CN110954031B - Method for detecting concentricity of core package of optical fiber preform - Google Patents
Method for detecting concentricity of core package of optical fiber preform Download PDFInfo
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
- G01B11/27—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
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- G—PHYSICS
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
- G01B5/24—Measuring arrangements characterised by the use of mechanical techniques for measuring angles or tapers; for testing the alignment of axes
- G01B5/25—Measuring arrangements characterised by the use of mechanical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
- G01B5/252—Measuring arrangements characterised by the use of mechanical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes for measuring eccentricity, i.e. lateral shift between two parallel axes
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Abstract
The invention relates to a method for detecting the concentricity of a core packet of an optical fiber preform rod, which comprises the steps of arranging an optical rod between a light source and a projection plate, wherein the light source, the projection plate and the optical rod are integrated into a whole; turning on a light source, obtaining clear fiber core projection and outer cladding layer projection on a projection plate, taking the central line of a light rod as a rotation axis, taking the rotation of the light rod by 180 degrees around the rotation axis as a detection period, taking the projection line of the central line of the light rod on the projection plate as a zero line, arranging M test sections along the length direction of a fiber core, wherein M is an integer larger than 1, recording the vertical distance difference between two sides of the fiber core projection of each test section and the zero line for one detection angle alpha in each rotation in one detection period, wherein the vertical distance difference is | D1-D2 | and the total recording is (180 °/α) × M times, when | D1-D2 | is maximum, the connecting line of the circle center of the outer cladding layer and the circle center of the fiber core is exactly vertical to the connecting line of the circle center of the outer cladding layer and the center of the light source, and adopting a formula D1/2 (| D1-D20/(d1+ d2)) calculating the core-envelope concentricity of the optical rods, where d is0The actual measured outer diameter of the core.
Description
Technical Field
The invention relates to a method for detecting the concentricity of a core and a cladding of an optical fiber preform.
Background
The global communication industry continues to develop, the rapid increase of the optical fiber demand is promoted, and the competition of the optical fiber industry is more and more intense. In order to further reduce the cost, the upstream product optical fiber preform (also referred to as "optical rod" for short herein) of the optical fiber is made large in size, i.e., "large rod" helps enterprises to control the manufacturing cost.
At present, large-sized optical fiber preforms with diameters exceeding 150mm have been successfully manufactured through innovation of processes and production capacities. Compared with the small-size optical fiber preform, the concentricity of the large-size optical fiber preform is more difficult to control and is an important influence factor for restricting the production qualification rate of the large-size optical fiber preform, so that the through-center degree of each large-size optical fiber preform is extremely necessary to be detected. The concentricity detection equipment owned by an enterprise at present has a certain application range of the outer diameter of the optical rod, and the outer diameter of the large-size optical rod is not suitable for the existing detection equipment as a new product. The extra purchase of the concentricity detection equipment suitable for the large-size light bar undoubtedly increases the production cost of enterprises.
At present, concentricity detection equipment still depends on import, and an autonomous concentricity detection method for development enterprises is one of the tasks of technical upgrading of optical fiber production enterprises.
Disclosure of Invention
The method is used for discussing the detection method of the concentricity of the core and the cladding of the large-size optical fiber preform rod, detecting the concentricity of the core and the cladding based on the optical principle, discussing the theoretical basis, and verifying the accuracy of the detection method by detecting the small-size optical rod and comparing the detection result with the detection result of the conventional detection equipment PK 2600. And finally, detecting the large-size optical rod, verifying the detection result by using an acid washing method, and judging the practicability and accuracy of the detection method applied to the concentricity detection of the large-size optical rod.
