JP3861992B2 - Optical fiber preform bending measurement method and measuring apparatus, and optical fiber preform manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for measuring the bending of an optical fiber preform that is made into a transparent glass for drawing an optical fiber in a drawing furnace, and a method for manufacturing the optical fiber preform.
[0002]
[Prior art]
An optical fiber is formed by placing an optical fiber preform made of transparent glass in a suspended state, placing it in a drawing furnace, gradually heating and melting the lower part, and taking it from the lower part at a predetermined speed. If the optical fiber preform has a large bend, the spindle shape at the lower end, which is softened by heating, becomes unstable, and the outer diameter and characteristics of the optical fiber obtained by drawing vary. In addition, there is a problem that the position of the optical fiber in the middle of drawing is shifted, and the optical fiber is broken by contacting the coating die that covers the surface of the optical fiber. Further, there is a problem that the optical fiber preform approaches or comes into contact with the wall surface of the drawing furnace, and the position in the drawing furnace is biased to make the drawing unstable.
[0003]
As a factor that causes the optical fiber preform to bend, it may be caused by the density distribution of the porous body, heating conditions, or the like when the porous glass is made into transparent glass. In addition, when heated and stretched to become an optical fiber preform having a predetermined diameter after being made into transparent glass, an axis for welding a glass rod for holding (dummy rod) for holding the transparent glass by a drawing device It may also be caused by a shift of etc. Furthermore, there are also heating and axial misalignment when the drawn optical fiber preform is cut to a predetermined length for drawing, and a glass rod for hanging and holding the drawn optical fiber is welded.
[0004]
A technique of stretching the optical fiber preform so that the optical fiber preform is not bent (see, for example, Japanese Patent Laid-Open No. 2000-264664), and correcting the bent optical fiber preform. A technique (for example, see JP-A-2001-31439) is known.
[0005]
In addition, if the optical fiber preform is set in a drawing furnace with a large bend and the drawing is performed, the above-described problems occur. Therefore, the bend of the optical fiber preform is measured in advance. (For example, refer to JP-A-9-189503 and JP-A-10-62299).
[0006]
FIG. 11 is a diagram showing a method and apparatus for measuring the bending of an optical fiber preform disclosed in the above-mentioned JP-A-9-189503. In the figure, 1 is a base, 2 is a support means, 3 is a position measuring device, 4 is a guide shaft, 5 and 6 are drive motors, 7 is an encoder, 8 is a limit switch, 9 is a storage / arithmetic processing unit, 10 is An optical fiber preform is shown.
[0007]
As shown in FIG. 2 (B), the bending measuring device for the optical fiber preform 10 is provided with support means 2 composed of a pair of rotating rollers on both sides of the base 1, and the optical fiber preform is attached to the support means 2. 10 is placed and a position measuring device 3 for measuring the outer diameter position of the optical fiber preform movable in the longitudinal axis direction of the optical fiber preform 10 is arranged. The position measuring device 3 includes a U-shaped measuring portion 3 a that surrounds the optical fiber preform 10 and a support portion 3 b that is screwed to the guide shaft 4, and the support portion 3 b is rotated by the guide shaft 4. It is moved in the longitudinal axis direction of the base material 10. The U-shaped measuring unit 3a is configured to measure the outer diameter position of the optical fiber preform 10 by irradiating, for example, laser light with the optical fiber preform 10 interposed therebetween. Detect the amount of radial deviation.
[0008]
The position measuring device 3 changes the measurement position in the longitudinal axis direction of the optical fiber preform 10 by rotating the guide shaft 4 with the drive motor 5. The range of the measurement position is performed from the L point to the R point of the optical fiber preform 10 inside the support means 2 and is measured at a predetermined pitch. The limit point 8 sets the L point and the R point in the range of the measurement position. The measurement position in the longitudinal axis direction is detected by the rotation of the guide shaft 4 using the encoder 7 and is input to the storage / calculation processing means 9 as position information in the axial direction of the optical fiber preform 10. Data of the outer diameter position measured at the measurement position in each axial direction is also input to the storage / calculation processing means 9. Further, these measurements are performed from two orthogonal side surfaces of X and Y by changing the rotational position of the optical fiber preform 10 by 90 degrees by driving the drive motor 6.
