JP6514929B2 - Optical fiber equipped ferrule and optical connector system - Google Patents

Description

  The present invention relates to an optical fiber ferrule and an optical connector system.

  A ferrule defined in JIS C 5981 (F12 type multi-fiber optical fiber connector: MT connector) is known as a resin fitting-type resin ferrule having guide pin holes on both sides of a plurality of side by side optical fiber holes. ing. In this type of ferrule, the optical fiber end face of the connection end face is physically connected (Physical Contact) by abutting the connection end faces of the opposing ferrules. In JIS C 5982 (F13 type multifiber optical fiber connector: MPO connector), the connection end face of the ferrule is obliquely polished. For example, FIG. 6 of Patent Document 1 also describes that the connection end face of the ferrule is obliquely polished. By obliquely polishing the connection end surface of the ferrule, the end surface of the optical fiber is also obliquely polished, and the characteristic of the return loss is improved.

  Patent Document 2 describes that when the obliquely polished connection end faces are butted, an axial deviation of the optical fiber occurs. In order to suppress an increase in light loss due to such an optical axis misalignment of the optical fiber, Patent Document 3 describes that a collimator lens is formed on a ferrule.

JP 2002-006177 A JP, 2005-181832, A JP, 2011-059486, A

  The ferrule described in Patent Document 3 requires a lens, which makes resin molding difficult and increases the manufacturing cost. On the other hand, in a situation where the MFD (Mode Field Diameter) is small without forming a lens in the ferrule, if the optical fiber is misaligned, the optical loss increases and the optical loss due to dust attached to the end face of the optical fiber also occurs. Cheap.

  An object of the present invention is to suppress light loss without providing a lens in a ferrule.

The main invention for achieving the above object is a ferrule having a plurality of fiber holes, a lensed fiber in which a GRIN lens is fusion spliced to the end of an optical fiber, and a flat plate capable of transmitting light propagating through the optical fiber. A flat plate attached to an end face of the ferrule, and a deformable solid refractive index matching material disposed on an inner face of the flat plate, the end face of the ferrule and the flat plate The end face of the lensed fiber inserted into the fiber hole is inclined with respect to a plane perpendicular to the optical axis of the lensed fiber inserted into the fiber hole, and the end surface of the lensed fiber abuts against the solid refractive index matching material fiber surface of the solid refractive index matching material is deformed, the solid refractive index matching material in the gap between the plate and the end surface of the lensed fiber is characterized in that it is filled It is an odd ferrule.

  Other features of the present invention will become apparent from the description of the specification and the drawings described below.

  According to the present invention, light loss can be suppressed without providing a lens in the ferrule.

FIG. 1 is an explanatory view of an end face 11 of the lensed fiber 1 and the ferrule 10. FIG. 2 is an explanatory view of the ferrule 10. FIG. 3A to FIG. 3C are explanatory diagrams of the state at the time of optical connection. FIG. 3A is an explanatory view of the optical connector system 20 in which the optical connector 21 having the ferrule with optical fiber 10 is inserted from both sides of the adapter 22. 3B and 3C are explanatory views of the positional relationship of the ferrule 10 in the adapter 22. FIG. FIG. 4 is a flowchart of a method of manufacturing the ferrule with an optical fiber. FIG. 5A is a perspective view of the ferrule 10 of the second embodiment. FIG. 5B is an explanatory view of the appearance at the time of filling of the adhesive (refractive index matching agent) in the second embodiment. FIG. 6 is a perspective view of a ferrule 10 of a modification of the second embodiment. FIG. 7 is an explanatory view of a ferrule 10 of a modification of the second embodiment. FIG. 8A is a perspective view of the ferrule 10 of the third embodiment. FIG. 8B is an explanatory view of the appearance at the time of filling of the adhesive (refractive index matching agent) in the third embodiment. FIG. 9 is an explanatory view of a ferrule 10 according to a modification of the third embodiment. FIG. 10A is an explanatory view of a state at the time of filling of an adhesive (refractive index matching agent) in a modification of the third embodiment. FIG. 10B is an explanatory view at the time of light connection in the optical connector system having the ferrule 10 of the modified example of the third embodiment. FIG. 11 is a flow chart of a method of manufacturing the optical fiber equipped ferrule 10 of the fourth embodiment. FIG. 12 is an explanatory view of the relationship between the hardness and thickness of the sheet of the solid refractive index matching material. FIG. 13A is an explanatory view of a ferrule 10 according to a fifth embodiment. FIG. 13B is an explanatory view of the appearance of the ferrule 10 of the fifth embodiment at the time of light connection. FIG. 14A is an explanatory view of a ferrule 10 according to a sixth embodiment.

  At least the following matters will be clear from the description of the specification and drawings to be described later.

  A ferrule having a plurality of fiber holes, a lensed fiber in which a GRIN lens is fusion-spliced to the end of an optical fiber, and a flat plate capable of transmitting light propagating through the optical fiber, attached to the end face of the ferrule A flat plate against which the end face of the lensed fiber inserted into the fiber hole abuts, and the end face of the ferrule and the flat plate are the optical axis of the lensed fiber inserted into the fiber hole A ferrule with a fiber is characterized in that it is inclined with respect to a plane perpendicular to the surface, and a gap between the end face of the lensed fiber and the flat plate is filled with a refractive index matching agent. According to such a ferrule with a fiber, light loss can be suppressed without providing a lens in the ferrule.

  Preferably, an antireflective film is formed on the outer surface of the flat plate. Thereby, the return loss can be suppressed.

  It is preferable that the ferrule has a recess recessed from the end surface of the ferrule, and the space surrounded by the flat plate and the recess be filled with the refractive index matching agent. This facilitates the filling of the refractive index matching agent.

  Preferably, a fiber groove for supporting the lensed fiber is formed on the bottom surface of the recess. This makes it difficult for the end of the lensed fiber to bend.

  The recess is formed with a fiber hole opening surface facing the inner surface of the flat plate and in which a plurality of the fiber holes are opened, and protrudes from the fiber hole opening surface to the side of the flat plate. Preferably, a projection is formed in contact with the edge. Thereby, distortion of the flat plate can be suppressed.

