JP5398409B2 - Optical connector - Google Patents

Description

  The present invention relates to an optical connector.

Single optical fiber connectors and multi-fiber optical connectors are frequently used in the optical interconnection technology.
In particular, as a multi-fiber optical connector, an MPO type optical connector or the like is often used (for example, see Patent Document 1). When an optical fiber is inserted into an optical fiber hole of an optical connector (hereinafter also referred to as a ferrule), the resin coating at the tip of the optical fiber is removed to form a bare optical fiber, which is inserted into the optical fiber hole. Further, the optical fiber may be inserted into the hole with the resin coating attached (see, for example, Patent Document 2 and Patent Document 3).
The MPO type optical connector employs a PC contact (PC: physical contact) in which the end face of the optical fiber is brought into direct contact without using a refractive index matching agent to prevent Fresnel reflection by the air layer.

Japanese Utility Model Publication No. 62-104203 JP 2003-322760 A JP 2004-258193 A

In order to connect the optical fiber to the PC, it is necessary to polish the optical fiber so as to surely protrude from the connection end face of the ferrule.
However, the process of polishing so that the tip of the optical fiber protrudes from the connection end face is complicated, and the connection characteristics become unsatisfactory due to an insufficient amount of protrusion of the optical fiber from the connection end face, variation in the protrusion amount, defective angle of the connection end face, etc. Sometimes. As the number of optical connector cores increases, it becomes more difficult to obtain stable optical characteristics in all optical fibers.
On the other hand, the spring pressure of the standard optical connector, that is, the biasing force of the built-in spring for abutting the ferrule is specified, and the connection pressure cannot be increased more than specified in order to compensate for variations in the optical fiber protruding amount. . Further, if the connection pressure is excessively increased, the optical fiber may be damaged.
In particular, in a multi-fiber optical connector in which optical fiber holes are arranged in a two-dimensional direction, the area of the connecting end surface is larger than that in which optical fiber holes are arranged only in a one-dimensional direction. This problem becomes significant. Since the manufacturing yield is also lowered, there arises a problem that the price of an optical connector having good connection characteristics is hardly lowered.
The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical connector capable of stably realizing a good PC connection state.

  In the optical connector according to claim 1 of the present invention, the optical fiber with resin coating is made of resin.
At least part of the resin coating layer of the optical fiber inserted through the optical fiber hole of the optical ferrule
Is bonded and fixed to the optical fiber hole, and the end face of the optical fiber is the joining end of the optical ferrule.
A plurality of optical fiber holes are formed, and the resin coating layer is at least one
The Young's modulus of the portion comprising the layers and covering the cladding layer is the Young's modulus of the constituent material of the optical ferrule.
Smaller, the tip of the optical fiber protrudes from the joining end face of the optical ferrule,
And it is PC-polished.
  An optical connector according to a second aspect of the present invention is the optical connector according to the first aspect, wherein the optical fiber hole is opened.
Are arranged in a plurality of rows on the joint end face.
  An optical connector according to a third aspect of the present invention is the optical connector according to the first or second aspect.
Two positioning member insertion holes are formed in the rod.
  An optical connector according to a fourth aspect of the present invention is the optical connector according to any one of the first to third aspects,
The optical fiber hole formed in the optical ferrule has an inner diameter of 126 to 129 μm, and the light
The optical fiber inserted into the fiber hole is an all-quartz optical fiber having an outer diameter of 80 μm.
The resin coating layer having an outer diameter of 125 μm is formed on the outer periphery of the bare fiber.
Features.
  An optical connector according to a fifth aspect of the present invention is the optical connector according to the fourth aspect, wherein the inner diameter of the optical fiber hole is
Is compliant with the JIS C 5982 or JIS C 5981 optical fiber hole specifications.
To do.
  An optical connector according to a sixth aspect of the present invention is the optical connector according to any one of the first to fifth aspects,
The Young's modulus of the portion covering at least the cladding layer of the resin coating layer is 1000 MPa to 100 MPa.
It is 00 MPa.
  The optical connector according to claim 7 of the present invention is the resin coating layer according to claim 4 or 5.
Is a primary coating layer having an outer diameter of 110 μm and a colored resin layer having an outer diameter of 125 μm formed thereon.
It is characterized by becoming.

