JP3455661B2 - Optical fiber connector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber connector suitable for connecting optical fibers with high dimensional accuracy.

[0002]

2. Description of the Related Art Conventionally, as an optical fiber connector, for example, one shown in FIG. 1 is known. The optical fiber connector 1 includes a pair of ferrules 2 and 2 and a split sleeve 3 for fitting the ferrules 2 and 2 together.
A pair of adapters 4, 4 for fitting and fixing the split sleeve 3
It consists of and. After the connection ends of the two optical fibers 5 and 5 are inserted into and fixed to the pores 22 of the pair of ferrules 2 and 2, the end faces that are the mutual contact surfaces of the ferrules 2 and 2 are spherically processed. , The ferrules 2 and 2 are respectively inserted from both ends of the split sleeve 3, and the split sleeve 3 is tightened from the outside with the adapters 4 and 4, and the two adapters 4 and 4 are inserted.
By joining and fixing the ferrules 2 and 2,
The spherically machined end surfaces of the optical fibers 5 are in contact with each other, and the split sleeve 3 is also tightened by the adapters 4 and 4,
5 is connected to each other.

As shown in FIG. 2, each of the ferrules 2 and 2 has a fine hole 22 centered on the outer diameter of a columnar main body 21 and processed with high precision. 22
After the connection end of the optical fiber 5 is inserted into the optical fiber, the optical fiber end surface is processed into a spherical surface, and the surfaces are pressure-bonded by joining and fixing the adapters 4 and 4. At this time, if there is an axis shift in the connection of the end faces of the optical fiber, optical loss occurs, so that extremely high accuracy is required for the outer diameter, the pore diameter, the length, etc. of the ferrule 2.
Therefore, as a material of the ferrule 2, a ceramic sintered body such as zirconia is used.

As shown in FIG. 3, the split sleeve 3 has a structure in which a slit 32 is opened in a cylindrical main body 31 along the axial direction thereof. The split sleeve 3 elastically holds and aligns the pair of ferrules 2 and 2.
A material using zirconia has also been developed as a material for the split sleeve 3. Tetragonal zirconia added with yttria is used as zirconia, and such zirconia has good workability, high toughness, high strength, and excellent properties. For example, Japanese Examined Patent Publication 8-3077
No. 5 gazette discloses that the material for ferrules is yttria,
An optical fiber connector using a zirconia sintered body containing a stabilizer such as magnesia or calcia is disclosed. Further, Japanese Patent No. 2551407 discloses an optical fiber connector using a zirconia sintered body containing a stabilizer such as yttria, magnesia, or calcia as a material of the split sleeve.

[0005]

However, the above-mentioned tetragonal zirconia sintered body containing yttria suffers from structural deterioration due to the phase transition from tetragonal to monoclinic at relatively low temperatures, and thus has poor durability. It has drawbacks. This deterioration is particularly likely to occur in an atmosphere containing a large amount of water vapor,
Recently, there has been a particularly serious problem when the optical fiber connector is used outdoors. That is, there is a problem that the surface layer of the ferrule or the like is deteriorated, and the volume expansion at this time causes the ferrule or the like to be deformed or the strength thereof to be reduced.

On the other hand, in the high toughness precision parts described in Japanese Patent Laid-Open No. 4-144962, zirconia containing ceria as a stabilizer is used. This zirconia sintered body is essentially a material that does not show low temperature deterioration like the above-mentioned yttria-stabilized zirconia, but its strength and hardness are significantly lower than those of the yttria-stabilized zirconia. There was a problem above.

Therefore, an object of the present invention is that it can be used without deterioration even in a harsh environment, has high strength and hardness, is suitable for connecting optical fibers with high dimensional accuracy, and is suitable for communication equipment. An object is to provide an optical fiber connector capable of sufficiently guaranteeing the required reliability.

[0008]

According to the optical fiber connector of the present invention, the connecting ends of two optical fibers are mounted in the pores of a pair of ferrules, and the pair of ferrules are fitted in a sleeve. In the optical fiber connector having a mating structure, the ferrule and / or the sleeve are
A zirconia-based composite in which a first phase composed of zirconia particles containing at least 90% by volume of tetragonal crystals containing ceria, titania , magnesia or calcia as a stabilizer and a second phase composed of alumina particles are dispersed. It is made of a ceramic sintered body, and the magnesia or
Lucia is 0.01 to 0.1 mol based on the total amount of zirconia.
% Characterized that you contain.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
First, the zirconia-based composite ceramic sintered body used in the present invention will be described while sequentially describing each phase constituting the same. 90% by volume or more (preferably 95% by volume or more) of the first phase zirconia particles is composed of a tetragonal crystal phase. Even if monoclinic crystals are generated, the ratio is 1
Since the content is suppressed to 0% by volume or less, high strength and high toughness based on the stress-induced phase transition can be obtained.