[0009]
The measured data is stored and calculated by the storage / arithmetic processing means 9, and the radial deviation and the outer diameter variation of the optical fiber preform 10 along the axial direction are calculated along the axial direction. The amount of bending can be measured quantitatively. Judgment is made based on the measured bending amount of the optical fiber preform to determine whether it is suitable for drawing an optical fiber, and the quality assurance of the optical fiber preform with respect to the drawn optical fiber material can be made accurate. I can do it.
[0010]
However, since the above-described optical fiber preform bending measurement apparatus receives the side portions at both ends of the optical fiber preform 10 by the support means 2, the measurement is performed by measuring the bending of the entire length of the optical fiber preform only at the central portion. I can't. In particular, since a glass rod for suspending and holding the optical fiber preform is attached to at least one end of the optical fiber preform, there may be a case where the axial deviation of the welded state cannot be measured. Further, since the outer peripheral surface of the optical fiber preform 10 is configured to contact and support the rotating roller of the support means 2, there is a problem that the surface of the optical fiber preform is easily damaged. Furthermore, as shown in FIG. 11B, when the support end of the optical fiber preform 10 is bent, the center of the optical fiber preform changes depending on the rotational position with respect to the rotation center of the optical fiber preform 10. However, measurement errors may occur.
[0011]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described circumstances, and includes an optical fiber including a glass rod that supports an optical fiber preform rotatably without damaging the outer peripheral surface of the optical fiber preform and is welded to an end portion. It is an object of the present invention to provide an optical fiber preform bending measurement method, a measuring apparatus, and an optical fiber manufacturing method capable of accurately measuring the bending state over the entire length of the preform.
[0012]
[Means for Solving the Problems]
The method for measuring the bending of the optical fiber preform according to the present invention is such that the amount of deflection of the center of the optical fiber preform relative to the rotation center of the optical fiber preform is not changed by rotation. Is held and fixed, the optical fiber preform is rotated, and the maximum distance and the minimum distance from the optical fiber preform surface are measured in a non-contact manner over the entire length of the optical fiber preform in the axial direction. It is characterized by measuring the amount of center swing.
[0013]
In addition, the optical fiber preform bending measurement apparatus of the present invention is configured so that the amount of deflection of the center of the optical fiber preform relative to the rotation center of the optical fiber preform is not changed by rotation. Fixing jig for holding and fixing both ends, driving means for rotating the optical fiber preform together with the fixing jig, measuring the maximum distance and the minimum distance from the optical fiber preform surface in a contactless manner, Measuring means for measuring the amount of swirling and moving means for moving the measuring means over the entire axial length of the optical fiber preform are provided.
[0014]
In addition, the method for manufacturing an optical fiber preform according to the present invention is such that the amount of deflection of the center of the optical fiber preform relative to the rotation center of the optical fiber preform is not changed by rotation. Rotate the optical fiber preform by rotating the optical fiber preform, measuring the maximum distance and the minimum distance from the optical fiber preform surface with a non-contact measuring instrument over the entire length of the optical fiber preform in the axial direction. Calculate the amount of run-out at the center of the base material relative to the center, calculate the linear regression equation for the amount of run-out at the center of the base material from the data on the amount of run-out at the center of the base material, Calculate the amount of deviation from the equation, calculate the new amount of deviation by dividing the data of the amount of deflection at the center of the base material in the axial direction of the optical fiber preform at the maximum position of the amount of deviation, and calculate the amount of deviation previously calculated The optical fiber preform is cut at the maximum position of That.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention will be described with reference to FIGS. 1A is a diagram for explaining the outline of the present invention, FIG. 1B is a diagram showing an example of a fixing jig, and FIGS. 1C to 1F are diagrams of optical fiber preform end portions. FIGS. 2A and 2B are diagrams illustrating examples of holding and fixing, FIGS. 2A and 2B are diagrams for explaining measurement of the amount of deflection of the optical fiber preform, and FIGS. 3A and 3B are measurement data. FIGS. 4A and 4B are diagrams for explaining the identification processing when the base material center and the rotation center intersect and do not intersect. In the figure, 10 is an optical fiber preform, 11 and 12 are fixtures, 13 is a fixture support member, 14 is a feed shaft, 15 is a measuring instrument, 16 is a guide shaft, 17 and 18 are drive motors, 19 is A memory / arithmetic processing device, 20 is a spring member, 21 is a contact member, D is a run-out amount (run-out amount), E is a deviation amount, S is a rotation center, and T is a base material center.