  The end face of the ferrule is formed with a groove formed to pass through the upper portions of the openings of the plurality of fiber holes, and at least a part of the inner wall surface constituting the groove is above the fiber holes It is desirable to be located in As a result, air bubbles are less likely to be formed at the end face of the lensed fiber.

  It is preferable that a solid refractive index matching material whose surface is deformed when the end face of the lensed fiber is abutted is disposed on the inner surface of the flat plate. As a result, air bubbles are less likely to be formed at the end face of the lensed fiber.

  It is desirable that both surfaces of the solid refractive index matching material have adhesiveness. Thereby, it becomes difficult to peel off the solid refractive index matching material from the end faces of the flat plate and the lensed fiber.

  Shore A hardness and thickness of the solid refractive index matching material are Shore A hardness of 0, thickness of 30 μm, Shore A hardness of 70, thickness of 30 μm, Shore A hardness of 70, thickness of It is desirable that it is within a range surrounded by four points of 50 μm point, Shore A hardness of 0, and thickness of 150 μm point. As a result, air bubbles are less likely to be formed at the end face of the lensed fiber that has been abutted against the solid refractive index matching material.

  An optical connector system having an adapter and two optical connectors inserted on both sides of the adapter, wherein each of the optical connectors includes a ferrule having a plurality of fiber holes and a GRIN lens at the end of the optical fiber A lensed fiber connected and a flat plate capable of transmitting light propagating through the optical fiber, the end face of the lensed fiber being attached to the end face of the ferrule and inserted into the fiber hole being abutted The end face of the ferrule and the flat plate are inclined with respect to a plane perpendicular to the optical axis of the lensed fiber inserted into the fiber hole, and the end face of the lensed fiber A gap between the flat plate and the flat plate is filled with a refractive index matching agent, the adapter has an inwardly projecting spacer, and the adapter By the ferrule is in contact with the spacer in part, the optical connector system, wherein the end faces of the ferrules are disposed opposite at a predetermined interval becomes apparent. According to such an optical connector system, light loss can be suppressed without providing a lens in the ferrule.

=== First Embodiment ===
<About the end face of lensed fiber 1 and ferrule 10>
FIG. 1 is an explanatory view of an end face 11 of the lensed fiber 1 and the ferrule 10. In addition, in order to make the explanation easy to understand, the dimensions and angles are exaggerated and illustrated.

  The lensed fiber 1 is an optical fiber which has a single mode optical fiber 2 and a GRIN lens 3 and in which the GRIN lens 3 is fusion-bonded to the tip of the single mode optical fiber 2.

  The GRIN lens 3 is a gradient index lens whose refractive index gradually decreases from the central axis toward the outer periphery. The graded index optical fiber can also be used as the GRIN lens 3 because the graded index optical fiber also has a gradually decreasing refractive index from the central axis toward the outer periphery. Further, the GRIN lens 3 has a predetermined length so as to function as a collimator lens. Specifically, the GRIN lens 3 has a length obtained by multiplying the pitch length, which is the length of a standing wave for one period, by (2n + 1) / 4 (here, n is an integer of 0 or more). The length of the GRIN lens 3 is, for example, 590 μm. Thus, light incident on the GRIN lens 3 from the single mode optical fiber 2 is converted into parallel light in the GRIN lens 3 and emitted from the GRIN lens 3. Conversely, parallel light incident on the GRIN lens 3 is converged in the GRIN lens 3 and is incident on the single mode optical fiber 2 from the GRIN lens 3.

  A flat plate 30 capable of transmitting an optical signal is disposed at the tip of the GRIN lens. The flat plate 30 is disposed to be inclined with respect to a plane perpendicular to the optical axis of the lensed fiber 1 in a state where the end face of the lensed fiber 1 is abutted. Here, the flat plate 30 is inclined at 8 degrees with respect to a plane perpendicular to the optical axis. Since the end face 11 of the ferrule 10 is inclined with respect to a plane perpendicular to the optical axis of the lensed fiber 1, the flat plate 30 is the optical axis of the lensed fiber 1 by arranging the flat plate 30 on the end face 11 of the ferrule 10. It will be placed inclined to the plane perpendicular to. By tilting the end face of the flat plate 30, it is possible to reduce the return loss. If the end face of the GRIN lens 3 is inclined, the length of the GRIN lens 3 changes, and the function as a collimator lens is lost.

  A refractive index matching agent is filled between the flat plate 30 and the end face of the lensed fiber 1. This is because the end face of the lensed fiber 1 is perpendicular to the optical axis and the flat plate 30 is inclined with respect to the plane perpendicular to the optical axis, so there is a gap between the end face of the lensed fiber 1 and the flat plate 30 It is because it occurs. The refractive index of the refractive index matching agent is adjusted to the same degree as the refractive index of the lensed fiber 1 or the flat plate 30 (refractive index of glass). In other words, the refractive index of the refractive index matching agent is adjusted to be closer to the refractive index of the lensed fiber 10 or the flat plate 30 than the refractive index of air. Therefore, Fresnel reflection can be suppressed by filling the refractive index matching agent.

  Next, paths of optical signals propagating through the two lensed fibers 1 will be described. Here, it is assumed that an optical signal propagates from the left lensed fiber 1 to the right lensed fiber 1.

  The optical signal propagated through the left lensed fiber 1 is emitted rightward from the outer inclined surface of the flat plate 30 via the refractive index matching agent and the flat plate 30. Since the outside of the inclined surface of the flat plate 30 is air, the light signal is refracted according to Snell's law (the refractive index of the flat plate 30 is, for example, 1.46). As a result, the light signal emitted from the left flat plate 30 is refracted upward (oppositely by about 3.9 degrees here) opposite to the side (downward) to which the inclined surface of the flat plate 30 faces.

  An optical signal (parallel light) propagated upward in the air by being inclined upward with respect to the optical axis is incident on the inclined surface of the right flat plate 30. The inclined surface of the right flat plate 30 is inclined at 8 degrees with respect to the plane perpendicular to the optical axis of the lensed fiber 1 and is disposed parallel to the left flat plate 30. As a result, the light signal incident on the inclined surface of the right flat plate 30 is refracted and propagates in the lensed fiber 1 through the flat plate 30 and the refractive index matching agent.

