation of the optical fiber diameter. On the other hand, according to the method and apparatus of the present invention, since only the whirling component from the chuck shaft at the lower end of the preform is removed, except for the irregular line position fluctuation component with respect to the outer diameter measuring device, You can draw at a certain position. Irregular line position fluctuations are also present in conventional devices and methods, and thus wire diameter fluctuations do not worsen. Since only the slow correction according to the rotation speed is performed, the gas in the drawing furnace is not disturbed and the wire diameter fluctuation is not deteriorated.

[0024]

EXAMPLES The present invention will be described in detail below based on examples.

(Embodiment) As shown in FIG. 1, an optical fiber preform 21 has a chuck 23 through a support rod 22.
Attached to. The chuck 23 includes a rotating unit 231.
And the XY moving section 232, and the whole is moved up and down by the lifting device 24. The optical fiber preform 21 is inserted into the drawing furnace 25, the lower end thereof is heated and melted, and the optical fiber 26
Is delineated. At the upper end of the drawing furnace 25, the support rod 22 is vertically slidably attached to the airtight ring 27, and the airtight ring 27 is horizontally slidable on the upper lid 251 of the drawing furnace 25. The discharge of the atmospheric gas in the drawing furnace 25 to the upper part of the drawing furnace 25 is suppressed to a negligible amount. The drawn optical fiber 26 is drawn out from a small opening 252 in the lower part of the drawing furnace 25, and the atmospheric gas supplied into the drawing furnace 25 from a supply device (not shown) is also released from this small opening 252. It The drawn optical fiber 26 passes through an outer diameter measuring device (measuring device) 28 capable of measuring a drawing position and a wire diameter, is coated with a protective resin by a coating device 29, and the coated resin is cured by a curing device 30. It is taken up by the capstan 32 via the guide roller 31 and taken up by the take-up device 33. The take-up speed of the capstan 32 is controlled so that the optical fiber outer diameter measured by the outer diameter measuring device 28 maintains a target value, and the preform 21
As the lower end of the heating and melting line is drawn, the lifting device 2
Since 4 is lowered, it is possible to draw the wire over the entire length of the preform 21. Reference numeral 34 is a control device for this purpose.

During this drawing, the preform 21 is rotated by the rotating portion 231 of the chuck 23, and
XY movement is performed by the XY moving unit 232. This XY motion is a rotation command of the rotation unit 231 or actual rotation information,
Based on the fiber position information of the outer diameter measuring device 28 and the current position command or position information of the XY moving unit 232, the calculator 35
Is calculated and the movement is instructed. Specifically, according to the rotation period f of the rotating unit 231, X = Rcos (2πf
t-θ), Y = X expressed by Rsin (2πft-θ)
Define the locus of the Y movement. As this locus, a circular motion is given as a base command, and R and θ are given to the outer diameter measuring device 2
Correction is made based on the fiber position information of 8. This correction may be performed continuously, or may be performed intermittently by dividing a certain fixed time. As is clear from the equation, in the base command, the rotation cycle and the revolution cycle match in this embodiment.

Further, a drawing method using this device will be described. φ80mm preform draw speed 500
The line was drawn at m / min. The preform rotation period (rotation period) was kept constant at 2 rpm. At the time of starting the drawing, the above-mentioned radius of gyration R = O was set, and only the rotation was performed to start the drawing. In this state, the position information of the outer diameter measuring device 28 is taken for 5 minutes (10 rotations), and x = rcos (2π
ft-ψ), y = rsin (2πft-ψ). Here, when f: rotation cycle = 2 rpm, t: time (minutes), and ft = n (integer), the chuck rotating unit 2
It is assumed that 31 is in the determined reference direction. The outer diameter measuring device 28 used here is capable of measuring the optical fiber position in the x and y biaxial directions, but since it is fitted to a circular orbit, the degree of freedom is 1 and the measurement is only in the uniaxial direction. But obviously the same can be done. At this time, the deviation from the fitting is ignored as random vibration. Here, the lower end of the preform 21 is x ′ = r′c
os (2πft−ψ), y = r′sin (2πft−
The calculation is performed by the arithmetic unit 35 as if it is circularly moving in (ψ). Here, r ′ = cr, and c is a constant obtained in advance, and the movement of the optical fiber position when the preform is moved by A in one direction by drawing the optical fiber without rotating it When the quantity a is measured, c is a number represented by A / a. Here, when r is smaller than a predetermined constant value (0.15 mm in this embodiment), the chuck X
When the Y motion is not corrected and r is larger than this value, X = R over the next fixed time (1 minute in this embodiment).
cos (2πft−θ) = r′cos (2πft−ψ +
π), Y = Rsin (2πft−θ) = r′sin (2
The control signal is changed so that it becomes (πft−ψ + π). At this time, x and X and y and Y are axes having the same direction. That is, R is increased by r ′ / 60 per second, and θ
Is increased by (ψ−π) / 60 (where 0 ≦ ψ
<Use ψ that becomes 2π). Thus, after 6 minutes, the chuck 23 has X = r'cos (2πft−ψ + π), Y =
If the state does not change by moving with r'sin (2πft−ψ + π), the lower end of the preform 21 excluding the irregular fluctuation is x ′ = X + r′cos (2πft−ψ) =
0, y ′ = Y + r′sin (2πft−ψ) = 0, and the fluctuation of the optical fiber 26 in the outer diameter measuring device 28 remains only the irregular component.

In the next 5 minutes, the line position fluctuation in the outer diameter measuring device 28 is fitted again by the circular motion of the period f,
If r at that time is larger than 0.15 mm, the next 1
The operation of correcting in minutes was repeated in this embodiment. However, unlike the first time, the XY moving unit 232 has already been
The calculation of the arithmetic unit 35 when the circle is moving is based on the following method.

