JPH0362004A - Method for observing optical fiber - Google Patents

Abstract

PURPOSE:To efficiently observe plural pieces of optical fibers with high observation accuracy by dividing the fibers to each of respective fiber groups and observing the fibers when the high observation accuracy is required and integrally observing all the optical fibers when the high observation accuracy is not required. CONSTITUTION:Plural pieces of the optical fibers 1a to 1h are divided to the plural fiber groups. The focus of the liquid crystal system is matched near the centers B2, C2 of the respective fiber groups and the optical fibers are observed by each of the respective fibers via this optical system. The focus of the liquid crystal system is matched near the center A1 of all the optical fibers and all the optical fibers are integrally observed. The fibers are observed by each of the respective optical fiber groups in a range where the blur of the image is relatively small when the high observation accuracy is required. All the optical fibers are simultaneously observed even if the blur of the optical fiber images increases more or less when the high observation accuracy is not required. Plural pieces of the optical fibers are observed with the high observation accuracy in this way.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to optical fibers that are connected to each other, such as when the ends of a plurality of optical fibers are brought together and fusion spliced together. This invention relates to a method for observing the end of a fiber.

[Conventional technology]

When the ends of multiple optical fibers grouped together in a tape are butted against each other and fused together, the angle is perpendicular to the optical axis of the optical fibers and approximately 45 degrees to the tape surface. 2. Description of the Related Art Optical fibers are imaged and observed from two inclined directions through an optical system such as a microscope.

Then, by image processing the obtained optical fiber image, it is possible to determine whether there is any abnormality in the shape of the optical fiber end before fusion splicing, or to determine whether there is any abnormality in the shape of the optical fiber end before and after fusion splicing. The amount of axis misalignment is measured, apI, and the splice loss after fusion splicing is estimated from these results.

[Problem to be solved by the invention]

However, since the optical fibers are observed from a direction oblique to the tape surface, the focal length of the optical system cannot be adjusted to all optical fibers. Therefore, the obtained optical fiber image becomes blurred, and the optical fiber observation accuracy decreases. This decrease in observation accuracy causes a decrease in the measurement accuracy of the amount of axial deviation between the optical fiber ends before and after the fusion splicing, and a decrease in the accuracy in estimating the splice loss after the fusion splice.

This observation accuracy decreases as the number of optical fibers increases and as the arrangement pitch of optical fibers increases.
It gets intense.

Therefore, in view of the above-mentioned circumstances, an object of the present invention is to provide an optical fiber observation method that can observe a plurality of optical fibers with high observation accuracy.

[Means to solve the problem]

In order to achieve the above object, in the optical fiber observation method according to the present invention, a plurality of optical fibers are divided into a plurality of fiber groups, an optical system is focused near the center of each fiber group, and the optical system is The method includes the step of observing the optical fibers for each group of fibers through the optical fibers, and the step of focusing the optical system near the center of all the optical fibers and observing all the optical fibers at once.

[Effect]

With this configuration, when high observation accuracy is required, multiple optical fibers can be observed for each fiber group within a range where the blurring of the optical fiber image is relatively small, resulting in high observation accuracy. If this is not required, all end fibers are observed at once even if the optical fiber image is somewhat blurred.

〔Example〕

Hereinafter, an example will be described in which the optical fiber observation method according to the present invention is applied when the ends of eight optical fibers grouped together in a tape are brought together and fusion spliced. This will be explained with reference to FIGS. 1 to 5.

FIG. 1 schematically shows a fiber observation system in an optical fiber fusion splicing apparatus to which the optical fiber observation method according to the present invention is applied.

The ends of the eight optical fibers 1a to 1h gathered together in a tape shape have their coatings removed and are held one by one in the V-grooves of a fiber holder (not shown). Fiber 18-1 held in fiber holder
The end of h extends in a direction perpendicular to the plane of the paper in FIG. are facing each other. A pair of discharge electrodes 2a and 2b for discharging and heating the optical fibers 1a to 1h are installed on the left and right sides of the optical fiber ends facing each other in this manner.
are provided facing each other in the direction in which they are lined up.

A mirror 3 is retractably inserted between the discharge electrodes 2a12b with its reflective surface perpendicular to the direction in which the optical fibers are arranged, and its reflective surface is directed toward the optical fiber. A light source 5 such as an LED is provided in a direction that is perpendicular to the optical axis direction of the optical fibers 1a to 1h and inclined at approximately 45 degrees to the direction in which the optical fibers 1a to 1h are lined up. The optical fibers 1a to 1h are illuminated by the light emitted from the light source 5. Further, the irradiated light from the light source 5 is reflected by the mirror 3 and is made to enter a microscope 6 provided on the opposite side with the optical fibers 1a to 1h in between. The microscope 6 can be positioned freely in the traveling direction of the light reflected by the mirror 3 and in the direction perpendicular to this direction.
A CCD camera 7 for image reception is integrally provided.