  In order to optically connect the left and right lensed fibers 1, it is necessary to shift the optical axis of the lensed fiber 1 in consideration of propagation of the refracted optical signal in the air. Specifically, when the distance between the end faces of the GRIN lens 3 is 900 μm, the shift amount G of the optical axis of the lensed fiber 1 is about 30 μm. The shift amount (= G / 2: offset amount) between the positioning portion (the positioning hole 13 or the positioning pin 14) of the ferrule 10 and the fiber hole 15 is about 15 μm. In the following description, the distance between the end faces 11 of the ferrule 10 for optically connecting the left and right lensed fibers 1 (the distance between the lensed fibers 1 in the optical axis direction) is L.

  In the present embodiment, it is not necessary to form a lens in the ferrule 10, so the manufacture of the ferrule 10 is easy. Further, since the MFD (Mode Field Diameter) of the optical signal propagating between the ferrules 10 is large, the optical loss can be suppressed even if the optical axis deviation of the lensed fiber 1 occurs to some extent, and the end surface of the lensed fiber 1 is attached The light loss due to dust can also be suppressed. In addition, the end faces 11 of the ferrule 10 do not need to be in contact with each other, and the end faces of the lensed fiber 1 are not in direct contact either. There is also an advantage that the end face of 1 is not easily damaged. Further, since the inclined surfaces of the flat plate 30 are not in direct contact with each other, there is also an advantage that the coating on the inclined surface of the anti-reflection treated flat plate 30 is less likely to be damaged.

<About ferrule 10>
FIG. 2 is an explanatory view of the ferrule 10. In the following description, the direction in which the two positioning holes 13 are arranged is referred to as "left-right direction". Further, the axial direction of the positioning hole 13 is referred to as "front-back direction", the side facing the ferrule 10 on the opposite side is referred to as "front", and the opposite side is referred to as "rear". Further, a direction perpendicular to the left-right direction and the front-rear direction is referred to as "vertical direction", the side provided with the adhesive filling window 16 is referred to as "upper", and the opposite side is referred to as "lower".

  The ferrule 10 is a member that holds the end of the lensed fiber 1. A collar 12 is formed on the rear side of the ferrule 10. The collar portion 12 is a portion protruding outward from the outer peripheral surface. The ferrule 10 including the collar 12 is integrally molded of resin. Within the ferrule 10, the ends of the plurality of lensed fibers 1 are held. The ferrule 10 of this embodiment has substantially the same configuration as a ferrule having an inclined end face defined by JIS C 5982 (F13 type multi-fiber optical fiber connector: MPO connector), and the positioning hole 13 and the fiber hole 15 etc. The dimensions and positional relationship of are as specified in the standard. However, when the end face 11 of the ferrule 10 is viewed from the front side, the position of the fiber hole 15 is shifted downward relative to the positioning hole 13 by an amount corresponding to G / 2 in FIG.

  The ferrule 10 has two positioning holes 13, a plurality of fiber holes 15, and an adhesive filling window 16. The ferrule 10 also has a flat plate 30 attached to the end face 11.

  The positioning hole 13 is a hole for inserting the positioning pin 14 (see FIG. 3A). The positioning holes 13 and the positioning pins 14 serve as positioning portions for positioning the ferrule 10. By inserting the positioning pins 14 into the positioning holes 13, the ferrules 10 are aligned with each other. The positioning holes 13 pass through the ferrule 10 in the front-rear direction, and are formed at intervals in the left-right direction so as to sandwich the plurality of fiber holes 15 from the left and right.

  The fiber hole 15 is a hole for inserting the end of the lensed fiber 1. The lensed fiber 1 is inserted into the fiber hole 15 as shown in FIG. The fiber hole 15 passes between the front end face 11 of the ferrule 10 and the adhesive filled window 16. The fiber holes 15 are formed in parallel in the front-rear direction, and the plurality of fiber holes 15 are arranged side by side in the left-right direction. Here, twelve fiber holes 15 are arranged in line in the left-right direction. The fiber hole 15 is a portion forming an optical path inside the ferrule 10 and is a hole parallel to the optical axis of the lensed fiber 1.

  The adhesive filling window 16 is a cavity for filling the adhesive. A fiber insertion port (not shown) for inserting the lensed fiber 1 is formed on the rear end face of the ferrule 10, and the lensed fiber 1 inserted from the fiber insertion port is used as the adhesive filling window 16 Crosswise, it will be inserted into the fiber hole 15. By filling the adhesive from the adhesive filling window 16, the lensed fiber 1 is fixed to the ferrule 10.

  At the front end face 11 of the ferrule 10, the positioning hole 13 is open and a plurality of fiber holes 15 are open. A flat plate 30 is attached to the front end surface 11 of the ferrule 10. Since the positioning hole 13 is not closed by the flat plate 30, the positioning pin 14 can be inserted into the positioning hole 13 even after the flat plate 30 is attached. On the other hand, the opening of the fiber hole 15 is closed by the flat plate 30.

  The front end face 11 of the ferrule 10 is inclined with respect to a plane perpendicular to the axial direction of the fiber hole 15. For this reason, the front end surface 11 of the ferrule 10 is inclined with respect to a plane perpendicular to the optical axis of the lensed fiber 1 inserted into the fiber hole 15. Further, since the end face of the lensed fiber 1 is perpendicular to the optical axis, the front end face 11 of the ferrule 10 is inclined with respect to the end face of the lensed fiber 1 inserted in the fiber hole 15.

  The end surface 11 on the front side of the ferrule 10 is inclined with respect to the vertical direction when viewed from the left and right direction. More specifically, the end surface 11 on the front side of the ferrule 10 is inclined at an angle of 8 degrees with respect to the vertical direction so that the upper side (the adhesive filling window 16 side) of the ferrule 10 is on the front side. That is, the front end face 11 of the ferrule 10 is inclined to face downward. By inclining the front end face 11 of the ferrule 10, it becomes easy to arrange the flat plate 30 in an inclined manner with respect to a plane perpendicular to the optical axis of the lensed fiber 1.