[0016]
In the present invention, as shown in FIGS. 1 and 2, both ends of an optical fiber preform 10 are sandwiched between a pair of fixing jigs 11 and 12 and pressed and fixed in the axial direction. , 12, and the amount of deflection of the optical fiber preform 10 is measured by calculating the amount of deflection (hereinafter referred to as the deflection amount) with which the base material center T rotates relative to the rotation center S. In the figure, an example of a vertical configuration for vertically supporting the optical fiber preform 10 is shown. The optical fiber preform 10 is fixed by placing the lower end 10 a on the lower fixing jig 11 and pressing the upper end 10 b with the upper fixing jig 12. The upper fixing jig 12 is movable together with the fixing jig support member 13 in the vertical direction, and is attached to the fixing jig support member 13 so as to be rotatable.
[0017]
As shown in FIG. 1 (B), it is preferable that a spring member 20 and a contact member 21 are interposed in one or both of the upper and lower fixing jigs 11 and 12. As the spring member 20, various members such as a leaf spring, a coil spring, elastic rubber, and elastic resin can be used. By interposing the spring member 20 in the fixing jig, the application of excessive force to the optical fiber preform 10 is alleviated, and the optical fiber preform 10 is held and fixed with a constant pressing force. The positional deviation of the fiber preform 10 can be prevented.
[0018]
As the contact member 21 that holds and fixes the end face of the optical fiber preform 10, members having various shapes can be used as illustrated in FIGS. 1C to 1F. The example of FIGS. 1C and 1D is for holding and fixing the end face of the optical fiber preform 10 by frictional force, and is suitable when the end face is formed in a flat shape. The example of FIG. 1 (E) is held and fixed by the conical hole 21a, which is suitable when the end face of the optical fiber preform 10 is not flat, and the optical fiber preform base T and the rotation center S coincide. There is an advantage that it is easy to make. The example of FIG. 1F is held and fixed using a gripping claw 21b such as a gripping screw, which is suitable when the end surface of the optical fiber preform 10 is indefinite, and no pressing is required. . In the case of the example of FIG. 1 (F), the end of the optical fiber preform cannot be measured, and scratches may occur, but this is a range that does not substantially affect the drawing.
[0019]
The lower fixing jig 11 is rotated by driving means such as a driving motor 17, and the optical fiber preform 10 is rotated together with the fixing jigs 11 and 12 about the rotation center S of the fixing jigs 11 and 12. The A measuring instrument 15 that is not in contact with the optical fiber preform 10 is arranged at the outer peripheral position of the optical fiber preform 10 so as to be able to translate with respect to the rotation center S. The measuring device 15 includes a measuring unit 15a and a support unit 15b, and the support unit 15b is moved in the vertical direction by a moving means including a guide shaft 16 having a spiral groove and a drive motor 18.
[0020]
Although not shown in the figure, the optical fiber preform 10 is a horizontal type that is arranged in the horizontal direction, and both ends of the optical fiber preform 10 are pressed and fixed in the axial direction by a fixing jig and rotated. Is also possible. However, in the case of the horizontal type, since the entire load of the optical fiber preform 10 is supported by the frictional force of the fixing jig, it is necessary to increase the pressing and holding force in the axial direction. It is hard to set to. In this respect, in the vertical type shown in the figure, the optical fiber preform 10 can be supported by the plane of the lower fixing jig member 11, and a large pressing force is not required for holding and fixing, and the optical fiber preform 10 can be set on the measuring device. It is easy, and it can be said that it is more advantageous than the horizontal type.
