WO2006129494A1

WO2006129494A1 - Method and device for measuring structure of parent material for optical fiber

Info

Publication number: WO2006129494A1
Application number: PCT/JP2006/309968
Authority: WO
Inventors: Yuuji Tobisaka
Original assignee: Shin-Etsu Chemical Co., Ltd.
Priority date: 2005-05-31
Filing date: 2006-05-18
Publication date: 2006-12-07
Also published as: JP4233098B2; JP2006337089A

Abstract

A method for measuring the noncircularity and eccentricity at the core portion (14) of a parent material (10) for optical fiber simultaneously, comprising a measuring step including an operation for moving the parent material (10) for optical fiber while irradiating the material (10) with light, an operation for measuring the distribution of relative outside diameter value by associating the variation in width of transmitted light from the core portion (14) with the amount of movement of the parent material (10) for optical fiber, and an operation for measuring the distribution of side end position of the clad portion (12) in the longitudinal direction of the parent material (10) for optical fiber, wherein the measuring step is performed every time when the parent material (10) for optical fiber is rotated about the central axis up to a predetermined rotational angle. The method further comprises a measurements storing step for recording a plurality of relative outside diameter value distributions and clad side end position distributions, and a step for calculating a plurality of noncircularities and eccentricities at the core portion (14) in the longitudinal direction of a parent material (10) for optical fiber based on the plurality of relative outside diameter value distributions and clad side end position distributions stored in the measurements storing step.

Description

Specification

Structure measuring apparatus and structure measuring apparatus for optical fiber preform

Technical field

[0001] The present invention relates to a structure measuring method and a structure measuring apparatus for an optical fiber preform. More specifically, a structural measurement that measures the non-circularity and eccentricity of a core in an optical fiber preform that has a core and a cladding that surrounds the core and is used as a raw material for optical fibers. The present invention relates to a method and a measuring device for implementing it.

[0002] Regarding the designated countries where incorporation by reference of documents is permitted, the contents described in the specification of the following patent application are incorporated into this application by reference, and are a part of the description of this specification.

Japanese Patent Application No. 2005—No. 159662 Filing May 31, 2005

Background art

[0003] In recent years, the influence of Polarization Mode Dispersion (hereinafter referred to as “PMD”) has attracted attention as one of the factors that limit the increase in distance and speed of optical communication. . PMD is a phenomenon in which the width of the incident optical signal pulse spreads as it propagates through the optical fiber, as two modes with mutually orthogonal polarization planes propagate through the optical fiber at slightly different speeds. means. When the effect of PMD increases, some of the different pulses on the optical signal overlap. For this reason, when the pulse width is reduced and communication is speeded up, the pulse cannot be discriminated on the receiving side, and the desired speedup cannot be achieved. In long-distance communication using optical signals, the probability that optical pulses will overlap and cause communication errors will increase.

[0004] A single-mode optical fiber has a core having a higher refractive index than the surroundings and a cladding surrounding the core, and light mainly propagates through the core. When the core is a perfect circle, the two modes with mutually orthogonal polarization planes are degenerated and cannot be distinguished. However, if the core is not circular, if the core is distorted in the process of manufacturing an optical fiber or fiber optic cable, the symmetry of the core breaks and the two modes propagate through the optical fiber. A speed difference occurs and PMD occurs. [0005] Therefore, as a method for suppressing the occurrence of PMD, there is a method for measuring the non-circularity of the core portion of the optical fiber preform and managing the quality of the optical fiber based on the measured non-circularity. . An optical fiber is manufactured by largely stretching an optical fiber preform. Therefore, when managing the PMD of an optical fiber based on the non-circularity of the optical fiber preform or its core, the optical fiber preform is used. Unless the non-circularity is measured in a fairly fine unit with respect to the material, the PMD in the optical fiber state cannot be predicted. For example, an optical fiber with a length of 1 km is only about 2.4 mm in the state of an optical fiber preform with an outer diameter of 80 mm. In addition, the length of the optical fiber preform with an outer diameter S of 18 mm is only about 0.2 mm.

[0006] Patent Document 1 describes a method for measuring the non-circularity of the core portion of an optical fiber preform. In the method described here, the optical fiber preform was rotated while irradiating the parallel light from the side surface while the optical fiber preform was immersed in the matching oil in the container, and the optical fiber preform was transmitted. The outer diameter of the core portion is measured based on the lightness distribution. By repeating the procedure for measuring the outer diameter in the length direction of the optical fiber preform, the noncircularity distribution in the optical fiber preform is calculated.

[0007] In the measurement method described above, when the outer diameter is measured at a certain position in the longitudinal direction of the optical fiber preform, the measurement is temporarily stopped and the optical fiber preform is moved in the longitudinal direction. After that, measure the outer diameter again. For this reason, in addition to the time required for the measurement work itself, work time for stopping, moving and restarting the measurement is required. Measurement end force at one position Even if the series of work up to the start of measurement work at the next position is automated and shortened to 1 second, the optical fiber preform with a length of 1, OOOmm is measured at lmm intervals It takes more than 16 minutes to move. In addition, when measuring a core material with a length of 500 mm at intervals of 0.2 mm, the travel time is up to 40 minutes or more. In addition, since the measurement work itself takes time, it takes a long time to measure the non-circularity over the entire length of the optical fiber preform by the method described in Patent Document 1.

