JPH09159860A - Optical fiber connector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the connector which has high package density and excellent optical characteristics. SOLUTION: When plugs 2-1 and 2-2 gripping optical fibers 1-1 and 1-2 with grip parts 2a respectively are inserted and fitted in an adapter 3 from both the sides, the tips of the optical fibers 1-1 and 1-2 are inserted into the array hole 3a of the adapter 3 and made to abut against each other. Then they deflect in a space 2b respectively and their connection end surfaces are pressed against each other with the buckling force of the optical fibers 1-1 and 1-2 and then surely connected together.

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 for connecting optical fibers to each other.

[0002]

2. Description of the Related Art As a conventional optical fiber connector, MU
And MT type optical fiber connectors will be described.

FIG. 9 shows an MU type optical fiber connector.
In the figure, 1 is an optical fiber, 2 is a plug, 3 is an adapter, and 9
Is a ferrule. The optical fiber 1 is fixed to the ferrule 9 in the plug 2, the end face is polished to a convex spherical surface, and this is fitted into the sleeve in the adapter 3 to connect the end faces of the optical fiber.

The MU type optical fiber connector has a plug cross-sectional area of 20 mm ² and an average insertion loss of 0.05 d per single core.
B, the optical characteristics with a return loss average of 50 dB are obtained.

FIG. 10 shows an MT type optical fiber connector. In the figure, 1 is an optical fiber, 9 is a ferrule, 10 is a guide pin, and 11 is a clamp spring. The optical fiber 1 is fixed to the plug, the end face is polished, and the two guide pins 10
The plugs are abutted to each other via, the end faces of the optical fibers are connected, and this state is held by the clamp spring 11. At this time, a refractive index matching agent is applied to the joint end surface to reduce reflection.

The MT type optical fiber connector can be multi-core. In the case of an 8-core connector with a 0.25 mm pitch, the plug cross-sectional area is 20 mm ² , the insertion loss average is 0.5 dB, and the return loss is a refractive index matching agent. Optical characteristics of 40 dB on average have been obtained by using this.

Comparing the MU type and MT type optical fiber connectors, the MT type has a higher packaging density, but the MU type has better optical characteristics. The difference in optical characteristics is due to the following reasons. The insertion loss depends on the positional accuracy of the connected optical fiber. The position accuracy is determined by the eccentricity of the ferrule and the sleeve in the MU type, and the position accuracy of the optical fiber from the guide pin in the MT type. Since the eccentricity accuracy can be made smaller, the insertion loss of the MU type is small. The return loss depends on the degree of adhesion between the optical fibers. The MU type has a convex spherical surface, and the optical fibers are in close contact with each other. However, the MT type has a large variation in protruding or pulling in the optical fiber end surface from the plug tip, and it is necessary to fill the gap with a refractive index matching agent. Therefore, since the refractive index temperature dependence of the refractive index matching agent is larger than that of glass, even if the return loss is high at room temperature, the return loss is 3 at high temperature or low temperature.
It will be reduced to about 0 dB.

[0008]

As described above, the MT type optical fiber connector has a higher packaging density, and the MU type optical fiber connector has better optical characteristics.
No fiber optic connector has the advantages of both. In the fields of optical transmission devices and optical circuit connections, there is a demand for an optical fiber connector that has a mounting density of the MT type optical fiber connector and optical characteristics of the MU type optical fiber connector.

[0009] The present invention has been made in view of the above,
An object of the invention is to provide an optical fiber connector having high packaging density and good optical characteristics.

[0010]

In order to achieve the above object, the present invention according to claim 1 fixes an optical fiber according to claim 2.
Individual plugs and an adapter interposed when the plugs are made to face each other and are joined together, and the two plugs have a holding portion for holding the optical fiber as a cantilever at one end, and the other end. Has a cavity for the optical fiber to bend, and the adapter has a structure for connecting and fixing the two plugs at both ends, and has an alignment hole for aligning and fixing the optical fiber at the center in the radial direction. An alignment member, the alignment hole of the alignment member has an inner diameter near the center in the longitudinal direction substantially equal to the outer diameter of the core of the optical fiber, and the inner diameters of both ends are larger than the outer diameter of the core of the optical fiber. The gist is that it is large and changes in a tapered shape.

According to the present invention of claim 1, when the plugs are fitted from both ends of the adapter, the optical fibers are properly butted in the alignment holes, and the connecting end face is pressed by the buckling force of the optical fibers. , Connected properly.

Further, the present invention according to claim 2 is based on claim 1.
In the invention described above, when the two plugs are respectively joined to the adapter, the gist is that the plugs are in surface contact with each other.

According to the second aspect of the present invention, when the plug is joined to the adapter, the plugs are in surface contact with each other,
The optical fibers are properly connected.

Further, the present invention according to claim 3 has a plug for fixing the optical fiber and a jack for fixing the optical fiber, and the plug has a holding portion for holding the optical fiber as a cantilever at one end. And has a cavity for the optical fiber to bend at the other end, the jack is a structure for connecting and fixing opposite to the plug, the optical fiber as a cantilever at the end not connected to the plug A holding part for holding, an aligning member having an aligning hole for aligning and fixing the optical fibers when connecting with a plug, and a cavity formed between the aligning member and the holding part, The inner diameter of the alignment hole near the center in the length direction is substantially equal to the outer diameter of the optical fiber core wire, and the inner diameters of both ends are larger than the outer diameter of the optical fiber core wire, and are changed in a tapered shape. Is the gist.

According to the third aspect of the present invention, when the plug and the jack are fitted together, the optical fibers are brought into proper contact with each other in the alignment holes and the buckling force of the optical fibers presses the connection end face to make it suitable. Connected properly.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the plug has an optical fiber aligning member which is slidable in the inside of the cavity. To do.

According to the present invention of claim 4, an optical fiber aligning member is provided inscribed in the cavity of the plug, and the aligning member slides in the cavity.

Further, the present invention described in claim 5 provides the invention according to claim 1.
The invention according to any one of claims 1 to 3, wherein the plug is configured to hold a plurality of optical fibers, and the alignment member has a plurality of alignment holes for aligning and fixing the plurality of optical fibers. And

According to the fifth aspect of the present invention, a plurality of optical fibers can be simultaneously connected at a high density with one optical fiber connector.

[0020] Further, the present invention described in claim 6 is based on claim 1.
The gist of the invention described in any one of (1) to (5) is that the plug or adapter is made of quartz.

The present invention according to claim 7 is the invention according to any one of claims 1 to 5, characterized in that the plug or adapter is made of borosilicate glass, Pyrex glass or crystallized glass. To do.

Further, the present invention described in claim 8 is based on claim 1.
The gist of the invention described in any one of (1) to (5) is that the plug or adapter is made of amber or fernico.

Further, the present invention described in claim 9 is based on claim 1.
The gist of the invention described in any one of (1) to (5) is that the plug or adapter is made of a liquid crystal polymer.

In the present invention as set forth in claims 6 to 9, the plug or adapter is made of quartz, borosilicate glass, Pyrex glass or crystallized glass, amber or Fernico, or liquid crystal polymer. All have a linear expansion coefficient of 1 × 10 ^-5 / K
It is as small as the following, and even if it expands and contracts due to temperature changes, the amount of deflection of the optical fibers decreases, the surface contact between the optical fibers becomes poor, and the amount of deflection of the optical fibers increases and radiation loss increases. There is no.