Ceria (CeO) contained in zirconia particles
₂ ) and titania (TiO ₂ ) both act as stabilizers for tetragonal zirconia, and the addition of titania is
Increasing the critical stress for stress-induced phase transition from tetragonal to monoclinic contributes to higher strength. The content of ceria in the zirconia particles of the first phase is not particularly limited, but is, for example, preferably 8 to 12 mol%, more preferably 10 to 12 mol% with respect to the total amount of zirconia. If this content is less than 8 mol%, tetragonal crystallization, which is a metastable phase, becomes insufficient and monoclinic crystals predominantly increase, resulting in a sample having cracks or microcracks inherent after sintering. If it exceeds 12 mol%, cubic crystals that are a high temperature stable phase will start to appear and the amount of tetragonal crystals will be less than 90% by volume, and sufficient strength and toughness can be obtained. There is a risk of disappearing.

Further, the inclusion of titania has the effect of promoting the grain growth of zirconia particles in addition to contributing to the enhancement of strength as the above-mentioned stabilizer, and it is more likely to be contained in the zirconia particles during the sintering process. It is possible to disperse many alumina particles, and it is effective for further strengthening. Here, the content of titania is not particularly limited, for example, relative to the total amount of zirconia,
It is desirable to keep it in the range of 0.02 to 4 mol%, and more preferably 0.05 to 1 mol%. If the content of titania is less than 0.02 mol%, a sufficient grain growth effect of zirconia cannot be obtained, and if it exceeds 4 mol%, coarsening of the zirconia particles may cause a significant decrease in strength. Not preferable.

[0012] first phase comprising zirconia particles, magnesia (MgO) or calcia (CaO) is further included. These act as stabilizers of tetragonal zirconia to contribute to high strength and high toughness, and also have a role as additives to contribute to the formation of needle crystals as the third phase described later. Content of the magnesia or <br/> calcium A contained in the first Aichu, compared di- zirconia total amount, 0. 01
0.1 to 0.1 mol%, more preferably 0.05 to 0.1 mol%. If this content is less than 0.01 mol%, there is a risk that the contribution to the enhancement of strength as a stabilizer and the contribution to the formation of needle crystals as the third phase may be reduced, and
If it exceeds 1 mol%, the needle-like crystals, which are the third phase, may grow large and the strength may decrease.

As described above, the zirconia particles as the first phase may be a three-component system consisting of only the essential components of zirconia, ceria and titania as described above, or to which one of magnesia and calcia is added. It can also be a component system. Further, the first phase may further contain a trace amount of impurities. Next, the alumina particles that are the second phase of the zirconia-based composite ceramic sintered body will be described.

The alumina particles constituting the second phase are present in the zirconia particles by being partly incorporated into the zirconia particles of the first phase during the sintering process. It is preferable from the viewpoint of increasing the strength of the sintered body. For that, it has to be very small,
The average particle size of the starting material is preferably 0.5 μm or less, more preferably 0.2 μm or less, still more preferably 0.1 μm or less.
μm or less. Further, in order to sufficiently exert the effect of being incorporated into the zirconia particles, the alumina particles present in the zirconia particles are preferably 2% by number or more based on all the alumina particles in the zirconia-based composite ceramic sintered body. The higher the ratio, the better.

The content of the alumina particles in the zirconia-based composite ceramic sintered body is not particularly limited, but is preferably 0.5 to 0.5 with respect to the entire sintered body.
It is 50% by volume, more preferably 30-40% by volume. If the content of alumina particles is less than 0.5% by volume, the effect of improving strength and toughness is small, and if it exceeds 40% by volume, the alumina particles sinter with each other and the alumina particles taken into the zirconia particles are reduced. In addition, the strength and toughness are gradually lowered, and when the content exceeds 50% by volume, alumina becomes a matrix, so that the strength and toughness are significantly deteriorated.

In the present invention, the third phase, which is a needle-like crystal phase of a composite oxide containing Ce, Al and O and Mg or Ca as constituent elements, is further dispersed in the zirconia-based composite ceramic sintered body. Is preferable from the viewpoint of improving the toughness value. The needle-shaped crystal phase that constitutes this third phase is
It is formed by the reaction of ceria, which was solid-soluted in the zirconia particles as a stabilizer, with magnesia or calcia, and alumina during the sintering process. The needle-shaped crystals have an effect of preventing the development of cracks in the sintered body and suppressing a decrease in toughness. However, if there are too many needle-like crystal phases, the number of fracture sources increases and the strength decreases, so it is desirable to keep the magnesia or calcia content within the above range.

