JP6049420B2 - Optical connector and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical connector and a manufacturing method thereof.

  An optical connector is a member used to connect two optical fibers so that the end faces of the two optical fibers are accurately abutted and an optical signal is transmitted between both optical fibers. For example, an optical fiber is fixed in a ceramic ferrule, and the end face of the optical fiber is exposed at the ferrule tip.

  With respect to such an optical connector, Patent Document 1 discloses a through hole for housing an optical fiber inside a ferrule, a portion that continues to the insertion portion of the optical fiber, and a portion whose inner diameter is polished that continues to this portion through a small step. A technique has been disclosed in which a ferrule having no edge at the boundary portion is formed by using the shape having the shape and the optical fiber is not damaged.

JP 2004-329846 A

  In the technique of Patent Document 1, the inner diameter polished through hole portion that houses and holds the optical fiber is set to have an inner diameter larger than the optical fiber diameter so that the optical fiber can be reliably inserted. By setting the diameter as described above, the optical fiber can be passed to the end of the through hole without being caught in the middle of the through hole.

  However, as described above, when the through hole inner diameter is larger than the optical fiber diameter, there is a problem that the position of the optical fiber center cannot be determined in the through hole in a plane orthogonal to the fiber center axis.

  The optical fiber and the ferrule are fixed by an adhesive placed in the through-hole, but the central axis of the optical fiber and the central axis of the through-hole do not coincide with each other due to the difference in diameter, and the through-hole It has become unclear where the center of the optical fiber is located with respect to the center, and the center axis of the ferrule and the core of the optical fiber are shifted from each other on the end face of the optical connector. In such a state, when the two optical connectors are brought into contact with each other, the center axis of the ferrule = the center axis of the through hole can be matched, but the center axis of the optical fiber = the core position must be matched. Connection loss occurred.

  This invention is made | formed in view of this point, The place made into the objective is providing the optical connector with easy positioning of a core and a small connection loss.

  In order to solve the above-described problems, an optical connector of the present invention includes an optical fiber and a through hole for accommodating the optical fiber in the axial direction, and the optical fiber accommodated in the through hole at a distal end portion. The through hole has a tapered shape whose diameter decreases toward the tip, and the optical fiber is in a portion existing in the through hole of the ferrule. The taper shape is tapered toward the tip.

  In a preferred embodiment, the taper angle of the through hole is greater than or equal to the taper angle of the optical fiber, and the difference between both taper angles is within 1 °.

  It is preferable that the periphery of the front end surface of the optical fiber is in close contact with the through hole.

  The cross section of the optical fiber and the cross section of the through hole may have the same shape. The cross section of the optical fiber and the cross section of the through hole are preferably any one of a circle, a regular polygon, and a combination of a single string and an arc.

  When the maximum diameter of the optical fiber is A, the hole diameter at the tip of the ferrule is B, and the hole diameter at the rear end of the ferrule is C, it is preferable that B <A <C.

  The optical fiber is preferably a multi-core fiber having a plurality of cores.

  An optical connector manufacturing method according to the present invention includes a step of inserting an adhesive into a through hole of a ferrule having a through hole for housing an optical fiber in an axial direction, and inserting the optical fiber into the through hole. A step of curing the adhesive, and a step of polishing the end face of the optical fiber exposed at the tip of the ferrule, wherein at least one tip portion of the optical fiber is tapered toward the tip. The ferrule has a tapered shape in which the diameter of the through-hole decreases toward the tip, and the tip portion of the optical fiber having the tapered shape is It has the structure inserted in a through-hole.

  The optical connector of the present invention can easily align the position of the core of the optical fiber with the central axis of the ferrule, and can easily align the core when the optical connectors are butted together.

