JPS62208008A - Deciding method for optical fusion splicing condition - Google Patents

Abstract

PURPOSE:To easily and speedily decides whether a connection is made normally or not by extracting the image of a welding part at the time of the fusion, and deciding the splicing condition from position shifts of the rising and falling parts of the light intensity distribution at a specific position. CONSTITUTION:When an optical fiber is fused, the light intensity distribution perpendicular to the axial direction of the fiber 1 is extracted at the connection center 13 of an area which is heated and seen brightly through a television camera and positions 12 and 14 at distance of about the diameter of the fiber 1 from the center 13 to both sides. Position shifts of rise parts ya,u, yb,u, and yc,u and fall parts ya,l, yb,l, and yc,l are observed. When the connection is made normally, those parts do not shift in position. If, however, an air bubble 5 is generated at the connection part 31, the interval between ya,u and ya,l of the light intensity distribution 25 at the center 13 increases and the air bubble can be detected. When the air bubble bursts or when the splicing part becomes a sphere, they can be detected from position shifts. In this way, whether the connection is normal or not is speedily and easily decided, so the method is effectively used to automatic connecting operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for determining the quality of an optical fiber splice when fusion splicing optical fibers.

[Prior Art] When fusion splicing known optical fibers, the following three types of connection failures can be considered.

(1) Due to excessive setting of the distance between the end faces of the pair of optical fibers to be connected, or due to excessive discharge power, the optical fiber 1
The end 2 of is shaped like a bead with a diameter d1 and is not connected. 1st
In the figure, 3 is the center of the beaded end 2.

(2) An air bubble 5 enters the center of the connection, and the connection part 4 becomes a balloon shape with a radius d2 as shown in FIG. 11, or the air bubble 5 blows out and becomes a balloon as shown in FIG. 12. The connection portion 6 has a deflated outer shape d3.

(3) Connection loss is 1 dB or more.

By the way, in the well-known fusion splicing of multimode fibers, if the conditions in the first and second terms do not occur, the splice loss is usually 1 dB or less, and the determination of splice failure is based on the first
This can be determined by the formation of balls shown in Section 1 and the formation of bubbles shown in Section 2.

Now, the automation technology conventionally used to detect balls and bubbles is generally complicated as described below. That is, the state of discharge heating during connection is observed with a television camera, and the state at a certain moment T1 is stored in the memory 8 as a still image 7 in a matrix shape, as shown in FIG. 13(A). .

Next, a certain threshold is set for the degree of shading of the still image, and the still image is differentiated to extract the outline as shown in Figure 13 (B). For each point in the matrix of the contour 9, the deviation d- or dTL from the reference line 10, which has been set in advance as a good case, is calculated, as shown in FIG. 13(C). . Here, the suffix i
indicates the i-th deviation, and U indicates the upper side of the optical fiber contour as L.
indicates the lower side. Depending on the degree of this deviation, it can be determined whether the optical fiber is a ball or whether air bubbles are mixed in.

However, the calculator used for such calculations is
It requires a computer as large as a so-called ordinary minicomputer, and also requires memory for storing still images, so it cannot be used in practical work locations such as inside manholes. Furthermore, regarding calculation time, although it requires a long time to improve the resolution, it usually requires a processing time of several tens of seconds, which has the disadvantage of not being able to meet the demands of on-site judgments that require real-time judgment. have In addition, image information stored as a still image is stored at time T.
1, and has the disadvantage that it requires an enormous amount of processing time to treat the balls and bubbles that occur after T1 each time.

Therefore, when using this technology, the judgment is usually made by accumulating still images after the fusion splicing is completed, but even then, it is unrealistic to require several tens of seconds of processing time, and the optical fiber It is impossible to use it as a judgment technique in automating the connection work.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to solve the problem when heating an optical fiber without causing a delay in the fusion splicing time of the optical fiber.
An object of the present invention is to provide an optical fiber fusion splicing state determination method that quickly determines the state of a spliced part.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a splicing center and two splices on both sides of the splicing center, which are approximately the diameter of the optical fiber 1, when fusion splicing optical fibers. The intensity distribution of the light generated when the optical fiber is heated in the direction perpendicular to the axis of the optical fiber is captured in a linear manner in real time at a total of three locations, and the rising part from the background and the rising part of the intensity distribution are The state in which the optical fibers are connected is determined from the fluctuation in the positions of the two points on the descending portion.

This method is significantly different from the conventional method in which a planar grayscale image is processed within a computer system.