[0021]
As the measurement unit 15a, for example, a laser outer diameter measuring instrument capable of measuring without contact with the optical fiber preform 10 can be used. The laser outer diameter measuring device is disposed so as to be movable in the axial direction with a certain distance from the rotation center S. The laser beam irradiated from the laser outer diameter measuring instrument is applied to the outer surface of the optical fiber preform 10, and only the maximum distance L1 between the measurement unit 15a and the outer surface of the optical fiber preform 10 is measured as shown in FIG. To do. At the position where the optical fiber preform 10 is rotated 180 degrees, only the minimum distance L2 between the measuring instrument 15 and the outer surface of the optical fiber preform 10 is measured as shown in FIG. Since the optical fiber preform 10 is rotated about the rotation center S and the distance between the rotation center S and the measuring instrument 15 is constant, if the outer diameter of the optical fiber preform 10 is uniform, (L1 -L2) / 2 is the deflection amount D at the center of the base material.
[0022]
Data such as the outer diameter position of the optical fiber preform 10 is measured from the measurement section 15a of the measuring instrument 15, and the axial position of the optical fiber preform 10 is determined from the rotation amount of the drive motor 18 that moves the support section 15b. Data is measured. These data are input to a storage / arithmetic processing unit 19 such as a computer, and at each position in the longitudinal direction of the optical fiber preform 10, a deviation amount of the center of the preform of the optical fiber preform 10 with respect to the rotation center S, That is, the shake amount D is stored and calculated, and is graphed as necessary. When the shake amount D is greater than or equal to a predetermined value, the use is disabled, and the bend is corrected or discarded.
[0023]
In the present invention, both end portions of the optical fiber preform are held and fixed so that the deflection amount D of the preform center T at each position in the longitudinal direction of the optical fiber preform 10 does not change due to rotation with respect to the rotation center S. . As a result, the base material center T at each position in the axial direction of the bent optical fiber base material 10 turns around the rotation center S in a circle having a constant radius, and an error due to the measurement direction occurs. Absent. Further, by using the fixing jigs 11 and 12 for fixing the optical fiber preform 10 by pressing the both ends 10a and 10b in the axial direction, the entire length of the optical fiber preform 10 is measured. You can also.
[0024]
Therefore, it is possible to measure not only a partial bend at the center portion as in the prior art, but the entire bend including the gripping glass rod in the drawing furnace welded to the end portion of the base material. Furthermore, since the member for holding the base material is not substantially in contact with the side surface of the optical fiber base material 10, the surface of the optical fiber base material 10 is not damaged, Quality can be improved.
[0025]
When the optical fiber preform 10 is fixed and held by pressing the fixtures 11 and 12, the optical fiber preform 10 is positioned between the rotation center S and the preform center T of the fixtures 11 and 12, as shown in FIG. Is difficult to match, and is fixed in a tilted state. It is often dependent on the skill level of the operator that the optical fiber preform 10 is not tilted and that the preform center T at both ends of the optical fiber preform is exactly aligned with the rotation center S. The workability is not good. Furthermore, it is almost impossible to fix the optical fiber preform assuming the center of the preform including the bending of the optical fiber preform. When the optical fiber preform 10 is tilted and fixed, or the center position is displaced and fixed, these tilts and deviations are added to the deflection amount D, and the actual bending amount of the optical fiber preform 10 is correctly measured. I can't. Therefore, it is necessary to be able to accurately measure the bending amount of the optical fiber preform even when the measurement is performed in a state where the inclination of the optical fiber preform or the center of the preform T is shifted.
[0026]
In the present invention, a virtual linear equation (hereinafter referred to as a linear regression equation) is calculated from the measured deflection amount D data of the base material center T, and based on this, the deflection amount of the optical fiber preform is corrected. To do. This will be described in detail with reference to FIG. FIG. 3A shows data measured by the method and apparatus shown in FIGS. 1 and 2, with the horizontal axis representing the axial position of the optical fiber preform and the vertical axis representing the deflection D of the center of the preform. FIG. It can be said that the curve connecting the measured values shows the whirling distribution of the base center T of the optical fiber base with the rotation center S as the zero line. However, in this figure, in addition to the bending of the optical fiber preform, the inclination of the preform and the displacement of the fixed position are included. The line indicated by the bold line is a line drawn through the center of the entire measurement value so as to represent the change state tendency of the shake amount D at each position as an optimum straight line, and this is expressed as the above-described linear regression equation. y = ax + b. In other words, this linear regression equation corresponds to the center of a bent optical fiber preform.