[0008] Patent Document 2 describes a method of measuring the non-circularity of the core portion of an optical fiber preform at high speed. In the measurement method described here, the operation of measuring the outer diameter distribution over the entire length while moving in the longitudinal direction of the optical fiber preform and the operation of rotating the optical fiber preform about its central axis are alternated. Over the entire length and circumference of the optical fiber preform The obtained outer diameter distribution value force also calculates the non-circularity of the core part. As a result, the rest period between each measurement can be shortened, and the non-circularity of the entire optical fiber preform can be obtained quickly.

[0009] On the other hand, FTTH (Fiber To The

With the spread of services such as Home), bending-resistant optical fibers used for indoor wiring and the like have been developed and put into practical use. Many optical fibers have a significant increase in transmission loss when bent to less than 60 mm, but this type of optical fiber has little increase in loss due to bending. However, since this type of optical fiber has a small mode field diameter, the effect of misalignment that occurs when connecting to other optical fibers is large. Therefore, if the core portion of the optical fiber is decentered, the connection loss due to the axis deviation is greatly affected. Therefore, as one of the quality evaluation criteria for optical fibers, it has become necessary to measure the eccentricity of the core. The eccentricity means the amount of displacement of the core center relative to the radial center of the optical fiber.

[0010] Patent Document 3 discloses a method and apparatus for measuring the eccentricity of the core portion of an optical fiber preform. In this apparatus, a base material for an optical fiber is attached to a gripping tool of a suspension device equipped with a rotation mechanism, and a base is mounted on a base that can be scanned along the longitudinal direction of the base material. The position of the clad and core are detected by the bright and dark pattern that has passed through the material. Further, after the measurement is repeated over the longitudinal direction of the base material, the eccentricity of the core is measured. The amount of deviation from the center of the base material of the core is also determined from the outer diameter, position and angular force of the optical fiber base and core. In addition, the amount of misalignment of the entire optical fiber preform is obtained by combining the data after determining the amount of deviation at several different angles (for example, two locations of 0 ° and 90 °). It is done. In this method, higher measurement accuracy can be obtained if the optical fiber preform is immersed in the matching oil. However, since the process of removing the matching filter after measurement is complicated, it is often measured in air!

Patent Document 1: Japanese Patent Laid-Open No. 2003-042894

Patent Document 2: Japanese Patent Application No. 2005-045329

Patent Document 3: Patent No. 3053509

Disclosure of the invention

Problems to be solved by the invention [0011] Structural measurements frequently performed on optical fiber preforms for the purpose of quality control include three types: non-circularity measurement, eccentricity measurement, and refractive index distribution measurement. In addition, as described above, dedicated measuring devices are used for non-circularity measurement and eccentricity measurement. For this reason, in order to perform multiple structural measurements on a single optical fiber preform, there is no other way than to prepare a dedicated measuring device for each and perform individual measurements. For this reason, it was one of the causes of the increase in the cost of optical fibers, which required a lot of work and work time for structural measurement, such as storage, transportation, and setup of measuring equipment.

[0012] Accordingly, an object of the present invention is to provide a structure measuring method and a structure measuring apparatus capable of efficiently performing the structure measurement of the optical fiber preform related to the PMD, which is regarded as a problem in high-speed communication. .

Means for solving the problem

[0013] As a first aspect of the present invention, there is provided a method for measuring a non-circularity and an eccentricity of a core portion of an optical fiber preform having a core portion and a cladding portion surrounding the core portion. While the optical fiber preform immersed in the optical fiber is irradiated with light from a direction perpendicular to the central axis of the core portion, the optical fiber preform is moved in a direction parallel to the central axis, and the optical fiber preform is moved. Of these, changes in the width of transmitted light that has passed through the core are recorded in association with the amount of movement of the optical fiber preform, and the relative outer diameter distribution of the core in the longitudinal direction of the optical fiber preform is measured. The relative outer diameter distribution measurement operation and the position of the steep contrast generated in the transmitted light that has passed through the boundary between the cladding and the matching oil are recorded in association with the amount of movement of the optical fiber preform, and used for optical fiber. A crack in the longitudinal direction of the base material A measurement procedure that includes a cladding side end position distribution measurement operation that measures the side end position distribution of the section, and the measurement procedure is executed each time the optical fiber preform is rotated to a predetermined rotation angle around the central axis. The measured value accumulation procedure for recording the plurality of relative outer diameter value distributions and the clad side edge position distribution associated with the rotation angle, and the plurality of relative outer diameter value distributions and And a structure measuring method including a calculation procedure for calculating a plurality of non-circularities and eccentricities of the core part in the longitudinal direction of the optical fiber preform based on the measurement of the position distribution on the clad side end. As a result, the non-circularity and the eccentricity of the core portion of the optical fiber preform can be measured simultaneously. Therefore, the work time required to measure the structure of the optical fiber preform can be shortened. The

[0014] The relative outer diameter value distribution measurement operation and the clad side end position distribution measurement operation are performed using individual light receiving sensors. This makes it possible to use sensors suitable for measuring the non-circularity and eccentricity of the core portion of the optical fiber preform. Therefore, the measurement accuracy can be improved, and at the same time, the cost of the structure measuring apparatus is not increased easily.