As shown in FIGS. 2A and 2B, ft =
If the lower end position of the preform 21 estimated by multiplying the position A of the chuck 23 and the position of the outer diameter measuring device 28 by n (n: an integer) by c is B and the origin is 0,

[0030]

[Outside 1]

Point B moves to the origin. By the triangle theorem

[0032]

[Equation 1]

It becomes That is, X = Rcos (2πft
−θ) and Y = Rsin (2πft−θ), X = R ′
cos (2πft−θ ′), Y = R′sin (2πft
-Θ ') is corrected for 1 minute. That is, R is increased by (R'-R) / 60 per second. The phase angle is incremented by (θ′−θ) / 60 per second after determining the angle at which cos in the above equation is 0 to π. sin (ψ−
When θ) = 0, θ is not changed. In the case of R = 0 at the start of drawing, if θ = 0 and θ ′ = ψ−π,
Can be treated equally.

An optical fiber was drawn by using the arithmetic unit 35 as described above. As a result, the non-circularity was 0.2% or less and the average was 0.12%, which was good over the entire length. Further, the wire diameter variation by the outer diameter measuring device of the wire drawing machine was ± 0.1 μm or less over the entire length. After the wire drawing, the variation of the outer diameter measurement value with other inspection devices was ± 0.3 μm or less.

(Comparative Example 1) An optical fiber was drawn by a conventional method. That is, rotation was not performed without changing other conditions. XY position adjustment was performed. As a result, the non-circularity was 0.8% at maximum and 0.47% on average. The wire diameter variation due to the wire diameter measuring machine is ± 0.15
It was as good as μm or less. After the wire drawing, the variation of the outer diameter measurement value with other inspection devices was ± 0.5 μm or less.
It is presumed that the measured outer diameter is inferior to that of this embodiment because the poor non-circularity also affects the outer diameter control.

(Comparative Example 2) The XY moving part of the chuck was fixed, and only the rotation at 2 rpm was performed to draw the wire. As a result, the measuring range (2
The optical fiber came to come off from (mm □), and the drawing was stopped. The non-circularity during this period was good at 0.2% or less, but the wire diameter fluctuation due to the outer diameter measuring device of the wire drawing machine was ±
It was as large as 0.4 μm. After the wire drawing, the variation of the outer diameter measurement value with other inspection equipment was ± 0.9 μm, which was worse than that of the conventional method.

[0037]

As described above, according to the apparatus and method of the present invention, the non-circularity can be improved and the fluctuation of the wire diameter is not adversely affected. This is especially effective when drawing a large-diameter, long-length preform at high speed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an optical fiber drawing device according to the present invention.

FIG. 2 is a graph for explaining a method for controlling XY motion of an optical fiber preform according to the present invention, and a graph when sin (ψ-θ), which is one of the control parameters, is> 0. And the graph when sin (φ−θ) <0 is (b).

FIG. 3 is a schematic configuration diagram of a conventional optical fiber drawing device.

[Explanation of symbols]

 21 Optical Fiber Preform (Optical Fiber Base Material) 22 Support Rod 23 Chuck 24 Lifting Device 25 Drawing Furnace 26 Optical Fiber 27 Airtight Ring 28 Outer Diameter Measuring Instrument (Measuring Device) 29 Coating Device 30 Curing Device 31 Guide Roller 32 Capstan 33 winding device 34 control device 35 computing unit 231 rotating unit 232 XY moving unit 251 upper lid 252 small opening

Claims (5)

[Claims] 1. A chuck for holding an optical fiber preform,
An elevating device having a function of elevating and lowering the optical fiber preform through the chuck, a drawing furnace for heating and melting the lower part of the optical fiber preform and drawing it into an optical fiber, and a position below the drawing furnace. And a coating device that applies a protective resin to the optical fiber, and a winding device that has a function of pulling and winding the optical fiber that has been drawn and coated, wherein the drawing furnace and the coating device are provided. Between the optical fiber horizontal 1
A measuring device for measuring the position in the axial or biaxial directions is provided, and the chuck has an XY moving part for moving the optical fiber preform in the horizontal biaxial directions and a rotating part for rotating the optical fiber preform. The rotation information or rotation command information of the optical fiber preform and horizontal biaxial position information or position command information and the horizontal 1-axis or 2-axis position information of the optical fiber,
An optical fiber drawing apparatus having an arithmetic unit having a function of calculating all of this information and changing the rotation and horizontal two-axis movement commands of the optical fiber preform. 2. An optical fiber preform is inserted into a drawing furnace by an elevating device having a chuck, and the preform is fed downward,
In the optical fiber drawing method, the lower part of the optical fiber is drawn while being heated and melted, the protective resin is coated on the drawn optical fiber, and the drawn optical fiber is drawn and wound. A method for drawing an optical fiber, which comprises: 3. The method of drawing an optical fiber according to claim 2, wherein the rotation cycle and the revolution cycle are matched in a command value before a correction signal is applied. 4. The position information of the drawn optical fiber on a horizontal plane is measured, and the trajectory is arithmetically processed so as to be fitted to a circular orbit of the rotation period, and the radius and phase of the obtained circular orbit and the 4. The optical fiber drawing method according to claim 3, wherein the radius and phase of revolution of the chuck are corrected based on numerical values calculated from the revolution radius and phase of the chuck. 5. The method of drawing an optical fiber according to claim 4, wherein the radius of the circular orbit of the trajectory of the optical fiber is controlled to be a fixed value or less.