[0027]
FIG. 3B is a diagram showing a difference E (hereinafter referred to as a deviation amount) between the shake amount indicated by the linear regression equation y and the shake amount D at each measurement position. This shows the difference from the shake amount D with the line shown by the linear regression equation y being the zero line. If this deviation amount E is small, it means that the actual bending amount is smaller than the bending amount measured by the deflection amount D. That is, it is calculated by assuming an optimal linear regression equation from the measurement data, and by calculating the difference of the shake amount based on this, the inclination of the optical fiber preform and the deviation of the fixed position are substantially canceled. As a result, the actual amount of bending of the optical fiber preform can be measured, and the pass / fail judgment can be performed appropriately.
[0028]
2 and 3 described above show an example in which the base material center T does not intersect with the rotation center S. Therefore, the difference (L1−L2) between the maximum distance L1 and the minimum distance L2 between the measuring instrument and the optical fiber base material. ) / 2 is always a positive value, and the deflection amount D of the base material center T is also indicated by a positive value. However, as shown in FIG. 4A-A, the optical fiber preform may be held and fixed with the preform center T intersecting the rotation center S. In this case, as shown in FIG. 4A-B, the actual deflection amount of the base material center T is a solid line through the coincidence point Z where the deflection amount P of the dotted line portion and the base material center T intersect the rotation center S. It is assumed that (P + R) is continuous with the amount of shake R of the part.
[0029]
However, since only the maximum distance L1 and the minimum distance L2 are measured between the measuring instrument and the optical fiber preform, the difference is always measured as positive. Therefore, with the base material center T intersecting the intersection Z of the rotation center S, the shake amount P of the dotted line portion is inverted to the plus side as shown by a solid line and measured as a positive shake amount Q, and (Q + R) Indicated. The primary regression equation in this case is calculated based on the shake amounts Q and R of the solid line portion, and is different from the actual one. Therefore, when differential processing is performed on the data consisting of the shake amount (Q + R) in the solid line portion, a differential value that rapidly changes from the minus side to the plus side at the intersection Z is obtained as shown in FIG. By detecting this abrupt change in the differential value, the plus-side shake amount Q is corrected as being the minus-side shake amount P, and a correct primary regression equation can be calculated.
[0030]
On the other hand, as shown in FIG. 4B-B, the optical fiber preform may be held and fixed in a state in which the preform center T contacts the rotation center S but has a coincidence Z ′ that does not intersect. . In this case, as shown in FIG. 4 (B-B), the measured shake amount is indicated by (Q ′ + R ′) on the plus side, and the shake amount similar to FIG. Become. However, when this shake amount (Q ′ + R ′) is differentiated, a differential value that gradually changes from the minus side to the plus side at the coincidence point Z ′ is obtained as shown in FIG. In this case, the first-order regression equation is calculated without correcting the plus-side shake amount Q ′ as correct.
[0031]
As described above, by differentiating the deflection amount of the base material center, it is possible to easily determine whether the base material center T intersects with the rotation center S or not, and calculate a correct linear regression equation. can do. Therefore, the maximum distance L1 and the minimum distance L2 are measured as the distance between the measuring device and the optical fiber preform even if the optical fiber preform is held and fixed without worrying about the inclination of the optical fiber preform or the center of the preform. With a simple method, the amount of deflection at the center of the base material can be measured correctly.
[0032]
Next, a specific example of the measurement of the bending of the optical fiber preform will be described with reference to FIGS. The length of the optical fiber preform 10 was 1000 mm, and the measurement position in the axial direction was every 100 mm. FIG. 5 shows a case where the optical fiber preform 10 is not bent and the preform center T coincides with the rotation center S. FIG. 5A is a diagram showing a fixed state of the optical fiber preform, FIG. 5B is a diagram showing a deflection amount at the center of the preform, and FIG. 5C is a diagram showing a deviation amount.