[0015] Through the clad side end position distribution measurement operation, the positions of the pair of side ends appearing at both ends of the optical fiber preform are measured using individual light receiving sensors. As a result, regardless of the thickness of the optical fiber preform, the side edge position of the cladding can be measured using a small light receiving sensor. Therefore, the scale and cost of the structure measuring apparatus are not increased easily.

[0016] As a second aspect of the present invention, there is provided a structure measuring apparatus for measuring a non-circularity and an eccentricity of a core part of an optical fiber preform having a core part and a cladding part surrounding the core part, The optical fiber preform is suspended to move the optical fiber preform in a direction parallel to the central axis of the core, and the optical fiber preform is rotated around the central axis. A suspension device, a container that contains an amount of matching oil that can immerse the optical fiber preform, and that allows the optical fiber preform immersed in the matching oil to move up and down by the lifting operation, and the interior of the container The optical fiber preform immersed in the matching oil is irradiated with parallel light in a direction orthogonal to the central axis, and received light is received from the light source and received through the optical fiber preform. With sensor and match The optical fiber preform immersed in guoil is irradiated with light from the direction perpendicular to the central axis of the core, while the optical fiber preform is moved in a direction parallel to the central axis. The change in the width of the transmitted light that has passed through the core is recorded in association with the amount of movement of the optical fiber preform, and the relative outer diameter distribution of the core in the longitudinal direction of the optical fiber preform is measured. The relative outer diameter distribution measurement operation and the position of the steep contrast generated in the transmitted light that has passed through the boundary between the cladding portion and the matching oil are recorded in association with the amount of movement of the optical fiber preform. Measurement procedure including the clad side end position distribution measurement operation to measure the clad side end position distribution with respect to the longitudinal direction of the base material, and the optical fiber base material is rotated around the central axis to a predetermined rotation angle. Every measuring hand Execute the order and associated with the rotation angle Based on the measured value accumulation procedure that records multiple relative outer diameter value distributions and cladding side edge position distributions, and the multiple relative outer diameter value distributions and clad side edge position distribution measurements accumulated in the measured value accumulation procedure, There is provided a structure measuring apparatus that executes a plurality of calculation procedures for calculating a plurality of non-circularities and eccentricities of a core portion in the longitudinal direction of a fiber preform. As a result, the non-circularity and eccentricity of the core portion of the optical fiber preform can be measured with a single structure measuring device. Accordingly, the scale of the structure measuring apparatus can be reduced, the work required for replacing the structure measuring apparatus can be omitted, and the cost and work time required for the structure measurement of the optical fiber preform can be reduced.

[0017] According to one embodiment, in the structure measuring apparatus, the light receiving sensor is used in the relative outer diameter value detection sensor used in the relative outer diameter value distribution measuring operation and in the cladding side end position distribution measuring operation. The structure measuring device according to claim 4, further comprising a side end position detection sensor. This makes it possible to use sensors suitable for measuring the non-circularity and eccentricity of the core portion of the optical fiber preform. Therefore, the measurement accuracy can be improved, and at the same time, the cost of the structure measuring apparatus is not increased easily.

[0018] Further, according to another embodiment, in the structure measurement apparatus, the position of the pair of side ends appearing at both ends of the optical fiber preform is determined by the light receiving sensor during the clad side end position distribution measurement operation. 6. The structure measuring apparatus according to claim 4, further comprising individual light receiving sensors that respectively detect light. As a result, regardless of the thickness of the optical fiber preform, the side edge position of the cladding can be measured using a small light receiving sensor. Therefore, the scale and cost of the structure measuring device are not increased easily.

[0019] However, the above summary of the invention does not enumerate all necessary features of the present invention. Sub-combinations of these feature groups can also be an invention.

The invention's effect

[0020] By the structure measuring method and the structure measuring apparatus described above, the non-circularity of the core portion of the optical fiber base material related to PMD, which is a problem in high-speed communication, and the core that causes problems when connecting optical fibers. It is possible to measure the eccentricity of the portion simultaneously with high accuracy and efficiency. Therefore, the work time required for the structure measurement of the optical fiber preform can be shortened. In addition, since the non-circularity and eccentricity can be measured with a single structure measurement device, the scale of the structure measurement device can be reduced. In addition to being able to reduce the cost, the work required for replacing the structure measuring device can be omitted, and the cost for measuring the structure of the optical fiber preform can be reduced.

Brief Description of Drawings

FIG. 1 is a diagram schematically showing the entire structure measuring apparatus 100.

FIG. 2 is a diagram schematically showing the arrangement of light sources 60 and sensors on one horizontal plane in the structure measuring apparatus 100.

FIG. 3 is a diagram schematically showing another arrangement example of the light source 60 and the sensor on one vertical plane in the structure measuring apparatus 100.