In addition to the first phase, the second phase, and the third phase, a trace amount of impurities may be further contained. Next, consideration will be given to the mechanism of strengthening the intragranular composite (so-called nanocomposite), which is a feature of the zirconia-based composite ceramic sintered body forming the fitting portion of the optical fiber connector of the present invention. The fine alumina particles incorporated in the crystal grains of the tetragonal zirconia stabilized with ceria / titania form a local residual stress field in the zirconia crystal grains due to the difference in thermal expansion. This residual stress field is
It increases the critical stress of stress-induced phase transition from tetragonal to monoclinic and contributes to the strengthening. Further, the residual stress field forms dislocations and subgrain boundaries in which the dislocations pile up in the zirconia crystal grains, resulting in high strength due to subdivision of the crystal grains. As described above, it is very important to compound the second phase with different thermal expansion coefficient in the zirconia crystal grains in order to realize the extremely high strength. It is possible to improve the strength of stabilized tetragonal zirconia to a level exceeding the above-mentioned yttria-based tetragonal zirconia.

Next, a method of manufacturing a ferrule using the zirconia-based composite ceramic sintered body will be described.
A first component for producing zirconia particles containing ceria and titania and magnesia or calcia, a second component for producing alumina particles, an organic binder, water, a plasticizer, etc. are appropriately added and kneaded, followed by a molding step In, a through-hole ceramic material having a prepared hole in the center of 20 to 100 μm is formed. At this time, as the molding process, press,
Any method such as extrusion or injection molding may be used.
The ceramic material thus obtained is fired at a high temperature of 1300 ° C. or higher in an oxidizing or non-oxidizing atmosphere to produce a zirconia-based composite ceramic sintered body. Next, a wire is passed through the prepared hole of the sintered body, and a hole is polished with a diamond paste or the like to finish it to a predetermined fine hole diameter. Further, as an outer diameter finish, the wire is passed through the center hole to perform centerless processing. In this hole polishing and outer diameter finishing, it is possible to finish the outer diameter accuracy, the hole diameter accuracy, the eccentricity, etc. to 1 to 2 μm. Next, the end face is chamfered in the end face finishing step to complete the ferrule. As the first component and the second component, those obtained by calcining a mixture obtained by a usual dry or wet method and pulverizing with a ball mill or the like to have a predetermined average particle diameter can be used.

Next, a method for manufacturing a split sleeve using the zirconia-based composite ceramic sintered body will be described.
A first component for producing zirconia particles containing ceria and titania and magnesia or calcia, a second component for producing alumina particles, an organic binder, water, a plasticizer, etc. are appropriately added and kneaded, followed by a molding step In, a through-hole ceramic material having a prepared hole slightly smaller than the product size is formed in the center. At this time, as the molding step, any method such as pressing, extrusion and injection molding may be used. The ceramic material thus obtained is fired at a high temperature of 1300 ° C. or higher in an oxidizing or non-oxidizing atmosphere to produce a zirconia-based composite ceramic sintered body. Next, after the outer diameter of this sintered body is processed to finish it to a predetermined outer diameter, a rod is passed through the prepared hole of the sintered body, and a hole is polished with diamond paste or the like to finish it to a predetermined hole diameter. In this hole polishing process, the hole diameter accuracy can be finished to 1 to 2 μm. Next, the end face is chamfered in the end face finishing step, and in the case of a sleeve, this is a finished product. Further, in the case of a split sleeve, a finished product is obtained by further performing a slitting process and opening a slit. As the first component and the second component, those obtained by calcining a mixture obtained by a usual dry or wet method and pulverizing with a ball mill or the like to have a predetermined average particle diameter can be used.

The zirconia-based composite ceramic sintered body obtained as described above has higher strength and toughness as compared with the conventional zirconia ceramics, and has a structural deterioration due to a phase transition in the presence of water vapor. Does not happen. Therefore, by using this zirconia-based composite ceramic sintered body as a ferrule and / or a sleeve,
It is possible to provide a highly reliable optical fiber connector that can be used even in a harsh environment and is suitable for connecting optical fibers with high dimensional accuracy.

The optical fiber connector of the present invention is not particularly limited in other constitutions as long as the zirconia-based composite ceramic sintered body is used as the material for forming the ferrule and / or the sleeve. One having the same configuration as the optical fiber connector shown in FIG.