[0033]
In FIG. 5, the optical fiber preform 10 is not bent and is accurately held and fixed by the fixing jigs 11 and 12 so that the centers thereof coincide with each other, and the preform center T and the rotation center S completely coincide with each other. As a result, as shown in FIG. 5B, the deflection amount at the center of the base material becomes zero at each measurement position of the total length of the base material. Therefore, the linear regression equation is y = 0. Further, as shown in FIG. 5C, the deviation amount E is also zero, and it can be determined that the optical fiber preform itself is not bent.
[0034]
FIG. 6 shows a case where the optical fiber preform 10 is not bent but the preform center T has a certain inclination with respect to the rotation center S. As in the case of FIG. 5, FIG. 6 (A) is a diagram showing the fixed state of the optical fiber preform, FIG. 6 (B) is a diagram showing the deflection amount at the center of the preform, and FIG. 6 (C) is the deviation amount. FIG.
[0035]
In FIG. 6, the optical fiber preform 10 is not bent, and the preform center T intersects with the rotation center S of the fixing jigs 11 and 12 and is held and fixed with a certain inclination. By correcting the data due to the intersection, as shown in FIG. 6B, the deflection amount D at the center of the base material becomes a deflection amount that increases at a constant rate from the lower end of the base material along the upper end direction. The maximum value of the amount D was 9.0 mm at the upper end point. The linear regression equation was calculated by the equation y = 0.001x-0.1. However, as shown in FIG. 6C, the deviation amount E becomes zero, and it can be determined that the optical fiber preform itself is not bent.
[0036]
FIG. 7 shows a case where the optical fiber preform 10 is bent but the preform center T is not inclined with respect to the rotation center S and the center positions of the upper and lower ends of the preform are not displaced. As in the case of FIG. 5, FIG. 7 (A) is a diagram showing the fixed state of the optical fiber preform, FIG. 7 (B) is a diagram showing the deflection amount at the center of the preform, and FIG. 7 (C) is the deviation amount. FIG.
[0037]
In FIG. 7, the optical fiber preform 10 has an arc-shaped bend having a curvature radius of 350 mm, and the preform center T is curved in an arc with respect to the rotation center S of the fixing jigs 11 and 12 but is inclined. In addition, the center of the upper and lower ends of the base material is also held and fixed. As shown in FIG. 7B, the deflection amount D of the base material center T is shown in a curved shape on one side of the zero line, and the maximum value of the deflection amount D is 0.357 mm at the central 500 mm point. Met. By analyzing the shake amount data, the linear regression equation was calculated by the equation y = 0.214. Since the curve is arcuate, the linear regression equation has a shape obtained by horizontally drawing a central portion of the deflection amount indicated by the curved shape. As shown in FIG. 7C, the deviation amount E is merely a change in the zero line position of the deflection amount D. The maximum value of the deviation amount is the sum of the plus side deviation amount and the minus side deviation amount, which is 0.357 mm, which is the same as the shake amount D calculated in FIG.
[0038]
FIG. 8 shows a case where the optical fiber preform 10 is bent and the preform center T is inclined with respect to the rotation center S. As in the case of FIG. 5, FIG. 8 (A) is a diagram showing a fixed state of the optical fiber preform, FIG. 8 (B) is a diagram showing a deflection amount at the center of the preform, and FIG. 8 (C) is a deviation amount. FIG.
[0039]
In FIG. 8, the optical fiber preform 10 has an arc-like curve with a curvature radius of 350 mm, and the preform center T is held and fixed with an inclination with respect to the rotation center S of the fixing jigs 11 and 12. As shown in FIG. 8B, the deflection amount D at the center of the base material is shown as a quadratic function increasing from one side (zero point) of the zero line to the other side. In this case, the maximum value of the deflection amount D including the inclination was 1.43 mm at the upper end point. By analyzing the shake amount data, the linear regression equation was calculated by the equation y = 0.014x−0.214. As shown in FIG. 8C, the deviation amount was generated on the plus side and the minus side of the zero line, and the maximum value of the sum of the deviation amounts was 0.371 mm. In this specific example, the inclination of the base material is canceled, and the maximum value of the deviation amount indicates the substantial shake amount of the optical fiber base material.