The technical scheme adopted by the invention for solving the problems is as follows: a method for detecting concentricity of core packet of prefabricated optical fiber rod includes preparing light source and projection plate, arranging light rod between light source and projection plate, aligning projection plate to light source and parallel light rod to projection plateThe three parts are separated into a line; turning on a light source, adjusting the distance between the light source and a light rod and between the light rod and a projection plate to obtain clear core projection and outer cladding projection on the projection plate, taking the central line of the light rod as a rotation axis, taking the light rod rotating 180 DEG around the rotation axis as a detection period, taking the projection line of the central line of the light rod on the projection plate as a zero line, arranging M test sections along the length direction of the fiber core, wherein M is an integer larger than 1, recording the difference between the vertical distances between two sides of the fiber core projection of each test section and the zero line every time the fiber core rotates by a detection angle alpha in one detection period, recording (180 DEG/alpha) M times together, when the distances between the outer cladding circle center and the fiber core are just vertical to the connecting line between the outer cladding center and the light source center, and defining the concentricity of the light rod by the distance D between the outer cladding center and the fiber core center, the formula D1/2 (| D1-D2 |) × (D)0/(d1+ d2)) the concentricity of the core and the cladding of the optical rod was calculated, where d is0The actual measured outer diameter of the core.
Specifically, the recording method of | d1-d2 | is that aiming at the fiber core projection of each test section on the projection board, the zero point of the scale is aligned to one side edge of the fiber core projection, the position of the scale is kept, the optical rod is rotated 180 degrees, the fiber core projection is inverted 180 degrees relative to the zero line, the distance between the edge of the new fiber core projection on the same side and the zero point of the scale is directly measured by the scale, namely | d1-d2 |
Preferably, the light source is a linear light source and is arranged in parallel with the light bar, and the light bar receives light as uniform and consistent as possible along the axial direction, so that the distortion of projection is reduced.
Preferably, the adjustment of the distance between the light source and the light rod and the distance between the light rod and the projection plate are based on the projection requirement that the projection width of the fiber core is several times of the width of the fiber core, and particularly, the requirement that the boundary of the fiber core projection on the projection plate is clear and distinguishable and the accurate measurement of the fiber core projection can be realized is met.
In order to facilitate accurate measurement, the projection of the fiber core is adjusted to be several times of the actual diameter of the fiber core by adjusting the imaging focal length, so that the projection of the fiber core can be conveniently measured.
Preferably, the axial uniformity of the optical wand can be assessed in terms of concentricity of the different test sections.
Compared with the prior art, the invention has the advantages that: the method is not limited by the specification of the optical rod, can particularly meet the concentricity detection of large-size optical fiber preforms, and has accurate and reliable result. The optical rod is not damaged, and expensive detection equipment is replaced.
Drawings
FIG. 1 is a schematic diagram of a detection principle of a core-envelope concentricity laser detection apparatus;
FIG. 2 is a schematic diagram of a convex lens imaging rule;
FIG. 3 is a schematic diagram of a method for detecting the concentricity of a core and a cladding based on an illumination method according to the present invention;
FIG. 4 is an exploded view of the core-envelope concentricity detection method based on illumination according to the principles of the present invention;
FIG. 5 is a schematic view of a first projection of the illumination-based method for detecting concentricity of a core and a cladding;
FIG. 6 is a schematic diagram of a second projection of the illumination-based method for detecting concentricity of a core and a cladding;
FIG. 7 is a schematic diagram of a third projection of the illumination-based method for detecting concentricity of a core package according to the present invention;
FIG. 8 is a core-envelope concentricity data set using the existing PK2600 apparatus of example 1;
FIG. 9 is a schematic view showing the operation of the detection method of the present invention for concentricity of optical rods in example 1;
FIG. 10 is a schematic view showing the operation of the detection method of the present invention for concentricity of an optical rod in example 2;
in fig. 1, 6 is an emitting end, 7 is a receiving end, and 8 is a light bar, and the light bar rotates for a certain angle and then is tested next time;
9 is a light source, 10 light rod cladding, 11 light rod core layer, 12 projection plate.
Detailed Description
The present invention will be described in further detail with reference to examples.