According to the present invention, the bare optical fiber is fixed to the ferrule via the resin coating layer formed thick on the cladding layer. For this reason, the resin coating layer functions as a buffer material against the pressing force (butting force) applied to the optical fiber during connection.
Due to the presence of the buffer material, the tip position of the bare optical fiber is easily retracted. That is, the tip of the bare optical fiber is easily retracted toward the optical fiber hole with respect to the connection pressure.
Therefore, since the connection end face is wide and the number of optical fibers to be connected is large, even if there is a variation in the amount of protrusion of the optical fiber from the connection end face after the polishing process, all light beams are used under an appropriate connection pressure. The amount of protrusion of the fiber is optimized. Thereby, the insertion loss of all the optical fibers can be kept low, and a good PC connection is maintained.

It is a figure which shows the ferrule of an example of the optical connector of this invention, (a) is a front view, (b) is sectional drawing which shows the optical fiber strand penetrated in the optical fiber hole of the ferrule shown to (a). is there. It is a figure which shows the ferrule shown in FIG. 1, (a) is a top view, (b) is a side view. It is the figure which expanded the principal part of the ferrule shown in FIG. It is a perspective view of the ferrule shown in FIG. An example of the optical connector of this invention is shown, (a) is a top view, (b) is a side view. It is sectional drawing which shows the other example of an optical fiber strand. It is a figure which shows an example of the optical component of this invention, (a) is a front view, (b) is a side view. It is a graph which shows a test result.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a view showing an optical ferrule (hereinafter sometimes referred to as a ferrule) of an example of the optical connector of the present invention, (a) is a front view, and (b) is the light of the ferrule shown in (a). It is sectional drawing which shows the optical fiber strand penetrated by the fiber hole. 2 is a view showing the ferrule shown in FIG. 1, in which (a) is a plan view and (b) is a side view. FIG. 3 is an enlarged view of the main part of the ferrule. FIG. 4 is a perspective view of the ferrule. FIG. 5 shows an example of the optical connector of the present invention, where (a) is a plan view and (b) is a side view.

  As schematically shown in FIG. 5, a multi-fiber optical connector 20 (hereinafter sometimes simply referred to as an optical connector), which is an example of the optical connector of the present invention, is assembled at the tip of an optical fiber 16, and an optical ferrule. 12, a housing 11 that accommodates the ferrule 12, a coupling 13 that is provided outside the housing 11, a spring 15 that is accommodated inside the housing 11, and a rear end side of the housing 11 And a boot 17 provided on the vehicle.

In the following description, the left side (connection direction) in FIG. 5 may be referred to as the front, and the opposite direction may be referred to as the rear. In addition, the direction corresponding to the short side of the joining end face 4 of the ferrule 12 (the vertical direction in FIG. 1A) is referred to as the thickness direction, and the direction corresponding to the long side (the horizontal direction in FIG. 1A) is the width. It is called direction.
The spring 15 applies a reaction force to the housing 11 and biases the ferrule 12 forward.
The boot 17 prevents sudden bending of the optical fiber 16 near the rear end of the optical connector 20.

  The tip of the optical fiber 16 is terminated by a ferrule 12 so as to be able to butt-connect. The optical fiber 16 is not limited to a specific type, but for example, an optical fiber cord having a multi-core tape fiber can be employed.

As shown in FIG. 1 and FIG. 2, the ferrule 12 includes a substantially rectangular parallelepiped ferrule body 2 into which an optical fiber 16 is introduced, and a flange portion 3 that is formed at the rear end portion and is wider than the ferrule body 2. Have
The ferrule 12 can be formed by integral molding using a resin such as silica-filled epoxy resin, polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), or the like.
The ferrule body 2 has an upper wall portion 2b and a lower wall portion 2c extending from the long side of the rectangular joining wall portion 2a, and side wall portions 2d and 2d extending from the short side.