FIG. 4 is a diagram schematically showing an arrangement example of a light source 60 and sensors on one horizontal plane in the structure measuring apparatus 100.

FIG. 5 is a flowchart F100 showing the procedure of the structure measuring method performed in the structure measuring apparatus 100.

FIG. 6 is a diagram schematically showing a light reception level in each sensor.

FIG. 7 is a flow chart F200 in the structure measuring apparatus 100.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention. In addition, all the combinations of features described in the embodiments are not necessarily essential for the solution of the invention. Example

FIG. 1 is a diagram schematically showing the structure of a structure measuring apparatus 100 that can measure the non-circularity and the eccentricity of the core portion 14 of the optical fiber preform 10. As shown in the figure, this structure measuring apparatus 100 includes a suspending device 20 for suspending an optical fiber preform 10 from above, a container 40 containing a matching filter 30, and a side cover of the container 40. And a light source 60 for irradiating the optical fiber preform 10 with the parallel light 80 and a light receiving sensor 70 for receiving the light emitted from the light source 60 and transmitted through the optical fiber preform 10.

[0024] The suspending device 20 holds the upper end of the optical fiber base material 10 and suspends it, lifts and lowers the optical fiber base material 10, and moves the optical fiber base material 10 around the vertical axis. It has a function to execute the rotation operation to rotate. The container 40 is emitted from the light source 60. A measurement window 50 that is transparent to the parallel light 80 is provided near the upper end thereof. Accordingly, the parallel light 80 emitted from the light source 60 is applied to the optical fiber preform 10 through the matching oil 30, and the parallel light 80 transmitted through the optical fiber preform 10 passes the matching oil 30. The light is received by the light receiving sensor 70.

FIG. 2 is a diagram schematically showing an optical arrangement from the light source 60 to the light receiving sensor 70 in a cross section obtained by cutting the structure measuring apparatus 100 on a horizontal plane including the parallel light 80. As shown in the figure, the parallel light 80 emitted from the light source 60 has a width wider than the outer diameter of the optical fiber preform 10, and the optical fiber is passed through the measurement window 50 and the matching oil 30. The entire base material 10 is irradiated. On the other hand, the light-receiving sensor 70 includes a pair of clad sensors 71 and 73 that receive parallel light 80 that has passed or passed through the vicinity of both side ends (upper and lower ends in the figure) of the optical fiber preform 10, and optical fibers. And a core part sensor 72 that receives parallel light 80 transmitted through the vicinity of the core part 14 of the base material 10.

Here, as the clad part sensors 71 and 73 and the core part sensor 72, a CCD camera can be used. However, it is preferable to use a CCD camera with a high resolution as the core sensor 72 and a CCD camera with a relatively low resolution as the sensors 71 and 73 for the core part.

[0027] The CCD camera has an area sensor type with a pixel number of about 500 to 1400 pixels in the horizontal direction and a line sensor type with a number of pixels of about 1000 to 8000 pixels. When measuring the eccentricity of an optical fiber preform with an outer diameter of 100 mm, the width of the scanning range is about 120 mm. Therefore, the resolution of the CCD camera is 120 mm / 500 to 8000 pixels, and the resolution is 0.24 to 0.02 mm / pixel. In other words, this means that when this type of CCD camera is used, an error of 0.04 mm may occur in the width direction. Therefore, the resolution is sufficient when measuring the side end position of the clad part 12 used for calculating the eccentricity ratio, which will be described later, and the clad part sensors 71 and 73 can be used.

[0028] On the other hand, an error of 0.04 mm corresponds to an error of 0.7% when the non-circularity is measured with respect to the core portion 14 having a diameter of 6 mm in the optical fiber preform 10 having an outer diameter of 100 mm. . Accordingly, it is not preferable to use a CCD camera having the same resolution as the clad sensors 71 and 73 as the core sensor 72. Note that the same high resolution sensor as the core sensor 72 is clad. Although it can be used as the part sensors 71 and 73, the use of an expensive high-resolution sensor increases the cost of the structure measuring apparatus 100. In this way, by separating and individually mounting the cladding part sensors 71 and 73 and the core part sensor 72, both high measurement accuracy and cost reduction of the apparatus can be achieved.

In the structure shown in FIG. 2, the clad sensors 71 and 73 are formed by stringing together a pair of light receiving elements. Accordingly, by appropriately moving the clad sensors 71 and 73, it is possible to easily cope with the optical fiber preform 10 having different outer diameters.

In the structure measuring apparatus 100 having the structure as described above, the parallel light 80 emitted from the light source 60 is translated with a width wider than the outer diameter of the optical fiber preform 10, and the cladding portion sensor 7 1 73 and core portion sensor 72 receive light. Here, parallel light 80 that has passed through a region including the boundary between the side end portion of the cladding portion 12 of the optical fiber preform 10 and the matching oil 30 is incident on the cladding portion sensors 71 and 73. Therefore, as will be described later, in the clad portion sensors 71 and 73, the position of the side end portion of the entire optical fiber preform 10 is detected. Further, the parallel light 80 in the region including the entire width of the core portion 14 is incident on the core portion sensor 72. Therefore, as will be described later, the core portion sensor 72 detects the outer diameter of the core portion 14.