Currently, the optical wand detection mainly relies on the PK2600 device, and the method for detecting the concentricity of the core and the cladding is to place the optical wand between a laser generator and a laser receiver, where the laser passes through the optical wand and then changes its direction, and the receiver records the position information when receiving the laser, as shown in fig. 1. And obtaining a plurality of position information after testing the same cross section of the optical rod at a plurality of angles, and obtaining the core package concentricity data of the optical rod through calculation.
The cross section of the core part of the optical rod is essentially a convex lens, and the inside of the core part of the optical rod is also provided with a convex lens with higher refractive index. And the convex lens imaging law is shown in figure 2.
The illumination method is to place a light bar in the middle, the left side is a light source, the right side is a projection plate, and the light source, the light source and the projection plate are arranged in a line, as shown in fig. 3, the light source adopts a linear light source and a cold light source.
Because light is propagated along a straight line in the same medium and cannot be reversed, the light rod can be decomposed into three parts, as shown in fig. 4, the half of the outer cladding facing the light source is regarded as a convex lens 1, the wire core is regarded as a convex lens 2 as a whole, and the half of the outer cladding facing away from the light source is regarded as a convex lens 3.
After the light is emitted by the light source, the light passes through the light rod and then a projection is left on the projection plate, the whole projection process is decomposed into three parts, namely three-time projection, the three-time projection is respectively carried out on the three parts of the light rod, and the specific analysis is as follows:
(1) the light is emitted by the light source and projected through the convex lens 1 as a spot W (Y 'X'), see fig. 5. When the light source is far enough away from the convex lens 1, the light spot projection W (Y 'X') is formed on the circular arc ACB by more than twice the focal length of the convex lens 1, and the vertical height Y 'X' thereof is linearly proportional to the vertical height XY of the light source. The distance between the light source and the light bar, namely the OP size, is adjusted, and the light spot vertical height (Y 'X') is changed in equal proportion according to the convex lens imaging rule.
In FIG. 5, P is the center of the light source, O is the center of the light bar, O 'is the center of the fiber core, and P' is the center of the projection W.
(2) The optical rod characteristics determine that the refractive index of the convex lens 2 is higher than that of both the convex lens 1 and the convex lens 3, and the convex lens 2 can be regarded as an opaque obstacle. The spot W (Y ' X ') is illuminated on the convex lens 2 as a second light source to obtain a shadow W ' (i.e., a ' B '), as shown in fig. 6. Since the distance between the light spot W (Y 'X') and the fiber core is fixed, namely the size of OP 'is unchanged, when X' Y 'is changed, A' B 'is changed correspondingly, and the vertical height of the shadow W' (A 'B') is in linear proportion to AB.
(3) The projection W ' (a ' B ') passes through the convex lens 3 leaving a projection W "(B" a ") on the projection plate. According to the law of convex lens imaging in fig. 2, the projection on the projection plate is a real image, the direction is opposite to the original object, and the size is in linear proportion, as shown in fig. 7. The vertical direction of projection W 'is A' B 'size and A' B 'linear proportional relation, and because straight line O' Q is the axis of convex lens, QA 'and O' A 'linear proportional relation, QB' and O 'B' linear proportional relation.
In summary, the fiber core projection formed on the projection plate after the light source passes through the light bar is linearly proportional to the outer diameter of the fiber core itself, and the directions are opposite, that is, QA "is linearly proportional to OA, and QB" is linearly proportional to OB.
The outer diameter of the core can be directly detected by the conventional detection device PK2600 without the limitation of the size of the optical rod, namely the outer diameter AB of the optical rod can be directly measured. Through adjusting the distance (the same horizontal line of three department) between light source, optical wand, the projection board three, adjust projection A "B" to AB's several times size to projection A "B" both sides edge is clear, and it is accurate to facilitate the use scale measurement. The central line of the optical rod (namely the central axis of the outer cladding layer) is taken as a rotating shaft, the optical rod is rotated around the rotating shaft, generally by 180 degrees, theoretically, when the connecting line of the center O ' of the fiber core and the center O of the outer cladding layer is vertical to the connecting line of the center of the light source and the center of the optical rod, the difference between OA and OB is the largest, namely the difference between QA ' and QB ' is the largest.