  The center position of the plurality of fiber holes 15 with respect to the positioning hole 13 is such that the end face 11 is inclined toward the mating ferrule toward the upper side (the adhesive filling window 16 side). It is offset from the lower side (opposite to the side of the adhesive filling window 16). That is, when the end face 11 of the ferrule 10 is viewed from the front side, the center positions (centroid positions) of the plurality of fiber holes 15 are shifted downward by an amount corresponding to G / 2 in FIG. ing. Thus, even if the optical signal is refracted by the inclined surface as shown in FIG. 1, optical connection is possible.

  The flat plate 30 is, for example, a glass plate capable of transmitting light propagating through the optical fiber 2. The inner (rear side) surface of the flat plate 30 faces the end face side of the lensed fiber 1, and the outer (front side) surface of the flat plate 30 is a flat plate 30 attached to the end face 11 of the mating ferrule 10 opposite.

  The shape of the flat plate 30 is a long plate shape in the left-right direction. However, the shape of the flat plate 30 is not limited to this shape, and may be another shape such as a trapezoidal shape or a rhombus shape as viewed from the front-rear direction. The dimension of the flat plate 30 in the left-right direction is such a length that the positioning hole 13 is not blocked while closing the openings of the plurality of fiber holes 15 aligned in the left-right direction. That is, the lateral edge of the flat plate 30 is located between the fiber hole 15 located at the end and the positioning hole 13.

  The outer surface (front side) of the flat plate 30 is coated with an antireflective film. For example, the antireflective film is an AR coat film in which two types of thin films having different refractive indexes are stacked. By forming an antireflective film on a flat plate, transmission loss and return loss can be reduced. Although there is a limitation in the volume that the film forming apparatus can process at one time, since the target object of the film forming process is the flat plate 30 alone, it is possible to set many flat plates 30 in the film forming apparatus. Can form an anti-reflection film on the flat plate 30. In the case where the AR coating is applied to the end face of the lensed fiber 1, or when the AR applied to the lensed fiber 1 in a state of being attached to the ferrule, etc., the throughput of the film forming apparatus is reduced. Coating of the protective film is costly.

  FIG. 3A to FIG. 3C are explanatory diagrams of the state at the time of optical connection. FIG. 3A is an explanatory view of the optical connector system 20 in which the optical connector 21 having the ferrule with optical fiber 10 is inserted from both sides of the adapter 22. 3B and 3C are explanatory views of the positional relationship of the ferrule 10 in the adapter 22. FIG. The optical connector system 20 has two optical connectors 21 each having an optical fiber ferrule 10 and an adapter 22 into which the two optical connectors 21 can be inserted from both sides.

  As shown in FIG. 3A, by inserting the optical connector 21 from both sides of the adapter 22, the end faces 11 of the ferrules 10 of the optical connector 21 are arranged to face each other, and the flat plates 30 attached to the end face 11 Are arranged facing each other. The positioning pin 14 protrudes from the ferrule 10 of the male optical connector 21, and the positioning pin 14 is inserted into the positioning hole 13 of the ferrule 10 of the female optical connector 21, whereby the ferrules 10 are positioned in the adapter 22. It will be aligned in the direction (horizontal direction and vertical direction) perpendicular to the pin 14. The ferrules 10 are made to face each other by reversing the upper and lower directions of the ferrules 10 (with the adhesive filling windows 16 turned in the opposite direction) so that the flat plates 30 become parallel to each other.

  Inside the adapter 22, a spacer 23 projecting inward is formed. The dimension in the front-rear direction of the spacer 23 corresponds to the distance L between the end surfaces 11 of the ferrule 10 described above. By the ferrule 10 coming into contact with the spacer 23, as shown in FIGS. 3B and 3C, the end faces 11 of the ferrule 10 are arranged to face each other at a predetermined distance L, and flat plates 30 attached to the end face 11 Are arranged opposite to each other at a predetermined interval. That is, when the ferrule 10 contacts the spacer 23 in the adapter 22, the ferrules 10 are aligned in the front-rear direction, and the flat plates 30 are aligned in the front-rear direction. Here, the end face 11 (inclined end face) on the front side of the ferrule 10 is in contact with the spacer 23. However, when the flange portion 12 of the ferrule 10 is in contact with the spacer 23, the end face 11 of the ferrule 10 is opposed at a predetermined distance L You may make it

<Method of manufacturing ferrule 10 with optical fiber>
FIG. 4 is a flowchart of a method of manufacturing the ferrule with an optical fiber.

  First, the lensed fiber 1 is created (S101). Specifically, first, a graded index optical fiber is fusion spliced to the single mode optical fiber 2, the fusion spliced graded index optical fiber is cut to a predetermined length, and the single mode optical fiber 2 is The GRIN lens 3 is formed. The end surface (cut surface) of the GRIN lens 3 at this time is perpendicular to the optical axis of the lensed fiber 1. The fusion splice is performed so that the outer diameter of the fusion spliced portion can be inserted into the fiber hole 15 (the fiber hole 15 of the inner diameter defined by the standard). A plurality of such lensed fibers 1 are prepared.

  Next, the operator prepares the above-mentioned ferrule 10, and arranges the flat plate 30 on the end face 11 of the ferrule 10 (S102). Since the front end face 11 of the ferrule 10 is inclined, the flat plate 30 is inclined with respect to a plane perpendicular to the axial direction of the fiber hole 15 of the ferrule 10 when the flat plate 30 is pressed against the end face 11 to make contact. Be placed.

