JP2002072012A - Manufacturing method of ferrule for optical fiber and ferrule for optical fiber manufactured using the same - Google Patents

Abstract

(57) [Summary] (Modifications) [Problem] To provide a ferrule for an optical fiber with high accuracy and easy processing. [Solution] A core wire insertion hole 7 is formed at the center of a cylindrical member by sandblasting. The cylindrical member has a part of a fiber insertion hole formed therein, is made of a sintered body having an average crystal grain size of 1 μm or less, and further has at least a core wire 2 of an optical fiber inside the cylindrical member. And the hole diameter of the butting portion 5 in the core wire insertion hole 7 is made smaller than the hole diameter of the fiber line portion.

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, information communication using an optical signal using an optical fiber has been widely performed as a high-speed and large-capacity communication means in terms of the amount of information transmitted and the speed. These communications are
A wide range of applications is expected 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 a core 2 as a center, and a protective portion 3 around the core 2.
Are formed. In order to make a connection with another optical fiber 1, in the optical connector, the protection portion 3 is removed at the distal end A of the optical fiber to be connected, and the optical fiber 1 is provided by the flanged cylinder 4 and the core wire at the distal end. 2 is held by an optical fiber ferrule 6.

As shown in the schematic cross-sectional view of FIG. 1B, the ferrule 6 for an optical fiber has a core wire insertion hole 7 into which the core wire 2 is inserted, and its corners are formed with curved surfaces 8a, 8b and 8c. Have a complicated shape. Further, the diameter of the core wire insertion hole 7 is constant, when the pore diameter of the butt portion of the core wire insertion hole 7 and d _j, the pore size of the fiber line portion and d _f, was d _j = d _f.

Since the length of the core wire insertion hole 7 is the same as the length of the optical fiber ferrule 6, the length of the optical fiber 1 is substantially the same as the length of the optical fiber ferrule 6 from the distal end A where the connection is made. The protective portion 3 is removed over the entire surface, and the core wire 2 is processed so as to be exposed.

The ferrule 6 for an optical fiber generally has a substantially cylindrical shape. For example, when the outer diameter of the ferrule 6 for an optical fiber is 1.25 mm, the inner diameter of the core wire insertion hole 7 of the ferrule 6 for an optical fiber 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, but the outer diameter of the optical fiber ferrule 6 will be 0.7 mm in the future. It is thought that the size will be further reduced to the following, and higher accuracy is required.

As a method of forming 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, in Japanese Patent Application Laid-Open No. 9-141704, an injection molding method is described. As shown in FIG. 4, a mold 51 includes a divided tip mold 52, a fiber mold 53, and a pin 54. And a base mold 55 having the same. The cavity formed by the cavity portion 56 is formed by a combination of molds, and the raw material is poured into the cavity 56 and formed into a ferrule shape.

Further, Japanese Patent Publication No. 1-45042 discloses a ferrule structure having a core wire insertion hole for inserting a core wire of an optical fiber, and a method of finishing the ferrule structure by firing the core wire insertion hole 7 at the center of the ferrule after firing. There is disclosed a process of polishing a surface of a core wire insertion hole with high accuracy by passing a wire coated with an abrasive such as diamond paste.

[0009]

However, in the production of ceramic ferrules, a conventional production method such as a press method, an extrusion molding method, an injection molding method or a transfer molding method involves firing a molded body having a core wire insertion hole. Deformation due to changes in the fluidity of the ceramic material flowing into the mold during molding, binder agglomeration in the mold due to uneven molding pressure, density difference in the molded body due to uneven filling, etc. And the core insertion hole is deformed, or the core insertion hole is displaced from the center axis, and the accuracy is reduced.

In addition, in the injection molding method described in Japanese Patent Application Laid-Open No. 9-141704, since the pins 54 of the mold are bent and deformed by the molding material during molding, a small-diameter core wire insertion hole is not formed at the center of the ferrule. However, there has been a problem that the accuracy is reduced and the yield is reduced.