During recording, the zero position of the scale is aligned to A 'on the projection plate, the A' and the B 'exchange positions after the light rod rotates 180 degrees, and the distance between the B' and the zero position of the scale is the difference value between QA 'and QB'. The geometric relationship in each figure can be known
When the difference between QA "and QB" is the maximum, the calculated OO' is the concentricity of the optical rod.
Experiments verify the accuracy and the practicability of the concentricity detection method.
Example 1
The test method of the invention is verified by taking a small-size optical rod as a detection object.
An 80-bar (bar number: DJ0701B1) is selected, the core diameter is 5.08mm measured by PK2600, the maximum value of the concentricity of the core package is 0.39, the average value is 0.325, and the center deviation of the specific core package is as follows:
| 0 | 36 | 72 | 108 | 144 | 180 | 216 | 252 | 288 | 324 | |
| 700 | 0.341 | 0.501 | 0.441 | 0.297 | -0.005 | -0.341 | -0.501 | -0.441 | -0.297 | 0.005 |
| 400 | 0.588 | 0.773 | 0.71 | 0.416 | -0.145 | -0.588 | -0.773 | -0.71 | -0.416 | 0.145 |
the values in the table are measured for PK2600 after 5 rotations of the light wand (a total of one revolution), with larger values indicating greater deviations of the two centers, and 400 and 700 being the lengths of the two test sections from the handle of the light baseball sampled.
Fig. 8 shows that the maximum deviation of the optical rod core package of the present embodiment is about 36 degrees, and the concentricity of the core package is about 0.773/2, which is 0.386 mm.
As shown in fig. 9, on a built test platform, the concentricity of the same optical rod is detected by the method, the measured deviation angle is consistent with the measured deviation angle, the projection width of the fiber core on the projection plate is about 34.5mm by adjusting the distance between the light source and the optical rod, the projection outer edge deviation of the core rod is about 5.1mm after the fiber core rotates 180 degrees, and the concentricity of the rod-core package can be calculated to be about 0.375mm by combining the core diameter with 5.08mm, which is similar to the measured value of a PK2600 device.
Example 2
The testing method of the invention is verified by taking a large-size optical rod as a detection object
Selecting one 120 rod (rod number: RI0902B2), drawing the optical rod because the optical rod cannot adopt PK2600 to directly detect the concentricity of the optical rod, directly entering a drawing process after heat preservation, and discarding the optical rod because the concentricity exceeds the standard and the optical fiber is withdrawn during initial inspection of the optical fiber. The results of the fiber tests showed a maximum concentricity of 1.15 and an average of 0.76.
As shown in fig. 10, on a built test platform, the projected outer diameter of the fiber core is measured to be about 35.5mm by using the method for detecting the concentricity of the core and the projected outer edge deviation of the core rod after rotating 180 degrees is measured for four times to be 8.3mm, 7.2mm, 6.5mm and 5.8mm respectively. The concentricity of the rod core package can be calculated to be 0.898mm, 0.779mm, 0.703mm and 0.627mm by combining the core diameter of the rod core package with 7.68mm, which is similar to the measurement value of an optical fiber.
After the deviation angle of the rod is marked, the acid washing stage is carried out. And (4) washing off a part of the side with large outer package deviation by acid to adjust the core package deviation. The cleaned optical rod enters a drawing stage, and the concentricity of a core cladding and the out-of-roundness of a cladding in optical fiber data are measured as follows:
as can be seen from the table, after pickling the clad layer, the concentricity value decreased greatly, but the clad layer non-circularity increased significantly. In the reference optical fiber quality parameters, the core-cladding concentricity is required to be not more than 0.6, the cladding non-circularity is not more than 1, and the following suggestions are provided after comprehensive consideration: when the concentricity of the core and the cladding of the large rod is measured by a lighting method, the large rod can directly enter a wire drawing process below 0.3, can be adjusted by an acid pickling cladding method from 0.3 to 0.6, and is judged whether to be subjected to acid pickling after being comprehensively considered from 0.6 to 0.8, and the large rod is discarded after exceeding 0.8.