[0040]
Although FIG. 8B shows an example of calculating a linear regression equation for the entire length of the optical fiber preform 10, there is a case where the optical fiber preform 10 is planned to be cut and used. . In this case, it is also possible to calculate a linear regression equation in the axial range in which the optical fiber preform 10 is cut, and to directly determine the shake amount and the deviation amount in the cut state.
[0041]
9 and 10 show that the amount of deflection of the optical fiber preform 10 is cut at the position where the bending amount of the optical fiber preform 10 is the maximum (500 mm position at the intermediate point) in the measurement of FIG. It is the figure which predicted quantity. 9A and 9B show the case of the lower part side of the optical fiber preform, FIG. 9A is a diagram showing a fixed state after cutting, and FIG. 9B is a deflection of the center of the preform obtained by dividing the lower data of FIG. The figure which shows quantity, FIG.9 (C) is a figure which shows deviation amount. FIG. 10 shows the case of the upper part side of the optical fiber preform. FIG. 10A shows a fixed state after cutting, and FIG. 10B shows the deflection of the center of the preform obtained by dividing the upper data in FIG. The figure which shows quantity, FIG.10 (C) is a figure which shows deviation amount.
[0042]
As shown in FIG. 9A, it is assumed that the optical fiber preform 10 has been cut at a position of 500 mm in the middle of the optical fiber preform 10, and the lower end of the optical fiber preform 10 ′ after the cut has the upper fixing jig 12 at the upper end. Is held and fixed by the fixing jig 12 ′ at the position where is lowered. The measurement data in FIG. 8 is divided at the cutting position, and data indicating the shake amount in FIG. 9B is obtained as the lower side data. In this case, the maximum value of the shake amount D was 0.357 mm. By analyzing the shake amount data, y = 0.007x−0.047 was calculated as a new linear regression equation. As shown in FIG. 9C, a new deviation amount is calculated by this new linear regression equation y, and the maximum value of the sum of the deviation amounts is 0.09 mm.
[0043]
As shown in FIG. 10A, it is assumed that the optical fiber preform 10 ″ is cut at a position of 500 mm in the middle of the optical fiber preform 10, and the lower end of the upper optical fiber preform 10 ″ after the cut is the lower fixing jig 11. 8 is held and fixed by the fixing jig 11 'at the position where the position is raised, and the measurement data in Fig. 8 is divided at the cutting position, and the data indicating the deflection amount in Fig. 10B is obtained as the upper side data. In this case, the maximum value of the shake amount D was 1.43 mm By analyzing the shake amount data, y = 0.0023x−0.886 was estimated as a new linear regression equation. 10C, a new deviation amount is calculated by this new linear regression equation y, and the maximum value of the sum of the deviation amounts is 0.06 mm.
[0044]
According to FIGS. 8 to 10, it is assumed that when a long optical fiber preform has a large deflection amount and is determined to be unsuitable for use as an optical fiber material, cutting is performed at the maximum position of the deflection amount. Then, a new linear regression equation is calculated with respect to the shake amount of the optical fiber preform after cutting, and a new deviation amount is calculated from the new linear regression equation. Such a determination can be predicted without actually cutting the optical fiber preform and re-measurement.
[0045]
【The invention's effect】
As is clear from the above description, by bending and holding the optical fiber preform in the axial direction, the optical fiber preform can be bent over the entire length without damaging the surface of the optical fiber preform. It is possible to measure, and it becomes possible to determine the quality more appropriately. In addition, by calculating the linear regression equation from the axial deflection of the optical fiber preform, it is possible to accurately measure even when the optical fiber preform is tilted or the center of the preform is displaced. Therefore, the amount of bending can be measured and workability can be improved. Further, even when the optical fiber preform is bent, it is possible to determine whether or not it can be used after being cut.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an embodiment of the present invention.
FIG. 2 is a diagram for explaining the measurement of the amount of deflection of the optical fiber preform of the present invention.