Further, in the polishing method disclosed in Japanese Patent Publication No. 1-45042, it is difficult to precisely machine the inner wall of the core wire insertion hole, and the inner diameter is processed in addition to the outer diameter.
There is a problem that the processing time becomes longer and 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]

The method of manufacturing a ferrule for an optical fiber according to the present invention is based on the finding that the use of sandblasting can improve the precision and facilitate the processing of the ferrule.

That is, the method of manufacturing a ferrule for an optical fiber of the present invention is characterized in that a core wire insertion hole is formed at the center of a cylindrical member by sandblasting.

In particular, it is preferable that at least a part of the fiber insertion hole is formed in the cylindrical member before sandblasting. Thereby, the burden on the processing by sandblasting of the optical fiber insertion hole is reduced.

Further, the columnar member has an average crystal grain size of 1.
It is preferred to be made of a sintered body of μm or less. After the sand blasting, the inner wall of the core wire insertion hole has a surface roughness of 2.
It is preferable to process to μm or less. As a result, the surface roughness of the inner wall of the formed core wire insertion hole can be reduced, and damage to the fiber core wire can be reduced.

The ferrule for an optical fiber according to the present invention is a ferrule having at least a core insertion hole for holding a core of an optical fiber inside a cylindrical member, wherein the diameter of the butted portion of the core insertion hole is d. _j , when the hole diameter of the fiber line portion is d _f , d _j <d _f , and in particular, a fiber insertion hole for holding an optical fiber inside the cylindrical member; It is preferable to include a core insertion hole for holding the core of the fiber. Thereby, the loss of the tip of the optical fiber can be prevented, and the connection of the optical cable becomes easy.

It is preferable that the sintered body has a mean crystal grain size of 1 μm or less. Thereby, damage to the side surface of the core wire of the optical fiber can be suppressed.

Further, the sintered body has a Young's modulus of 150-150.
Preferably, it is 250 GPa. This gives P
Even when C (Physical Contact) bonding is performed, the entire ferrule is not easily deformed, but the curved surface portion at the tip of the ferrule is easily deformed due to partial contact, thereby enabling reliable optical fiber connection.

Further, it is preferable that the length of the core wire insertion hole is 5 mm or less. This makes it possible to securely hold the optical fiber core wire with the adhesive,
Since a space in which the optical fiber core wire itself bends when performing the C-joining can be ensured, it is possible to surely join the optical fibers. Moreover, the processing cost of sandblasting can be reduced.

Further, it is preferable that the surface roughness of the inner wall of the core wire insertion hole is 2 μm or less. This allows
Scratches generated on the side surface of the core wire of the optical fiber to be inserted can be reduced, and scattering factors during light propagation can be reduced.

[0022]

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 FIGS.

The present invention is characterized in that the cylindrical member is perforated by sandblasting, thereby producing the ferrule shown in FIGS.

First, a cylindrical member 2 having no fiber insertion hole and core wire insertion hole as shown in FIG.
6 or a cylindrical member 36 in which a part 37 of the fiber insertion hole as shown in FIG. 3B is formed in advance by a conventional method such as press molding, injection molding, transfer molding, or the like. At this time, it is preferable that the cross sections of the cylindrical members 26 and 36 have a shape close to the final shape such as a perfect circle.

That is, the cylindrical member 26 previously forms at least a part of the fiber insertion hole or the core wire insertion hole, particularly an optical fiber insertion hole for which high precision is not required, by another method such as an injection molding method or a press molding method. In advance, it is preferable to sandblast only the core wire insertion hole that requires high precision. By already forming a part of the optical fiber insertion hole by another method, the part to be sandblasted is reduced,
The processing time, the abrasive material required for the processing, the ferrule material removed by the processing, and the like are reduced, and the cost can be further reduced.

The material for forming the ferrule for an optical fiber of the present invention includes ceramic sintered bodies such as zirconia, alumina, silicon nitride, silicon carbide, aluminum nitride, cordierite, stainless steel and other Ni, Fe, C
metals such as r, Co, Cu and alloys thereof, inorganic substances such as glass, polyimide resin and engineering plastic,
Although any organic resin such as a polymer liquid crystal can be used, it is particularly preferable to use a sintered body mainly composed of the ceramics and having an average crystal grain size of 1 μm or less.