In FIG. 2, the clad part sensors 71 and 73 and the core part sensor 72 are separated and arranged side by side. In practice, however, all sensors may be placed in the same housing. Further, the same function can be realized by various structures such as omitting the measurement window 50 and arranging the light source 60 and the light receiving sensor 70 in the container 40.

FIG. 3 is a longitudinal sectional view showing another layout of the light receiving sensor 70 in the structure measuring apparatus 100. As shown in the figure, in this layout, clad sensors 71 and 73 are arranged on the same plane as the light source 60, and in the same manner as in the layout shown in FIG. Directly receives parallel light 80 transmitted through 30 and measurement window 50. On the other hand, the core portion sensor 72 receives the reflected light whose propagation direction is converted by 90 ° via the mirror 90. For this reason, the core portion sensor 72 is disposed above the clad portion sensors 71 and 73. With such a layout, an inexpensive commercially available line sensor with high resolution can be used without interfering with the clad sensors 71 and 73. Can be placed.

FIG. 4 is a horizontal sectional view showing still another layout of the light receiving sensor 70 in the structure measuring apparatus 100. As shown in the figure, in this layout, the arrangement of the light source 60 and the clad sensors 71 and 73 is the same as the layout shown in FIG. On the other hand, the core portion sensor 72 is disposed to face a surface adjacent to the surface on which the cladding portion sensors 71 and 73 of the rectangular container 40 are disposed. Further, the light source 62 for the core part is disposed so as to face the surface facing the surface on which the sensor 72 for the core part is disposed. Such a layout greatly increases the degree of freedom related to the dimensions and arrangement of the core sensor 72. In addition, measurement windows 50 are formed on four surfaces of the container 40 so as not to obstruct the optical path of the parallel light 82 that reaches the core light source 62 and the core sensor 72. In addition, it is preferable to consider so that the measurement by the clad sensors 71 and 73 and the measurement by the core sensor 72 do not affect each other. It is also desirable to consider problems caused by adjustment of the measurement position in the longitudinal direction of the optical fiber base material 10, correction of the tilt of the workpiece, and measurement of the same surface.

FIG. 5 is a flowchart F100 showing the structure measuring method performed using the structure measuring apparatus 100 having the above structure, step by step. The figure mainly shows the measurement procedure in the structure measurement method.

As shown in FIG. 5, first, in the suspension device 20 that holds the optical fiber preform 10 in the structure measuring device 100, the rotation function is initialized and the rotation angle is returned to the reference angle ( S100). Next, the suspension device 20 is instructed to start the descent of the optical fiber preform 10 (light 110), and the optical fiber preform 10 is lowered to the measurement start position while being immersed in the matching oil 30 in the container 40 (S120). ). Subsequently, the optical fiber preform 10 is started to be lifted by the suspending device 20 while irradiating the parallel light 80 to the light source 60 optical fiber preform 10 through the measurement window 50 (S130). Next, the intensity distribution of the parallel light 80 transmitted through the optical fiber preform 10 is measured by the light receiving sensor 70 as outer diameter information and position information of the optical fiber preform 10. (S 140). By repeating the measurement related to S 130 and S 140, when the irradiation position of the parallel light 80 reaches the measurement end position of the optical fiber preform 10, the lifting device 20 lifts the bow I of the optical fiber preform 10. Is stopped immediately (S160). Next, the optical fiber preform 10 is rotated by the suspension device 20 at a rotation angle corresponding to a predetermined number of divisions (S180). If the number of rotations does not reach the predetermined number of divisions (S180: NO), the optical fiber preform 10 is lifted again to the measurement start position, and the operations from S120 to S180 are repeated. On the other hand, when the rotation operation in S180 reaches the predetermined number of divisions (S180: YES), the optical fiber preform 10 is pulled up from the container 40, and the suspending device 20 returns to the origin before the start of measurement. (S190). Further, in the structure measuring apparatus 100, the shape calculation of the optical fiber preform 10 described later is performed (S200).

[0037] It should be noted that the number of divisions in the circumferential direction of the optical fiber preform 10 in the rotation operation (S180) (hereinafter referred to as the number of circumferential divisions) is 7 to 20 suitable for measuring the non-circularity of the core diameter. Yes, the numerical force obtained by dividing 360 ° by the number of circumferential divisions This is the angle pitch when the optical fiber preform 10 is rotated in one operation S180. In addition, the number of frequency divisions is V because the data includes noise, so an accurate measurement value was obtained in the case of 20 and a rough non-circularity was obtained at high speed! / 高速5 is good. Even if the number of circumferential divisions is larger than 20, the accuracy is not improved so much. In addition, when the number of circumferential divisions is 16, FFT (Fast Fourier Transform) can be performed, so that detailed examination of the shape can be performed easily. For normal measurement, it is preferable to set the number of divisions to about 10 in consideration of accuracy and measurement speed.

FIG. 6 is a diagram schematically showing the intensity distribution of the parallel light 80 received by the clad part sensors 71 and 73 and the core part sensor 72. Hereinafter, the measurement value accumulation procedure for storing the information obtained by the measurement procedure as described above as data for use in the calculation procedure described later will be described with reference to FIG.