  Next, the worker bonds the lensed fiber 1 and the flat plate 30 to the ferrule 10 (S103). When the lensed fiber 1 and the flat plate 30 are bonded to the ferrule 10, the end face of the lensed fiber 1 is in contact with the flat plate 30 butting against it. Since the end face of the lensed fiber 1 is perpendicular to the optical axis and the flat plate 30 is inclined with respect to the plane perpendicular to the optical axis, there is a gap between the end face of the lensed fiber 1 and the flat plate 30, The gap is filled with an adhesive that serves as a refractive index matching agent. Since the gap between the end face 11 of the ferrule 10 and the flat plate 30 is small, an adhesive (refractive index matching is made by applying an adhesive to the boundary between the end face 11 of the ferrule 10 and the flat plate 30 using capillary action. Agent) is infiltrated inside. Here, an ultraviolet curing adhesive is used as a refractive index matching agent, and when the adhesive is penetrated and then ultraviolet rays are irradiated through the flat plate 30, the adhesive is cured and the end face of the lensed fiber 1 is flat Bonded to 30. Further, since the ultraviolet curing adhesive penetrates also between the end face 11 of the ferrule 10 and the flat plate 30, the flat plate 30 is adhered to the end face 11 of the ferrule 10 when ultraviolet rays are irradiated through the flat plate 30. A thermosetting adhesive may be used instead of the ultraviolet curable adhesive. Also, the worker fixes the lensed fiber 1 to the ferrule 10 by filling the adhesive 10 into the ferrule 10 from the adhesive filling window 16.

  By the above operation, the ferrule with an optical fiber 10 is manufactured. When the ferrule 10 with an optical fiber manufactured in this way is arranged oppositely as shown in FIG. 1 and optically connected, it is possible to realize an optical loss of about 0.7 dB and a return loss of about 60 dB. It is.

  In the optical connector system 20 (see FIG. 3A) according to the first embodiment described above, the two ferrules 10 are disposed to face each other, and the flat plates 30 are separated by a predetermined distance by the ferrules 10 contacting the spacer 23. It is arranged facing each other. Thereby, as shown in FIG. 1, the flat plates 30 are aligned in the front-rear direction, and the lensed fibers 1 of the two ferrules 10 can be optically connected. These ferrules 10 have a lensed fiber 1 and a flat plate 30, and the flat plate 30 is made of the lensed fiber 1 with the end face of the lensed fiber 1 inserted into the fiber hole 15 abutted. It is disposed at an angle to a plane perpendicular to the optical axis. Since the flat plate 30 is inclined, and the MFD (Mode Field Diameter) of the light signal is large by the GRIN lens 3, light loss can be suppressed and no lens is formed in the ferrule 10. It is easy to manufacture. Further, since only the flat plate 30 is disposed in an inclined manner, the step of obliquely polishing the end face of the ferrule 10 is unnecessary.

=== Second Embodiment ===
In the first embodiment, an adhesive serving as a refractive index matching agent is applied to the boundary between the end face 11 of the ferrule 10 and the flat plate 30, and the adhesive is made to penetrate inside by capillary action. However, the method of filling the refractive index matching agent is not limited to this.

  FIG. 5A is a perspective view of the ferrule 10 of the second embodiment. FIG. 5B is an explanatory view of the appearance at the time of filling of the adhesive (refractive index matching agent) in the second embodiment.

A recess 17 is formed on the front end surface 11 of the ferrule 10 of the second embodiment. The recess 17 is a portion recessed from the end face 11 on the front side, and is a portion forming a space filled with an adhesive serving as a refractive index matching agent. In the recess 17, a fiber hole opening surface 17A, a bottom surface 17B and a side surface 17C are formed.
The fiber hole opening surface 17 </ b> A is an inner wall on the rear side in the recess 17, and is positioned on the rear side with respect to the end surface 11 of the ferrule 10. The fiber hole opening surface 17A is a surface opposed to the inner surface of the flat plate 30, and a plurality of fiber holes 15 are opened in the horizontal direction in the fiber opening surface.
The bottom surface 17 </ b> B is an inner wall that constitutes the bottom of the recess 17. Here, a fiber groove is formed on the bottom surface 17B, and the lensed fiber 1 inserted into the fiber hole 15 is supported from the bottom surface 17B on the fiber groove (see FIG. 5B). Thereby, the end of the lensed fiber 1 does not have to be bent in the recess 17.

  In the second embodiment, as shown in FIG. 5A, the worker arranges the flat plate 30 on the end surface 11 of the ferrule 10 (see S102 in FIG. 4). Next, the worker bonds the lensed fiber 1 and the flat plate 30 to the ferrule 10 (see S103). Also in the second embodiment, when the lensed fiber 1 and the flat plate 30 are bonded to the ferrule 10, the end face of the lensed fiber 1 is in contact with the flat plate 30 butting against it. However, in the second embodiment, the worker fills the space surrounded by the flat plate 30 and the recess 17 with an adhesive serving as a refractive index matching agent. That is, an adhesive serving as a refractive index matching agent is filled in the space surrounded by the flat plate 30, the fiber hole opening surface 17A, the bottom surface 17B and the side surface 17C. According to the second embodiment, since the recess 17 is filled with the refractive index matching agent (adhesive), the end faces of the flat plate 30 and the lensed fiber 1 are compared with the case where the adhesive is permeated using capillary action. And the time for filling the refractive index matching agent can be shortened.

Modification of Second Embodiment
FIG. 6 is a perspective view of a ferrule 10 of a modification of the second embodiment. FIG. 7 is an explanatory view of a ferrule 10 of a modification of the second embodiment. In FIG. 7, for the sake of explanation, the ferrule 10 in the side view is shown as a partial cross section, and the lensed fiber 1 is inserted in the fiber hole 15.

  The ferrule 10 of the modified example has two-dimensionally arranged fiber holes 15. Here, 12 rows of fiber holes 15 aligned in the left and right direction are arranged in 4 rows in the vertical direction. When a plurality of optical fiber holes 15 are two-dimensionally arranged, when the end face 11 of the ferrule 10 is viewed from the front side, the center position (centroid position) of the plurality of fiber holes 15 is shown with respect to the positioning hole 13 It is better to shift downward by an amount corresponding to G / 2 of 1. That is, the end face 11A is inclined toward the mating ferrule toward the upper side (side of the adhesive filling window 16), and the center position of the plurality of fiber holes 15 is lower than the positioning hole 13 (adhesion It is preferable to be in a position shifted to the side opposite to the side of the agent filling window 16).

