JPH03180735A - How to measure the shape of fused fiber - Google Patents

Abstract

PURPOSE:To measure the shape including fusion splicing depth without any destruction by detecting the position of reflected light beam from a fiber surface parallel to a plane where the perpendicular direction of the fiber surface contains both optical axes of a projection system and a light receiving system. CONSTITUTION:Two-unit melt-stuck fibers 1 and 2 are observed through a line sensor 33. At this time, light passing through the slit 22 of the projection system is reflected by the fibers 1 and 2 and made incident on a line sensor 34 as a part of the light receiving system. At this time, the image of a circular image formation range is obtained on the line sensor side and a part of the image is made incident on the sensor 34. Namely, reflected light is generated once at transverse directional center positions (a) and (b) of the fibers 1 and 2 corresponding to the bottom part of the recessed part of the fusion spliced part, reflected light is generated twice at positions (c) and (d) on the fiber flank inside of the peak of the fibers, and multiple reflected light from the reverse surface of the fibers is generated at positions (e) and (f). Then only the reflected light at the position (h) is detected in a cut image.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for measuring the shape of a multi-core optical fiber in which a plurality of optical fibers are arranged in parallel and fused together.

<Prior art> As shown in Fig. 2, the technique of measuring the shape of the fused optical fiber 1.2 is indispensable because the fused state is related to the performance of the coupler manufactured by the subsequent drawing process. is necessary.

In other words, in the situation where the coupler is completed, the third
As shown in the figure, the input power P of the optical fiber 1゜2 into the boat 3 or 4, or the output power P2P3 or P2"p of the boats 5 and 6 relative to Pl, the ratio of H to the output power P2/P,
P, /P, again;yop 2t/P,"P3"/P,'
What determines this is the shape of the fused part.

Therefore, a technique for measuring the shape of the fused portion is essential as a technique for stably manufacturing optical couplers.

An example of a conventional shape measurement technique is measuring the cross-sectional shape of a fiber. in this case,
A fiber is cut with a fiber cutter as shown in the cross section shown in FIG. 2, and the cross-sectional shape is observed under a microscope from the direction shown in FIG. 2a.

However, when measuring the shape of an optical coupler instead of such a destructive inspection, a non-destructive measurement technique is also essential for measuring the performance of the coupler.

A laser micrometer is an example of this non-destructive measurement technology. This laser micrometer has the configuration shown in FIG. 4, and scans a laser beam 7 as a rotating mirror 8 rotates, converts it into parallel light by an F/θ lens 9, and scans a subject 10. The scanning light is focused onto a detector 12 by a condensing lens 11.

Here, since the scanning light reaching the detector 12 is blocked by the subject 10 for a certain period of time, the time interval in which the scanning light decreases is counted by a clock pulse, and the rotation speed of the rotating mirror 8, that is, the scanning speed is measured. By obtaining this, the external shape of the subject 10 can be determined.

<Problems to be Solved by the Invention> However, in the above-mentioned shape measurement, it is not possible to measure up to the fusion depth 1 or 4' shown in FIG. 2. That is, the external dimensions related to the performance of the turntable cannot be obtained by non-destructive measurement as shown in FIG.

An object of the present invention is to provide a shape measurement method that enables shape measurement including the fusion depth by non-destructive measurement.

Means for Solving the Problems> The present invention achieves the above-mentioned objects by fusion splicing of multicore fibers consisting of a plurality of fibers arranged and fused so that the fiber axes are parallel and included in the same plane. In the method of measuring the shape of the part, the normal direction of the plane containing both the optical axes of the light emitting system and the light receiving system by the optical cutting method is aligned with the direction perpendicular to the fiber axis in the plane containing the fiber axis of the multi-core fiber. and detecting the position of the reflected light from the fiber surface where the perpendicular direction of the fiber surface is parallel to a plane including both the optical axes.

<Example> The present invention will now be described in detail with reference to FIG. 1 and FIGS. 5 to 7. FIG. 1 is a block diagram for explaining the method of this embodiment. In FIG. 1, a light projecting system and a light receiving system based on the light sectioning method are arranged on the left and right with the light irradiation part and the light reflection part of the laser beam in the center.

The light projection system includes a light source 20. A light guide 21 is provided, followed by a slit 22, a condensing lens 23, and an objective lens 24 along the optical axis.

On the other hand, the light receiving system includes a camera 33 having an objective lens 31, a condensing lens 32, and a line sensor 34 along the optical axis.

Here, when considering a surface that includes both the optical axes of the light projecting system and the light receiving system using this light cutting method, the slit 22 and the line sensor 34 are arranged so as to coincide with the normal direction of this surface.

Further, the focal positions of the objective lenses 24 and 31 are made to coincide.

In this example, first, the normal direction of the plane constituted by the optical axis of the light emitting system and the optical axis of the light receiving system by the optical cutting method is orthogonal to the fiber axis in the plane constituted by the fiber axis of the 26 fusion fiber. The optical axis of the light emitting system and the optical axis of the light receiving system are aligned so that the normal direction of the plane constituted by the fiber axis coincides with the central axis of the optical axis of the light projecting system and the optical axis of the light receiving system.