[0039] As shown in FIG. 6, the transmitted light that has passed through the optical fiber preform 10 and the matching oil 30 and reached the light receiving sensor 70 has an optical characteristic of the transmitted substance. A corresponding intensity distribution is formed. Regarding the positions of the clad sensors 71 and 73 and the core sensor 72, when setting up each sensor, replace the round bars having different diameters with the optical fiber preform 10, It is preferable to adjust so that the image projected on each sensor is the same size.

[0040] Therefore, in the parallel light 80 received by the clad sensor 71, 73, the optical fiber The parallel light 80 transmitted through the matching oil 30 without passing through the base material 10 has a uniform Kyoto distribution. On the other hand, the parallel light 80 that has passed through the optical fiber preform 10 has an intensity distribution that changes continuously according to the thickness of the cladding 12 of the optical fiber preform 10. Furthermore, since the surface of the optical fiber preform 10 forms a steep angle with respect to the parallel light 80 at the side end when viewed from the clad part sensors 71 and 73 side, the parallel light 80 Sensors 71 and 73 are hardly reached. Therefore, positions E and E with the lowest received light intensity are

1 4 Corresponds to the position of the outermost edge of the optical fiber preform 10.

In the parallel light 80 received by the core sensor 72, the intensity of the parallel light 80 transmitted through the core part 14 having a high refractive index and the clad part 12 having a relatively low refractive index are provided. There is a difference in the intensity of the transmitted parallel light 80. Furthermore, since the surface of the core part 14 forms a steep angle with respect to the parallel light 80 at the side end of the core part 14 when viewed from the core part sensor 72 side, the parallel light 80 is Almost no part sensor 72 is reached. Therefore, the interval between positions E and E where the light receiving intensity is the lowest in the non-core sensor 72 is the optical fiber preform.

twenty three

Corresponds to the outer diameter of 10 core parts 14.

From the position information obtained from the parallel light 80 received by the clad sensors 71 and 73 and the core sensor 72 as described above, a value necessary for calculation of the structure measurement can be obtained. That is, the pixel position at the upper left end of the clad sensor 73 is “0”, the pixel position at the upper left end of the core sensor 72 is “A”, and the pixel position at the left end of the clad sensor 71 is “B”. In this case, the positions of the side end portions of the cladding portion 12 and the core portion 14 of the optical fiber preform 10 can be expressed as follows. Note that these pieces of positional information may be converted into actual dimensions using a coefficient for converting the pixels obtained separately after being digitized into actual dimensions.

Clad left edge; El,

Clad right end; B + E4,

Cladding diameter; B + E4- El,

Core left end; A + E2,

Core right end; A + E3

Core diameter; E3- E2

Eccentricity: (2A + E2 + E3) Z2— (E1 + B + E4) Z2 Further, as described above, the optical fiber preform 10 is supported by the suspension device 20 in the structure measuring apparatus 100. Further, the suspending device 20 can raise and lower the optical fiber preform 10 and rotate it. Therefore, the position information value obtained as described above is stored in combination with the position and rotation angle of the optical fiber preform 10 when the measurement is executed. Specifically, the lifting and lowering operations in the suspending device 20 are formed by combining ball screws, wheel trains, chains, etc., and the optical fiber is counted by counting the pulses generated by the encoders linked to these members. Information on the elevation position and rotation angle of the base material 10 can be obtained.

[0044] It should be noted that each of the clad part sensors 71 and 73 and the core part sensor 72 is coupled to an individual image processing device, and information on the raising / lowering position and the rotation angle is received from the suspension device 20 in common. As a result, the processing speed of information processing related to the structure measurement can be improved. The image processing apparatus used in such a case can be formed by a personal computer, a board computer, or the like with an appropriate interface and clad. In addition, three image processing boards each incorporating a position detection program can be mounted on a single information processing device, and the image processing results can be calculated at high speed. In this case, information can be extracted quickly and easily by reading the position information written in the memory, but the processing speed of each image processing board and the output timing of the calculation result must be taken into account. In the case of V and deviation, the configuration should be advantageously selected in consideration of cost, processing speed, etc. The measurement results converted into data by the above operations are stored in an information storage means or a recording medium that can be accessed from an information processing apparatus that executes a calculation procedure described later.

[0045] Based on the measurement values converted into data as described above, the non-circularity and the eccentricity of the core portion 14 of the optical fiber preform 10 can be calculated as described later. . However, for the measured values obtained by actual measurement, it is preferable to perform outlier removal processing and shaping processing to interpolate values between measurement positions.

That is, as described above, the measurement in the structure measuring apparatus 100 is performed by the plurality of light receiving sensors 70 while being raised or lowered at each angle rather than being stopped and rotated at each measurement position in the longitudinal direction. It is measured individually. For this reason, there are cases where the measurement position in the longitudinal direction does not match with the data of each angle and each sensor. Interpolation with measured values is performed to shape the data at each angle as the same position data in the longitudinal direction, and based on the core diameter data after shaping, the core non-circularity and bias at each position in the longitudinal direction. Calculate the core ratio. By performing this interpolation, it is possible to eliminate the restriction on the movement speed due to the restriction on the alignment accuracy that does not need to be measured by aligning the measurement position in the longitudinal direction at each angle at the time of measurement. Measurement is possible.

