JPH03118502A - Manufacture of laser fiber bundle - Google Patents

Abstract

PURPOSE:To suppress a leak of a refrigerant and a decrease in transmission efficiency without deteriorating fibers themselves by heating and pressing the fibers and splicing an end surface of a fiber bundle by fusion. CONSTITUTION:Both terminal parts 21 of the laser fiber bundle 1 are projected from a pipe 5 and their tips are bundled and tightened up with metallic wires 6 so as to facilitate their handling in a next process. The laser fiber bundle 1 is inserted into a press mold 8. A heater for heating and a thermocouple 10 are incorporated in the molds 8a and 8b and the side of insertion into a molding part S is tapered 7 decreasing in diameter from the external end part to the inside. The fiber bundle 1 is pressed while shifted in the circumferential direction and then laser fibers at the end part of the laser bundle 1 are spliced by fusion without any gap.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for manufacturing fiber bundles, and is particularly applicable to laser fiber bundles that require heat resistance and end sealability to improve reliability. It is something that can be done.

[Prior Art] Conventionally, in order to use a fiber bundle formed by bundling a plurality of fiber strands as an optical path, in particular, the end portion of the fiber bundle facing the light source or receiver has been bundled and the end face has been shaped. is being carried out. That is, the end portion of the fiber bundle is fixed by filling the gap between the fiber strands.

Conventionally, methods for forming the end portions of fiber bundles into bundles include methods using an organic adhesive, methods using a low-melting point glass fusion method, and methods using a boric acid elution etching method.

The method using an organic adhesive involves inserting a fiber bundle into a holder, applying an organic adhesive, such as a thermosetting epoxy resin adhesive, to both ends of the fibers from the east end face of the fibers, and curing the fibers to secure the ends. After that, the end faces are polished to produce a fiber bundle.

Further, as a method using low melting point glass, there is a technique described in, for example, Japanese Patent Application Laid-Open No. 55-65907. According to this, low melting point glass is powdered (approximately 10 μm
A suspension of low melting point powdered glass is created by pulverizing the fibers (before and after) and mixing with a solvent such as alcohol, and the low melting point powdered glass is infiltrated into the gap between the fiber strands at the end of the fiber bundle. . Then, the end portion of this fiber bundle is heated to melt the low melting point powdered glass and fix the fiber strands to produce a fiber bundle.

Furthermore, as an acid elution etching method, for example,
There is a technique described in, for example, Japanese Patent No. 2-15491. According to this method, multiple fiber wires are packed into a glass pipe that dissolves well in acid to form a fiber bundle of any thickness, and after making sure that both ends of the fiber bundle do not dissolve in acid, Melt only the glass pipe by dipping it into the solution. In this way, the fiber bundle is manufactured by leaving the glass pipes at both end portions and leaving the other intermediate portion as only the fiber bundle with the glass pipes removed.

[Problems to be Solved by the Invention] However, while there are no problems when the above-mentioned method is applied to fiber bundles used for purposes other than lasers, there are problems especially when applied to laser fiber bundles used as laser media. is problematic. That is, unlike ordinary fiber bundles used as optical paths for weak light from incandescent bulbs and light emitting diodes, laser fiber bundles used as laser media generate heat, so they must have heat resistance and sealing properties for cooling. is required. This will be explained with respect to the laser oscillation device shown in FIG. 2, for example.

Figure 2 shows a Xe flash lamp 2 for pulse laser use.
2 and a laser fiber bundle 2 as the laser medium.
FIG. 3 is a conceptual diagram of the configuration of a laser emission device in which No. 3 is used. A Xe flash lamp 22 and a laser fiber bundle 23 are built into the lamp house 25, and the laser fiber bundle 23 is excited by the Xe flash lamp 22.
Laser oscillation occurs inside the lamp house, and this laser is amplified by repeating reflection between a total reflection mirror 26 and a semitransparent reflection mirror 27 provided outside the lamp house 25 via the laser fiber bundle 23, and a semitransparent reflection mirror 27 is provided outside the lamp house 25. It is adapted to be taken out from a transparent reflecting mirror 27.

