JPH03102304A - Axis aligning method for optical fiber - Google Patents

Abstract

PURPOSE:To suppress connection loss below a targeted value at all times by measuring the quantity of a relative axis shift between optical fiber end parts to be connected and adjusting the heat time of a connection part according to the shift quantity. CONSTITUTION:The tip parts of the optical fibers 1 and 2 to be connected are irradiated by a light source 7 and a transmission image is photographed by a CCD camera 10 through a magnifying lens 8. The transmission image is converted into a video signal, which is sent to an image processing part 11 and converted into a binary value, then the relative axis shift quantity of the connection part is measured. This measured value is sent to a central control part 12 to retrieve the shortest discharge time corresponding to the axis shift quantity from a discharging time map stored previously in a ROM and a specific discharging voltage is applied to discharging electrodes 6a and 6b through a discharging control part 13. Consequently, even if an initial shift quantity is large, the connection is made with lower loss than the targeted value.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for aligning optical fibers.

[Conventional technology]

When performing fusion splicing of optical fibers, splicing loss is reduced by aligning the axes of the optical fibers to be spliced.

As a method of aligning the mutual axes of optical fibers, when the ends of the optical fibers that are butted against each other are melted and connected, the surface tension of the fused optical fibers causes the mutual axis misalignment of the optical fibers to be connected. A method is known that utilizes the self-centering effect, which naturally corrects the problem.

In this method, even if there is some relative axis misalignment between the ends of optical fibers that are butted against each other, fusion splicing is performed by discharge heating in that state, and the heating time is relatively long (for example, , about 15 seconds). By allowing a longer heating time in this way, the outer diameter of the cladding, which was misaligned before connection, is naturally aligned due to the surface tension of the molten cladding, and the core is aligned accordingly. .

When fusion splicing multiple optical fibers at once,
Since it is difficult to precisely align the axes of all the optical fibers and butt them together, the alignment method described above is suitable.

[Problem to be solved by the invention]

However, conventionally, the time for heating the optical fiber to produce the self-aligning effect due to surface tension is fixed at a time determined from the results of preliminary experiments, and the amount of initial axis misalignment before connection is fixed. Regardless of the situation, the optical fiber was heated uniformly. The heating time of the optical fiber determined by preliminary experiments is set to a relatively long time (for example, 15 seconds) in order to sufficiently reduce the splice loss even if the initial axis misalignment is large to some extent, in order to increase the yield. ).

For this reason, if the initial axis misalignment before connection is relatively small, even though it is possible to connect with low loss in a relatively short heating time, the discharge will occur more than necessary, causing wear and tear on the discharge electrode. The result was that the process was accelerated. In addition, if the initial axis misalignment was unexpectedly large, the self-aligning effect occurred at a slow rate, so the splice loss could not be reduced completely within the fixed heating time as described above. .

Therefore, in view of the above-mentioned circumstances, an object of the present invention is to provide an optical fiber alignment method that can suppress the wear and tear of the discharge electrode and realize a low-loss connection even if the initial axis misalignment is large. It is said that

[Means to solve the problem]

In order to achieve the above object, in the optical fiber alignment method according to the present invention, the amount of relative axis deviation between the ends of the optical fibers to be aligned is measured, and the connection between the ends of the optical fibers is determined. The heating time is adjusted according to the measured relative axis deviation amount.

[Effect]

With such a configuration, in the optical fiber alignment method according to the present invention, splice loss due to optical fiber axis misalignment can be reduced to an acceptable level with the minimum necessary discharge heating time depending on the amount of initial axis misalignment. The loss is reduced below the possible loss target value.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a block diagram of an optical fiber fusion splicing apparatus to which the present invention is applied.

As shown in the figure, the ends of a plurality of optical fibers 1 and 2 held together in a tape shape have their coatings removed, and V?
A plurality of V?s formed on the top surfaces of m blocks 3 and 5? g(
(not shown) and are held one by one. Then, (2) the relative positional relationship between the groove blocks 3 and 5 is adjusted so that the ends of these optical fibers 1 and 2 are opposed to each other.

Discharge electrodes 6a and 6b are provided near the ends of the optical fibers 1 and 2 facing each other in the direction in which the optical fibers are arranged, with the ends of the optical fibers in between. A high voltage required for discharge is applied between the discharge electrodes 6a and 6b by a discharge voltage circuit 15, and this voltage application causes a discharge arc to fly between the electrodes and heat the end of the optical fiber. Ru. and,
After the end portions of the optical fibers start being heated by electric discharge, the optical fibers are immediately pushed together to perform fusion splicing of the optical fibers.

Furthermore, light i is placed above the ends of the opposing optical fibers 1 and 2.
19f7 is arranged, and an optical system such as a magnifying lens 8 and a CCD camera 10 are arranged below.

The light emitted from the light source 7 passes through the ends of the optical fibers 1 and 2 and enters the CCD camera 10 via the magnifying lens 8. A lateral transmission image of the area can be obtained. The fiber transmission image obtained here is converted into a video signal and sent to the image processing section 11. The image processing unit 11 performs processing such as binarizing the brightness distribution of the fiber transmission image based on the video signal related to the fiber transmission image inputted from the CCD camera 10, and then connects the opposing optical fiber ends to each other. The previous relative axis deviation amount (initial pongee deviation amount) etc. are measured with high precision.

The measurement results here are manually input to the central control unit 12. The central control unit 12 is composed of a CPU% ROM SRAM, a clock, etc., and can reduce the connection loss to a loss target value or less according to the input measurement result of the initial axis deviation amount from the discharge time map stored in advance in the ROM. The minimum necessary discharge time is searched, and a discharge signal corresponding to this is output to the discharge control section 13.

Note that the search for the discharge time is performed, for example, according to the largest initial axis deviation amount among the initial axis deviation amounts of the plurality of pairs of optical fibers. The discharge time map will be described later.

Discharge control unit 13 receiving a discharge signal from central control unit 12
controls the discharge high voltage circuit 15 according to this discharge signal. The discharge high voltage circuit 15 is configured to apply a predetermined high voltage necessary for discharge between the discharge electrodes 6a and 6b for a time corresponding to the discharge signal under the control of the discharge control section 13.

FIG. 2 shows the relationship between the splice loss due to optical fiber axis misalignment and the discharge heating time as a graph in which the horizontal axis represents the discharge heating time and the vertical axis represents the splice loss. As shown,
Optical fiber splice loss due to axis misalignment decreases as discharge heating time increases. If the initial misalignment before connection is small, the connection loss due to misalignment will be reduced to below the tolerable loss target value in a relatively short discharge time of 10 seconds or less, and the initial misalignment will be It is understood that even if the connection loss is large, the connection loss will be reduced to below the loss target value by discharging for about 20 seconds.

Therefore, since there is such a relationship between splice loss due to optical fiber axis misalignment and discharge heating time, it is necessary to increase the discharge time depending on the initial axis misalignment amount of the optical fiber when the initial axis misalignment amount is large. A discharge time map is prepared such that the discharge time can be shortened as the initial axis deviation amount becomes shorter, and this map is stored in advance in the ROM of the central control unit 12 as described above.

FIG. 3 shows an example of a discharge time map. According to this map, when the amount of initial axis deviation is the maximum allowable value (d), the central control unit 12 outputs a discharge signal to make the discharge ■ax heating time the maximum of 20 seconds, and the initial axis deviation is As the amount becomes smaller, the discharge heating time is shortened, and a discharge signal is outputted to make the discharge heating time at least 8 seconds.

This makes it possible to reduce the splice loss due to optical fiber axis misalignment to an allowable loss target value or less in the minimum necessary discharge heating time.

The present invention was applied to the above-described optical fiber fusion splicing apparatus to perform fusion splicing of single mode multi-core optical fibers. As a result, as shown in Table 1, the average value of the connection loss between optical fibers remained almost the same and the standard deviation became smaller compared to the conventional case. Furthermore, wear and tear on the discharge electrodes 6a and 6b was suppressed, and their durability was approximately 1.5 times that of the conventional one (see Table 1).

Table 1> By the way, in the above-mentioned embodiment, the case where the present invention is applied when connecting multi-core optical fibers has been described.

However, the method for aligning optical fibers according to the present invention is not limited to this, and it is desirable to perform additional discharge heating on the spliced portion of already spliced optical fibers, correct the residual misalignment, and further reduce splicing loss. It can also be applied in cases.

Using the above-mentioned optical fiber fusion splicing device, first measure the amount of axis misalignment on both sides of the spliced part of the fusion spliced optical fiber,
When additional discharge was performed for a corresponding period of time to additionally heat the connection part, as shown in Figure 4, compared to the case where additional discharge was performed uniformly for a certain period of time (for example, 10 seconds) with a conventional connection device, the The connection loss could be effectively reduced.

FIG. 4(a) is a graph showing the change in splice loss when optical fiber axis alignment is performed by additional discharge by applying the present invention, and FIG. It is a graph showing a change in connection loss when additional discharge is performed for a certain period of time.

〔Effect of the invention〕

As explained above, in the optical fiber alignment method according to the present invention, the splice loss due to the axis misalignment of the optical fiber can be set to an allowable loss target with the minimum necessary discharge heating time according to the amount of initial axis misalignment. It is designed to be reduced below the value. Therefore, wear and tear on the discharge electrodes can be suppressed, and even if the amount of initial axis misalignment is large, a connection with low loss can be realized. Further, since the desired connection efficiency can be obtained with the minimum necessary discharge heating time, the working time can be shortened.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an optical fiber fusion splicing device to which the optical fiber alignment method according to the present invention is applied, Fig. 2 is a chart showing the relationship between optical fiber splice loss and discharge heating time, and Fig. 3 The figure shows a discharge time map, and FIG. 4 shows the change in connection loss due to additional discharge. 1, 2...Optical fiber, 3, 5...V groove block,
6 a s 6 b...Discharge electrode, 7...Light source, 8
...Magnifying lens, 10...CCD camera, 11...
- Image processing unit, 12... Central control unit, 13... Discharge control unit, 15... Discharge voltage circuit.

Claims (1)

[Claims] A method for aligning optical fibers for batch fusion splicing of multi-core optical fibers, the method comprising: aligning the ends of a group of optical fibers with the ends of another group of optical fibers aligned therewith; The amount of axis misalignment relative to the end is measured,
Optical fiber alignment, characterized in that a time period for heating a connecting portion between an end of the group of optical fibers and an end of the other group of optical fibers is adjusted according to the amount of relative axis misalignment. Method.