[0047] Further, in the longitudinal direction of the optical fiber preform 10, changes in the diameter of the core portion, the position of the cladding portion, and the like continuously and smoothly change. Therefore, if fluctuations with respect to adjacent measurement values change in particular, this can be excluded as an abnormal value. That is, for example, it is possible to determine that the average of three measured values including adjacent data is within a predetermined allowable range, and to exclude a value exceeding the allowable range as an abnormal value. Specifically, the preferred method is to perform a polynomial approximation of each longitudinal data group, X as the vertical position and Y as the data, and the approximate value falls within a predetermined tolerance. This is a method for judging whether or not there is a problem. According to this method, it is possible to cope with data changes in a long span. For the polynomial approximation, the 6th to 10th orders are appropriate, and if it is less than 6th order, it cannot follow the fluctuation of the original core diameter, and normal values are easily judged as abnormal values. On the other hand, if it exceeds the 10th order, it is easy to pick up consecutive abnormal values and the abnormal values may be judged as normal values, which is not preferable.

FIG. 7 is a flowchart F200 showing the shaping process as described above, following the operation procedure. As shown in the figure, first, the rotation angle (No. 1 in the figure) of the optical fiber preform 10 when the measurement data to be processed is measured is specified (S210). Next, a polynomial approximation is executed from the longitudinal position and the relative outer diameter value of the core portion, and it is determined whether or not each measured value is within an allowable range for the obtained polynomial approximation (S220). ). In this way, abnormal values included in the measured values are eliminated.

[0049] In the measurement value interpolation, first, in the longitudinal direction of the optical fiber preform 10, a position where the calculation of the interpolation value is to be first executed is searched and specified (S230). Next, the previous and next measured values to be referred to when calculating the interpolated value at that position are searched (S240). Furthermore, after checking that the values before and after the reference are not abnormal values (S250), an interpolation value is calculated (S280) and interpolated at that position. The interpolated value D that interpolates between measured values at a specific position X in the longitudinal direction of the optical fiber preform 10 is measured at a position before the position X. Fixed value and pixel position are% and D, respectively, and data after position X is% and D.

In the case of 1 1 2 2, it can be calculated by the following formula [Formula 1].

[Number 1]

[0050] In this way, when an interpolation is made between a certain measurement value and an adjacent measurement value, it is checked whether the interpolation position has reached the end position! /. If the interpolation position has reached the end position (S290: YES), the interpolation processing from S240 to S280 is performed after the position to be interpolated is shifted by a predetermined interval corresponding to the measurement interval (S270). Repeated. On the other hand, if the interpolation position has reached the end position (S290: YES), the angle number of the measured value is checked, and if the angle number has not reached the number of circumferential divisions (S300: NO), in S120 Increase the angle number by one (S260) and repeat the process from S220 force to S290 again. On the other hand, if the angle number has reached the number of circumferential divisions (S300: YES), the process is terminated. In this way, continuous measurement value data can be obtained while removing abnormal values over the entire length of the optical fiber preform 10.

[0051] From the measured value data obtained as described above, the non-circularity can be obtained as follows. That is, the core part relative outer diameter value at a certain angle, when the angle is set to 0, the elliptical component having two cycles in one round is Fourier-analyzed according to the following formula [Equation 2], thereby The amplitude of the component can be calculated.

[Equation 2] v = a-cos (2 + b-sm (ζθ)

[0052] Subsequently, when the amplitude of the cos component in the amplitude of the elliptic component is a and the amplitude of the sin component is b, the ellipticity of the core portion 14 can be obtained according to the following equation [Equation 3]. it can. The ellipticity can be treated as a non-circularity.

[Equation 3]

[0053] The eccentricity of the core portion 14 can be obtained as follows. That is, if the symbols shown in FIG. 6 are used as the value of the cladding position and the value of the core position in one longitudinal position in the data subjected to the shaping process and the interpolation process, a certain angular force optical fiber The amount of eccentricity when looking at the base material 10 can be expressed as the following equation [Equation 4].

Picture p _-day , no 2 ₌ · + Ε ₂ (Θ) + Ε, (Θ) _ _Ει (θ) + Β + Ε (Θ)

twenty two

[0054] At one position in the longitudinal direction of the optical fiber preform 10, assuming that the eccentricity of the core portion when viewing the position from the angle Θ is h, the pulley analysis is performed according to the following equation [Equation 5]. By executing, the eccentricity h, which is one cycle per round, is obtained.

[Equation 5]

h-c-cos (of + d

[0055] Furthermore, assuming that the amplitude of the cos component of the eccentricity h is c and the amplitude of the sin component is d, the deviation divided by the outer diameter value of the clad 12 at that position according to the following equation [Equation 6]: A core rate is required. Therefore, by obtaining the eccentricity for each position in the longitudinal direction of the optical fiber preform 10, a distribution of the eccentricity over the entire length of the optical fiber preform 10 can be obtained.