[0022]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples. Na
Of the following examples, Examples 1 and 2 are the techniques of the present invention.
It is a reference technology that is out of the scope. Examples 3 to 6
1 illustrates an embodiment of the present invention. <Examples 1 and 2> Specific surface area of zirconia powder having a specific surface area of 15 m ² / g and containing ceria in the amount shown in Table 1 relative to the total amount of zirconia is 25
Table 1 titania powder m ² / g with respect to zirconia total amount
The mixed powder obtained by adding the amount shown in was mixed in a wet ball mill for 24 hours using ethanol as a solvent. After drying the powder,
It was calcined in the air at 950 ° C. for 3 hours. Α-Alumina powder having an average particle size of 0.2 μm was added to the obtained calcined powder so as to be 30% by volume with respect to the entire zirconia-based composite ceramic sintered body, and wet-ball mill mixing was performed for 24 hours using ethanol as a solvent. . After that, the mixed powder obtained by drying is uniaxially pressed under conditions of 10 MPa and 150
A disk-shaped molded body was obtained by cold isostatic pressing under MPa conditions. This molded body was exposed to the air at 150
Pressureless sintering was performed under the conditions of 0 ° C. and 2 hours.

When the obtained sintered body was observed with a scanning electron microscope and a transmission electron microscope, it was confirmed that some fine alumina particles were present in the zirconia crystal grains. Further, the average particle size of zirconia and alumina was determined by the intercept method using a scanning electron microscope using a sintered body whose polished surface was heat-treated. Next, the sintered body is cut, ground, and surface-polished to obtain a flat end product, and the three-point bending strength at room temperature is measured by the method specified in JIS-R1601 and the fracture toughness value is measured by the IF method. did. Further, when the crystal phase was identified by X-ray diffraction, it was confirmed that the zirconia crystal phase consisted of tetragonal crystals of 95% by volume or more and monoclinic crystals of 5% by volume or less, and no cubic crystal was observed. Furthermore, the ratio (R) of the alumina particles present in the zirconia particles to all the alumina particles was determined. Here, this ratio is obtained by observing with a transmission electron microscope or a scanning electron microscope using a sintered body whose polished surface is heat-treated, and the number (S) of all the alumina particles present in the field of view and the zirconia grains. The number (n) of alumina particles present in the
/ S) × 100. In addition, an excess severe hydrothermal test was conducted to examine the change over time of the mirror surface when held at 200 ° C. in a steam atmosphere at 1 atmosphere for 24 hours.

The above results are shown in Tables 1 and 2. <Examples 3 to 6> Table 1 shows the amount of ceria based on the total amount of zirconia.
The amount of titania powder having a specific surface area of 25 m ² / g and magnesia or calcia having an average particle size of 0.3 μm are added to the zirconia powder having a specific surface area of 15 m ² / g shown in Table 1 with respect to the total amount of zirconia. The mixed powder
Wet ball mill mixing was performed for 24 hours using ethanol as a solvent. After the powder was dried, it was calcined in the air at 950 ° C. for 3 hours. An α-alumina powder having an average particle size of 0.2 μm was added to the obtained calcined powder in an amount shown in Table 1 with respect to the entire zirconia-based composite ceramic sintered body, and ethanol was used as a solvent for 24 hours in a wet ball mill. Mixed. After that,
A sintered body was obtained in the same manner as in Example 1.

When the obtained sintered body was observed with a scanning electron microscope and a transmission electron microscope, it was confirmed that some fine alumina particles were present in the zirconia crystal grains. Further, in the sintered body, Ce, Al and O, and M
It was confirmed that the third phase composed of the acicular crystal phase of the composite oxide containing g or Ca as a constituent element was further dispersed.

Tables 1 and 2 show the results of various physical property measurements and an excess severe hydrothermal test performed on the obtained sintered body in the same manner as in Example 1. <Comparative Example 1> A zirconia sintered body containing 3 mol% of yttria used for a ferrule and a sleeve of a conventional optical fiber connector was obtained in the same manner as in Example 1, and various physical properties were measured by the same method as in Example 1. Tables 1 and 2 show the results of the extreme severe hydrothermal test. <Comparative Example 2> A zirconia sintered body containing 12 mol% of ceria was obtained in the same manner as in Example 1, and the results of various physical property measurements and excess severe hydrothermal tests performed in the same manner as in Example 1 are shown in Tables 1 to 1. 2 shows. [Ferrule Production and Evaluation] A ferrule 2 was produced using the zirconia sintered bodies obtained in Examples 1 to 6 and Comparative Examples 1 and 2, and one end thereof was formed with a metal flange 7 as shown in FIG. A load (W) was applied from above to the other end of the support, and the load (W) at which breakage occurred in the supporting portion of the metal flange 7 was measured. The ferrule using the zirconia sintered body containing 12 mol% of ceria of Comparative Example 2 has a strength of 10 kg.
It was found that the ferrules using the zirconia sintered bodies of Examples 1 to 6 have a sufficient strength of about 25 kg or more, although they do not withstand the use of general optical fiber connectors.