According to a tenth aspect of the present invention, there is provided a hollow buckling portion having one end opened and a grip portion formed on the other end side of the buckling portion, the grip portion and the buckling portion being penetrated. And a first member having a first holding portion for holding the first optical fiber extending a predetermined accommodation extra length from the opening end portion in a cantilever manner, and the first member in one opening portion. The tip of the optical fiber is inserted and the second optical fiber is inserted through the other opening for a predetermined length. The alignment hole is formed at the end of the alignment hole where the one opening is formed. A fitting portion to be fitted to the fitting portion, an abutting surface which is formed at a position corresponding to the tip of the second optical fiber so as to project to the outer peripheral portion of the fitting portion, and the opening end of the buckling portion abuts, A second holding the inserted second optical fiber in the other opening of the alignment hole And a second member having a gripping portion, an opening end of the buckling of the first member is the second
When the fitting portion of the second member is inserted into the hollow buckling portion of the first member until it abuts against the abutting surface of the member, the first optical fiber extends from the one opening. The first optical fiber is inserted into the alignment hole and is surface-connected to the second optical fiber, and the first optical fiber is buckled in the buckling portion due to the predetermined accommodation length to ensure the surface connection of both optical fibers. , The predetermined accommodation extra length that causes this buckling depends on the thermal expansion coefficient of the first and second members and the first and second optical fibers and the radiation loss of the first and second optical fibers. The gist is that it is set based on this.

According to the tenth aspect of the present invention, the first aspect
When the fitting portion of the second member is inserted into the hollow buckling portion of the first member until the open end of the buckling portion of the first member hits the abutting surface of the second member, the first optical fiber Is inserted into the alignment hole from one opening to make a surface connection with the second optical fiber, and the first optical fiber is buckled in the buckling portion due to the predetermined accommodation extra length, and the surface connection of both optical fibers is made. The predetermined accommodation surplus length that ensures the above-mentioned buckling and causes the thermal expansion coefficient of the first and second members and the first and second optical fibers and the radiation loss of the first and second optical fibers. Even if the first and second members and both optical fibers expand and contract due to temperature change, the buckling amount of the optical fibers is reduced and the surface contact between the optical fibers becomes poor. The amount of buckling of the optical fiber does not increase and radiation loss does not increase.

The invention according to claim 11 is the invention according to claim 10, wherein each of the first and second members is quartz, borosilicate glass, Pyrex glass,
The gist is that it is made of a material selected from the group consisting of crystallized glass, amber, Fernico, and liquid crystal polymer.

According to the present invention of claim 11,
And the second member is made of a material selected from the group consisting of quartz, borosilicate glass, Pyrex glass, crystallized glass, amber, Fernico, and liquid crystal polymer, all of which have a linear expansion coefficient of 1 × 10. ^-5 / K
Even if it is as small as below, the buckling amount of the optical fibers will decrease even if it expands and contracts due to temperature changes, and the surface contact between the optical fibers will become poor, and the buckling amount of the optical fibers will increase and radiation loss will increase There is nothing to do.

Furthermore, the present invention according to claim 12 comprises an outer cylindrical member having a hollow buckling portion and having a first predetermined length and a first predetermined linear expansion coefficient, and inside the outer cylindrical member. And a one end of the outer tubular member is integrally formed with the one end of the outer tubular member, the one end of which is open to form a hollow portion, which has a second predetermined length and a second predetermined linear expansion coefficient. And the second
An inner cylindrical member having a product of a predetermined length and a second predetermined linear expansion coefficient equal to the product of the first predetermined length and the first predetermined linear expansion coefficient, and closing of the inner cylindrical member. A first light which is formed at the other end and which penetrates the inner tubular member and the buckling portion and extends from the opening end portion of the buckling portion which is the other end of the outer tubular member by a predetermined accommodation extra length. A first member having a first gripping portion for holding the fiber in a cantilever manner, and a tip of the first optical fiber inserted into one opening,
An alignment hole into which the second optical fiber is inserted for a predetermined length from the other opening, and a fitting portion formed at an end of the alignment hole where the one opening is formed and fitted into the buckling portion An abutting surface which is formed at a position corresponding to the tip of the second optical fiber so as to project to the outer peripheral portion of the fitting portion, and the opening end of the buckling portion abuts, and the other opening of the alignment hole. A second member having a second holding portion holding the inserted second optical fiber in the section, and the first member
The fitting portion of the second member is inserted into the hollow buckling portion of the first member until the open end of the buckling portion of the second member hits the abutting surface of the second member. If
When the first optical fiber is inserted into the alignment hole through the one opening and is surface-connected to the second optical fiber, the first optical fiber is buckled in the buckling portion due to the predetermined accommodation length, and both light beams are transmitted. The surface connection of the fibers is ensured, and the product of the first predetermined length of the outer tubular member and the first predetermined linear expansion coefficient is the second predetermined length of the inner tubular member and the second predetermined line. The gist is that the predetermined accommodation extra length of the first optical fiber does not change even if the outer tubular member and the inner tubular member expand and contract due to temperature change, which is equal to the product of the expansion coefficient.

In the present invention according to claim 12, the first
If the fitting portion of the second member is inserted into the hollow buckling portion of the first member until the open end of the buckling portion of the first member hits the abutting surface of the second member, When the optical fiber is inserted into the alignment hole from one opening and is surface-connected to the second optical fiber, the optical fiber is buckled in the buckling portion due to the predetermined accommodation length to ensure the surface connection of both optical fibers. And the first predetermined length of the outer tubular member and the first
Is equal to the product of the second predetermined length and the second predetermined linear expansion coefficient of the inner tubular member, and even if the outer tubular member and the inner tubular member expand or contract due to temperature change. Since the predetermined accommodation length of the first optical fiber does not change, the connection between the first and second optical fibers is not affected by the temperature change, and the connection between both optical fibers is stable.

According to a thirteenth aspect of the present invention, there is provided a hollow buckling portion having one end opened and a grip portion formed on the other end side of the buckling portion, the grip portion and the buckling portion being penetrated. And a first member having a holding portion for holding one or a plurality of optical fibers extending in a predetermined accommodation extra length from the end face of the opening in a cantilever manner, and processed into a flat surface including a substrate portion at one end One or a plurality of substrate-type optical waveguides having an end face, and mounted near the end face of the optical waveguide,
One or a plurality of optical fiber guides having one or a plurality of optical fiber insertion holes, and aligning the optical axes of the optical fiber and the optical waveguide when the optical fiber is inserted into the optical fiber insertion hole And when the end face of the opening of the first member and the end face of the optical waveguide are fitted, the optical fiber is inserted into the optical fiber insertion hole of the optical fiber guide, and both ends A first member and a second member that fixes the substrate-type optical waveguide in a state where the surfaces are fitted to each other, and the opening end face of the first member and the optical waveguide end face are butted to each other. When the tip end face of the optical fiber is abutted against the end face of the optical waveguide in a state where the optical fiber is inserted into the optical fiber insertion hole of the optical fiber guide, the optical fiber has the predetermined accommodation extra length. Ri buckled in said buckling, and summarized in that to sustain the front end surface and the end faces are butted force of the optical waveguide of the optical fiber by the restoring force of the optical fiber buckled.

In the present invention according to claim 13, the first aspect
Butt the end face of the opening of the member and the end face of the optical waveguide,
When one or more optical fibers are inserted into the insertion holes of one or more optical fiber guides and the tip end of each optical fiber is abutted against the end face of each optical waveguide, each optical fiber is accommodated in a predetermined manner. The excess length causes the buckling in the buckling portion, and the restoring force of the buckled optical fiber maintains the force of abutting the end faces of the optical fibers and the end faces of the optical waveguides. Physical contact between the surfaces is realized, and optical connection with small connection loss and large return loss or high-density multi-core connection is realized.

According to a fourteenth aspect of the present invention, in the invention according to the thirteenth aspect, the tip end surface of the optical fiber is processed so as to be vertical and flat with respect to the optical axis of the optical fiber. Or, it is processed into a spherical shape so that the vicinity of the core is convex, or is formed by removing the clad outer peripheral portion of the end face formed by cleavage to reduce the cross-sectional area. It is a gist that, when the tip end face and the end face of the optical waveguide are butted against each other, surface contact between the both end faces is ensured at least in the core portion of the optical fiber and the optical waveguide.

In the fourteenth aspect of the present invention, the tip end surface of the optical fiber is processed into a plane which is perpendicular to the optical axis, or is processed into a spherical shape so that the vicinity of the core is convex, or It is formed by removing the clad peripheral part of the cleaved end face to reduce the cross-sectional area.When the tip face of the optical fiber and the end face of the optical waveguide are abutted, the core part of the optical fiber and the optical waveguide In, the surface contact of both end surfaces is ensured.