[Equation 6] Eccentricity = m average ^ l c ^c- ⁺ t ^d ^ 卜 outer ^ 圣^{x 100} [ ^% ] Although the present invention has been described using the embodiment, the technical scope of the present invention Is not limited to the range described in the above embodiment. Various changes or modifications to the above embodiment It will be apparent to those skilled in the art that improvements can be made. It is clear that the embodiment described above can be included in the technical scope of the present invention with such changes or improvements. Industrial applicability

Since the core non-circularity and eccentricity at each position in the longitudinal direction of the base material can be measured efficiently and simultaneously, this contributes to a reduction in the management cost of the base material.

Claims

The scope of the claims

[1] A method for measuring a non-circularity and an eccentricity of a core portion of an optical fiber preform having a core portion and a cladding portion surrounding the core portion,

A base material for moving the optical fiber preform in a direction parallel to the central axis while irradiating the optical fiber preform immersed in the matching oil with directional force light perpendicular to the central axis of the core portion. Material movement operation,

The change in the width of the transmitted light that has passed through the core portion of the light is recorded in association with the amount of movement of the optical fiber preform, and relative to the core portion in the longitudinal direction of the optical fiber preform. Relative outer diameter value distribution measurement operation for measuring the outer diameter value distribution,

The position of the steep contrast generated in the transmitted light that has passed through the boundary between the cladding and the matching oil is recorded in association with the amount of movement of the optical fiber preform, and the longitudinal direction of the optical fiber preform is recorded. The clad side edge position distribution measurement operation to measure the clad side edge position distribution and

Having a measurement procedure comprising

The measurement procedure is executed each time the optical fiber preform is rotated around the central axis to a predetermined rotation angle, and the plurality of relative outer diameter value distributions and the clad side ends associated with the rotation angle are executed. A measurement accumulation procedure to record the position distribution;

Based on the plurality of relative outer diameter value distributions accumulated in the measurement value accumulation procedure and the clad side end position distribution measurement, a plurality of non-circularity ratios of the core part in the longitudinal direction of the optical fiber preform and Calculation procedure to calculate the eccentricity rate and

A structure measuring method comprising:

[2] The structure measurement method according to claim 1, wherein the relative outer diameter value distribution measurement operation and the clad side end position distribution measurement operation are performed using individual light receiving sensors.

[3] The position of the pair of side ends appearing on both side ends of the optical fiber preform is measured using the individual light receiving sensors over the cladding side end position distribution measurement operation. Item 3. The structure measurement method according to Item 2.

[4] A structure measuring apparatus for measuring a non-circularity and an eccentricity of a core portion of an optical fiber preform having a core portion and a cladding portion surrounding the core portion, The optical fiber preform is suspended and moved up and down to displace the optical fiber preform in a direction parallel to the central axis of the core, and the optical fiber preform is rotated around the central axis. A suspension device capable of rotating,

A container that contains an amount of matching oil that can immerse the optical fiber preform, and that allows the optical fiber preform immersed in the matching oil to move up and down by the lifting operation;

A light source that irradiates parallel light in a direction perpendicular to the central axis to the optical fiber preform immersed in the matching oil inside the container;

A light receiving sensor that receives the parallel light irradiated from the light source and transmitted through the optical fiber preform;

With

A base material for moving the optical fiber preform in a direction parallel to the central axis while irradiating the optical fiber preform immersed in matching oil with a directional force light perpendicular to the central axis of the core portion. Material movement operation,

The change in the width of the transmitted light that has passed through the core portion of the light is recorded in association with the amount of movement of the optical fiber preform, and relative to the core portion in the longitudinal direction of the optical fiber preform. Relative outer diameter value distribution measurement operation for measuring outer diameter value distribution, and

The position of the steep contrast generated in the transmitted light that has passed through the boundary between the cladding and the matching oil is recorded in association with the amount of movement of the optical fiber preform, and the longitudinal direction of the optical fiber preform is recorded. Cladding side edge position distribution measurement operation to measure the cladding side edge position distribution

A measurement procedure including:

Each time the optical fiber preform is rotated to a predetermined rotation angle around the central axis, the measurement procedure is executed, and the plurality of relative outer diameter value distributions and the clad side ends associated with the rotation angle are executed. A measurement accumulation procedure to record the position distribution;

Based on the plurality of relative outer diameter value distributions accumulated in the measurement value accumulation procedure and the clad side end position distribution measurement, a plurality of non-circularity ratios of the core part in the longitudinal direction of the optical fiber preform and Calculation procedure for calculating the eccentricity rate and Structure measuring device that performs.

[5] The light receiving sensor separately includes a relative outer diameter value detection sensor used in the relative outer diameter value distribution measurement operation and a side end position detection sensor used in the cladding side end position distribution measurement operation. 5. The structure measuring device according to claim 4, comprising:

[6] The light receiving sensor includes individual light receiving sensors that respectively detect positions of a pair of side edges that appear at both side edges of the optical fiber preform during the cladding side edge position distribution measurement operation. The structure measuring device according to claim 4 or 5.