Here, the laser fiber bundle 23 generates heat during laser oscillation. This generation of heat significantly deteriorates the oscillation characteristics of the laser fiber bundle 23. In order to avoid this deterioration, a cooling medium 28 is allowed to flow inside the lamp house 25. In order to efficiently cool the laser fiber bundle 23, the fibers in the middle part of the laser fiber bundle 23 are not fixed and are left in a free state, but the end part 24 supported in the lamp house 25 is cooled by a cooling medium. 2
Each fiber strand is firmly fixed and sealed to prevent leakage. Note that if the refrigerant is a gas, the leaked gas will be dissipated, so airtightness is not required as strictly as long as the gas is not harmful. This can cause serious problems in the operation of the device, so particularly high sealing performance is required. A liquid that does not deteriorate the laser medium, such as water, which has high refrigerant efficiency, is generally used as a coolant in a laser oscillation device.

The above is an overview of the laser oscillation device, and as can be understood from this, the laser fiber bundle is particularly required to have heat resistance and sealability.

Now, when the manufacturing method of each of the above-mentioned fiber bundles is applied to the above-mentioned laser fiber bundle, the following problems occur.

First, in the method using organic adhesive, the heat generated during laser oscillation melts the organic adhesive between the fiber strands at the end of the laser fiber bundle, creating a gap between the fiber strands. Therefore, the sealing performance is deteriorated, and the coolant that cools the laser fiber bundle leaks to the outside, and the coolant exhibits a lens effect, causing the optical axis with the reflecting mirror to shift and causing the laser to no longer oscillate. Furthermore, there was another drawback in that the organic adhesive that had dissolved out adhered to the end face of the bundle end portion, leading to deterioration of oscillation efficiency.

On the other hand, in the method of brazing the end portion of the bundle with low melting point glass described in JP-A-55-65907, the fibers may be bent due to heat during fusion, and the low melting point glass may not fit between the fiber strands. Therefore, there was a problem that complete sealing performance could not be obtained at the terminal portion.

In addition, in the method described in Japanese Patent Publication No. 62-15491,
When using phosphate-based laser fibers, they often have poor acid resistance (when melting a glass vibrator in an acid solution, not only the glass pipe but also the laser fiber may be attacked by the acid). There was a drawback that

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art by directly fixing fiber strands to each other instead of indirectly fixing the fiber strands together, without deteriorating the fiber itself. It is an object of the present invention to provide a method for manufacturing a laser fiber bundle that can suppress coolant leakage and reduction in transmission efficiency.

[Means for Solving the Problems] Therefore, the present invention has been made to achieve the above-mentioned object, and the method for manufacturing a laser fiber bundle of the present invention provides a method for manufacturing a laser fiber bundle used in a laser optical path. A plurality of laser fiber bundles are bundled together to form a laser fiber bundle, and the ends of this laser fiber bundle are put into a press mold, and pressure is applied radially inward to the ends of the laser fiber bundle while heating. By deforming the laser fiber wires, these laser fiber wires are fused to each other and the ends of the laser fiber bundle are fixed, and this fixation is performed at both ends.

The present invention will be explained in further detail below.

First, in order to bundle the laser fiber strands, the τ laser fiber strands are cut to be slightly longer than the desired length of the laser fiber bundle and are bundled in the number required for the desired laser fiber bundle.

Of course, the laser fiber strands may be cut after the required number of laser fibers are bundled into a desired laser fiber bundle.

Next, the laser fiber bundle thus formed is inserted into the holding pipe. This pipe is used for guiding the press mold described later and for holding the laser fiber bundle. Therefore, the outer ends of the pipe are tapered and are shorter than the length of the fiber bundle so that both ends of the laser fiber bundle protrude from the pipe. Then, the tip of the laser fiber bundle coming out from inside the pipe is tightened with a wire or the like to bundle the laser fiber strands so that they do not shift.

Then, one end of the bundled laser fiber bundle is placed in a press mold, the wires, etc. that were tightening the laser fiber bundle are released, and the temperature is increased from room temperature to the temperature at which the laser fiber wire deforms for about 30 minutes while applying pressure. The laser fiber is heated at that temperature for 30 to 60 minutes while applying pressure to deform and fuse one end of the laser fiber to the laser fiber strand until there is no gap.

Next, the same operation is performed on the other end to fuse the laser fiber wire.

In this way, the laser fiber strands at both ends are deformed and fused together, and a laser fiber bundle with no gap between the laser fiber strands at both ends is obtained.