When the ferrule is composed of an aggregate of fine crystal particles having an average particle size of 1 μm or less, these fine crystal particles are easily removed by sandblasting, and particles having a large particle size remain inside the core wire insertion hole. The insertion of the core wire is not hindered, and the occurrence of cracks due to processing can be suppressed.

Therefore, even if the abrasive is injected at a high pressure,
Since it is harder to deform than a plastic resin having flexibility or a metal having malleability, high-speed and high-precision processing can be performed, and a processed surface can be finished more smoothly. Further, the occurrence of cracks can be prevented as compared with glass.

The sintered body has a Young's modulus of 150 to 150.
250 GPa, especially 170-230 GPa, 190-2
It is preferably 10 GPa. Since the Young's modulus is sufficiently high, the entire ferrule is unlikely to be deformed, the reliability of supporting the optical fiber core wire is increased, and even when a PC (Physical Contact) joint is used to butt the ferrule, the ferrule at the curved surface at the tip end is used. It is easy to be deformed by contact, and reliable optical fiber connection becomes possible.

Therefore, among ceramics, especially, zirconia or alumina is mainly used, and the Young's modulus is 150-2.
The one controlled to 50 GPa is preferable.

It should be noted that firing is required for ceramics, sintered metals, and glass, but sandblasting can be performed on a molded body or a sintered body. A molded body is preferred in terms of processing speed, and a sintered body is preferred in terms of improving accuracy.

In particular, when sand blasting is performed on the sintered body, it is preferable that the outer diameter be processed beforehand by grinding or the like. This is because if the outer diameter processing is performed after the core wire insertion hole is formed first, the center of the hole and the center of the outer diameter are different, so it is necessary to make the outer diameter large in advance and provide extra cutting margin, which leads to cost reduction. It is preferable to finish at least the outer diameter processing because it easily leads to the rise.

In the sand blasting, as shown in FIG. 3 (c), a cylindrical member 36 without a core wire insertion hole is held by a holding jig, and the end face where the core wire insertion hole is formed covers other than the hole 38 for drilling. This is performed by forming a cap 39 with a resist. As the resist at this time, a conventional photosensitive resin or the like, a thermosetting resin or the like can be used.However, from the viewpoint of productivity, a cavity made of resin or metal and having the same diameter as the cylindrical member is used. It is desirable to use a cap material having a hole having the same diameter as the optical fiber core wire at the position of the optical fiber insertion hole when the cylindrical member is inserted into the cavity. For example, a resin cap having a 120 μm hole at the center can be used.

The resin cap material is put on the cylindrical member, and an abrasive is blown from the hole of the cap material toward the surface of the cylindrical member at a high pressure in a direction indicated by an arrow in FIG. Processing is performed. As a result, a pore size of d _j of butt portion 15 of the core wire insertion hole to support the core of the optical fiber, the diameter of the fiber line portion 19 when the d _f, 2 as the d _j <d _f (b) It is possible to work into the tapered shape as shown, and by adopting this shape, when the optical fiber is inserted, it can be prevented from being caught, preventing the occurrence of defects such as chipping at the tip of the conventional optical fiber, as well as inserting the optical fiber and Since the application of the adhesive for fixing the optical fiber is simplified, the labor for manufacturing the optical connector and connecting the optical cable can be greatly reduced.

Examples of abrasives for sandblasting include commonly used ceramic powders such as alumina, glass beads, silicon carbide and silicon nitride powders, plastic powders such as hard plastics made of ethyl cellulose and urea resin, and calcium carbonate and the like. Any of these inorganic powders can be suitably used. Further, a powder beam etching method can be used as an example of high-precision sandblasting.

The particle size of the above-mentioned abrasive grains depends on the size of the core wire insertion hole to be formed, but is 0.1 to 100 μm, especially 1 to 5 μm.
0 μm, more preferably 3 to 50 μm, more preferably 5 to 20
μm is preferred. And 0.1-10 for finishing
A particle size of μm is preferred.

It is not necessary to keep the sandblasting conditions constant, and the abrasive grains and the spraying conditions can be adopted according to the material. The abrasive may be subjected to sandblasting with fine particles or calcium carbonate as a finish after rough cutting. For example, in the case of ceramics, glass, and the like, the diameter of the abrasive grain injection port at the start and end and the injection pressure are changed to control the shape of the core wire insertion hole and the surface roughness of the inner wall of the core wire insertion hole. Is preferred. In particular, it is preferable that the surface roughness of the inner wall is controlled to 2 μm or less, particularly 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 if necessary, finishing can be performed for the purpose of further adjusting the shape of the inner surface of the ferrule insertion hole and the end of the core wire insertion hole. For example, by wet etching
The core wire insertion hole can be finished with an accuracy equal to or smaller than the crystal grain size of the ceramic sintered body that is the ferrule material described above, and the accuracy of the ferrule is improved. In addition, by passing a wire coated with an abrasive such as diamond paste through the core insertion hole and accurately polishing the inner wall of the core insertion hole, the sharp edges of the ceramic crystal present on the inner wall surface of the core insertion hole are rounded. In addition, it is possible to prevent the optical fiber core wire from being damaged and to reduce the loss of transmission light.

As described above, according to the method for manufacturing an optical fiber ferrule of the present invention, sandblasting is used, and in particular, the core wire insertion hole is formed by post-processing.
Accuracy can be improved and ferrule processing can be facilitated. Moreover, it is possible to improve the surface condition of the inner wall of the core wire insertion hole, reduce the deformation of the entire ferrule, and facilitate the deformation of the tip of the ferrule.

FIG. 1 shows a ferrule for an optical fiber according to the present invention, which is highly accurate and easily manufactured by the above manufacturing method. According to the present invention, the diameter of the butted portion in the core wire insertion hole 7 for holding the core wire of the fiber is d.
_{When j,} the pore size of the fiber line portion was d _f, it is characterized in that it is d _j <d _f.

Further, by the d _j <d _f, there is no trouble such as caught when inserting the optical fiber from the flanged cylinder side to the core wire insertion hole, the occurrence of defects such as the fiber tip can be prevented upon insertion At the same time, the insertion of the optical fiber becomes easy, so that the labor of manufacturing the optical connector and connecting the optical cable can be greatly reduced, and the cost can be suppressed.

FIG. 2 is another example showing a partial configuration of the optical connector. The optical fiber 11 has a core wire 12 as a center and a protection portion 13 formed around the core wire 12. In order to make a connection with another optical fiber 11, in the optical connector, the protection portion 13 is removed at the tip A of the optical fiber to be connected, and the optical fiber 11 is provided by the cylindrical body 14 with the flange and the core wire at the tip. 12 is an optical fiber ferrule 1
6.

The optical fiber ferrule 16 is
As shown in the schematic cross-sectional view of FIG. 2B, a core wire insertion hole 17 for inserting the core wire 12 is formed, and a corner thereof has a curved surface 18.
It has a complex shape with a, 18b and 18c. Further, the diameter of the core wire insertion hole 17 is constant, when the pore diameter of the butt portion of the core wire insertion hole 17 and d _j, the pore size of the fiber line portion and d _f, is d _j <d _f.

The optical fiber ferrule 16 shown in FIG. 2B has a fiber insertion hole 20, and the length of the core wire insertion hole 17 is the same as that of the core wire insertion hole 7 shown in FIG. Sandblasting can be performed in a shorter time in a shorter time. The optical fiber 11 is processed so that the protection portion 13 is removed from the distal end portion A where the connection is made, over a length substantially equal to the length of the core wire insertion hole 17, and the core wire 12 is exposed.

Further, the material for forming the ferrule for an optical fiber is preferably a sintered body mainly composed of the above ceramics. The use of ceramics makes it possible to utilize the characteristics of high rigidity, less deformation, less displacement of the optical fiber insertion portion, and excellent durability.

In particular, the sintered body has a Young's modulus of 150 to 2
Preferably it is 50 GPa. As a result, the ferrule itself has high toughness, so that the ferrule can be damaged by dropping or the like, or the impact of the ferrule butt during optical fiber connection can be absorbed, thereby preventing the ferrule and the optical fiber from being chipped. In addition, P
Also in the case of using the C-joint, the tip of the ferrule is easily deformed, and reliable optical fiber connection is possible.

Further, it is preferable that the length of the core wire insertion hole is 5 mm or less. As a result, the optical fiber core wire can be securely held by the adhesive, and at the same time, a space where the optical fiber core wire itself bends at the time of the above-described PC joining can be secured, so that the reliable optical fiber butt joining can be performed. .

Further, the surface roughness of the inner wall of the core wire insertion hole is preferably 2 μm or less. This allows
Scratches generated on the side surface of the optical fiber core wire to be inserted can be reduced, and scattering factors during light propagation can be reduced.

[0049]

EXAMPLE 1 40 parts by weight of a thermoplastic binder and 100 parts by weight of dioctyl phthalate were added as a solvent to 100 parts by weight of zirconia powder having an average particle diameter of 0.2 μm and mixed, and the outer diameter was 1.25 mm by an injection molding method. A ferrule molding material having a length of 11 mm was prepared. This is injection-molded into a mold, so that the end face has a curved surface and a part 3 of the fiber insertion hole shown in FIG.
7 having a diameter of 1.5 mm and a length of 11
A mm cylindrical member was formed.

The obtained cylindrical member is fired at 1460 ° C.
A zirconia sintered body was obtained. Next, this was externally ground to obtain a substrate. This base was formed into a columnar member having a perfect circle and a diameter of 1.25 mm by outer diameter processing.

A resin cap material having a hole of 0.12 mm in the center was covered on the cylindrical member, and sand blasting was performed in which polishing was performed by spraying an abrasive at a high pressure from the hole of the cap material onto the surface of the cylindrical member. For sandblasting, 4 kg / cm ² of alumina abrasive grains having an average particle size of 20 μm were used.
, And pierced. Thereafter, the particles were changed to calcium carbonate abrasive particles having an average particle diameter of 10 μm, and sandblasting was performed in the same manner as in the case of alumina abrasive particles to form a core wire insertion hole having a length of 3 mm.

The surface of the core wire insertion hole of the obtained ferrule is
As before, polishing was performed with high precision using an abrasive such as diamond paste.

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 core wire insertion hole was measured with a micrometer. The shift of the center position is measured by a micrometer using 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 core wire insertion hole formed on the center axis 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 core wire insertion hole was determined by cutting the ferrule at the center in the longitudinal direction, taking a scanning electron microscope (SEM) photograph at a magnification of 1000 at 10 locations, and then measuring each photograph. The maximum unevenness was measured in a range of 100 μm, and an average value at 10 points was calculated to determine the roughness.

Further, the average crystal grain size of the ferrule was measured at 40 points by a scanning electron microscope (SEM) of the cross section of the ferrule from a microstructure photograph by an intercept method, and the average value was calculated.

As a result, for all the samples, the surface roughness of the core wire insertion hole was 1.0 μm or less, and the average crystal grain size was 0.3 μm.
Met. In addition, the distance X relating to the displacement of the core wire insertion hole
Was 0.8 μm. Example 2 The same material as in Example 1 was injection-molded in the same manner to obtain a shape having a curved surface on the end face, having no fiber insertion hole as shown in FIG. 11mm
A cylindrical member was formed.

Next, this was externally ground to obtain a substrate. The cross section of this base is a perfect circle with a diameter of 1.25 m by external diameter processing.
m cylindrical member.

A resin cap material having a hole of 0.12 mm in the center portion was covered on the cylindrical member, and sandblasting was performed by spraying an abrasive at a high pressure from the hole of the cap material onto the surface of the cylindrical member. In sandblasting, alumina abrasive grains having an average particle diameter of 20 μm were injected with compressed air of ² kg / cm ² to perform perforation processing. After that, it was changed to calcium carbonate abrasive grains having an average particle diameter of 10 μm, and sand blasting was performed similarly to alumina abrasive grains to form through holes.

The obtained cylindrical member is fired at 1460 ° C.
A zirconia sintered body was obtained. The surface of the core wire insertion hole of the ferrule made of this sintered body was precisely polished with a polishing material such as diamond paste as in the past.

The ferrule thus obtained was subjected to the measurement of the displacement of the center of the insertion hole, the surface roughness of the inner wall of the core wire insertion hole, and the average crystal grain size of the ferrule as in Example 1.

As a result, for all the samples, the surface roughness of the core wire insertion hole was 1.0 μm or less, and the average particle size was 0.3 μm. The average of the distance X related to the displacement of the core wire insertion hole was 1.0 μm. Comparative Example An injection mold as shown in FIG. 4 was used. The diameter of the pin 54 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 core wire insertion holes consisted of fired surfaces, and the surface roughness was 0.5 μm.
m or less, and the average crystal grain size of 50 μm from the inner wall surface is 0.3
μm. Further, the distance X relating to the displacement of the core wire insertion hole was 5 μm.

[0063]

According to the ferrule for an optical fiber of the present invention,
By forming a core insertion hole into which the core of the optical fiber is inserted by sandblasting at the center of the cylindrical member, a high-precision ferrule can be easily formed.

[0064]

[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 shows another configuration of the optical fiber ferrule of the present invention, in which (a) is a cross-sectional view showing a partial configuration of an optical connector, and (b) is a cross-sectional view of the optical fiber ferrule.

FIGS. 3A and 3B show a cylindrical member used for forming a ferrule of the present invention, wherein FIG. 3A is a cross-sectional view of a cylindrical member having no fiber insertion hole therein, FIG. (B) It is sectional drawing of the cylindrical member provided with a cap in a butting part.

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

[Explanation of symbols]

 Reference numerals 1, 11, optical fibers 2, 12, core wires 3, 13, protective portions 4, 14, flanged cylinders 5, 15, butting portions 6, 16, optical fibers Ferrule 7, 17: core wire insertion hole 8a, 8b, 8c, 18a, 18b, 18c: curved surface 9, 19: fiber wire portion 20: fiber insertion hole A: tip

Claims (10)

[Claims] 1. A method of manufacturing a ferrule for an optical fiber, wherein a core wire insertion hole is formed at the center of a cylindrical member by sandblasting. 2. The method for manufacturing an optical fiber ferrule according to claim 1, wherein at least a part of a fiber insertion hole is formed in said cylindrical member before sandblasting. 3. The method for manufacturing an optical fiber ferrule according to claim 1, wherein said cylindrical member is made of a sintered body having an average crystal grain size of 1 μm or less. 4. The method for manufacturing an optical fiber ferrule according to claim 1, wherein after sandblasting, the inner wall of the core wire insertion hole is processed to a surface roughness of 2 μm or less. 5. A ferrule having a core insertion hole for holding at least a core of an optical fiber inside a cylindrical member, wherein the diameter of the butting portion in the core insertion hole is _dj , and the diameter of the fiber line is d. when is _f, an optical fiber ferrule, characterized in that the d _j <d _f. 6. A ferrule for an optical fiber according to claim 5, further comprising a fiber insertion hole for holding an optical fiber and a core wire insertion hole for holding a core wire of the optical fiber inside the cylindrical member. . 7. The ferrule for an optical fiber according to claim 5, wherein the ferrule is made of a sintered body having an average crystal grain size of 1 μm or less. 8. The sintered body has a Young's modulus of 150 to 250 G.
The ferrule for an optical fiber according to any one of claims 5 to 7, wherein Pa is Pa. 9. The ferrule for an optical fiber according to claim 5, wherein the length of the core wire insertion hole is 5 mm or less. 10. A surface roughness of an inner wall of the core wire insertion hole is 2 μm.
The ferrule for an optical fiber according to any one of claims 5 to 9, wherein m is equal to or less than m.