The microscope 6 is equipped with optical fibers 1a to 1 emitted from a light source 5.
The light reflected by mirror 3 after passing through h, or
The light transmitted through the optical fiber after being reflected by the mirror 3 is received, and side transmitted images of the ends of the optical fibers 1a to 1h are formed. In this way, by receiving the light before and after being reflected by the mirror 3, it is possible to generate a beam that is perpendicular to the optical axis direction of the optical fiber and tilted at approximately 45 degrees with respect to the direction in which the optical fibers 1a to 1h are lined up. Lateral transmission images of the end of the optical fiber viewed from two directions can be obtained. The transmitted image obtained here is converted into a signal by the CCD camera 7, and this imaging signal is sent to an image processing circuit (not shown). The image processing circuit performs processing such as binarizing the brightness distribution of the fiber transmission image based on the image signal manually input from the CCD camera 7, and then calculates the shape of the optical fiber end before fusion splicing. It is determined whether there is any abnormality in the
The amount of axis misalignment between the optical fiber ends before and after fusion splicing is measured, and the splice loss after fusion splicing is estimated from these results.

Next, the operation when the optical fiber observation method according to the present invention is applied to the optical fiber fusion splicing apparatus configured as described above will be described with reference to FIGS. 1 and 2. FIG. 2 is a flowchart illustrating an example of a process for collectively welding multi-core optical fibers.

First, the optical fibers 1a to 1h are placed in the V groove (
(not shown) (step Sl). Is the optical fiber V? After being set to g, the set switch is turned on.
(step S2), and the following operations are automatically executed. At this time, the microscope 6 is positioned at a position where the optical axis center of the microscope m6 almost coincides with the light transmitted near the center of all optical fibers (for example, position A2 in Fig. 1), and its focus is at the center. The optical fibers 1d and 1e are placed in the middle of each other. The transmitted image of the end of the optical fiber obtained at this time is as shown in L7 in FIG. 3(a). The outermost optical fiber 1a among the optical fibers 1a to 1h
The transmitted images of optical fibers 1d and 1h are blurred compared to the transmitted images of optical fibers 1d and 1e near the center because the focal length of the microscope is not adjusted. Even so, it is sufficient for visual observation of fiber conditions that do not require high precision, such as whether each optical fiber is accommodated in a V-groove.
Visual observation of the state of the fiber, which does not require such high precision, is performed using this transmitted image.

Next, the microscope 6 is sequentially positioned at positions B2 and c2 shown in FIG. The second fiber group is divided into two fiber groups, and the end face positions, end face intervals, etc. of the optical fibers constituting each fiber group are precisely measured (step S3). FIG. 3(b) shows a transmitted image of the optical fiber when the microscope 6 is positioned at the position 82 and its focus is set between the optical fibers 1b and 1c. The transmission images of the optical fibers obtained in this case are the optical fibers 1a to 1d.
Since the optical fiber 1a is relatively focused,
It is suitable for measurements that require high precision, such as measuring the end face position of optical fibers 1a to 1d, based on this transmitted image.
Precise measurement of the end face position is performed. on the other hand,
FIG. 3(C) shows a transmitted image of the optical fiber when the microscope 6 is positioned at position 02 and its focus is set between the optical fibers 1f and 1g. The transmitted image of the optical fiber obtained in this case is different from the case where the microscope M6 is positioned at the position 82, and the optical fibers 1e to 1h are relatively focused. Therefore, the optical fibers 1e to 1
It is suitable for a total of 1) IIJ which requires high precision, such as a total of 1JIJ of the end face position of the optical fibers e to 1h, and the precise end face positions of the optical fibers e to 1h are measured based on this transmitted image.

Next, the distance between the opposing optical fiber end faces is reduced, and the end faces of the first fibers with the minimum end face distance are matched (step S4).

After this matching, the microscope vL6 is B, B.

2 The optical fibers are sequentially positioned at C1C2 positions, and each fiber group is divided into two groups and observed from two directions, and the amount of axis misalignment, end face angle, etc. before the fusion splicing of the first fibers is precisely determined for each fiber group. It is measured (step S5).

After this measurement, mirror 3 shows the discharge voltage t! ! i! 2a, 2b
They are pulled out from each other and evacuated. Then, a discharge voltage is applied between the discharge electrodes 2a and 2b, and discharge fusion between the optical fibers is performed (step S6). During discharge fusion, the microscope @m6 is positioned at position A1, and the discharge state is observed from the image of the discharge sparks obtained.