  Also in the modification, a recess 17 is formed on the front end surface 11 of the ferrule 10. The recess 17 is formed with a fiber hole opening surface 17A, a bottom surface 17B and a side surface 17C, and in the modification, a protrusion 17D is further formed. The protruding portion 17D is a portion protruding to the front side (the side of the flat plate 30) from the upper edge of the fiber hole opening surface 17A, and is a portion contacting the upper edge of the flat plate 30. The left and right edges and the lower edge of the flat plate 30 are in contact with the end surface 11 of the ferrule 10, and the upper edge of the flat plate 30 is in contact with the protrusion 17D. Thereby, the distortion of the flat plate 30 due to the contraction of the adhesive filled in the recess 17 can be suppressed. In particular, in the modification, since the plurality of fiber holes 15 are two-dimensionally arranged, the recess 17 is formed deep, and the contraction of the adhesive increases the influence on the flat plate 30. It is particularly effective to form

=== Third Embodiment ===
FIG. 8A is a perspective view of the ferrule 10 of the third embodiment. FIG. 8B is an explanatory view of the appearance at the time of filling of the adhesive (refractive index matching agent) in the third embodiment.

  A groove 18 is formed on the front end face of the ferrule 10 of the third embodiment. The grooves 18 are formed along the left-right direction so as to penetrate the upper portions of the openings of the plurality of fiber holes 15. As shown to FIG. 8B, the groove | channel 18 is formed in the cross-sectional V-shape, and has the lower surface 18A and the slope 18B. The lower surface 18 </ b> A is located near the center of the openings of the plurality of fiber holes 15. The inclined surface 18 B is an inner wall surface constituting the groove 18, and at least a part thereof is located above the fiber hole 15. The lower edge (rear edge) of the slope 18B is located at the rear edge of the lower surface 18A, and the upper edge (the front edge: the edge at the end face 11 of the ferrule 10) is located above the fiber hole 15.

  The end of the groove 18 is exposed to the outside of the flat plate 30. Here, the left and right ends of the groove 18 are formed so as to reach the upper surface of the ferrule 10 so that the left and right ends of the groove 18 are exposed above the flat plate 30. Thereby, a gap 18C by the groove 18 is formed at the boundary between the end face 11 of the ferrule 10 and the flat plate 30, and the adhesive can be filled from the gap 18C.

  In the third embodiment, as shown in FIG. 8A, the worker arranges the flat plate 30 on the end face 11 of the ferrule 10 (see S102 in FIG. 4). Next, the worker bonds the lensed fiber 1 and the flat plate 30 to the ferrule 10 (see S103). Also in the third embodiment, when the lensed fiber 1 and the flat plate 30 are bonded to the ferrule 10, the end face of the lensed fiber 1 is in contact with the flat plate 30 butting against it. However, in the third embodiment, the worker fills the adhesive from one of the two gaps 18C of the groove 18 at the boundary between the end face 11 of the ferrule 10 and the flat plate 30. The adhesive flows into the inside along the groove 18 and is filled therein. At this time, even if air bubbles are formed inside, since the air bubbles move to the upper side than the fiber hole 15, it is possible to suppress the formation of air bubbles on the end face of the lensed fiber 1.

<Modification of Third Embodiment>
FIG. 9 is an explanatory view of a ferrule 10 according to a modification of the third embodiment. FIG. 10A is an explanatory view of a state at the time of filling of an adhesive (refractive index matching agent) in a modification of the third embodiment.

  The ferrule 10 of the modified example has two-dimensionally arranged fiber holes 15. Here, 12 rows of fiber holes 15 aligned in the left and right direction are arranged in 4 rows in the vertical direction. When a plurality of optical fiber holes 15 are two-dimensionally arranged, when the end face 11 of the ferrule 10 is viewed from the front side, the center position (centroid position) of the plurality of fiber holes 15 is shown with respect to the positioning hole 13 It is better to shift downward by an amount corresponding to G / 2 of 1.

  Also in the modification, the groove 18 is formed along the left-right direction so as to penetrate the upper part of the openings of the plurality of fiber holes 15 aligned in the left-right direction. In the modified example, since the rows of the fiber holes 15 aligned in the lateral direction are arranged in four rows in the vertical direction, the grooves 18 are also formed in four rows in the vertical direction. The left and right ends of the groove 18 are formed to extend to the side surface of the ferrule 10. Thereby, a gap 18C by the groove 18 is formed at the boundary between the end face 11 of the ferrule 10 and the flat plate 30, and the adhesive can be filled from the gap 18C. Since the gaps 18C are formed in each of the four rows of grooves 18, it is possible to keep the adhesive flowing in the respective grooves 18. If the gaps 18C at the left and right ends of the four rows of grooves 18 are made common (when the adhesive is branched from the commonized gaps 18C and the adhesive is poured into the four rows of grooves 18), the adhesive Grooves 18 that are hard to flow are generated. For this reason, it is desirable that gaps 18C be formed in each of the four rows of grooves 18.

  FIG. 10B is an explanatory view at the time of light connection in the optical connector system having the ferrule 10 of the modified example of the third embodiment. Also in the modified example, when the ferrule 10 contacts the spacer 23, the end faces 11 of the ferrule 10 are arranged to face each other at a predetermined distance L.

  In a modification, the left and right ends of the groove 18 are formed to extend to the side surface of the ferrule 10. For this reason, if the spacer 23 contacts the end face 11 of the ferrule 10 at the site where the groove 18 is formed, the spacer 23 may be shaken. In this case, the positional relationship between the ferrules 10 in the front-rear direction or the flat plates 30 There is a possibility that the positional relationship in the front-rear direction may be shifted. Therefore, in the modification, the recess 23A is formed in the spacer 23 so as not to contact the portion where the groove 18 is formed. Thereby, the positions of the ferrules 10 in the front-rear direction and the positions of the flat plates 30 in the front-rear direction can be accurately aligned.

=== Fourth Embodiment ===
In the first to third embodiments, the fluid-like refractive index matching agent (adhesive) is filled in the gap between the lensed fiber 1 and the flat plate 30. However, in this case, air bubbles may be formed on the end face of the lensed fiber 1. On the other hand, in the fourth embodiment, the soft solid refractive index matching agent (solid refractive index matching material) is disposed on the flat plate 30, and the lensed fiber 1 is abutted against the soft solid refractive index matching material. The formation of air bubbles at the end face of the optical fiber 1 is suppressed.

  FIG. 11 is a flow chart of a method of manufacturing the optical fiber equipped ferrule 10 of the fourth embodiment.

  First, a lensed fiber is created (S201). The process of S201 is the same as the process of S101 of FIG.

  Next, the worker arranges the solid refractive index matching material between the ferrule 10 and the flat plate 30 (S202). The solid refractive index matching material is a light transmitting sheet-like member, and is a solid refractive index matching agent. The refractive index of the solid refractive index matching material is substantially the same as that of the above-mentioned adhesive (refractive index matching agent). The material of the solid refractive index matching material is, for example, acrylic, epoxy, vinyl, silicone, rubber, urethane, methacrylic, nylon, bisphenol, diol, polyimide, fluorinated epoxy, fluorine And high molecular weight acrylic materials.

  The solid refractive index matching material is disposed on the rear surface of the flat plate 30. That is, the solid refractive index matching material is disposed on the surface on which the lensed fiber 1 is abutted. For this reason, the solid refractive index matching material faces the opening of the fiber hole 15. For example, a sheet-like (film-like) solid refractive index matching material is attached to the area facing the fiber hole 15 in the surface on the side of the recess 17 of the flat plate 30 in FIG. The solid refractive index matching material is disposed on the flat plate 30 by applying a liquid refractive index matching agent to the flat plate 30 and then solidifying it, instead of attaching the sheet-like solid refractive index matching material to the flat plate 30. Also good.

  The solid refractive index matching material has such a hardness that the surface is deformed when the end face of the lensed fiber 1 is abutted. This can suppress the formation of air bubbles on the end face of the lensed fiber 1.

  FIG. 12 is an explanatory view of the relationship between the hardness and thickness of the sheet of the solid refractive index matching material. The horizontal axis indicates the thickness of the solid refractive index matching material, and the vertical axis indicates the Shore A hardness (HSA). As a solid refractive index matching material, the thing of area | region RD in a figure can be used conveniently. Region RC and region RD in the drawing are divided by a straight line connecting point P1 (HSA 70, thickness 50 μm) and point P2 (HSA 0, thickness 150 μm).

  In the area RA (area where the Shore A hardness is greater than 70), the hardness is too high, so the followability of the surface of the solid refractive index matching material when the lensed fiber 1 is abutted is low. Therefore, a gap (air bubble) is easily generated at the end face of the lensed fiber 1. However, even when the solid refractive index matching material in the region RA is used, air bubbles in the end face of the lensed fiber 1 can be suppressed as compared with the case where the solid refractive index matching material is not provided.

  In the region RB (a region where the Shore A hardness is 70 or less and the thickness is smaller than 30 μm), the solid refractive index matching material is too thin, so the end face of the lensed fiber 1 is rough or a plurality of lensed fibers If the end face of 1 is not aligned, a gap (air bubble) is easily generated at the end face of the lensed fiber 1. However, even when the solid refractive index matching material in the region RB is used, bubbles in the end face of the lensed fiber 1 can be suppressed as compared with the case where the solid refractive index matching material is not present.

  In the region RC (a region where the Shore A hardness is 70 or less and the thickness is larger than the straight line connecting the point P1 and the point P2), the distance between the end face of the lensed fiber 1 and the plane of the flat plate 30 becomes too large. It is not appropriate. However, even when the solid refractive index matching material in the region RC is used, bubbles in the end face of the lensed fiber 1 can be suppressed as compared with the case where the solid refractive index matching material is not provided.

  As described above, the region RD (a region whose thickness is smaller than the straight line including the point P1 and the point P2 in the region having a Shore A hardness of 70 or less and a thickness of 30 μm or more) is appropriate. It becomes an area. That is, a range enclosed by four points (HSA0, thickness 30 μm), (HSA 70, thickness 30 μm), (HSA 70, thickness 50 μm), (HSA0, thickness 150 μm) in the figure as solid refractive index matching materials It is desirable to use the ones inside.

  It is desirable that both surfaces of the solid refractive index matching material have adhesiveness. As a result, the solid refractive index matching material does not easily separate from the flat plate 30, and after the end face of the lensed fiber 1 abuts on the solid refractive index matching material, the solid refractive index matching material and the end face of the lensed fiber It becomes difficult to peel off. As such a solid refractive index matching material, it is possible to use a film made of a pressure-sensitive adhesive material made of a polymer material, and from the viewpoint of environmental resistance and adhesiveness, silicone and acrylic materials are generally used. Can be used.

  Next, the worker bonds the lensed fiber 1 and the flat plate 30 to the ferrule 10 (S203). In the fourth embodiment, when the lensed fiber 1 and the flat plate 30 are bonded to the ferrule 10, the end face of the lensed fiber 1 is butted against and brought into contact with the flat plate 30 via the solid refractive index matching agent. There is. When the end face of the lensed fiber 1 is abutted against and brought into contact with the solid refractive index matching material of the flat plate 30, the end face of the lensed fiber 1 is perpendicular to the optical axis, and the flat plate 30 is perpendicular to the plane perpendicular to the optical axis Although it is inclined, when the surface of the solid refractive index matching material is deformed along the end face of the lensed fiber 1, the gap between the end face of the lensed fiber 1 and the flat plate 30 is filled with the solid refractive index matching material Be done. The worker adheres the lensed fiber 1 and the flat plate 30 to the ferrule 10, for example, by filling the recess 17 with an adhesive. Also, the lensed fiber 1 is fixed to the ferrule 10 by filling the adhesive filling window 16 with the adhesive. Thus, the ferrule with an optical fiber 10 is manufactured.

  According to the fourth embodiment described above, it is possible to suppress the formation of air bubbles on the end face of the lensed fiber 1 by abutting the lensed fiber 1 on the soft solid refractive index matching material disposed in the flat plate 30.

=== Fifth Embodiment ===
FIG. 13A is an explanatory view of a ferrule 10 according to a fifth embodiment. Also in the fifth embodiment, as in the previous embodiment, the front end face 11 of the ferrule 10 is with respect to a plane perpendicular to the optical axis of the lensed fiber 1 (plane perpendicular to the axial direction of the fiber hole 15) It is inclined. Further, the flat plate 30 attached to the end face 11 is also disposed to be inclined with respect to the plane perpendicular to the optical axis of the lensed fiber 1.