The laser fiber bundle and the bundle holder are bonded together using low melting point glass.

At this time, since the fibers are bundled, the laser fiber will not be deformed or deteriorated by the low melting point glass.
The laser fiber bundle and bundle holder can also be bonded without any gaps.

[Function] After the end of the laser fiber bundle is heated to the deformation temperature of the laser fiber strand, the end of the laser fiber bundle is
When pressure is applied radially inward to the extent of contacting the press mold, a synergistic effect of heat and pressure occurs, resulting in thermocompression bonding of the ends of the laser fiber bundle. That is, since all the laser fiber strands at the ends are thermally deformed and fused to each other, the gaps between the fiber strands are directly established by each fiber strand itself without using an intervening material.

In this way, when the fiber wires are directly fused together,
Even if heat is generated in the laser fiber bundle, the fusion bond will not be released until the temperature increase due to the heat reaches the heat resistance limit of the laser fiber wire. That is, the laser fiber handle can withstand use up to the heat resistance limit of the laser fiber wire.

Example] FIG. 1 is a perspective view of a laser fiber bundle manufactured by an example of the manufacturing method of the present invention. Here, a case will be described in which this laser fiber bundle is used as a laser medium of a laser oscillation device.

Also, here, when we refer to a laser fiber strand, we refer to a unit fiber line consisting of a core and a cladding, when we refer to a laser fiber bundle, we refer to a bundle of multiple laser fiber strands, and when we refer to a laser fiber handle, we refer to a terminal. Each means something with its parts fixed.

■ is a laser fiber bundle composed of a large number of laser fiber wires 1a bundled together, the laser fiber wires 1a at both end portions 21 are fused together to make them watertight, and the other intermediate portions are bonded to each other to increase cooling efficiency. Therefore, it is free. A bundle holder 2 is attached to the end portion 21 of the laser fiber bundle and is used to hold the bundle in the laser oscillation device;
is the bundle holder 2 and the terminal part 21 of the laser fiber bundle 1
It is a low melting point glass that fills the gap between the two and fixes them together.

4 is the east end face of the laser fiber facing the total reflection mirror and the partial reflection mirror of the laser oscillation device. The fused cross-sectional shape of the laser fiber strands 1a on the east end face 4 of the laser fiber is shown as a rhombus, but this shape is not limited to the rhombus, but may also be a polygon such as a hexagon, a circle, a semicircle, or other shapes. In short, it is sufficient that the laser fiber wire 1a itself is fused so that it does not deform and the coolant does not leak. In particular, the cross-sectional shape of the laser fiber wire 1a is ideally hexagonal as shown in the enlarged view, and in this way, the minimum diameter can be formed without any gaps.

Now, an example of a method for manufacturing the laser fiber bundle shown in FIG. 1 mentioned above will be described.

First, in order to fabricate a 20 cm long laser fiber bundle from a large number of fibers made of phosphate laser glass with a diameter of 200 μm, the fibers were The element 1i11a was cut into a slightly longer length.

After cleaning these many fiber strands with isopropyl alcohol and drying them, they are inserted into a holding quartz glass vibrator 5 and bundled into a circular cross-section, as shown in FIG. Note that the cross-sectional shape may be other than circular.

The number of laser fiber strands to be inserted is approximately 900, and this value is the number required to fuse a large number of fiber strands each having a diameter of 200 μm to a diameter of 6 mm without any gaps. Incidentally, on the outer circumferential side of both ends of the holding quartz glass pipe 5, there are tapers 25 which serve as guides for smooth insertion into a press mold, which will be described later. It is attached so that

In FIG. 3, both end portions 21 of the laser fiber bundle I to be fused are protruded from the vibrator 5 by approximately 25 mm, and their tips are shown with metal wires 6 to facilitate handling in the next step. Bundle and tighten. The pipe 5 used in this example has an outer diameter of 10.0 mm and an inner diameter of 6.8 mm. Regarding the inner diameter, so that the pipe 5 can be easily extracted from the laser fiber bundle 1 after fusion,
It is necessary to move smoothly with the laser fiber bundle 1 inserted.