Further, the present invention according to claim 15 is, in the invention according to claim 13 or 14, characterized in that the plurality of optical fiber insertion holes are provided in the optical fiber guide of the same member.

In the fifteenth aspect of the present invention, the plurality of optical fiber insertion holes are formed in the same optical fiber guide.

[0037]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional perspective view showing the structure of an optical fiber connector according to the first embodiment of the present invention. In the figure, 1 (1-1, 1-2) is an optical fiber, 1a is an optical fiber coating, 2 (2-1, 2-2) is a plug, 2
a is an optical fiber grip, 2b is a space for bending the optical fiber, 3 is an adapter, 3a is an alignment hole for the optical fiber, 3b
Is a support portion of the alignment hole. The figure is a cross-sectional view, and the upper part shows the plug 2 (2-1, 2-2) before being fitted to the adapter 3, and the lower part shows it after the fitting. In the figure, L is the length of the buckling part, and L is
₁ is the amount of protrusion of the optical fiber from the plug 2, and L ₂ is the distance from the center of the adapter 3 to the surface of the alignment hole support portion on which the plug 2 abuts. The plug 2 is a space 2 for bending the optical fiber.
b, and the optical fiber 1 has a space 2b for bending the optical fiber.
Is fixed by an adhesive or the like at the grip portion 2a so as to form a cantilever. At the time of fitting, the tip of the plug 2 is abutted against the side surface of the support portion 3b of the alignment hole. The optical fiber 1 projects L ₁ from the tip of the plug 2, and the projection amount L ₁ is set to be larger than the distance L ₂ from the center of the adapter 3 to the surface of the alignment hole support portion on which the plug 2 abuts, and L ₁ −L ₂ > 0.

When the plug 2 is fitted into the adapter 3, the optical fiber 1 is inserted into the alignment hole 3a for the optical fiber. By providing a taper at the entrance, even if the tip of the optical fiber 1 is displaced from the center position, this is absorbed and the optical fiber can be smoothly inserted. Two plugs 2-1 and 2
-2 is fitted to the adapter 3, the optical fibers 1-1, 1
-2 tip is abutted in the alignment hole, optical fiber 1-
The amount L ₁ -L _{2 that} is excessively projected from the respective plugs 2-1 and 2-2 of _{1, 1-2} is pushed into the two optical fiber bending spaces 2b with an appropriate distribution.

FIG. 2 shows the pressing force generated at the time of fitting with respect to the pushing amount. Buckling force P is expressed by equations (1) and (2),
In the buckling region, it is determined only by the length L of the buckling part,
It is constant regardless of the pushing amount.

[0041]

[Equation 1] Therefore, the allocation need not be specified. Further, the boundary value ΔL _c between the elastic region and the buckling region is expressed by equation (3).

[0042]

(Equation 2) Here, E is the elastic modulus of the optical fiber, I is the second moment of area, and d is the outer diameter. In the case of a general glass optical fiber, E = 76 GPa, d = 125 μm, and L = 8.
In the case of mm, P = 0.57N (58 gf), ΔL _c = 5
μm. Therefore, the protrusion amount L ₁ -L ₂ is 5 in this case.
If it is set to more than μm, it will always buckle. L of two plugs
There is a slight difference in processing accuracy between the two optical fibers, and there is a difference in the buckling force between the two optical fibers. If two protrusions are pushed into a plug with a small buckling force, only this optical fiber will buckle. However, there is no problem in this state,
This buckling force is applied to the connection surface as a pressing force. Even if there is a difference in the buckling force, both the optical fibers will buckle if the forces are balanced in the axial direction due to the frictional force between the optical fiber and the alignment hole.

Incidentally, the plugs 2-1 and 2-2 and the adapter 3
Can be fixed at the time of fitting with a screw, a clamp mechanism, or the like.

The alignment hole 3a has an inner diameter of 126 μm, and the end face is an optical fiber having the same polishing as the MU type optical fiber connector. The insertion loss is 0.05 dB and the return loss is 50
Good optical characteristics equivalent to those of the MU type optical fiber connector of about dB can be obtained. In the cleaved optical fiber,
Since there is a burr on the end face, there is a gap even during connection, the return loss does not increase, and the insertion loss decreases slightly.

FIG. 3 is a sectional perspective view showing the structure of the optical fiber connector according to the second embodiment of the present invention. In the figure, 1 (1-1, 1-2) is an optical fiber, 1a is an optical fiber coating, 2 is a plug, 2a is an optical fiber gripping portion, 2b is a space for deflecting an optical fiber, 4 (4-1, 4-
2) is a jack, 4a is an alignment hole for the optical fiber, 4b is a space for bending the optical fiber, 4c is an optical fiber gripping part, 4
d is a plug abutting surface. The optical fiber 1-
1 projects from the tip of the plug 2 by L ₁ as in the first embodiment.

In FIG. 3, the plug 2 is connected to the jack 4-
The optical fiber connector 91 shown in the lower part of FIG.
The optical fiber connector 92 shown in the lower right part of FIG.

The jack 4-1 is a type in which the optical fiber is buckled in the optical fiber bending space 4b in the jack.
This is a structure in which the plug 2-2 and the adapter 3 in FIG. 1 are combined. The optical fiber 1-2 is L ₁ -L in the alignment hole 4a.
It is fixed by the optical fiber gripping portion 4c in a state of protruding by ₂ from the center of the alignment hole 4a to the plug fitting side. When the plug 2 and the jack 4-1 are fitted by this structure, the optical fibers 1-1 and 1-2 are joined in the alignment hole as described in the first embodiment, and the joining surfaces are joined by the respective buckling forces. Press to obtain the optical connection.

The jack 4-2 eliminates the space for bending the optical fiber, and the tip of the optical fiber 1-3 is arranged at a position where the tip of the optical fiber 1-3 is pulled in L ₂ from the plug abutting surface 4d in the alignment hole.
It is fixed by the grip portion 4c. With this structure, plug 2
When one of the optical fibers does not buckle in the first embodiment, the buckling force of the optical fiber of the plug presses the joint surface to obtain an optical connection. The jack 4-2 has an advantage of being smaller than the jack 4-1 because it does not use a space for bending an optical fiber.

In the above embodiment, the plugs 2-1 and 2-1 are used.
-2 is fitted from both ends of the adapter 3, or the plug 2 and the jacks 4-1 and 4-2 are fitted, the bare optical fibers are butted against each other in the alignment hole, and the buckling force of the optical fibers causes the connection end surface to be connected. Is pressed, the ferrule and the spring member are unnecessary, the number of members is small, the sleeve is small at the outer diameter of the optical fiber, and the optical fiber end face is low-reflectance-polished, so that it is simple, compact, and has good optical characteristics. A fiber connector becomes feasible.

FIG. 4 is a sectional view showing the structure of an optical fiber connector according to the third embodiment of the present invention. In the figure, 1 is an optical fiber, 1a is a coating, 2 is a plug, and 2a.
Is an optical fiber grip, 2b is a space for bending the optical fiber,
3 is an adapter, 3a is an alignment hole for an optical fiber, 3b is a support part of the alignment hole, and 5 is an optical fiber butting jig.
The figure is a cross-sectional view. The upper part shows the plug 2 before being fitted to the adapter 3, and the lower part shows it after the fitting. In the figure, L is the length of the buckling portion, L ₁ is the amount of protrusion of the optical fiber from the plug 2, L ₂ is the distance from the center of the adapter 3 to the surface of the alignment hole supporting portion where the plug 2 abuts, ΔL Is the amount by which the optical fiber 1 is pushed into the plug 2 when the plug 2 is fitted into the adapter 3, and ΔL = L ₁ −L ₂ , δ is the optical fiber 1 at the time of fitting.
Is the amount of deflection. The optical fiber butting jig 5 has a concave surface with a depth L ₁ . The optical fiber butting jig 5 is installed at the tip of the plug 2, and the optical fiber 1 is fixed to the optical fiber grip 2a of the plug 2 with the optical fiber abutting the concave surface of the jig 5, and the optical fiber 1 is removed from the plug 2. Only L _{1 is} projected. If the plug 2 is fitted to the adapter 3 in this state and the optical fibers abut at the center of the alignment hole, the optical fiber is pushed into the plug by ΔL.