An optical fiber was adhered and fixed to the ferrule, and the end face of the ferrule was polished to a convex spherical surface having a radius of curvature of about 13 mm with diamond abrasive grains. Approximately 1K between the convex spherical surfaces of the two ferrules thus obtained
A force of g was applied and the pieces were left to stand for about 1 month in a state of a temperature of 85 ° C. and a relative humidity of 85%, and the change in the end face shape before and after the test was observed. As a result, in the ferrule using the yttria-stabilized zirconia sintered body of Comparative Example 1, the radius of curvature was flattened to 70 mm, which is about 5.5 times.
It was found that the ferrule using the zirconia sintered body of No. 6 showed no change at all and was extremely stable. [Production and Evaluation of Sleeve] Next, using the zirconia sintered bodies obtained in Examples 1 to 6 and Comparative Examples 1 to 2, thin pipe-shaped zirconia sintered bodies were produced by the same manufacturing method as the ferrule. Then, after cutting to a length of 1.4 mm, the inner diameter is 2.489 mm and the outer diameter is 3.20 using diamond paste or the like.
After finishing to 0 mm, the width of one side is 0.5 mm in the length direction.
A slit sleeve was made by inserting the slits. When a ferrule having an outer diameter of 2.499 ± 0.0005 mm was inserted into this split sleeve and a lateral force was applied, the split sleeve made of the yttria-stabilized zirconia sintered body of Comparative Example 1 was easily broken. However, no fracture was observed in the split sleeves made from the zirconia sintered bodies of Examples 1 to 6.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

In the optical fiber connector according to the present invention, the zirconia-based composite ceramic sintered body used as a constituent material of the ferrule and / or the sleeve has higher strength and higher toughness than conventional zirconia ceramics. In addition, there is little structural deterioration due to phase transition in a water vapor atmosphere. Therefore, the optical fiber connector of the present invention can be used without deterioration even in a harsh environment, has high strength and hardness, is suitable for connecting optical fibers with high dimensional accuracy, and is required for communication equipment. It is an optical fiber connector that can sufficiently guarantee the reliability of the optical fiber.

[Brief description of drawings]

FIG. 1 is a cross-sectional view taken along the axial direction showing an example of an optical fiber connector.

2 is a longitudinal sectional view showing a ferrule used in the optical fiber connector of FIG.

3 is an external view showing a split sleeve used in the optical fiber connector of FIG.

FIG. 4 is a schematic sectional view of a ferrule breaking strength measuring system.

[Explanation of symbols]

1 Optical fiber connector 2 ferrules 3 sleeves 4 adapter 5 optical fiber 22 pores

Front page continuation (72) Inventor Etsuji Sugita 1-3-1 Gotenyama, Musashino City, Tokyo NTT Advanced Technology Corporation (72) Inventor Masanori Shinomoto 1667 Tamura, Hiratsuka, Kanagawa Prefecture Pilot (56) Reference JP-A-4-243961 (JP, A) JP-A-6-325611 (JP, A) JP-A-6-345549 (JP, A) JP-A-7-63950 ( JP, A, JP 8-201655 (JP, A), JP, 8-268755 (JP, A), JP, 59-144620 (JP, A), JP, 60-148006 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 6/38

Claims (3)

(57) [Claims] 1. An optical fiber connector having a structure in which connecting ends of two optical fibers are fitted in respective pores of a pair of ferrules and the pair of ferrules are fitted in a sleeve. / Or the sleeve comprises ceria and titania , magnesia or calcia as stabilizers, a first phase consisting of zirconia particles at least 90% by volume tetragonal, and a second phase consisting of alumina particles. It is formed of a zirconia-based composite ceramic sintered body in which a phase is dispersed, and the magnesia or
Calcia is 0.01 to 0.1 based on the total amount of zirconia.
Optical fiber connector which is characterized that you containing mol%. 2. The optical fiber connector according to claim 1, wherein in the zirconia-based composite ceramic sintered body, a part of the second phase alumina particles is present in the first phase zirconia particles. 3. A zirconia-based composite ceramic sintered body comprising a needle-like crystal phase of a composite oxide containing Ce, Al and O and Mg or Ca as constituent elements.
The fiber optic connector of any of claims 1 to 2 , wherein the phases are further dispersed.