Next, the 2-core fusion 11 fiber is observed using the line sensor camera 33. At this time, the light ζ passing through the slit 22 of the light projecting system is reflected by the fusion fiber 1°2 and enters the line sensor 34 which is a part of the light receiving system.

At this time, an image of a circular imaging range shown in FIG. 5 is obtained on the line sensor side (the outer diameter line of the fiber is not actually visible), and a part of the image is incident on the line sensor 34. That is, the widthwise central portion of each of the fused fibers 1 and 2.

The opening corresponds to the top of the fiber - twice-reflected light is generated, the widthwise central part of the fused fibers 1 and 2 E produces the once-reflected light corresponding to the bottom of the concave part of the fused part, and the part C, Second, twice-reflected light is generated on the side surface of the fiber inside the top of the fiber, and multiple reflected light is generated from the back surface of the fiber. In the cut image shown in FIG. 5, the line sensor 34 detects only the elongated portion (reflected light from part E in FIG. 5) perpendicular to the axis of the fused fiber in the imaging range. .

The received light image by the line sensor 34 shown in FIG. 5 is obtained by moving the entire light cutting optical system up and down in the direction of the central axis in FIG. Move as shown. That is, in FIG. 6, the projected slit light of the light cutting optical system is reflected by the fusion fiber and forms a light cut image on the imaging plane 35. In this case, when the light cutting optical system is moved up and down, the reflected light path moves, and if the center is centered on FIG. The image moves left and right (in the direction of the fiber axis).

As a result, the reflected light received by the line sensor changes depending on the vertical position of the light cutting optical system, and this movement causes
Obtain the reflected light from each part of B, H2, H, H, and G.

If the heights of the above-mentioned light-cut optical images when these points come on the line sensor are Z for A, J for B, Zb for E, and Zc for E, then the depth l' of the concave portion of the 26 fused fiber is It is given by the following formula.

If the diameters of the two fibers are the same, Z = z, and if they are different, 2≠zb, so the average depth from the top is determined.

In this way, the reflected light near the point perpendicular to the central axis of the optical axes of the emitter and receiver systems in the area hit by the slit light of the 2° fused fiber is developed two-dimensionally into a line perpendicular to the optical axis of the receiver system. The image is formed on the plane containing the sensor. Then, the entire light cutting optical system is moved up and down in the central axis direction of the optical axis of the light emitting/receiving system, and the height of the light cutting optical system is determined when the reflected light corresponding to the top of the fiber and the bottom of the recess reaches the line sensor. From the difference, the shape of the recess and the depth l' of the recess can be measured.

Here, to describe a specific example, a 2° fused fiber in which two fibers each having an outer diameter of 125 μm were fused together was measured using the method according to the present invention. A halogen lamp was used as illumination light and guided by a bundled optical fiber. As a floodlight lens x50
Use objective, slit width is 30 μm x as 1 imaging lens
A 50mm objective is used, a 20x condenser lens is used as the light receiving system's condensing lens, and the line sensor has a pixel size of 14μm x 14
A device with a total number of elements of 2048 μm was used. A linear encoder with a reading resolution of 0.01 μm was used to read the height of the optical system.

A computer controlled the movement of the optical system, read the linear encoder, and processed the output signal from the line sensor.

The reproducibility of the measured value of the depth V of the recess in 10 repeated measurements was 0.3 μm in standard deviation.

<Effects of the Invention> As described above, by using the method according to the present invention, it has become possible to measure the depth of the recess of a Zc fused fiber, which could not be measured using the conventional method. By incorporating this device into a coupler manufacturing device as an 0NLINE measuring device, it becomes possible to control with high accuracy the amount of fusion in the process of fusion bonding two fibers.

[Brief explanation of drawings]

Fig. 1 is a block diagram for use in an embodiment of the present invention, Fig. 2 is an explanatory diagram of the fiber cutting method, Fig. 3 is an explanatory diagram of the coupler, Fig. 4 is an explanatory diagram of the conventional example, and Fig. 5 is an explanatory diagram of the fiber cutting method. The figure shows the imaging range in the method of the present invention, FIG. 6 is an explanatory diagram of optical path movement, and FIG. 7 is a diagram showing how the imaging range changes during movement. In the figure, 1.2 is a fiber, 22 is a slit, 24.31 is an objective lens, 33 is a line sensor camera, and 22, 2, 2, 2, 2, 3 and 3 are reflection parts. Patent application agent Sumitomo Electric Industries Co., Ltd.

Claims (1)

[Scope of Claim] A method for measuring the shape of a fused portion of a multi-core fiber consisting of a plurality of fibers arranged and fused so that the fiber axes are parallel and included in the same plane, comprising: light projection using an optical cutting method; The normal direction of the plane containing both the optical axes of the system and the light receiving system is made to coincide with the direction perpendicular to the fiber axis in the plane containing the fiber axis of the multicore fiber, and the normal direction of the fiber surface is aligned with the direction that is perpendicular to the fiber axis in the plane containing the fiber axis of the multi-core fiber. A method for measuring the shape of a fused fiber, the method comprising detecting the position of reflected light from the fiber surface that is parallel to the surface of the fused fiber.