Next, the laser fiber bundle 1 shown in FIG. 3 described above is inserted into a press mold 8 as shown in FIGS. 4 and 5. The press mold 8 is divided into two, consisting of a fixed mold 8a on the pressed side and a movable mold 8b on the pressed side. When the distance d between the two is about 2 mm, the molded part S at the center is made to form a cylindrical space with a diameter of 5 mm. Heaters for heating are installed in the molds 3a and 3b.
and a thermocouple 10 are built-in, and a taper 7 is provided on the side to be inserted into the molding part S with a diameter decreasing from the outer end toward the inside.
When inserting the end portion 21 of the laser fiber bundle 1 into the molded part S, it is sufficient to insert it until the taper 25 of the vibrator 5 on the side of the laser fiber bundle I abuts against the taper 7 on the side of the molds 8a and 8b. At this time, the metal wire 6 wound around the tip of the laser fiber bundle 1 is removed. After insertion, the movable mold 8b on the pressing side is pressed radially inward by applying force to the push rod 9 to the extent that it contacts the laser fiber bundle 1.

After the laser fiber bundle 1 is set in the molds 3a and 3b, it is heated to 550 to 580'C in about 30 minutes. While maintaining that temperature, mold 3a, 3 every few minutes.
Slightly widen the space between b to release the radially inward pressure, and press 90
The vibrator 5 and the fiber bundle 1 are rotated one by one, and the pressing stroke is set to 0.03 to 0.06 mm.

When the fiber bundle 1 is pressed while being shifted in the circumferential direction in this manner, the laser fiber strands 1a at the end portions of the laser fiber bundle 1 are fused together without a gap.

In this example, the fusion time was 30 to 60 minutes, and the fusion diameter was 6.
It was set to mm. What you need to be careful about at this time is:
Since the laser fiber bundle I is heated above the glass transition temperature, the fibers are easily bent. To avoid this, the pipe 5 and the laser fiber bundle 1 must be held fixed. Therefore, although not shown, the holding vibrator 5 and the laser fiber bundle 1 were suspended from above to prevent bending.

The cross section of the fused portion of the laser fiber bundle 1 thus obtained is deformed, and the fiber strand 1a and the fiber strand 1a
There was no gap between them. If the fiber strands 1a are ideally arranged and this fusion is ideally performed, the cross-sectional shape will be hexagonal as described above, and the minimum diameter will be achieved.

After performing the above operations on both end portions 21 and removing the holding pipe 5, as shown in FIG. Fix by fusion. The reason why the bundle holder 2 is fused and fixed is to facilitate attachment of the laser fiber bundle to the laser oscillation device. The bundle holder 2 is made of a cylindrical body made of metal, for example stainless steel, and has a taper 11 on one end of which the diameter decreases from the outer end toward the inside in order to facilitate the filling of the low-melting glass 3.
is formed.

As shown in FIG. 6, with the laser fiber bundle 1 standing vertically, the fused portion of the laser fiber bundle 1 is protruded from the tip of the bundle holder 2 by about 2 mm and fixed. Low melting point glass 3 having a particle size of about 1.0 to 0.1 mm is packed into the taper 11 of the bundle holder 2.

Then, by placing this in an electric resistance furnace (not shown) and heating it to around 400'C, which is the melting temperature of the low melting point glass 3, the small gap between the fused part of the laser fiber bundle 1 and the bundle holder 2 is sealed. The low melting point glass 3 is infiltrated and both are fused together.

Finally, as shown in FIG. 7, the end face of the fused portion of the laser fiber bundle l is polished. A bundle holder 2 with the end portion 21 of the laser fiber bundle l fused is inserted into an insertion hole provided in the center of a disc-shaped polishing jig 12 and fixed, and the end face of the polishing jig 12 and the bundle holder are fixed. Make the end surface of ingredient 2 the same surface. A protective vibrator 15 is attached to the polishing jig 12 to prevent the laser fiber bundle 1 from breaking. Then, the end face of the laser fiber bundle 1 was polished using polishing sand and the polishing wheel 13 until the end face of the fused portion of the laser fiber bundle 1 and the end face of the bundle holder 2 were aligned. In this example, the end face of the fused part of the laser fiber bundle 1 was polished until the end face of the handle holder 2 was aligned, but the fused part of the laser fiber bundle 1 protruded from the bundle holder 2. It doesn't matter if you finish it in the middle. Finally, the above operation was performed on both end faces to produce a laser fiber bundle with a holder.