The front end face of the joint wall 2a is a joint end face 4 on which the tip of the optical fiber 1 is positioned and fixed so as to be able to butt and connect.
A plurality of optical fiber holes 6 into which the optical fiber strands 1 are inserted and guide pin holes 7 (positioning member insertion holes) are formed in the joining wall portion 2a. The optical fiber hole 6 and the guide pin hole 7 are formed from the inner space 2e to the joining end surface 4, and the inner surface of the end portion on the inner space 2e side is a tapered surface.
The plurality of optical fiber holes 6 and the guide pin holes 7 are formed in parallel to each other, and the pitch of each optical fiber hole 6 is equal.

The optical connector 20 in the illustrated example is a push-on type optical connector having the same function as an MPO type optical connector (MPO: Multifiber Push-On) defined in JIS C 5982.
The outer shape of the ferrule 12 is similar to the shape of the plug (also referred to as a ferrule or MT ferrule) defined by the standard and JIS C 5981, and the diameter of the optical fiber hole 6 is the same as the standard (JIS C 5981 or JIS C 5982) is preferably 126 to 129 μm. The error of the optical fiber hole diameter conforms to the above standard.

The joining end face 4 of the ferrule 12 can be subjected to PC polishing (PC: Physical Contact). Since the ferrule 12 is made of a resin material (epoxy resin or the like) whose hardness is lower than that of the material constituting the optical fiber 1 (for example, quartz glass), the joint end face 4 is formed so that the optical fiber 1 protrudes. It is possible to polish.
In the PC polishing, the bonding end face 4 and the optical fiber element 1 are simultaneously polished so that the optical fiber element 1 protrudes from the bonding end face 4 of the ferrule 12.
The polished shape of the tip of the optical fiber may be any shape as long as the protruding optical fibers are in direct contact with each other and PC-connected. For example, SPC polishing or AdPC polishing in which the return loss of PC polishing is further improved can be employed. Further, the flat surface polishing in which the ferrule body is flat-polished to protrude only the fiber and is convex-polished can be adopted.

The guide pin hole 7 is for inserting and fitting a guide pin for positioning with another optical connector to be butt-connected to the optical connector 20.
A window portion 2f used for injecting adhesive into the internal space 2e of the ferrule 12 is formed on the upper wall portion 2b.
However, FIG. 2 is a diagram schematically showing the internal structure of the two-dimensional array type optical connector. An opening for introducing the optical fiber 1 is formed on the rear surface side of the ferrule 12, and a window 2f is formed on at least one of the upper and lower walls 2b and 2c.

As shown in FIG. 1A, the openings 6 a of the optical fiber holes 6 are arranged in one or more rows on the joining end surface 4.
In the illustrated example, a plurality of openings 6a arranged in a row in the width direction are formed in multiple stages in the thickness direction. Specifically, twelve openings 6a arranged in parallel are formed in six parallel stages. That is, the openings 6a are formed in six rows.
The number and arrangement form of the optical fiber holes 6 are not limited to this. For example, 12 × 2 stages (24 cores), 12 × 3 stages (36 cores), 12 × 5 stages (60 cores), etc. Can be used without limitation.
The number of openings 6a per row is not limited to 12, and may be 4, 8, 16, or the like.

As shown in FIGS. 4 and 5, the optical fiber 1 is led out from a multi-core tape fiber (hereinafter referred to as an optical fiber ribbon) 21 drawn from the optical cord 16 and introduced into the optical fiber hole 6. Yes. Reference numeral 21 a is a coating for integrating the plurality of optical fiber wires 1.
As shown in FIGS. 2 and 3, the optical fiber strands 1 are fixed to the respective optical fiber holes 6, and the end portions of these optical fiber strands 1 protrude from the joining end face 4 of the ferrule 12.
As shown in FIG. 4, in this example, a plurality of optical fiber ribbons 21 are introduced into the ferrule 12, and the optical fiber strands 1 that are led out from the ends of the tape coating of the optical fiber ribbons 21. Are inserted into the optical fiber holes 6 in the same row. In the illustrated example, the optical fiber 1 constitutes the optical fiber ribbon 21, but a single optical fiber or the like may be used.