FIG. 3 is a diagram for explaining a deflection amount, a linear regression equation, and a deviation amount at the center of the base material of the present invention.
FIG. 4 is a diagram for explaining data processing when an optical fiber preform center intersects a rotation center.
FIG. 5 is a view when the optical fiber preform is fixed without being bent and tilted.
FIG. 6 is a view when the optical fiber preform is fixed without being bent and tilted.
FIG. 7 is a view when the optical fiber preform is bent and fixed without tilting.
FIG. 8 is a diagram showing a case where the optical fiber preform is bent and is tilted and fixed.
FIG. 9 is a view for explaining one of optical fiber preforms cut into two;
FIG. 10 is a diagram for explaining the other side of the optical fiber preform cut into two;
FIG. 11 is a diagram illustrating a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Optical fiber preform | base_material, 11, 12 ... Fixing jig, 13 ... Fixing jig support member, 14 ... Feed axis, 15 ... Measuring instrument, 16 ... Guide axis, 17, 18 ... Drive motor, 19 ... Memory | storage and calculation Processing device, 20 ... spring member, 21 ... contact member, D ... run-around amount (run-out amount), E ... deviation amount, S ... rotation center, T ... base material center.

Claims (8)

Hold and fix both ends of the optical fiber preform so that the rotation amount of the optical fiber preform does not change due to rotation with respect to the rotation center of the optical fiber preform, and rotate the optical fiber preform. The maximum distance and the minimum distance from the surface of the optical fiber preform are measured without contact over the entire axial length of the optical fiber preform, and the amount of run-out of the preform center with respect to the rotation center is measured. A method for measuring the bending of an optical fiber preform. The method for measuring the bending of an optical fiber preform according to claim 1, wherein both ends of the optical fiber preform are held and fixed by pressing in the axial direction. A linear regression equation of the swing amount of the base material center is calculated from the data of the swing amount of the base material center, and a deviation amount between the swing amount of the base material center and the primary regression equation is calculated. The method for measuring the bending of an optical fiber preform according to claim 1. At the maximum position of the deviation amount, the data on the amount of deflection at the center of the base material is divided in the axial direction of the optical fiber preform, and a new linear regression equation is calculated from the divided data, and a new deviation is obtained. The method for measuring a bending of an optical fiber preform according to claim 3, wherein the amount is measured. A fixing jig for holding and fixing both end portions of the optical fiber preform so that the amount of deflection of the center of the optical fiber preform does not change due to rotation with respect to the rotation center of the optical fiber preform, and the optical fiber preform A driving means for rotating the material together with the fixing jig, a measuring means for measuring a maximum distance and a minimum distance from the surface of the optical fiber base material in a non-contact manner and measuring a swing amount of the base material center with respect to the rotation center; An apparatus for measuring the bending of an optical fiber preform, comprising moving means for moving the measuring means over the entire axial length of the optical fiber preform. 6. The optical fiber preform bending measurement apparatus according to claim 5, wherein the fixing jig is configured to be pressed through a spring member. 6. The optical fiber preform according to claim 5, further comprising a storage / calculation device that stores and calculates the deflection data of the center of the preform measured by the measuring unit and the position data of the moving unit. Bending measuring device. Hold and fix both ends of the optical fiber preform so that the rotation amount of the optical fiber preform does not change due to rotation with respect to the rotation center of the optical fiber preform, and rotate the optical fiber preform. The maximum distance and the minimum distance from the surface of the optical fiber preform are measured by a non-contact measuring device over the entire axial length of the optical fiber preform, and the swing of the center of the preform with respect to the rotation center is measured. And calculating a linear regression equation of the swing amount of the base material center from the data of the swing amount of the base material center, and a deviation between the swing amount of the base material center and the primary regression equation Calculating the amount, and calculating the new deviation amount by dividing the data of the deflection amount of the base material center at the maximum position of the deviation amount in the axial direction of the optical fiber preform, and calculating the deviation amount previously calculated The optical fiber preform is cut at the maximum position of Method for manufacturing an optical fiber preform, characterized in that.

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