FIG. 2A is a schematic diagram illustrating an end surface of a tip portion of the optical connector according to the first embodiment, and FIG. 2B is a schematic diagram illustrating a cross section of the optical connector according to the first embodiment. 6 is a schematic diagram illustrating an end face of an optical fiber used in an optical connector according to Embodiment 2. FIG. 6 is a schematic diagram illustrating an end face of an optical fiber used in an optical connector according to Embodiment 3. FIG. It is a schematic diagram which shows the end surface of the optical fiber used for the optical connector which concerns on Embodiment 4. (A) is a typical figure which shows the end surface of the front-end | tip part of the optical connector which concerns on a comparison form, (b) is a typical figure which shows the cross section of the optical connector which concerns on a comparison form.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity.

(Embodiment 1)
An optical connector according to Embodiment 1 is shown in FIG. The optical connector 100 is used to pass an optical signal transmitted through the optical fiber 20 to another optical fiber, and the optical fiber 20 is inserted into the through hole 12 extending in the central axis direction of the substantially cylindrical ferrule 10. And the end face of the optical fiber 20 is exposed at the tip of the ferrule 10. Two such optical connectors 100 are prepared and inserted into a cylindrical sleeve, and the optical fibers are connected by abutting and fixing the tips. The tip surface of the ferrule 10 and the tip surface of the optical fiber 20 are flush with each other.

  The optical fiber 20 of the present embodiment is a single core optical fiber in which the core 22 exists only at the central axis portion, and the shape of the fiber cross section is circular. The cross-sectional shape of the through hole 12 of the ferrule 10 is also circular.

  In this embodiment, the through hole 12 of the ferrule 10 has a tapered shape whose diameter gradually decreases toward the tip side. In FIG. 1B, the left end is the tips of the optical connector 100 and the ferrule 10. The optical fiber 20 also has a tapered shape in which the diameter gradually decreases toward the tip in at least the through hole 12.

  The taper angle of the through hole 12 is greater than or equal to the taper angle of the optical fiber 20. Due to this relationship, the periphery of the front end surface of the optical fiber 20 is in close contact with the through hole 12 at the front end portion of the optical connector 100. doing. A gap is formed between the optical fiber 20 and the through-hole 12 as it goes to the rear end of the optical connector 100, so that an adhesive 30 is put therein to adhere and fix the ferrule 10 and the optical fiber 20. . The taper angle is an angle formed by the central axis and the inner wall of the through hole 12 and an angle formed by the central axis and the outer wall of the optical fiber 20.

  Next, connection between optical connectors will be described.

  In connecting the two optical connectors 100, it is important that the cores 22 of the optical fibers 20 are abutted without misalignment. That is, the cores 22 through which optical signals pass must be brought into contact with each other over the entire exposed surface of the optical fiber 20, and when the contact area between the cores 22 decreases, the connection loss increases. End up.

  For example, in the optical connector 200 according to the comparative embodiment shown in FIG. 5, the inner diameter of the through hole 212 of the ferrule 210 is constant in the axial direction, and the diameter of the optical fiber 220 is also constant. Since the optical connector 200 is formed by inserting the optical fiber 220 into the through hole 212 of the ferrule 210, the diameter of the through hole 212 is set larger than the diameter of the optical fiber 220. Therefore, in the optical connector 200 according to the comparative embodiment, a gap is formed between the through hole 212 and the optical fiber 220 over the entire axial direction in the ferrule 210. An adhesive 230 is placed in the gap to fix the ferrule 210 and the optical fiber 220.

  As shown in FIG. 5 (a), the optical connector 200 according to the comparative embodiment has an end face where the central axis of the ferrule 210 and the central axis of the optical fiber 220 (the core 222 exists) do not coincide with each other. End up. As described above, the optical fiber is connected by the optical connector by abutting the end faces of the two optical connectors inserted into the sleeve, so that the two optical connectors are connected so that their central axes substantially coincide with each other. The Since the central axis of the optical connector is the central axis of the ferrule, when two optical fibers 220 are connected using two optical connectors 200 according to the comparative embodiment, the deviation between the cores 222 is a maximum with the optical fiber 220. This is the difference in diameter from the through hole 212. When the optical fiber 220 is a single mode fiber having a diameter of 124 μm and an optical fiber having a mode field diameter of 9.2 μm (λ = 1.31 μm), and the diameter of the through hole 212 of the ferrule 210 is 127 μm, the cores 222 The maximum deviation is 3 μm, and a connection loss of 0.46 dB occurs in the calculation.

  On the other hand, in the optical connector 100 according to the present embodiment, as shown in FIG. 1A, the outer periphery of the optical fiber 20 is in close contact with the through-hole 12 of the ferrule 10 at the tip surface, and the central axis of the optical fiber 20 And the central axis of the ferrule 10 coincide with each other. Accordingly, when the two optical connectors 100 are connected to each other, the cores 22 in the central axis portion of the optical fiber 20 are connected to each other without being substantially displaced. In this way, when the deviation between the cores 22 is 0, there is no calculation connection loss.

  Thus, in this embodiment, since both the through-hole 12 of the ferrule 10 and the optical fiber 20 have a taper shape, the outer periphery of the optical fiber 20 is entirely in the through-hole 12 of the ferrule 10 at the distal end surface of the ferrule 10. Since the core 22 of the optical fiber 20 is positioned on the central axis of the ferrule 10 in close contact with each other, the optical connectors 100 are inserted into the sleeves, and both the cores 22 are abutted without being displaced by just abutting the tips. Can be contacted. For this reason, it is possible to perform a connection with a small connection loss by simply inserting the two optical connectors 100 into the sleeve and abutting them.

  Next, the manufacturing method of the optical connector 100 of this embodiment is demonstrated.

  The ferrule 10 in which the through hole 12 has a tapered shape can be formed by injection molding or the like. In this case, the mold for forming the through hole may be tapered, or the through hole may be tapered after a ferrule having a through hole with a constant diameter is created.

  The optical fiber 20 having a tapered tip portion is formed by tapering the tip of an optical fiber having a constant diameter. There are various types of taper processing such as thermal processing, cutting and polishing processing, and melt processing. However, melt processing using hydrofluoric acid is simple and preferable because the taper angle can be adjusted accurately. In the melt processing using hydrofluoric acid, for example, a tip portion of a predetermined length of the optical fiber is immersed in hydrofluoric acid, and the optical fiber is pulled up at a constant speed and then the hydrofluoric acid is removed. In addition, what is necessary is just to process the optical fiber 20 so that the part which exists in the through-hole 12 may have a taper shape.

  When the tapered ferrule 10 and the optical fiber 20 are prepared, an adhesive is inserted into the through hole 12 of the ferrule 10. Although the kind of adhesive agent is not specifically limited, It is preferable to use a thermosetting adhesive agent so that a post process may be simplified.

  Then, the optical fiber 20 is inserted into the through hole 12 from the rear end of the ferrule 10. The through-hole 12 of the ferrule 10 is set so that the diameter of the rear end is larger than the diameter of the non-tapered portion of the optical fiber 20 and the diameter of the tip is larger than the tip diameter of the tapered optical fiber 20. Preferably, with such a setting, the tip of the optical fiber 20 protrudes from the tip of the through hole 12, and the insertion ends when the diameter of the optical fiber 20 and the diameter of the tip of the through hole 12 coincide with each other. At the tip, the optical fiber 20 is in close contact with the through-hole 12 over the entire circumference.

  Next, the adhesive is cured to fix the optical fiber 20 and the ferrule 10. If it is a thermosetting adhesive, it may be in a high temperature state.

  Then, the tip of the optical fiber 20 is polished so that it is flush with the tip of the ferrule 10. Thus, the optical connector 100 of this embodiment is completed.

  In addition, the said manufacturing method is an example, Comprising: You may manufacture by another manufacturing method. For example, the adhesive may be inserted after the optical fiber 20 is inserted into the through hole 12.

  The optical connector 100 according to the present embodiment can easily abut the cores 22 of the optical fibers 20 without misalignment by a conventionally known method such as insertion into a sleeve without special positioning, and connection loss. Can be kept low. Moreover, the optical connector 100 of this embodiment can be easily manufactured only by preparing the ferrule 10 which has the taper-shaped through-hole 12, and the optical fiber 20 whose front-end | tip part is a taper shape. Further, the ferrule 10 having the tapered through-hole 12 and the optical fiber 20 having a tapered tip can be easily manufactured.

(Embodiment 2)
The second embodiment is different from the first embodiment in that the optical fiber to be used is a multi-core fiber, and the other points are the same as those in the first embodiment. Therefore, the differences from the first embodiment will be described below. .

  The end face of the optical fiber used in this embodiment is shown in FIG. This optical fiber 23 is a multi-core fiber having a total of seven cores 24 having a circular cross-sectional shape, one in the center of a circular clad 41 and six in a hexagonal arrangement around the circumference. That is, the arrangement of the core 24 is one at each vertex of the regular hexagon and one at the center of the regular hexagon in the cross section of the fiber, and the center of the regular hexagon is located on the central axis of the optical fiber 23.

  Also in the present embodiment, as in the first embodiment, the optical fiber 23 having the tapered shape is inserted into the ferrule having the through hole having the tapered shape, so that an optical connector is formed. The tip end face is in close contact with the through hole.

  When connecting multi-core fibers like this embodiment, in order to suppress a connection loss, it is necessary to face a plurality of cores without deviation. For this purpose, the central axes of the two optical fibers need to coincide with each other, and at the same time, the rotation angles around the central axes need to coincide.

  In the optical connector of the present embodiment, the central axis of the ferrule and the central axis of the optical fiber coincide with each other, so that the central axes of the two optical fibers coincide with each other only by inserting the optical connector into the sleeve and abutting the end face. Can do. Further, in the optical connector, for example, if a mark is written at the intersection of a line connecting one vertex of the regular hexagonal arrangement of the core 24 and the center of the optical fiber and the outer surface of the ferrule, the two optical connectors are inserted into the sleeve. Only by making the marks coincide, the rotation angles can be made coincident. As described above, in the present embodiment, the connection of two multi-core fibers can be easily performed while suppressing the connection loss in all the cores.

(Embodiment 3)
The third embodiment is different from the second embodiment in that the cross-sectional shape of the optical fiber to be used is a so-called D-type, and the other points are the same as those in the second embodiment. Is described below.

  The end face of the optical fiber used in this embodiment is shown in FIG. This optical fiber 25 is a so-called D-type whose cross-sectional shape is a part of a circle cut out, one at the center of the D-type cladding 42 (which is the center of a circle without a notch), A multi-core fiber having a total of seven cores 26 in a regular hexagonal arrangement. The D type is a figure composed of a combination of a single string and an arc, and the center angle of the arc is larger than 180 °.

  The through hole of the ferrule in the present embodiment has a D-shaped cross-sectional shape that is the same as the outer shape of the optical fiber 25, and has a tapered shape whose diameter decreases toward the tip. In addition, in the ferrule that accommodates an optical fiber having a D-shaped cross section, the through hole has a tapered shape whose diameter decreases toward the tip portion. It is a D shape similar to the shape of the above, and the radius of curvature of the arc decreases toward the tip.

  The optical connector of this embodiment also has the same effect as that of the second embodiment. In the present embodiment, the D-shaped string portion can also serve as a mark for adjusting the rotation angle.

(Embodiment 4)
The fourth embodiment is different from the second embodiment in that the cross-sectional shape of the optical fiber to be used is a regular hexagon, and the other points are the same as those in the second embodiment. This will be described below.

  The end face of the optical fiber used in this embodiment is shown in FIG. This optical fiber 27 has a regular hexagonal cross-sectional shape, one at the center of the regular hexagonal clad 43, and six at a position corresponding to each vertex of the clad 43 around the center. This is a multi-core fiber having seven cores 28.

  The through-hole of the ferrule in the present embodiment has a regular hexagonal shape whose cross-sectional shape is the same as the outer shape of the optical fiber 27, and has a tapered shape whose diameter decreases toward the tip.

  The optical connector of this embodiment also has the same effect as that of the second embodiment. In the present embodiment, the hexagonal shape of the through hole itself or the vertex of the hexagon can also serve as a mark for adjusting the rotation angle.

(Other embodiments)
The above-described embodiment is an exemplification of the present invention, and the present invention is not limited to these examples, and these examples may be combined or partially replaced with known techniques, common techniques, and known techniques. Also, modified inventions easily conceived by those skilled in the art are included in the present invention. For example, the shape of the outer shape of the ferrule may be a shape in which the outer periphery of the tip is cut obliquely in addition to the cylindrical shape, or a part called a flange may be attached to the rear end of the ferrule.

  The taper angle of the ferrule through hole is not particularly limited, but is preferably 0.2 ° or more and 1 ° or less. Similarly, the taper angle of the tip portion of the optical fiber is preferably 0.2 ° or more and 1 ° or less in accordance with the taper angle of the through hole.

  In the case of using a multi-core fiber, the number of cores and the arrangement of the cores are not particularly limited, and a multi-core fiber having a known number of cores and a core arrangement can be used. The outer shape of the optical fiber is not limited to a circular cross section, D shape, and regular hexagon, and may be a square, a regular pentagon, a regular octagon, or the like. In addition, in the case of a polygon, there may be a shape with a corner dropped due to restrictions on manufacturing of the optical fiber, and the shape with such a corner dropped is also included in the polygon of the present application.

  As described above, the optical connector according to the present invention can easily connect optical fibers with low connection loss, and is useful as a connection component of optical fibers for optical communication.

10 Ferrule 12 Through-hole 20 Optical fiber 22 Core 23 Optical fiber (multi-core fiber)
24 core 25 optical fiber (multi-core fiber)
26 core 27 optical fiber (multi-core fiber)
28 Core 30 Adhesive 41 Clad 42 Clad 43 Clad 100 Optical connector 200 Optical connector 210 Ferrule 212 Through hole 220 Optical fiber 222 Core 230 Adhesive

Claims (6)

Optical fiber,
A ferrule having a through-hole for housing the optical fiber in the axial direction and exposing a tip end surface of the optical fiber housed in the through-hole at a tip portion;
The through hole has a tapered shape that decreases in diameter toward the tip and continues to the tip .
The optical fiber has a tapered shape that tapers toward the tip in a portion existing in the through hole of the ferrule ,
The taper angle of the through hole is equal to or greater than the taper angle of the optical fiber, and the difference between the two taper angles is within 1 °.
An optical connector in which a periphery of a front end surface of the optical fiber is in close contact with the through hole . And cross-section of said optical fiber, and the cross section of the through-holes have the same shape, the optical connector described in claim 1. 3. The optical connector according to claim 2 , wherein the cross section of the optical fiber and the cross section of the through hole are any one of a circle, a regular polygon, and a combination of a single string and an arc. 4. Any one of claims 1 to 3 wherein B <A <C, where A is the maximum diameter of the optical fiber, B is the hole diameter at the tip of the ferrule, and C is the hole diameter at the rear end of the ferrule. An optical connector described in one. The optical fiber is a multi-core fiber having a plurality of cores, the optical connector disclosed in any one of claims 1 to 4. A step of inserting an adhesive into the through hole of the ferrule having a through hole for housing the optical fiber in the axial direction;
Inserting an optical fiber into the through hole;
Curing the adhesive;
Polishing the end face of the optical fiber exposed at the tip of the ferrule,
The optical fiber has a tapered shape in which at least one tip portion tapers toward the tip,
The ferrule has a tapered shape in which the through hole has a diameter that decreases toward the tip and continues to the tip .
The taper angle of the through hole is equal to or greater than the taper angle of the optical fiber, and the difference between the two taper angles is within 1 °.
The periphery of the end face of the optical fiber is in close contact with the through hole,
A method for manufacturing an optical connector, wherein the tapered end portion of the optical fiber is inserted into the through hole.

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