When the thus obtained laser fiber bundle with a holder was set in a laser oscillation lamp house and the laser fiber bundle was irradiated with a 600 J Xe flash lamp using water as a coolant, 6. IJ, 11054
n lasers oscillated. Even after repeating this several times, no coolant leaked from the laser fiber bundle, and the laser oscillation efficiency did not deteriorate.

As described above, according to this embodiment, the end portions 2I of the laser fiber bundle 1 are directly fixed by fusing the laser fiber strands 1a together without using any inclusions, so that the fused Even if heat is generated due to laser oscillation,
It can withstand the heat sufficiently, and therefore, as in the case of bonding with an organic adhesive, the organic adhesive may melt and the refrigerant leaks, or it may adhere to the end face of the bundle end, reducing oscillation efficiency. Never. In addition, when fusing low-melting point glass, the fiber may bend due to the heat generated during fusing, or the low-melting point glass may not fit between the strands sufficiently, causing the gaps between the fiber strands to There is no possibility that the sealing performance will be impaired. Furthermore, since no acid solution is used, unlike in the case of the acid leaching etching method, there is no possibility that the laser fiber will be attacked by acid.

Therefore, the method of this embodiment can also be applied to phosphate-based laser fibers that do not have excellent acid resistance.

Additionally, the end portion of the laser fiber bundle 1 is molded into a press mold 8.
Since the laser fibers 1a are pressurized while being heated, the laser fiber strands 1a are reliably fused together, and unlike the case where they are indirectly bonded or fused, much higher watertightness can be achieved.

Furthermore, when applying pressure while heating the end portion of the laser fiber bundle 1 with the press mold 8, the laser fiber bundle 1 is shifted in the circumferential direction at 90 degree intervals, so that pressure is applied uniformly in the circumferential direction. As a result, uniformity of fusion bonding is promoted, and therefore the laser fiber strands 1a can be more completely fused together.

As described above, according to this embodiment, the fiber wire itself is deformed and the fiber wires are directly fused together, so a bundle can be fabricated without deteriorating the fiber wire itself, and during laser oscillation. Even if the input power is increased more than ever before, organic adhesives and low-melting glass will no longer melt due to heat, and the decline in oscillation efficiency can be suppressed. There will be no more water leakage.

In addition, although the above embodiment describes the case of manufacturing a laser fiber bundle for a laser oscillation device, the present invention is not limited to a laser fiber bundle for a laser oscillation device, but can also be used for a laser amplification device. be able to. Furthermore, it can be applied to bundles for measuring the temperature of high-temperature areas.

In addition, although we have described the case where a press mold is used to thermocompress the laser fiber bundle, the method is not limited to this, and any method may be used as long as it can uniformly thermocompress the laser fiber bundle. do not have.

[Effects of the Invention] As explained above, according to the method for manufacturing a fiber bundle of the present invention, the ends of the fiber bundle are fused by heating and pressurizing the fiber strands, so that the fibers themselves are Leakage of coolant and reduction in transmission efficiency can be effectively suppressed without deterioration, and a highly reliable laser fiber bundle can be obtained.

[Brief explanation of drawings]

Fig. 1 is a perspective view of an example of a laser fiber bundle according to the manufacturing method of the present invention, Fig. 2 is a conceptual diagram of the configuration of a general laser oscillation device, and Fig. 3 shows a laser fiber bundle inserted into a holding pipe. Fig. 4 is a plan view of the press, Fig. 5 is a cross-sectional view of the press showing pressure applied to the laser fiber bundle, and Fig. 6 shows the laser fiber bundle with the end portions fused together. FIG. 7 is an illustration showing a method of polishing the end face of the laser fiber bundle. 1 is a laser fiber bundle, la is a laser fiber wire, 2
3 is a bundle holder, 3 is a low melting point glass, 5 is a holding pipe, 6 is a metal wire, 8 is a press mold, 10 is a thermocouple, 15 is a protection pipe, and 2F is a terminal portion (end portion).

Claims (1)

[Claims] A laser fiber bundle is formed by bundling a plurality of laser fiber strands used in the laser optical path, and pressure is applied radially inward to the end portion of the laser fiber bundle while heating the end portion of the laser fiber bundle. In addition, the laser fiber bundle is characterized in that by deforming each laser fiber strand at the end, the laser fiber strands are fused to each other and the end of the laser fiber bundle is fixed. manufacturing method.