The shape of the optical fiber during buckling is a sine wave shape as shown in FIG. 5 and equation (4) (for example,
Material Mechanics, Okumura, Corona, pp. See 289-301). The radius of curvature R is expressed by equation (5). The radius of curvature becomes the minimum value R _min.
And is a function of L and δ.

[0052]

(Equation 3) After the fitting, the length of the optical fiber at the buckling portion becomes L + ΔL, so that the expression (7) is established, and the relationship between ΔL and δ is expressed by the expression (8).

[0053]

(Equation 4) Here, Elliptic () is an elliptic integral. Therefore, ΔL can be determined from the equations (6) and (8) so that the radius of curvature becomes equal to or larger than the allowable value.

For example, if a 1.3 μm band single mode optical fiber is used and L = 10 mm and ΔL = 0.2 mm, it is possible to set δ = 0.9 mm and R _min. = 5.6 mm, and bend An increase in loss due to loss can be suppressed to 0.01 dB or less. Further, since breakage of the optical fiber occurs at R = 3 mm or less, if the set value is made larger than this, breakage does not occur.

As described in the first and second embodiments, only one optical fiber may buckle. In this case, the maximum pushing amount is 2ΔL. Therefore, in the case of the above 1.3 μm band single mode optical fiber, by setting ΔL = 0.1 mm, it is possible to suppress increase in loss and prevent breakage.

According to this embodiment, it is possible to control the deflection δ of the buckling portion by controlling ΔL, and to increase the bending loss and prevent the breakage due to the increased deflection.

FIG. 6 is a partial sectional perspective view showing the structure of an optical fiber connector according to the fourth embodiment of the present invention.
In the figure, 1 is an optical fiber, 1a is a cover, 2 is a plug, 2c is a notch, 3 is an adapter, 3a is an alignment hole for an optical fiber, 3b is an alignment hole supporting portion for an optical fiber, 3c.
Is a penetrating portion for the tip of the plug. Adapter 3 is plug 2
Has a penetrating portion 3c so that the tips thereof are butted. The notch 2c at the tip of the plug 2 is for avoiding the alignment hole support 3b for the optical fiber. The optical fiber 1 projects from the tip of the plug 2 by ΔL.

In FIG. 6, only one plug 2 is shown and the other plug is omitted, but as in the case of the first embodiment shown in FIG. 1, two plugs 2 are provided. Inserted and fitted into the adapter 3 from both sides, the alignment hole 3 of the adapter 3
Two optical fibers 1 are connected in a.

According to the present embodiment, the amount of protrusion of the optical fiber can be reduced, so that the protection of the optical fiber is improved.
Further, since the dimension L ₂ used in the first, second, and third embodiments is not necessary, the dimension to consider the error is reduced by one, and the accuracy of the protrusion amount can be improved.

FIG. 7 is a sectional perspective view of an optical fiber connector according to the fifth embodiment of the present invention. In the figure,
1 is an optical fiber, 1a is a coating, 2 is a plug, 2a is an optical fiber gripping portion, 2b is a space for bending an optical fiber, 3 is an adapter, 3a is an alignment hole for an optical fiber, 3b is a support portion of the alignment hole, 6 Is an optical fiber alignment member, 6a is an alignment hole for the optical fiber of the alignment member 6, and 7 is a spring. The figure is a cross-sectional view. The upper part shows the plug 2 before being fitted to the adapter 3, and the lower part shows it after the fitting. The other plug is omitted in the drawing after fitting. Actually, the optical fiber buckles only after the plugs are fitted from both ends. Aligning member 6
Has an alignment hole 6a for the optical fiber, is arranged at the tip of the plug 2, and slides in the optical fiber bending space 2b while being pressed from the rear by the spring 7. When the plug 2 is fitted into the adapter 3, the aligning member 6 is housed in the optical fiber bending space 2b, and only the tip of the optical fiber 1 is aligned with the alignment hole 3a.
Is inserted into. When the plug 2 is removed from the adapter 3, the spring 7
Thereby, the aligning member 6 returns to the original position.

According to this embodiment, first, the alignment property of the optical fiber is improved, and the tapered opening provided at the entrance of the through hole of the adapter 3 may be small. Further, by setting the protrusion amount of the centering member 6 from the tip of the plug 2 to be equal to the protrusion amount L _{1 of the} optical fiber to be set, the protrusion amount of the optical fiber can be easily set. Furthermore, the protection of the optical fiber is improved. Note that this embodiment can be used in combination with the structure of the third embodiment in which the tips of the plugs are butted.

Regarding the tapered opening, the fitting accuracy of the plug and the adapter is ± 50 μm, the center position accuracy of the aligning hole of the aligning member and the aligning member is ± 10 μm, the inner diameter accuracy of the aligning hole is ± 1 μm, and the opening diameter accuracy is ±±. By setting the thickness to 10 μm, the opening diameter can be set to 0.25 mm, and the optical fiber interval is 0.25 mm as used in the ribbon fiber when the number of cores is increased as in the following embodiment. Optical fibers can be mounted at small intervals.

FIG. 8 is a partial sectional perspective view showing the structure of an optical fiber connector according to the sixth embodiment of the present invention.
In the figure, 1 (1-1, 1-2) is an optical fiber, 1
a is a cover, 2 is a plug, 2a is an optical fiber gripping portion, 2b
Is a space for deflecting an optical fiber, 4 is a jack, 4a is a group of alignment holes for the optical fiber, 4c is an optical fiber gripping portion, 4d is a plug abutting surface, 4e is a jack frame, 6 is an optical fiber aligning member, and 6a is an aligning member. Alignment holes for the optical fiber of the core member 6 and 8 are leaf springs.

In FIG. 8, the optical fiber connector shown in the lower part of the figure is formed by fitting the plug 2 into the jack 4, and the sectional view shown in the right part of the figure is a group of aligned holes of the jack 4. 4a and the optical fiber 1-2 inserted in the alignment hole group 4a are shown in an enlarged manner.

In the optical fiber connector shown in FIG. 8, the optical fiber group 1-1 is arranged in the plug 2 in the vertical and horizontal directions of 8 cores, and a total of 64 cores are mounted. The structure of the fifth embodiment is adopted at the tip of the plug 2 and the aligning member 6 is installed. The aligning member 6 projects by ΔL from the tip of the plug 2 so that the optical fiber pushing amount on the plug side is ΔL, and the optical fiber group 1-is aligned with the tip surface of the aligning member 6.
The end of 1 is arranged. Dispersion of tip placement is ±
It can be set to about 5Δm. The centering member 6 is formed by using the leaf spring 8 in order to secure a space where the optical fiber group 1-1 bends.
From the back. An alignment hole group 4a is arranged in the jack 4 in the same arrangement as that of the plug, and the optical fibers in the optical fiber group 1-2 are fixed to the respective jacks 4c so that their tips are located at the plug abutment surface 4d. Has been done. The alignment hole group 4a and the optical fiber gripping portion 4c are floated in the jack frame 4e to facilitate fitting. Also, using the aligning member 6,
By setting the opening of the entrance of the alignment hole 4a to 0.25 mm, the pitch between the optical fibers is 0.25 mm. Therefore, the width of 2 mm is enough for the eight cores, and the plug 2 can be made small in size of about 5 mm in length and width. Plug 2
And the jack 4 are fitted together, the optical fiber groups 1-1 and 1-2
Are abutted against each other in the alignment holes, and the joint surfaces are pressed by the respective buckling forces.

According to this embodiment, an optical fiber connector which can be mounted at a higher density can be realized. Further, even if the positions of the tips vary among a plurality of optical fibers, the variation is absorbed by the buckling portion for each connection pair, so that a refractive index matching agent is unnecessary and a high return loss can be stably obtained.