As shown in FIG. 1B, the optical fiber 1 includes a bare optical fiber (hereinafter sometimes referred to as an optical fiber bare wire) 8 and a resin coating layer 9 formed on the outer periphery thereof. The resin coating layer 9 includes a primary coating layer 9a and a colored coating layer 9b formed on the outer periphery thereof.
As the bare optical fiber 8, an all-quartz single mode optical fiber, an all-quartz multimode optical fiber, or the like can be used. Reference numeral 8a is a core of the bare optical fiber 8, and 8b is a cladding layer.

The primary covering layer 9a is an inner peripheral portion formed so as to cover the cladding layer 8b of the bare optical fiber 8, and the constituent material thereof is a resin material such as urethane acrylate, epoxy acrylate, butadiene acrylate, or the like. And UV curable resin.
The Young's modulus of the primary coating layer 9a is made smaller than the Young's modulus of the material constituting the ferrule 12.
If the Young's modulus of the primary coating layer 9a is too high, as will be described later, the optical fiber strand is fixed inside the optical fiber hole and is difficult to move, and some optical fiber elements due to variations in the tip of the optical fiber are caused. Although there is a possibility that the loss of the wire 1 cannot be reduced, by setting the Young's modulus within the above range, it is possible to realize a stable connection with low loss in all the optical fiber wires 1.

The Young's modulus of the primary coating layer 9a is, for example, 1000 MPa to 10000 MPa.
If the Young's modulus of the primary coating layer 9a is too low, the position of the optical fiber strand becomes unstable inside the optical fiber hole, and when connecting pressure is applied between the optical fiber of the counterpart optical connector, The connection may become unstable and loss may increase.
If the Young's modulus of the primary coating layer 9a is too high, as described above, there is a possibility that the loss of some of the optical fiber strands 1 due to variations in the tip of the optical fiber cannot be reduced.
By setting the Young's modulus within the above range, it is possible to realize a stable connection with low loss in all the optical fiber strands 1.

The colored resin layer (sometimes referred to as a colored coating) 9b enhances the discriminability of the optical fiber 1, and is formed of an ultraviolet curable resin such as urethane acrylate, epoxy acrylate, or butadiene acrylate. Can do.
As shown in FIG. 6, the optical fiber 1 may have a configuration in which the colored coating 9b is not formed. In this case, the Young's modulus of the entire resin coating layer 9 is in the above range.

The optical fiber 1 is introduced into the ferrule 12 from the rear end side, inserted into the optical fiber hole 6, and at least a part of the optical fiber 1 is bonded and fixed to the inner surface of the optical fiber hole 6.
Note that at least a part of the optical fiber is bonded and fixed in some cases, the entire length of the optical fiber is bonded and fixed along the longitudinal direction of the optical fiber hole, or only a part of the optical fiber is bonded and fixed. Means.

When the joining end faces 4 of the pair of optical connectors 20 are brought into contact with each other, the optical fiber strands 1 are brought into contact with each other, whereby the optical connector 20 is optically connected. At this time, a guide pin (not shown) is inserted and fitted into the guide pin hole 7 so that the optical connector 1 is accurately positioned.
As described above, the optical fiber 1 has the primary coating layer 9a made of resin in a portion extending into the optical fiber hole. Due to the elasticity of the primary covering layer 9, the pressing force (butting force) of the optical fiber 1 at the time of connection is adjusted.
For this reason, the protrusion amount of the optical fiber 1 from the joining end face 4 is optimized, and good PC connection is maintained.
Therefore, even when the number of the optical fiber strands 1 is large, troubles such as an increase in optical loss and disconnection can be prevented, and stable optical characteristics can be maintained. For example, the insertion loss of all the optical fiber strands 1 can be 0.5 dB or less.

The optical connector to which the present invention is applied is not limited to the optical connector of the type defined in JIS C 5982 or JIS C 5981, and applies to all optical connectors and optical ferrules that adopt the PC connection method. be able to.
As an optical connector type other than the MPO type optical connector and the MT type connector, it is possible to adopt the MTP, MPX, OGI, and HBMT types.
Further, the present invention has an excellent effect even when applied to a single-fiber optical connector.
As a single optical connector, it can be used for a 2.5 mm diameter SC ferrule standardized by JIS and IEC, or a MU ferrule having a smaller diameter than the SC ferrule. In addition, as an optical connector type using a small-diameter optical ferrule, there is an LC type optical connector.
All of these have an optical fiber hole diameter of about 125 μm, and by inserting the optical fiber with a resin coating having an outer diameter of 125 μm having the above-described configuration into this optical fiber hole, it is good without performing precision polishing. PC connection state can be realized.

However, the structure described above can be applied to optical components other than optical connectors as long as PC connection is possible.
In the following description, the same components as those of the optical connector 20 shown in FIGS.
FIG. 7 shows an optical fiber array which is an example of the optical component of the present invention. This optical fiber array 30 includes a plurality of optical fiber introduction grooves 31 (optical fiber insertion holes) into which the above-described optical fiber 1 is introduced. Part) and a lid 33 for sandwiching the optical fiber 1 between the array substrate 32 and the array substrate 32.
The front end surfaces of the array substrate 32 and the lid portion 33 are joint end surfaces 34 on which the tips of the optical fiber strands 1 are positioned and fixed so that they can be connected to each other.
The optical fiber 1 is fixed to the array substrate 32 and the lid 33 with an adhesive 35. The tip of the optical fiber 1 protrudes from the joining end surface 34.

The joining end face 34 is subjected to PC polishing. The optical fiber 1 can be protruded from the joining end face 34 by PC polishing.
The Young's modulus of the primary coating layer 9a can be 1000 MPa to 10000 MPa. By setting the Young's modulus within this range, it is possible to realize stable connection with low loss in all the optical fiber strands 1.
It is preferable that the Young's modulus of the primary coating layer 9 a is smaller than the Young's modulus of the material constituting the array substrate 32 and the lid portion 33.

When the joint end face 34 of the optical fiber array 30 is PC-connected to another light emitting / receiving element, the pressing force of the optical fiber 1 at the time of connection is adjusted by elastic deformation of the resin coating layer 9.
Therefore, the protruding amount of the optical fiber 1 from the joining end face 34 is optimized, and good PC connection is maintained.

The optical connector 20 shown in FIGS. 1 to 5 was produced as follows.
The optical fiber 1 has a core 8a (outer diameter 50 μm) and a cladding layer 8b (outer diameter 80 μm), and a primary coating made of urethane acrylate-based ultraviolet curable resin on the outer periphery of the optical fiber bare wire 8 made of quartz. A layer 9a (outer diameter 110 μm) was provided, and a colored coating layer 9b (outer diameter 125 μm) was provided on the outer periphery thereof.
The Young's modulus of the primary coating layer 9a was as shown in Table 1. In any of the examples, the Young's modulus of the primary coating layer 9a was set lower than the Young's modulus of the constituent material of the ferrule 12.

As shown in FIG. 1 (a), a 72-core optical connector was produced in which the openings 6a of the optical fiber holes 6 were formed in 6 rows, 12 in one row.
This optical connector (ferrule) has a resin square shape similar to the outer shape of a plug (also referred to as ferrule or MT ferrule) defined according to JIS C 5982 and JIS C 5981. The diameter of the optical fiber hole 6 was set to 126 μm to 129 μm according to the standard. The optical fiber hole 6 was filled with an epoxy resin adhesive, and the optical fiber 1 was bonded to the inner surface of the optical fiber hole 6.
The gap between the optical fiber and the optical fiber hole is very narrow compared to the diameter of the optical fiber itself, and the amount of adhesive is very small. The impact on the is very small.
A pair of optical connectors 20 were PC-connected, and the insertion loss of the optical fiber 1 was measured. The measurement was performed 4 times and the maximum value of insertion loss was recorded. An example of typical measurement results is shown in Table 1.
FIG. 8 shows an example of the result of measuring the insertion loss using the optical connector 20 in which the Young's modulus of the primary coating layer 9a is set lower than the Young's modulus of the constituent material of the ferrule 12. It shows the value of insertion loss.

From FIG. 8, it can be seen that by setting the Young's modulus of the primary coating layer 9a to be lower than the Young's modulus of the constituent material of the ferrule 12, the insertion loss can be reduced in all the optical fiber strands 1.
From Table 1, it can be seen that the insertion loss could be kept low by setting the Young's modulus of the covering layer 9 to 1000 MPa to 10000 MPa.

By setting the optical fiber hole diameter of the optical ferrule to the optical fiber hole diameter adopted as a standard, the following advantages can be obtained.
For example, when inserting a standard optical fiber having a diameter of 250 μm (with resin coating) into an optical fiber hole of an optical ferrule, the diameter of the optical fiber hole needs to be 250 μm or more.
However, since the optical fiber hole diameter of a standard optical ferrule is 126 to 129 μm, in order to manufacture an optical ferrule having an optical fiber hole diameter corresponding to a diameter of 250 μm, a molding die equipment, a manufacturing process, and manufacturing conditions are required. It must be changed drastically, resulting in an increase in manufacturing cost and a deterioration in manufacturing yield. Furthermore, it becomes impossible to mount the optical fiber on the optical ferrule having a limited size at high density.
In the present invention, the outer diameter of the resin-coated optical fiber is 125 μm and can be inserted into the standard optical fiber hole of the optical ferrule, so that the molding tool equipment, the manufacturing process, and the manufacturing conditions can be used as they are. It becomes like this. As a result, an optical connector having good connection characteristics, particularly a multi-fiber optical connector, can be manufactured at low cost, although high-density mounting is possible.

DESCRIPTION OF SYMBOLS 4 ... Joint end surface, 6 ... Optical fiber hole, 6a ... Opening, 8 ... Bare optical fiber, 9 ... Primary coating layer, 12 ... Ferrule, 20 ... Optical connector , 30... Optical fiber array (optical component), 34.

Claims (7)

A resin-made multi-core optical ferrule (12) having a joining end face (34) in which a plurality of optical fiber holes (6) are two-dimensionally arranged, and a plurality of multimode optical fibers respectively bonded and fixed to the plurality of optical fiber holes With strands,
Each of the plurality of multimode optical fiber strands has substantially the same diameter as the inner diameter of the plurality of optical fiber holes including the resin coating layer, and a resin coating layer is attached to each of the plurality of optical fiber holes. It is still glued to the inner surface,
The resin coating layer comprises at least one layer,
Of the resin coating layer, the portions (9, 9a) covering the clad layer (8b) have a Young's modulus of 2 GPa urethane acrylate resin smaller than both the constituent resin of the multi-core optical ferrule and the clad layer. And
Only the PC polishing is applied to the joint end face of the multi-core optical ferrule to which the plurality of multi-mode optical fiber strands are bonded and fixed, and each of the plurality of multi-mode optical fiber strands protrudes from the joint end face. Let
With respect to all of the plurality of multimode optical fiber strands, the amount of protrusion with respect to the joining end face is optimized by using elastic deformation of the resin coating layer, and PC connection is possible. And an optical connector (20) stably set to 0.5 dB or less.   The optical connector according to claim 1, wherein the multi-mode optical fiber constitutes an optical fiber ribbon and is led out from a tip end thereof.   The optical connector according to claim 1, wherein the optical fiber holes are arranged in a plurality of rows on the joining end surface.   The optical connector according to any one of claims 1 to 3, wherein the optical ferrule has two positioning member insertion holes (7). The inner diameter of the optical fiber hole of the optical ferrule is 126 to 129 μm,
The multi-mode optical fiber is obtained by forming the resin coating layer having an outer diameter of 125 µm on the outer periphery of an optical fiber bare wire (8) having an outer diameter of 80 µm which is an all-silica optical fiber. 5. The optical connector according to any one of 4 above.   6. The optical connector according to claim 5, wherein an inner diameter of the optical fiber hole of the optical ferrule conforms to a JIS C 5982 or JIS C 5981 optical fiber hole.   The optical connector according to claim 5 or 6, wherein the resin coating layer comprises a primary coating layer (9a) having an outer diameter of 110 µm and a colored resin layer (9b) having an outer diameter of 125 µm formed thereon.

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