In conclusion, the two tests are carried out, the illumination method for detecting the concentricity of the optical fiber preform core package is feasible, the test result is accurate, and the operation is simple and convenient. However, there is no standard test platform, so that the detection is difficult to find the projected edge of the fiber core due to more interference factors, and therefore the detection is described as follows:
1. the distance among the light source, the light bar and the projection plate can be adjusted so as to find the optimal focal distance to ensure that the projection is clear. During actual detection, the light rods with different outer diameters need to be searched for the positions of a proper light source, the light rods and the projection plate, so that detection personnel can conveniently and quickly operate to find a clear fiber core projection boundary.
2. The light bar has more surface ripples, the projection distortion is serious after the single-point light source irradiates, and a linear light source is suggested, the length of the linear light source is consistent with the length of the light bar, and a light source with high white light (cold light) brightness is preferred.
3. In order to avoid interference, the whole detection device is required to be installed in a darkroom to eliminate the interference of ambient light.
Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that modifications and variations of the present invention are possible to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A method for detecting concentricity of a core packet of an optical fiber preform is characterized by comprising the following steps: preparing a light source and a projection plate, arranging a light rod between the light source and the projection plate, wherein the projection plate is opposite to the light source, and the light rod and the projection plate are spaced in parallel and form a line; turning on the light source, adjusting the distance between the light source and the light rod, and the distance between the light rod and the projection plate to obtain clear fiber core projection and outer cladding projection on the projection plate, using the central line of the light rod as a rotating shaft, and using the light rodRotating 180 degrees around the rotating shaft to form a detection period, taking the projection line of the central line of the optical rod on a projection plate as a zero line, arranging M test sections along the length direction of the fiber core, wherein M is an integer larger than 1, recording the difference between the vertical distances of two projected edges of the fiber core of each test section and the zero line every time the optical rod rotates by a detection angle alpha in one detection period, namely | D1-D2 |, and recording (180/alpha) M times in total, wherein when | D1-D2 |, the connecting line of the circle center of the outer cladding layer and the circle center of the fiber core is just vertical to the connecting line of the circle center of the outer cladding layer and the center of the light source, and the concentricity of the optical rod is defined by the distance D between the circle center of the outer cladding and the circle center of the fiber core, and then the formula D =1/2 (| D1-D2 |) (D2 × (D)0/(d1+ d2)) calculating the core-envelope concentricity of the optical rods, where d is0Actual detected outer diameters for the fiber cores;
the recording method of the said | d1-d2 | is, aiming at the fiber core projection of each testing section on the projection board, aligning the zero point of the scale to one side edge of the fiber core projection, keeping the scale position still, rotating the optical rod 180 °, making the fiber core projection reverse 180 ° relative to the zero line, and directly measuring the distance between the new fiber core projection edge on the same side and the zero point of the scale by the scale, namely | d1-d2 |.
2. The method for detecting the concentricity of a core pack of an optical fiber preform according to claim 1, wherein: the light source is a linear light source and is arranged in parallel with the light bar.
3. The method for detecting the concentricity of a core pack of an optical fiber preform according to claim 1, wherein: the outer diameter of the projection of the fiber core is adjusted according to the projection requirement that the outer diameter of the projection of the fiber core is several times of the outer diameter of the fiber core, so that the outer diameter of the projection of the fiber core on the projection plate can be accurately measured.
4. The method for detecting the concentricity of a core pack of an optical fiber preform according to claim 1, wherein: and evaluating the axial uniformity of the optical rod according to the concentricity of different test sections.
5. The method for detecting the concentricity of a core pack of an optical fiber preform according to claim 1, wherein: the 180 degrees are integral multiples of alpha.
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| CN111879220B (en) * | 2020-06-29 | 2023-02-21 | 中国电子产品可靠性与环境试验研究所（（工业和信息化部电子第五研究所）（中国赛宝实验室）） | PCB back drilling alignment detection device and method |
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