FIG. 11 is a sectional view showing the structure of an optical fiber connector according to the seventh embodiment of the present invention. In the figure, 1 (1-1, 1-2) is an optical fiber, 1a is an optical fiber coating, 2 is a plug, 2a is an optical fiber gripping portion, 2b is an optical fiber buckling portion, 2c is a plug tip surface, Three
Is a jack, 3a is an optical fiber alignment hole, 3b is an optical fiber insertion taper, 3c is a plug abutting surface, 4 is an adhesive, 5 is an adhesive injection hole, and 6 is a plug-jack fixing clip. The linear expansion coefficient of the plug material is 1 x 1
It is set to 0 ^-5 / K or less. The figure is a cross-sectional view, and the upper stage shows before fitting and the lower stage shows after fitting.

The optical fibers 1-1 and 1-2 are fixed to the plug 2 and the jack 3 with an adhesive 4, respectively. At this time, the optical fiber 1-1 protrudes from the plug tip surface 2c by ΔL as an absorption extra length to the buckling portion 2b, and the tip of the optical fiber 1-2 is the plug contact surface 3 of the jack.
It is fixed to match c. When the plug 2 is fitted in the jack 3 and the plug tip surface 2c and the abutting surface 3c are abutted to each other and both are fixed by the clip 6, the optical fiber 1-1 is inserted into the alignment hole 3a, and the optical fiber 1-
1 and 1-2 hit each other, and the buckling portion absorption surplus length ΔL is the length L
Is absorbed by the buckling portion of the optical fiber 1-1, and the optical fiber 1-1 buckles and bends by δ. The buckling force at this time presses the optical fiber connecting surface, and by shaping the end surface of the optical fiber into a surface having no unevenness, the end surfaces are brought into close contact with each other and optical fiber connection with less reflection can be realized.

Here, it is necessary to control the deflection amount δ so that the radiation loss due to bending at the buckling portion 2b does not become excessive. δ can be controlled by ΔL as shown in equation (8). Further, the buckling force P, which is the force to bring the connection surfaces into close contact with each other, can be controlled by the buckling length L as shown in the equation (1). From the required buckling force, L is around 10 mm. Buckling length L = 10mm using 1.3μm band single mode optical fiber
In this case, by setting ΔL = 0.1 mm, the amount of deflection does not become excessive, and the radiation loss due to the bending of the optical fiber at the buckling portion can be suppressed to 0.01 dB or less.
The experimental results are shown by white circles in FIG.

In this embodiment, the linear expansion coefficient of the material of the plug is set to 1 × 10 ^-5 / K or less, and as a result, a buckling length of 10 mm is a general use range of -20 to 7
The change in buckling length can be suppressed to 0.01 mm in the temperature range of 0 ° C. Since the upper limit of ΔL at which the radiation loss due to buckling does not become excessive is about 0.1 mm, the intermediate value ΔL = 0.
If it is set to 05 mm, even if ΔL changes relatively due to temperature change, ΔL is 0 or less, or 0.1 m.
It is possible to maintain the close contact state of the spliced part even within the operating temperature range and to suppress the generation of radiation loss due to the excessive amount of deflection, and to maintain a good optical fiber connection even in the operating temperature range. Become.

The coefficient of linear expansion of quartz according to claim 7 is the same as that of the optical fiber and is small, 0.5 × 10 ⁻⁶ / K, and ΔL is not changed at all even with temperature change.

[0072] the linear expansion coefficient of the glass-based material, borosilicate glass 5 × 10 ^-6 / K, Pyrex is 3 × 10 ^-6 /
Crystallized glass called K, neoceram, or pyroceram is 0.7 to 2 × 10 ⁻⁶ / K, and 1 × 10
^-5 / K or less. These glass materials are cheaper than quartz and easy to process.

Amber (nickel-based alloy) and Fernico (iron-nickel-cobalt-based alloy, also called Kovar) are low linear expansion coefficient metals, and the linear expansion coefficient is 1 to 2 ×.
It is as low as 10 ⁻⁶ / K, 4 to 5 × 10 ⁻⁶ / K. Since it is a metal, it is easy to cut, and this is also suitable as a connector member for shaving.

The liquid crystal polymer is a polyester-based material having a linear expansion coefficient of 1 × 10 ^-5 / K or less, which is a material that can be injection-molded and is suitable as a connector member for mass production.

If ΔL is calculated by the following procedure, it can be applied more accurately than when it is determined from the minimum bending radius (R _min. ) Of the buckling portion, and can be applied to optical fibers having different characteristics and different operating wavelengths. Becomes

As described above, the relationship between the shape of the optical fiber at the time of buckling, the curvature R, and the buckling absorption surplus length ΔL and the deflection δ is expressed by the equations (4), (5) and (8). . Also, the radiation loss coefficient α per unit length when the curvature R is AWSnyde
r, I.White, and DJ Mitchell, "Radiation from bent op
tical waveguides, "Electron., Lett., 11, pp.332-333,19
From 75, the following formula (9)

(Equation 5) Given by Where a is the core radius of the optical fiber,
v, u, and w are normalized frequencies, propagation constants of the core and the cladding layer. The normalized frequency v is calculated by the following equation (1
0), (11)

(Equation 6) The propagation constants u and w are expressed by the following equations (12) and (1
3)

(Equation 7) (See, for example, Ohkoshi, Okamoto, Hotate, "Optical Fiber", Ohmsha, pp. 61-70).
Here, nc is a core refractive index, and Jn and Kn are n-th first
Seed and modified Bessel functions of the second kind.

Substituting the above equation into the following equation (14),
The total radiation loss of the buckling portion is obtained by integrating the radiation loss calculated from the curvature of each point along the buckling shape.

[0078]

(Equation 8) The calculated value obtained by the procedure described above is shown by the solid line in FIG. It is in good agreement with the measured value, and the validity of this procedure can be seen.

Therefore, the loss generated from the parameters of the optical fiber, the wavelength of the light used, the buckling length, and the buckling absorption surplus length can be calculated. It is possible to calculate the upper limit value of the buckling absorption surplus length ΔL by repeating the calculation so that the calculated value does not exceed the predetermined value.

FIG. 13 is a sectional view showing the structure of a plug used in the optical fiber connector according to the eighth embodiment of the present invention. The plug 21 shown in the figure is inserted into the jack 3 shown in FIG. 11 to form an optical fiber connector, and replaces the plug 2 of FIG.

The plug 21 shown in FIG. 13 is provided with a hollow large-diameter outer cylindrical portion 21a on the outer side.
A small-diameter inner cylindrical portion 21b is inserted into a, and both are joined and integrated at the rear end which is one end. Small diameter inner cylindrical portion 21b disposed inside
Has a hollow portion formed on the rear end side, and the front end opposite to the rear end is formed in a solid state, but the optical fiber 1 penetrates through the center of the solid front end. ing. The optical fiber 1 is adhered with an adhesive 4 from above the coating 1a at a portion of the inner cylindrical portion 21b near the rear portion of the solid front end portion.

A hollow portion 21c at the front end of the outer cylindrical portion 21a
Constitutes a buckling portion corresponding to the space in which the optical fiber 1 bends, and the buckling portion 21c projects inside the jack 3 shown in FIG. 11 to insert the optical fiber alignment hole 3a and the optical fiber insertion hole. The fitting portion where the taper 3b is formed is fitted as shown by the dotted line. Then, in this way, the buckling portion 21c of the plug 21 is connected to the jack 3
When it is inserted into the fitting portion of, the front end portion of the outer cylindrical portion 21a of the plug 21 abuts the plug abutting surface 3c of the jack 3 and stops.

The length of the outer cylindrical portion 21a of the plug 21 is
L ₁ as shown, and the length of the inner cylindrical portion 21b is L
₂ and when the fitting portion of the jack 3 is fitted as described above, the length from the front end portion of the outer cylindrical portion 21a to the bottom portion of the optical fiber insertion taper 3b at the tip of the fitting portion of the jack 3 Is L ₀ . Then, the total length L ₁ of the outer cylindrical portion 21a of the inner cylindrical portion 21b the length L ₂ and the L
_The length obtained by subtracting ₀ , that is, the length from the tip of the inner cylindrical portion 21b to the bottom of the optical fiber inserting taper 3b is defined as L.

The optical fiber 1 inserted in the plug 21 and fixed at the solid front end of the inner cylindrical portion 21b.
Extends in the hollow buckling portion 21c and extends a little longer than the front end portion thereof, that is, a predetermined accommodation extra length ΔL.

Then, as described above, the fitting portion of the jack 3 is fitted into the buckling portion 21c of the plug 21, and the front end portion of the outer cylindrical portion 21a of the plug 21 is brought into contact with the plug abutting surface 3c of the jack 3. When inserted until it abuts, the tip of the optical fiber 1 of the plug 21 comes into surface contact with the tip of the optical fiber 1 in the alignment hole 3a of the jack 3, and the optical fiber 1 is in the buckling portion 21c due to the accommodation length ΔL. The optical fiber 1 is flexed and curved at, so that the two optical fibers 1 are reliably connected.

Further, in the plug 21 of the optical fiber connector shown in FIG. 13, when the linear expansion coefficient of the outer cylindrical portion 21a is α ₁ and the linear expansion coefficient of the inner cylindrical portion 21b is α ₂ , the outer cylindrical portion 21a and the inner cylindrical portion 21a The cylindrical portion 21b is configured to have the following relationship.

L ₁ α ₁ = L ₂ d _2, that is, the outer cylindrical portion 21a and the inner cylindrical portion 21b are configured so that their elongation lengths due to thermal expansion are the same.

Therefore, when the fitting portion of the jack 3 of FIG. 3 is inserted into the buckling portion 21c of the plug 21 and the plug 21 and the jack 3 are fitted as described above, the optical fiber 1 of the plug 21 The length of the optical fiber 1 required for the buckling in the buckling portion 21c is L ₁ -L ₂ , but this buckling length L ₁ -L ₂ changes the temperature of the environment by ΔT, The lengths of the outer cylindrical portion 21a and the inner cylindrical portion 21b are respectively L ₁ and L ₂ to L ₁ + α ₁ L ₁ ΔT and L ₂ +.
Even if it changes to α ₂ L ₂ ΔT, α ₁ L ₁ = α ₂ L ₂
Therefore, it does not change. That is, since the buckling length L ₁ -L ₂ of the optical fiber 1 is always constant, the optical fiber 1
Since the accommodation length ΔL does not change, the optical fiber 1 always buckles in the same manner, and a stable connection state can be maintained even with temperature changes.

FIG. 14 is a sectional view showing the structure of an optical fiber connector according to the ninth embodiment of the present invention. The optical fiber connector shown in the figure connects an optical fiber and an optical waveguide, and the optical waveguide in this case is a substrate type optical waveguide.

In FIG. 14, 1 is an optical fiber made of a quartz material, 1a is an optical fiber coating, 2 is a plug, and 2a.
Is an optical fiber gripping portion, 2b is an optical fiber buckling portion, 2c is a plug tip surface, 4 is an adhesive, and 6 is a fixing clip for a plug and a jack. Further, 3 is a jack, 13 is a glass block, 12 is an optical waveguide made of a quartz material, 12a is an optical waveguide substrate, 12c is an optical waveguide end face including the end faces of the optical waveguide substrate 12a and the glass block 13, and 14 is an optical fiber guide. , 14a are optical fiber insertion holes.
In FIG. 14, the upper part shows the state before the plug 2 and the jack 3 are fitted together, and the lower part shows the state where the plug 2 and the jack 3 are fitted together. The linear expansion coefficient of the material of the plug 2 is 1 × 10 ⁻⁵ / K or less.

Here, in order to adjust the plug 2 to an appropriate position in the vertical direction with respect to the optical waveguide 12 and to easily attach the optical fiber guide 14 to the optical waveguide end face 12c, the plug 2 is attached to the optical waveguide end face 12c. The glass block 13 is adhered. After the glass block 13 is bonded onto the optical waveguide 12, the end face 12c of the optical waveguide is polished so as to be vertical and flat with respect to the optical axis. The optical waveguide 12 and the optical waveguide substrate 12a are fixed to the jack 3. Also,
The optical fiber 1 is fixed to the plug 2 with an adhesive 4. At this time, the optical fiber 1 is made to protrude from the plug tip surface 2c by ΔL as an extra absorption length to the buckling portion 2b. This ΔL is adjusted to an appropriate length as described in the seventh embodiment.

Now, when the plug 2 is fitted into the jack 3 and the plug tip end face 2c and the optical waveguide end face 12c are in contact with each other and fixed by the clip 6, the optical fiber 1 is inserted into the insertion hole 14a of the fiber guide 14. The tip of the optical fiber 1 abuts the optical waveguide end face 12c, the buckling portion absorption excess length ΔL is absorbed by the buckling portion 2b having the length L, and the optical fiber 1 buckles and bends. The buckling force at this time presses the connection surface at the tip of the optical fiber 1 against the optical waveguide end surface 12c, and physical contact between these surfaces is realized. Thereby, the optical fiber 1 and the optical waveguide 1
Since the core and the clad of No. 2 have almost the same refractive index, the return loss becomes very large. At this time, the optical fiber guide 14 causes the optical axes of the optical fiber 1 and the optical waveguide 12 to coincide with each other, and their cores are accurately butted against each other.
The connection loss is minimized. That is, the connection loss is reduced to the theoretical loss due to the mismatch of the field distribution of the guided modes of the optical fiber 1 and the optical waveguide 12. According to the above principle, it is not necessary to use a refractive index matching agent in this connection.

In the present embodiment, the tip of the optical fiber 1 is polished so as to be flat with respect to the optical axis, spherically shaped so that the core portion is convex, or simply cleaved. Can be formed. When cleaving, burrs formed near the outer periphery of the clad at the tip are removed. Since both end faces undergo elastic deformation when the tip of the optical fiber 1 is abutted against the end face 12c of the optical waveguide, it is not necessary to make both end faces completely flat in order to realize the aforementioned physical contact. Further, with respect to the end face 12c of the optical waveguide, a work-affected layer having a different refractive index is formed on the surface only by polishing, and therefore, a higher return loss can be obtained by removing it. As a method for removing it, wet etching using an acid solution or the like, dry etching such as ion etching, or polishing using cerium oxide or SiO ₂ particles can be considered. Alternatively, as another method of forming the optical waveguide end face 12c, it is possible to use a cleavage plane. When a Si single crystal substrate is used as the optical waveguide substrate 12a, when the optical waveguide 12 is cleaved together with the optical waveguide substrate 12a, the substrate is cleaved flat along the crystal plane, so that the cleavage plane of the optical waveguide 12 is also It becomes almost flat. Since there is no work-affected layer on the cleaved surface, there is an advantage that the labor for removing the work-affected layer unlike polishing is not required.

For the purpose of obtaining a larger return loss, it may be possible to polish the end face 12c of the optical waveguide obliquely without making it perpendicular to the optical axis. In this case, the tip end surface of the optical fiber also needs to be inclined accordingly. However, when the optical fiber 1 and the optical waveguide 12 are butted,
It becomes difficult to realize physical contact, and the deviation of the optical axis easily occurs.

Also, semiconductors, multi-component glasses and LiN
When an optical waveguide made of a material such as an optical crystal such as bO ₃ is optically connected to a silica-based fiber, the refractive index of the core and the clad of the optical waveguide is significantly different from those of the silica-based optical fiber, and thus physical contact can be realized. However, the return loss cannot be increased sufficiently. In this case, a sufficiently large return loss can be obtained by polishing the end face of the optical waveguide to remove the work-affected layer and then applying an antireflection coating to the face. The same applies when connecting a plastic optical fiber and an optical waveguide.

Furthermore, this embodiment is not limited to the case where one optical waveguide and an optical fiber are optically connected, but the following first
As will be described in detail in the embodiment of No. 0, a case where a plurality of optical waveguides and optical fibers are collectively optically connected, that is, multicore connection is also applied.

15 and 16 are perspective views showing the structure of the optical fiber connector according to the tenth embodiment of the present invention. The optical fiber connector shown in the figure is configured such that one optical fiber and one optical waveguide are optically connected in the embodiment of FIG. 14 to optically connect a plurality of optical fibers and a plurality of optical waveguides. 15 and 16 represent the same components as those shown in FIG. 14. More specifically, FIG. 15 and FIG.
The optical fiber connector is a multi-fiber connector for collectively optically connecting four optical fibers and four optical waveguides arranged in the lateral direction, each of which is shown in FIG. Is a component. Further, FIG. 15 shows a state before the plug 2 and the jack 3 are fitted together, and in FIG. 16, the plug 2 and the jack 3 are located on the right side.
Is shown in a fitted state. 15 and 16, a clip corresponding to the clip 6 of FIG. 14 for fitting the plug 2 and the jack 3 is omitted.

The optical fiber 1 projects from the plug tip surface 2c by an amount corresponding to ΔL shown in the seventh embodiment. When the plugs 2 are fitted into the jacks 3 and fixed, the respective optical fibers 1 are inserted into the corresponding guide holes 14a and collide with the end faces 12c of the optical waveguide and buckle. And high density, small insertion loss in each heart,
An optical connection with a large return loss is realized.

As a method of constructing the fiber guide 14, a plurality of single fiber guides having only one optical fiber insertion hole in the same component are individually mounted at positions corresponding to optical waveguides, and the same component is used. It is conceivable that a multi-fiber guide having a plurality of optical fiber insertion holes is attached to the. The single-fiber guide may be a microtube or a molded component, and the multi-fiber guide may be a combination of a plurality of microtubes, a molded component, a V-groove array substrate, or the like. . In the case of the molded part, a cylindrical or V-groove-shaped thin tube can be considered as the optical fiber insertion hole. The V-groove substrate is an Si substrate anisotropically etched,
A machined glass substrate may be considered.

[0100]

As described above, according to the present invention,
The plug is fitted from both ends of the adapter, or the plug and the jack are fitted, the optical fiber is abutted in the alignment hole accurately, and the buckling force of the optical fiber presses the connection end face. As described above, a ferrule and a spring member are not required, the number of members is small, and the sleeve is as small as the outer diameter of the optical fiber, and a simple and small optical fiber connector can be realized. Also, when the plug is joined to the adapter, the plugs are in surface contact with each other and the optical fibers are properly connected.

Further, according to the present invention, when the plug and the jack are fitted to each other, the optical fibers are properly butted in the alignment hole, and the connecting end face is pressed by the buckling force of the optical fibers to properly connect them. To be done. Further, an optical fiber aligning member is provided inscribed in the cavity of the plug, and the aligning member is configured to slide in the cavity, so that the optical fiber can be easily inserted into the alignment hole of the adapter. And improve the protection of the optical fiber.

Further, according to the present invention, a plurality of optical fibers can be simultaneously connected with a high density by one optical fiber connector, and even if the tips of the plurality of optical fibers are varied, each connection pair is different. Variations are absorbed in the buckling portion, a refractive index matching agent is not required, and a high return loss can be stably obtained.

According to the invention, the plug or adapter is made of quartz, or borosilicate glass, Pyrex glass or crystallized glass, or amber or Fernico, or a liquid crystal polymer, which all have a linear expansion coefficient of 1 × 10. ^It is as small as ^-5 / K or less, and even if it expands and contracts due to temperature changes, the amount of deflection of the optical fibers decreases, the surface contact between the optical fibers becomes poor, and the amount of deflection of the optical fibers increases, causing radiation loss. Never increase.

Further, according to the present invention, the fitting portion of the second member is made hollow in the first member until the open end of the buckling portion of the first member abuts against the abutting surface of the second member. When the first optical fiber is inserted into the buckling portion of the first optical fiber, the first optical fiber is inserted into the alignment hole from one opening, and the first optical fiber is surface-connected to the second optical fiber. It buckles in the buckling section to ensure the surface connection of both optical fibers,
The predetermined accommodation extra length that causes this buckling is set based on the thermal expansion coefficients of the first and second members and the first and second optical fibers and the radiation loss of the first and second optical fibers. Therefore, even if the first and second members and both optical fibers expand and contract due to temperature change, the buckling amount of the optical fibers is reduced and the surface contact between the optical fibers becomes poor, and The amount of buckling does not increase and radiation loss does not increase.

Further, according to the present invention, each of the first and second members is made of a material selected from the group consisting of quartz, borosilicate glass, Pyrex glass, crystallized glass, amber, Fernico, and liquid crystal polymer. Since all of them are configured to have a small linear expansion coefficient of 1 × 10 ⁻⁵ / K or less, even if they expand and contract due to temperature changes, the amount of buckling of the optical fibers is reduced, and the surface contact between the optical fibers is poor. Moreover, the amount of buckling of the optical fiber does not increase and radiation loss does not increase.

Furthermore, according to the present invention, the fitting portion of the second member is made hollow in the first member until the open end of the buckling portion of the first member abuts on the abutting surface of the second member. When the first optical fiber is inserted into the alignment hole through one opening and is surface-connected to the second optical fiber, the first optical fiber is inserted into the buckling portion due to the predetermined accommodation extra length. It buckles to ensure the surface connection of both optical fibers,
The product of the first predetermined length of the outer tubular member and the first predetermined linear expansion coefficient is equal to the product of the second predetermined length of the inner tubular member and the second predetermined linear expansion coefficient, and the temperature change Even if the outer tubular member and the inner tubular member expand and contract, the predetermined accommodation surplus length of the first optical fiber does not change. Therefore, the connection of the first and second optical fibers is not affected by the temperature change. The optical fiber connection is stable.

According to the present invention, the end face of the opening of the first member and the end face of the optical waveguide are butted against each other, and one or more optical fibers are inserted into the insertion holes of the one or more optical fiber guides, respectively. Then, when the tip end face of each optical fiber is abutted against the end face of each optical waveguide, each optical fiber is buckled in the buckling portion due to the predetermined accommodation extra length, and the restoring force of the buckled optical fiber causes The optical contact between the end face of each optical waveguide and the end face of each optical waveguide is maintained to achieve physical contact between the faces of the optical fiber and the optical waveguide, resulting in low connection loss and high return loss or optical connection. Multi-core connection is realized.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view showing a configuration of an optical fiber connector according to a first embodiment of the present invention.

FIG. 2 is a graph showing the pressing force generated at the time of fitting with respect to the pressing amount in the first embodiment of FIG.

FIG. 3 is a sectional perspective view showing a configuration of an optical fiber connector according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of an optical fiber connector according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a bent shape of an optical fiber.

FIG. 6 is a partial cross-sectional perspective view showing a configuration of an optical fiber connector according to a fourth embodiment of the present invention.

FIG. 7 is a sectional perspective view of an optical fiber connector according to a fifth embodiment of the present invention.

FIG. 8 is a partial cross-sectional perspective view showing a configuration of an optical fiber connector according to a sixth embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a conventional MU type optical fiber.

FIG. 10 is a diagram showing a configuration of a conventional MT type optical fiber.

FIG. 11 is a sectional view showing a configuration of an optical fiber connector according to a seventh embodiment of the present invention.

12 is a graph showing insertion loss with respect to the pushing amount in the optical fiber connector of FIG.

FIG. 13 is a sectional view showing the structure of a plug used in an optical fiber connector according to an eighth embodiment of the present invention.

FIG. 14 is a sectional view showing a configuration of an optical fiber connector according to a ninth embodiment of the present invention.

FIG. 15 is a perspective view showing a configuration of an optical fiber connector according to a tenth embodiment of the present invention.

FIG. 16 is a perspective view showing a configuration of an optical fiber connector according to a tenth embodiment of the present invention.