[Materials]

According to the present invention, it is possible to quickly and easily determine whether the state of the optical fiber fusion splicing is good or bad, so when automating the optical fiber splicing work, it is possible to determine whether the state of the spliced part is good or bad by observing the state of the spliced part instead of humans. It has the advantage that it can be used effectively as a technology.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing one embodiment of the invention, where 11 indicates the area where the optical fiber 1 is heated during heating and appears bright in the television camera, in this case a good connection. shows. Reference numerals 12, 13, and 14 indicate a total of three positions a in the X direction, including the connection center for extracting the light intensity distribution and two positions on both sides of the connection center about the diameter of the optical fiber 1.

These are lines indicating b and c.

FIG. 2 shows the light intensity distributions 15, 16, 17 in the X direction on the lines 12, 13, 14 in the X direction, and the maximum light intensities of each are Ia, Ib, and Ic.

When the connection is good in this way, the rising position of the light intensity distribution at each point ycL, □; yb, 1. L;yo, u
and falling position yyu, L; y; ybpJI
C,1 does not change.

Next, FIG. 3 shows a television camera image when the end of the optical fiber becomes a bead, and FIG. 4 shows the light intensity distribution at positions 12, 13, and 14. Here, 18.18° is a bead-shaped region, and this region is heated and appears bright. 1
9, 20.21 are the light intensity distributions at positions 12, 13.14, respectively.

As shown in FIG. 4, when both ends of the optical fiber 1 are beaded, the light intensity distribution 20 at the center position 13 will be at the same level as the background, while the light intensity distribution 19 at the positions 12 and 14 on both sides will be at the same level as the background.
．． In No. 21, the distance between the rising part and the falling part is 1.4 times the diameter of the optical fiber, which is approximately equal to the diameter d1 of the ball. Therefore, it becomes possible to detect the state of the ball.

FIG. 5 shows the temporal variation of the light intensity distribution at the position 14 on one side, where 22 indicates the distribution at the initial stage of heating, and the optical fiber is not beaded. The interval between the rising edge and the falling edge is equal to the diameter of the optical fiber.

23 is the distribution when it starts to form a ball, and the interval between the rise and fall is becoming slightly wider. 21 shows a completely loose distribution.

In this way, a ball can be detected by observing the temporal variation of the light intensity distribution at one position.

Next, FIG. 6 shows a television camera image when bubbles are generated, and FIG. 7 shows a light intensity distribution.

In FIG. 6, 31 is a bubble 5 that is heated and appears bright.
24.25. in FIG. 7.
26 is the light intensity distribution at each point 12, 13, and 14.

When bubbles are generated, only the interval between the rise and fall of the light intensity distribution 25 in the central portion 13 widens, so that the bubbles can be detected from this difference. Here, when the interval between the rise and fall of the light intensity distribution 25 fluctuates by ±20% or more compared to the interval at the initial stage of heat fusion during the fusion splicing time, for example during the stable discharge time, the connection part 31 bubble 5
It can be determined that this has occurred.

Of course, as in the case where a ball is generated, the central part 13
You may also observe temporal fluctuations in the light intensity distribution 25.

Next, FIG. 8 shows a television camera image when bubbles are generated and then ejected and collapsed, and FIG. 9 shows a light intensity distribution.

In Fig. 8, 27 indicates an area where bubbles are collapsed and appear bright.In Fig. 9, 28, 29, and 30 indicate each point 1.
2, 13, and 14 are shown.

In this case, only the interval between the rise and fall of the light intensity distribution 29 in the central portion 13 becomes narrower, so that the collapse of the bubble can be detected.

As explained above, by observing the light intensity distribution linearly in the direction perpendicular to the axial direction of the optical fiber at the heating center of the optical fiber and the positions on both sides thereof, which are about the diameter of the optical fiber, ) When the optical fiber is well connected, (2) both ends of the optical fiber become beaded,
Three states can be distinguished: (3) when no connection is made and (3) when bubbles are generated at the connection.

By the way, the light intensity distribution inside such a TV camera is
It can be easily observed by using a commonly available television signal processing device (for example, Hamamatsu Photonics C-1000, etc.). Furthermore, the rise and fall positions can be transferred as coordinates to a general-purpose microcomputer in real time. Therefore, the degree of displacement of each point can be detected by comparing the coordinates sent one after another. In terms of time order, one coordinate capture can be considered to take several m5ec. This time is approximately 1,710,000 in the prior art described above.

Therefore, in the present invention, it is possible to judge the quality of an optical fiber fusion splicer at high speed using a simple device.

[Effects of the Invention] As explained above, according to the present invention, it is possible to quickly and easily determine whether the state of the optical fiber fusion splicing is good or bad. It has the advantage that it can be effectively used as a discrimination technology to observe the state of the product and judge whether it is good or bad.

[Brief explanation of drawings]

Figures 1 to 9 show how various optical fiber connections are observed using the embodiments of the present invention; Figure 1 is a schematic diagram showing a television camera image of a good connection; Fig. 2 is a distribution diagram showing the light intensity distribution according to the present invention, Fig. 3 is a schematic diagram showing a television camera image when the connection part becomes a ball, and Fig. 4 shows the light intensity distribution at each point in that case. Figure 5 is a diagram showing the temporal variation of the light intensity distribution on one side of the diagram, Figure 6 is a schematic diagram showing the television camera image when bubbles occur, and Figure 7 is the light intensity distribution at that time. Figure 8 is a schematic diagram showing the TV camera image when seven bubbles are collapsed, Figure 9 is a distribution diagram showing the light intensity distribution, and Figure 1O is a diagram showing the optical fiber connection part that has become bead-shaped. Figure 11 is a schematic diagram showing the connection where bubbles have occurred, Figure 12 is a schematic diagram showing the connection where bubbles have occurred.
The figure is a schematic diagram showing a connection when a bubble collapses. Figures 13 (A) to (C) are conventional techniques in which images of the connection are captured as still images into the computer's memory, and this information is then differentiated. FIG. 3 is a conceptual diagram showing how the deviation from the reference position is calculated after the calculation is performed. DESCRIPTION OF SYMBOLS 1... Optical fiber, 2... Ball-shaped end of optical fiber, 3... Center of ball, 4... Connection where bubbles are generated, 5... Air bubbles, 6... 7. A still image of the optical fiber stored in the memory 8 of the computer. 9. Outline of the optical fiber. 10. Standard. Line, 11... Area that appears bright when there is a good connection, 12.1
3.14...Light intensity distribution measurement position, 15.16.17
...Light intensity distribution, 18.18°...A region that appears bright in a bead shape, 1
9.20, 21, 22, 23.24, 25, 26.28
2930...Light intensity distribution, 27...A region where bubbles are generated and further squirted and appear bright, 31...A region where bubbles are generated and appear bright.

Claims (1)

[Claims] 1) In determining the connection state when fusion splicing optical fibers, an image of the fused portion of the optical fiber is taken out during the fusion splicing, and in the image of the fused portion, Extract the light intensity distribution in the direction perpendicular to the axial direction of the optical fiber at the connection center of the fused portion and at two positions separated from the connection center by about the diameter of the optical fiber, and determine the rise of the light intensity distribution. 1. A method for determining an optical fiber fusion splicing state, characterized in that the fusion splicing state of the optical fiber is determined by observing positional fluctuations of a falling part and a falling part. 2) In the method for determining the state of optical fiber fusion splicing as set forth in claim 1, the optical fibers are connected by heating and fusion by electric discharge, and within the stable discharge time, the rising part of the light intensity distribution and A method for determining the state of an optical fiber fusion splice, characterized by observing a change in the position of a trailing edge. 3) In the method for determining the state of optical fiber fusion splicing according to claim 1 or 2, the rise and rise of the light intensity distribution at positions spaced about the diameter of the optical fiber on both sides from the center of the connection A method for determining an optical fiber fusion splicing state, comprising: determining that the optical fiber has not been spliced when the distance between the positions of the descending portions is 1.4 times or more compared to when the fusion was started. 4) In the optical fiber fusion splicing state determination method according to claim 1 or 2, the interval between the positions of the rising and falling parts of the light intensity distribution at the splicing center is within the fusion splicing time. A method for determining the state of an optical fiber fusion splice, characterized in that it is determined that a bubble has entered the splicing portion when the spacing varies by ±20% or more compared to an initial spacing. 5) In the method for determining the state of optical fiber fusion splicing according to claim 1 or 2, observation is made at the splicing center and a second position spaced from the splicing center on both sides by about the diameter of the optical fiber. A method for determining the state of optical fiber fusion splicing, characterized in that it is determined that a good splice has been made when the interval between the rising and falling positions of the light intensity distribution does not vary within the fusion splicing time.