JPS6228635A - Inspecting method for cut section of optical fiber - Google Patents

Abstract

PURPOSE:To easily identify the condition of the cut section and an optical fiber, by detecting the acoustic emission produced when the optical fiber is cut with a sensor. CONSTITUTION:After an optical fiber (not shown in the figure) is set on a plate spring 1 or optical fiber guiding plate 7, a fine streak is formed in the surface of the fiber with an edge 2. Then the optical fiber is cut by giving a bending stration to the fiber by bending the plate sprint 1. Since the stress- strain energy is released at the moment when the optical fiber is cut, an acoustic pulse (acoustic emission) is produced at the time of destruction. The acoustic pulse is detected with a sensor 8 and observed by means of an oscilloscope 10 through an amplifier 9. Since the acoustic emission is continuously observed for a period of about three seconds when the cut section becomes a flat perpendicular face, the cut condition can be identified easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for inspecting a cut surface of an optical fiber for determining whether the cross-sectional shape of a cut optical fiber is acceptable or not.

(Prior art) In the conventional optical fiber cutting method, the surface of the optical fiber to be cut is made minute scratches with a sharp blade made of diamond or steel, and then the optical fiber is cut by applying tensile force and bending force. This method is commonly used. In addition, as a special example, a method is used in which a carbon dioxide laser beam is used to melt a small area on the fiber surface and cause a small scratch, and then tensile force and bending force are applied, or a thin metal wire is wound around the fiber. A method has been proposed in which a temperature gradient is generated within the fiber using heat generated by passing an electric current through the fiber, and the fiber is cut using thermal stress.

Both methods make use of the phenomenon of fiber destruction, and after making a small scratch that becomes the starting point for fracture, when stress is applied to this scratched part, the scratch progresses greatly, making it difficult to cut the fiber. reach. Therefore, if the fracture progresses in a direction perpendicular to the fiber, the cut plane will be a good vertical plane.

However, with conventional technology, bending stress is applied manually during cutting, so the conditions do not necessarily match each time the cutting is made, resulting in the cut surface being slanted, or in extreme cases buckling and not being flat. In some cases.

If such a cutting failure occurs, it becomes necessary to re-cut the fiber when measuring optical loss, connecting fibers, etc., and there is a drawback that the working capacity is reduced. Furthermore, the outer diameter of the fiber is as small as 125 μm, and it is not possible to visually determine if the cut has failed, so the cut surface must be observed using a microscope, etc.
Another drawback was that it could not be identified in a short time.

(Problem to be solved by the invention) Immediately after cutting the optical fiber, by a relatively simple method,
It is an object of the present invention to provide a method for inspecting a cut surface of an optical fiber, which can identify the quality of the cut surface of an optical fiber in a short time.

(Means for Solving the Problem) The present invention places a sensor near the optical fiber cutting point that can detect acoustic emissions generated when cutting the optical fiber, so that the cut surface becomes a good vertical mirror surface immediately after cutting. identify whether it is or not.

FIG. 1 is a configuration diagram of an embodiment of the present invention, where ■ is a leaf spring, 2 is a blade, 3 is an arm, 4 is a shaft, 5 is a holding plate, 6 is a spring, 7 is an optical fiber guide plate, 8 is an acoustic emission sensor, 9 is an amplifier, and 10 is an oscilloscope.

Parts 1 to 7 are equivalent to conventional optical fiber cutters,
After setting the optical fiber on the leaf spring 1 or the optical fiber guide plate 7, a blade 2 is used to create minute scratches on the surface of the optical fiber, and then the leaf spring 1 is bent to give a bending strain to the optical fiber. Cut. At the moment the optical fiber breaks, the stress and strain energy applied to it is released, so an acoustic pulse is generated at the time of breakage.
Propagates through optical fiber.

This acoustic pulse is called acoustic emission, and by observing this acoustic emission, the state of destruction can be known.

In the present invention, an acoustic emission sensor 8 is disposed in an optical fiber cutter, and the pulse of acoustic emission at the time of break is amplified by an amplification a9, and observed with an oscilloscope 10 to identify whether the cut surface of the optical fiber is good or bad. .

Figure 2 shows the observed pulses; (a) is the pulse when the cut surface is a good vertical plane, and (b) is the pulse when the cut surface is broken in a complicated way and is not flat. be. If the cut plane is a clean vertical plane, acoustic emissions are observed to last for about 3 m5ec.

The interval between individual pulses is approximately 2.5 μsec, and the aggregate form of these pulses is shown in Figures 2 (a) and (b).
A waveform like the one shown is observed. If the cut surface is complexly fractured, as shown in Figure 2 (b), 10m5ec.
The acoustic emissions described above can be observed. Fracture surfaces with complex shapes tend to occur when large strain energy is released, and are often observed when fracture occurs under high loads. This is because, since the released energy is large, the energy required for the growth of flaws at the time of fracture is also large, resulting in the fractured surface having a complicated shape.

Therefore, acoustic emission pulses are also observed over a long period of time.

Therefore, by observing the entire acoustic emission waveform, it is possible to judge whether the cut surface is good or bad.

Furthermore, by making good use of the above-mentioned characteristics, if an acoustic emission pulse continues for 10 m5ec or more, a buzzer sounds an alarm, so that the quality of the cut surface can be determined at the moment of cutting.

(Effects of the Invention) As explained above, in the method for inspecting the cut surface of an optical fiber according to the present invention, it is possible to identify the quality of the cut surface immediately after cutting, so that the optical fiber can be cut cleanly when measuring or connecting the optical fiber. If necessary, it only takes a short time to re-cut the cut due to a defect, which has the advantage of shortening the working time.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIGS. 2(a) and 2(b) are diagrams showing acoustic emission pulses when cutting an optical fiber. 1 Leaf spring 2-blade 3 Arm 4 Shaft 5 Holding plate 6 Spring 7 Optical fiber guide plate 8 Acoustic emission sensor 9 Amplifier
10 Oscilloscope patent applicant
Nippon Telegraph and Telephone Corporation Figure 1, 1 5. q-added nose 10-1 year old sheas score

Claims (1)

[Claims] 1. After creating small scratches on the surface of the optical fiber with a blade,
The optical fiber is cut by applying tensile force and bending force to the optical fiber, and immediately after that, an amplifier amplifies the output signal of a sensor that can detect the acoustic emissions generated when the optical fiber is cut, which is placed near the optical fiber cutting point. A method for inspecting a cut surface of an optical fiber, characterized by inspecting the quality of the cut surface by identifying it with an oscilloscope.