[Explanation of symbols]

 1,1-1,1-2 optical fiber 1a coating 2,2-1,2-2 plug 2a optical fiber gripping portion 2b optical fiber bending space 3 adapter 3a optical fiber alignment hole 3b alignment hole support portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naruyuki Mitachi 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Yoshiaki Takeuchi 3-chome Nishishinjuku, Shinjuku-ku, Tokyo No. 2 inside Nippon Telegraph and Telephone Corporation (72) Inventor Shuichiro Asakawa 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation

Claims (15)

[Claims] 1. Two plugs for fixing an optical fiber,
An adapter that intervenes when the plugs are opposed to each other and joined, and the two plugs have a holding portion that holds the optical fiber as a cantilever at one end, and the optical fiber bends at the other end. The adapter has a structure for connecting and fixing the two plugs to both ends, and an aligning member having an aligning hole for aligning and fixing the optical fibers at a center portion in a radial direction. The aligning hole of the aligning member has an inner diameter in the vicinity of the center in the longitudinal direction substantially equal to the outer diameter of the optical fiber core wire, and the inner diameters of both ends are larger than the outer diameter of the optical fiber core wire and are tapered. Optical fiber connector characterized by changing. 2. The optical fiber connector according to claim 1, wherein when the two plugs are respectively joined to the adapter, the plugs are in surface contact with each other. 3. A plug for fixing an optical fiber, and a jack for fixing the optical fiber, wherein the plug has a holding portion for holding the optical fiber as a cantilever at one end and the optical fiber for the other end. The jack has a structure for connecting and fixing it opposite to the plug, a holding portion for holding the optical fiber as a cantilever at the end not connected to the plug, and a connection with the plug. An alignment member having alignment holes for aligning and fixing the optical fibers when
And a cavity formed between the aligning member and the holding portion, wherein the aligning hole of the aligning member has an inner diameter near the center in the longitudinal direction substantially equal to the outer diameter of the core of the optical fiber and both ends. The inside diameter of the portion is larger than the outside diameter of the core of the optical fiber, and changes in a taper shape. 4. The optical fiber connector according to any one of claims 1 to 3, wherein the plug has an optical fiber centering member which is slidably inscribed in the cavity. 5. The plug is configured to hold a plurality of optical fibers, and the alignment member has a plurality of alignment holes for aligning and fixing the plurality of optical fibers.
The optical fiber connector according to any one of 1 to 3. 6. The optical fiber connector according to claim 1, wherein the plug or the adapter is made of quartz. 7. The optical fiber connector according to claim 1, wherein the plug or the adapter is made of borosilicate glass, Pyrex glass, or crystallized glass. 8. The optical fiber connector according to claim 1, wherein the plug or the adapter is made of amber or fernico. 9. The optical fiber connector according to claim 1, wherein the plug or the adapter is made of liquid crystal polymer. 10. A hollow buckling portion having one end opened, and a gripping portion formed on the other end side of the buckling portion, the gripping portion and the buckling portion penetrating the inside thereof from the opening end. A first member having a first holding portion that holds the first optical fiber extending a predetermined accommodation length in a cantilever manner, and a tip of the first optical fiber is inserted into one opening. An alignment hole into which the second optical fiber is inserted for a predetermined length from the other opening, and a fitting formed in an end portion of the alignment hole where the one opening is formed and fitted into the buckling portion Portion, an abutting surface that is formed at a position corresponding to the tip of the second optical fiber so as to project to the outer peripheral portion of the fitting portion, the abutting surface against which the opening end of the buckling portion abuts, the other opening of the alignment hole Second section having a second gripping section holding the inserted second optical fiber A member, and the fitting portion of the second member is attached to the first member until the opening end of the buckling portion of the first member abuts the abutting surface of the second member. When inserted into the hollow buckling portion, the first optical fiber is inserted into the alignment hole from the one opening to make a surface connection with the second optical fiber, and the first optical fiber is The predetermined accommodation extra length that causes the buckling in the buckling portion by the predetermined accommodation extra length to ensure the surface connection of both optical fibers and causes the buckling is the first and second members and the first member. , An optical fiber connector which is set based on the coefficient of thermal expansion of the second optical fiber and the radiation loss of the first and second optical fibers. 11. Each of said first and second members comprises:
The optical fiber connector according to claim 10, which is made of a material selected from the group consisting of quartz, borosilicate glass, Pyrex glass, crystallized glass, amber, Fernico, and liquid crystal polymer. 12. An outer tubular member having a hollow buckling portion and having a first predetermined length and a first predetermined linear expansion coefficient,
A second predetermined length and a second predetermined length are provided in the outer tubular member, one end of which is integrally formed with one end of the outer tubular member, and the one end of which is open to form a hollow portion. And the product of the second predetermined length and the second predetermined linear expansion coefficient is equal to the product of the first predetermined length and the first predetermined linear expansion coefficient. An inner cylindrical member and a closed end of the inner cylindrical member, the inner cylindrical member and the buckling portion are penetrated, and a predetermined distance is provided from the opening end of the buckling portion that is the other end of the outer cylindrical member. A first member having a first holding portion for holding the first optical fiber extending in the accommodation excess length in a cantilever manner, and the tip of the first optical fiber is inserted into one opening, An alignment hole into which the second optical fiber is inserted for a predetermined length from the other opening, and the one opening of the alignment hole is formed. A fitting portion which is formed at the end portion and is fitted into the buckling portion, and which is formed at a position corresponding to the tip of the second optical fiber so as to project to the outer peripheral portion of the fitting portion. And a second member having a second gripping portion holding the inserted second optical fiber in the other opening of the alignment hole. , The hollow buckling of the first member until the open end of the buckling portion of the first member abuts against the abutting surface of the second member. The first optical fiber is inserted into the alignment hole through the one opening and is surface-connected to the second optical fiber, the first optical fiber is inserted into the buckling portion due to the predetermined accommodation length. It buckles to ensure the surface connection of both optical fibers, and The product of the first predetermined length and the first predetermined linear expansion coefficient is the second predetermined length of the inner tubular member and the second
Is equal to the product of the predetermined linear expansion coefficient of the above, and the predetermined accommodation extra length of the first optical fiber does not change even if the outer tubular member and the inner tubular member expand and contract due to temperature change. . 13. A hollow buckling portion having one end opened, and a grip portion formed on the other end side of the buckling portion, the grip portion and the buckling portion penetrating the inside of the buckling portion from the opening end surface. A first member having a holding portion for holding one or a plurality of optical fibers extending in a predetermined accommodation extra length in a cantilever manner, and one having an end surface processed into a flat surface including a substrate portion at one end Alternatively, a plurality of substrate-type optical waveguides and one or a plurality of optical fiber insertion holes mounted near the end face of the optical waveguide are provided, and when the optical fiber is inserted into the optical fiber insertion hole, When one or a plurality of optical fiber guides for aligning the optical axes of the optical fiber and the optical waveguide with the end surface of the opening of the first member and the end surface of the optical waveguide are fitted, The optical fiber of the fiber guide The optical fiber is inserted into the fiber insertion hole, and the first member and the second member for fixing the substrate type optical waveguide in a state where the both end surfaces are fitted to each other are provided. The end face of the opening of the first member is abutted against the end face of the optical waveguide, and the tip end face of the optical fiber is protruded toward the end face of the optical waveguide in a state where the optical fiber is inserted into the optical fiber insertion hole of the optical fiber guide. When applied, the optical fiber buckles in the buckling portion due to the predetermined accommodation length, and the tip end surface of the optical fiber and the end surface of the optical waveguide are projected by the restoring force of the buckled optical fiber. An optical fiber connector characterized by sustaining the applied force. 14. The tip end surface of the optical fiber is processed so as to be vertical and flat with respect to the optical axis of the optical fiber, or is processed into a spherical shape so that the vicinity of the core is convex. Or, it is formed by removing the clad outer peripheral portion of the end face formed by cleavage to reduce the cross-sectional area, and when the end face of the optical fiber and the end face of the optical waveguide are abutted, at least 14. The optical fiber connector according to claim 13, wherein surface contact between the both end faces is ensured in the core portion of the optical fiber and the optical waveguide. 15. The optical fiber connector according to claim 13, wherein the plurality of optical fiber insertion holes are provided in the optical fiber guide of the same member.