After the discharge splicing, the microscope 6 is again sequentially positioned at the positions B-82, ■C1C2, and the amount of axis deviation of each optical fiber after the fusion splicing of the optical fibers is precisely measured for each fiber group. At the same time, each fiber group is precisely inspected for connection defects by external observation (
Step S7). From the amount of axial deviation of the destination fiber measured here, the amount of axial deviation measured before fusion splicing, etc., the splice loss of the optical fiber after fusion splicing is estimated by an arithmetic circuit (not shown).

After the inspection after fusion splicing, there is no need to closely observe the tip fiber, so the microscope 6 is positioned at position A2,
The calculated estimated value of splice loss is displayed on a liquid crystal display means (not shown) or the like (step S9). After that, when the reset switch is turned on, the initial state before the set switch is turned on is restored (step 5).
IO).

In addition, in the embodiment described above, the mirror 3 is connected to the discharge electrodes 2a, 2
This is a case where the present invention is applied to a type of fusion splicing apparatus for optical fibers inserted between the optical fibers 1a to 1h.As shown in FIG.
A light source 5 is disposed above the optical fibers along the direction in which they are lined up, and a light source 5 is disposed diagonally below and to the right of the optical fiber, and the irradiated light from the light source 5 is transmitted by a microscope 6 disposed diagonally below and to the left of the tip fiber. It can also be applied to fusion splicing devices of the receiving type. Furthermore, in the above-mentioned embodiment, a case is explained in which eight fiber optics grouped together in a tape shape are observed, but the number of fiber optics to be observed is not limited to this. The present invention is also applicable to observing 12 optical fibers arranged in a shape. In this case, if high observation accuracy is required, the 12 fibers may be divided into three groups of four fibers each for observation, or the 12 fibers may be divided into four groups of three fibers each. It can also be observed.

Figure 5 shows the relationship between the axis misalignment measurement accuracy of the tip fiber and the total number of optical fibers observed, with the axis misalignment measurement error of the optical fiber where the measurement accuracy decreases the most, that is, the optical fiber located on the outside. ing. When eight optical fibers grouped into a tape are observed at once without applying the present invention, the axis deviation meter δp1 error has an average error of 0.5 μm at the outermost optical fiber. On the other hand, when the present invention is applied to measure the amount of axis misalignment for each of the four optical fibers, the measurement error is suppressed to less than half, with an average of 0.22 μm. That is, the average needle Apj error is 0.
With relatively high accuracy similar to when observing four optical fibers of 22 μm, 8
The amount of axis deviation of the tip fiber will be measured.

Note that if the fiber image obtained by the CCD camera 7 is displayed on an image display means such as a television, it becomes possible to check for poor cutting or abnormal discharge on the end face of the tip fiber on the displayed screen.

〔Effect of the invention〕

As explained above, according to the optical fiber observation method according to the present invention, when high observation accuracy is required, multiple optical fibers are connected to each fiber group within a range where the blurring of the optical fiber image is relatively small. If high observation accuracy is not required, all the fibers can be observed at once. Therefore, a plurality of optical fibers can be observed efficiently with high observation accuracy.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a part of an optical fiber fusion splicing device to which the optical fiber observation method according to the present invention is applied, and FIG. 2 is an operation of the optical fiber fusion splicing device shown in FIG. 1. 3 is a diagram showing a transmitted image of an optical fiber, and FIG. 4 is an optical fiber fusion splicing apparatus to which the optical fiber observation method according to the present invention is applied. FIG. 5, which is a diagram showing a part of a device different from the shown device, is a chart showing the relationship between the axial deviation meter ip+ accuracy and the number of optical fibers observed. las lbs lc, ld, le, 1fs Ig. 1h...Optical fiber, 2a, 2b...Discharge electrode, 3
...Mirror 5...Light source, 6...Microscope, 7...
・CCD Kamef O

Claims (1)

[Scope of Claims] An optical fiber observation method that obtains a side transmission image of a plurality of optical fibers arranged in a line and observes the plurality of optical fibers from the transmission image brightness distribution, the method comprising: Divide the optical fibers into a plurality of fiber groups, focus the optical system for obtaining the side transmission image near the optical fiber located approximately at the center of each fiber group, and separate the plurality of optical fibers into each group. The method includes a step of observing each fiber group, and a step of focusing the optical system near an optical fiber located approximately in the center of the plurality of optical fibers and observing the plurality of optical fibers all at once. An optical fiber observation method characterized by: