JP2002040293A - Ferrule for optical fiber and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a ferrule for an optical fiber having high accuracy and easy processing. A ferrule having an insertion hole (7) for an optical fiber (1), wherein the insertion hole (7) is provided in a central axis portion of a cylindrical member (26) by laser processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrule for an optical fiber used for inserting the distal ends of a pair of optical fibers and a method of manufacturing the ferrule.

[0002]

2. Description of the Related Art In recent years, in terms of information transmission amount and speed, high speed and
Information communication using optical signals using an optical fiber as a large-capacity communication means has been widely performed. Such information transmission is expected to be applied to a wide range of applications, from maintenance as a communication network to data transfer between information devices.

In the information transmission using these optical fibers, it is necessary to connect the optical fibers to each other and between the optical fiber and the optical information equipment, and an optical connector is used. Figure 1
(A) is an example showing a partial configuration of an optical connector. The optical fiber 1 has an optical fiber core 2 as a center and a protection part 3 formed around the optical fiber core 2. In order to connect with another optical fiber, in the optical connector, the protection portion 3 is removed at the tip A of the optical fiber to be connected, and the optical fiber 1 is connected to the flanged cylinder 4 and the light at the tip. The fiber core 2 is held by an optical fiber ferrule 6.

[0004] The optical fiber 1 is processed so that the protective portion 3 is removed from the distal end portion A where the connection is made, over substantially the same length as the length of the optical fiber ferrule 6, and the optical fiber core wire 2 is exposed.

As shown in the schematic sectional view of FIG. 1B, the optical fiber ferrule 6 is
Is formed, and the curved surfaces 8a, 8b
And 8c.

The ferrule 6 for an optical fiber generally has a substantially cylindrical shape. For example, when the outer diameter is 1.25 mm, the inner diameter of the fiber insertion hole is about 0.125 mm. Each of these ferrules requires extremely high submicron dimensional accuracy for the purpose of holding and fixing a small-diameter optical fiber and connecting the same.
It is expected that the size will be further reduced to 7 mm or less, and higher accuracy is required.

As a method of manufacturing a ferrule for an optical fiber,
A pressing method, an extrusion molding method, an injection molding method or a transfer molding method has been conventionally used. For example, JP-A-9-
In the 141141 publication, an injection molding method is described. As shown in FIG. 4, a mold 11 is divided into a base mold 15 having a divided tip mold 12, a fiber mold 13, and a pin 14. It is configured. A cavity formed by the cavity portion 16 is formed by a combination of dies, and the raw material is poured into the cavity 16 and formed into a ferrule shape.

Further, Japanese Patent Publication No. 1-45042 discloses a ferrule structure having an insertion hole for inserting an optical fiber, and a method for finishing the ferrule structure, wherein after firing, a wire is inserted into an insertion hole for inserting an optical fiber at the center of the ferrule. And applying a polishing material such as diamond paste to the wire through the wire to polish the surface of the insertion hole with high accuracy.

[0009]

However, in a conventional manufacturing method such as a press method, an extrusion molding method, an injection molding method or a transfer molding method, a heat treatment such as firing a molded body having an insertion hole is performed. For example, in the production of ceramic ferrules, due to changes in the fluidity of the ceramic material flowing into the mold during molding, agglomeration of the binder in the mold due to uneven molding pressure, density difference in the molded body due to uneven filling, etc. There has been a problem that firing deformation occurs, the insertion hole is deformed, the insertion hole is displaced from the central axis, and accuracy is reduced.

In addition, according to the injection molding method described in Japanese Patent Application Laid-Open No. 9-141704, the pin 14 of the mold is flexed and deformed by the molding material at the time of molding. There has been a problem that the yield decreases.

Further, in the polishing method disclosed in Japanese Patent Publication No. 1-45042, it is difficult to precisely process the inner wall of the insertion hole, and the inner diameter is processed in addition to the outer diameter. However, there is a problem that the processing cost increases.

Accordingly, it is an object of the present invention to provide a ferrule for an optical fiber which has high accuracy and is easy to process.

[0013]

According to the ferrule for an optical fiber of the present invention, it is possible to improve the precision by forming the insertion hole by post-processing, and to improve the surface condition of the insertion hole by using laser processing. And that the ferrule can be easily processed.

That is, the ferrule for an optical fiber of an optical fiber according to the present invention is a ferrule having an insertion hole, wherein the inner wall of the insertion hole has a surface melted by heat. The insertion hole is formed at the center of the cylindrical member by laser processing.

[0015] With this, the insertion hole can be formed with high precision by laser processing after the outer diameter processing of the ferrule is completed, the accuracy of the inner wall of the obtained insertion hole is sufficient, and the insertion hole is formed based on the conventional insertion hole. The complicated outer diameter processing performed becomes unnecessary, and the difficulty of the processing step is remarkably improved.

The surface roughness of the inner wall of the insertion hole is 2 μm.
m or less. Accordingly, it is possible to reduce scratches generated on the side surface of the optical fiber core wire to be inserted, and to reduce scattering factors at the time of light propagation.

Further, it is preferable that the material is made of ceramics. When ceramics are used, deformation is small due to high rigidity, displacement of the optical fiber insertion portion can be reduced, and durability is excellent.

In particular, 50 μm from the inner wall surface of the insertion hole.
It is preferable that the average particle diameter of the crystal particles existing in the region within 5 μm is 5 μm or more. Thereby, it is possible to suppress the damage generated in the optical fiber core wire due to the fine crystal particles.

Further, it is preferable that the melted surface be an etched surface. Thereby, the giant particles formed on the inner wall surface can be removed, the giant particles can be prevented from dropping during the processing after the insertion of the optical fiber, the strength of the ferrule can be prevented from being reduced, and the stress generated during use as a connector can be prevented. Avoid destruction below.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a ferrule for an optical fiber according to the present invention will be described with reference to FIG.

The present invention is characterized in that the insertion hole into which the optical fiber of the ferrule shown in FIG. 1 is inserted and fixed is perforated by laser processing.

First, a cylindrical member 26 having no insertion hole as shown in FIG. 2 or a cylindrical member 36 having a part 37 of the insertion hole as shown in FIG. , Injection molding, transfer molding and the like. At this time, it is preferable that the cylindrical members 26 and 36 have a shape close to the final shape such as a perfect circle.

As a material for forming the ferrule for an optical fiber of the present invention, generally used zirconia is used, and alumina, silicon nitride, silicon carbide, aluminum nitride,
Ceramics such as cordierite, stainless steel and other metals and alloys such as Ni, Fe, Cr, Co, and Cu, inorganic substances such as glass, polyimide resins, engineering plastics, and organic resins such as polymer liquid crystals can be used. It is possible.

Note that firing is required for ceramics, sintered metal, and glass, but laser processing is preferably performed after firing.

In the laser processing, a cylindrical member having no insertion hole is held by a holding jig, and the laser irradiation axis is aligned with the center axis of the cylindrical member so as to enhance the processing accuracy. At this time, since there may be a mechanical displacement of about 5 to 10 μm due to play of the fixing screw in holding the cylindrical member or the like, the position of the jig for holding the cylindrical member is adjusted using a micrometer control mechanism or the like. Adjust and perform precise alignment. The laser spot is appropriately adjusted depending on the fiber diameter.
m, and is effective for forming an insertion hole of 10 to 80 μm.

Then, for example, a laser having a spot diameter of 125 μm is irradiated to form a through hole having a diameter of 125 μm. Further, while irradiating a laser having a spot diameter of 100 μm and rotating the laser irradiation axis, a diameter of 125 μm was obtained.
m may be formed.

The laser used for drilling is not particularly limited, and a known laser such as a CO ₂ laser, a YAG laser, an excimer laser or the like can be used. The type and material of the laser depend on the hole diameter and the material used. You can choose. For example, in the case of ceramics, since a hole diameter of about 5 μm can be handled and positioning accuracy can be achieved up to 0.05 μm, a YAG laser can be suitably used.

It is not necessary to make the laser processing conditions constant, and the irradiation profile can be adopted according to the material. For example, in the case of ceramics and glass, if high-power laser light is directly irradiated, cracks may occur due to heat shock.Therefore, the laser is irradiated intermittently, and the ferrule main body rapidly rises in temperature. Prevent or process Before or after laser irradiation, weaken output before or after laser irradiation, broaden the irradiation spot, irradiate laser with weakened output to heat cylindrical member in advance, mitigate heat shock, process It is preferable to combine techniques such as gradually changing the output of the laser. Also, to mitigate heat shock,
The laser irradiation may be performed in a state where the cylindrical member is heated in advance by a heating means such as a heater.

As described above, the inner wall of the insertion hole of the ferrule in which the insertion hole is formed is characterized by being formed from a smooth molten surface by the heat of the laser beam. In particular, the inner wall has a surface roughness of 2 μm. Hereinafter, it is particularly preferably 1 μm or less, more preferably 0.5 μm or less, and most preferably 0.2 μm or less. In the present invention, a smooth inner wall surface can be obtained, but it is desirable to perform a process such as wet etching as a finishing process in order to further shape the inner surface of the ferrule insertion hole and the shape of the end of the insertion hole.

In the case of a ceramic ferrule, it is preferable that the inner wall of the insertion hole is melted at a high temperature, and the average particle diameter of crystal grains existing in a region within 50 μm from the inner wall surface is 5 μm or more.

Then, if desired, the inner wall of the insertion hole can be etched. Inside the insertion hole, depending on the combination of processing conditions and materials, giant particles may be formed by grain growth, and there is a possibility that shedding may occur during insertion of the optical fiber and subsequent processing, and by etching, It is preferable to remove the giant particles.

[0032]

EXAMPLE 1 100 parts by weight of zirconia powder having an average particle diameter of 0.2 μm, 40 parts by weight of a thermoplastic binder, and dioctyl phthalate as a solvent were added and mixed, and the outer diameter was 1.25 mm by injection molding. A ferrule molding material having a length of 11 mm was prepared. This was injection-molded into a mold to form a cylindrical member having a curved surface at the end face, having no insertion hole shown in FIG. 2, and having dimensions of 1.5 mm in diameter and 11 mm in length.
Thereafter, firing was performed at 1460 ° C. to obtain a zirconia sintered body, which was used as a base.

The center axis of the substrate and the laser irradiation axis are aligned with each other, and a YAG laser is used.
Drilling was performed at 1 mm and an output of 6 W to obtain an insertion hole having an inner diameter of 0.125 mm and the shape shown in FIG. At this time, the perforation was performed for 120 seconds in total by intermittent irradiation in which laser irradiation and stop were performed every other second. By repeating the above operation, 100 molded bodies were produced.

The end face of the obtained ferrule was observed with a CCD camera, and the deviation between the center of the base and the center of the insertion hole was measured with a micrometer. The deviation of the center position is measured by using a micrometer to measure a distance X between the center position of the ferrule set from the outer diameter portion of the ferrule and the center position of the insertion hole formed in the center of the ferrule. Then, those having an average value of the distance X of 2 μm or less were determined as non-defective products.

Further, the surface roughness of the inner wall of the insertion hole was determined by cutting the ferrule at the center in the longitudinal direction, taking a scanning electron microscope (SEM) photograph of 1000 times at 10 places, and then measuring 100 μm for each photograph. Measure the maximum unevenness in the range of
The average value of the locations was calculated to be the roughness.

Further, the average particle size of 50 μm from the inner wall surface was measured at 40 points by a scanning electron microscope (SEM) from a microstructure photograph by an intercept method, and the average value was calculated.

As a result, for all the samples, the insertion holes were composed of a molten surface, the surface roughness was 1.2 μm or less, and the average particle size at 50 μm from the inner wall surface was 6.5 μm. Also,
The average of the distance X relating to the displacement of the insertion hole was 0.8 μm. Example 2 In the same manner as in Example 1, injection molding was performed to form a cylindrical member shown in FIG. afterwards,
Firing was performed to obtain a zirconia sintered body.

The obtained cylindrical member was held on the side surface of the cylinder, the center portion was aligned with the laser, and perforation was performed.
At this time, the perforation processing is intermittent irradiation in which laser irradiation and stop are performed every second, and irradiation is performed for a total of 25 seconds, and FIG.
Was obtained. At this time, the thickness of the zirconia portion to be substantially drilled with a laser was 2 mm.

The obtained ferrule was evaluated in the same manner as in Example 1. As a result, for all 100 samples, the insertion holes consisted of a molten surface, the surface roughness was 1.0 μm or less, and the average particle size at 50 μm from the inner wall surface was 6.0 μm. Further, the distance X relating to the displacement of the insertion hole was 0.7 μm or less. Example 3 In the same manner as in Example 2, a ferrule insertion hole was formed by laser processing, and finally an etching process was performed using aqua regia.

The obtained ferrule was evaluated in the same manner as in Example 1. As a result, for all 100 samples, the insertion holes consisted of a molten surface, the surface roughness was 0.8 μm or less, and the average particle size at 50 μm from the inner wall surface was 5.5 μm.
Further, the distance X relating to the displacement of the insertion hole was 0.7 μm or less. Comparative Example An injection mold as shown in FIG. 4 was used. The diameter of the pin 14 was 0.125 mm. Injection molding was performed using the same raw materials as in Example 1, and the obtained molded body was 1460 ° C.
And the outer diameter was processed. The evaluation was made in Example 1.
Was performed in the same manner as described above.

In Example 1, 100 ferrules were manufactured.
Was evaluated in the same way as As a result, for all 100 samples, the insertion holes consisted of a baked surface, the surface roughness was 0.5 μm or less, and the average particle size at 50 μm from the inner wall surface was 0.3 μm. Further, the distance X relating to the displacement of the insertion hole is 5 μm.
Met.

[0042]

According to the ferrule for an optical fiber of the present invention,
By forming a cylindrical member and forming an insertion hole for inserting an optical fiber core at the center of the cylindrical member by laser processing, a high-precision ferrule can be easily formed.

[0043]

[Brief description of the drawings]

FIG. 1 shows a configuration of an optical fiber ferrule of the present invention, in which (a) a cross-sectional view showing a partial configuration of an optical connector;
(B) It is sectional drawing of the ferrule for optical fibers.

FIG. 2 is a schematic sectional view showing a cylindrical member used for forming a ferrule of the present invention.

FIG. 3 is a schematic sectional view showing another cylindrical member used for forming a ferrule of the present invention.

FIG. 4 is a sectional view of a mold used in a conventional injection molding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical fiber 2 ... Optical fiber core wire 3 ... Protective part 4 ... Flanged cylinder 6 ... Optical fiber ferrule 7 ... Insertion hole 8a, 8b, 8c ... Curved surface A: Tip

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kiyohiro Sakasegawa 1-4, Yamashita-cho, Kokubu-shi, Kagoshima F-term in Kyocera Research Institute (reference) 2H036 QA13 QA16 QA20

Claims (8)

[Claims] 1. A ferrule having an insertion hole for an optical fiber, wherein an inner wall of the insertion hole has a surface melted by heat. 2. A ferrule for an optical fiber according to claim 1, wherein the inner wall of said insertion hole has a surface roughness of 2 μm or less. 3. The ferrule for an optical fiber according to claim 1, wherein the ferrule is made of a ceramic. 4. The ferrule for an optical fiber according to claim 3, wherein the average diameter of the crystal grains present in a region within 50 μm from the inner wall surface of the insertion hole is 5 μm or more. 5. The method according to claim 1, wherein the inner wall of the insertion hole is formed by etching a molten surface.
5. The ferrule for an optical fiber according to any one of items 1 to 4. 6. A method of manufacturing a ferrule for an optical fiber, wherein an insertion hole is formed at the center of a cylindrical member by laser processing. 7. The method for manufacturing a ferrule for an optical fiber according to claim 6, wherein said cylindrical member is made of ceramics. 8. The method for manufacturing an optical fiber ferrule according to claim 6, wherein an inner wall of the insertion hole is etched after the laser processing.