  In the fifth embodiment, the end surface 11 on the front side of the ferrule 10 is viewed from above (a direction perpendicular to the left and right direction in which the two positioning holes 15 line up and the axial direction of the positioning holes 15 (vertical direction When viewed from)), it is inclined 8 degrees to the left and right direction. For this reason, the flat plate 30 attached to the end face 11 is also inclined at 8 degrees with respect to the left and right direction when viewed from above.

  FIG. 13B is an explanatory view of the appearance of the ferrule 10 of the fifth embodiment at the time of light connection. Also in the fifth embodiment, the end faces 11 of the ferrule 10 are disposed to face each other, and the flat plates 30 are disposed to face each other. By inserting the positioning pin 14 into the positioning hole 13 of the ferrule 10, the ferrules 10 are aligned in a direction (left and right direction and vertical direction) perpendicular to the positioning pin 14 in an adapter (not shown).

  In the fifth embodiment, the ferrule 10 is made to have the same upper and lower directions (with the adhesive filling window 16 in the same direction) so that the inclined end faces 11 of the ferrule 10 become parallel to each other. Are facing each other. For this reason, in the fifth embodiment, the position of the fiber hole 15 in the vertical direction is the same as the position of the positioning hole 13 in the vertical direction (however, in the fifth embodiment, the plurality of fiber holes 15 are positioned The side of the hole 13 is shifted in the lateral direction by an amount corresponding to G / 2 in FIG.

  Also in the fifth embodiment, when the ferrule 10 contacts the spacer 23, the end faces 11 of the ferrule 10 are disposed to face each other at a predetermined distance L, and the flat plates 30 are disposed to face each other at a predetermined distance. Be done. That is, when the ferrule 10 contacts the spacer 23, the ferrules 10 are aligned in the front-rear direction, and the flat plates 30 are aligned in the front-rear direction.

=== Sixth Embodiment ===
FIG. 14A is an explanatory view of a ferrule 10 according to a sixth embodiment.
In the sixth embodiment, the front end surface 11 of the ferrule 10 is a surface perpendicular to the axial direction (longitudinal direction) of the positioning hole 13 and is not inclined. However, in the sixth embodiment, the axial direction of the fiber hole 15 is inclined at 8 degrees with respect to the axial direction of the positioning hole 13. Therefore, when the lensed fiber 1 is inserted into the fiber hole 15, the front end face 11 of the ferrule 10 is inclined with respect to the plane perpendicular to the optical axis of the lensed fiber 1. Further, the flat plate 30 attached to the end face 11 is also disposed to be inclined with respect to a plane perpendicular to the optical axis of the lensed fiber 1.

  FIG. 14B is an explanatory view of the appearance of the ferrule 10 of the sixth embodiment at the time of light connection. Also in the sixth embodiment, the end faces 11 of the ferrule 10 are disposed to face each other, and the flat plates 30 are disposed to face each other. By inserting the positioning pin 14 into the positioning hole 13 of the ferrule 10, the ferrules 10 are aligned in a direction (left and right direction and vertical direction) perpendicular to the positioning pin 14 in an adapter (not shown). In the sixth embodiment, the ferrules 10 have the same top and bottom orientation (the adhesive filling window 16 has the same orientation) so that the fiber holes 15 of the opposing ferrules 10 are parallel to each other. 10 are facing each other.

  Also in the sixth embodiment, when the ferrule 10 contacts the spacer 23, the end faces 11 of the ferrule 10 face each other at a predetermined distance L (not the distance in the front-rear direction but the distance in the optical axis direction of the lensed fiber 1). And the flat plates 30 are arranged opposite to each other at a predetermined interval. That is, when the ferrule 10 contacts the spacer 23, the ferrules 10 are aligned in the front-rear direction, and the flat plates 30 are aligned in the front-rear direction. In the sixth embodiment, the thickness in the front-rear direction of the spacer 23 is slightly smaller than L.

=== Others ===
The above embodiments are for the purpose of facilitating the understanding of the present invention, and are not for the purpose of limiting the present invention. It goes without saying that the present invention can be modified and improved without departing from the gist thereof, and that the present invention includes equivalents thereof.

1 lensed fiber,
2 single mode optical fiber,
3 GRIN lens,
10 ferrules,
11 end face,
12 buttocks,
13 positioning holes,
14 Positioning pins,
15 fiber holes,
16 adhesive filled windows,
17 recesses,
17A fiber hole opening surface,
17B bottom,
17C side,
17D overhang,
18 grooves,
18A bottom,
18B slope,
18C gap,
20 optical connector system,
21 optical connector,
22 adapters,
23 spacers,
23A recess,
30 flat plates

Claims (9)

A ferrule having a plurality of fiber holes,
A lensed fiber in which a GRIN lens is fusion spliced to the end of the optical fiber,
A flat plate capable of transmitting light propagating through the optical fiber, the flat plate being attached to an end face of the ferrule ;
A deformable solid refractive index matching material disposed on the inner surface of the flat plate;
Have
The end face of the ferrule and the flat plate are inclined with respect to a plane perpendicular to the optical axis of the lensed fiber inserted into the fiber hole;
The end face of the lensed fiber inserted into the fiber hole is abutted against the solid refractive index matching material, the surface of the solid refractive index matching material is deformed, and the end face of the lensed fiber and the flat plate A ferrule with a fiber, wherein the gap is filled with the solid refractive index matching material . A ferrule with a fiber according to claim 1, wherein
A ferrule with a fiber, wherein an antireflective film is formed on the outer surface of the flat plate. A ferrule with a fiber according to claim 1 or 2, wherein
The ferrule is formed with a recess recessed from the end face of the ferrule,
A ferrule with a fiber, wherein a space surrounded by the flat plate and the recess is filled with an index matching agent. A ferrule with a fiber according to claim 3, wherein
A ferrule with a fiber, wherein a fiber groove for supporting the lensed fiber is formed on the bottom surface of the recess. It is a ferrule with a fiber according to claim 3 or 4,
The recess is formed with a fiber hole opening surface facing the inner surface of the flat plate and in which a plurality of the fiber holes are opened,
A ferrule with a fiber, characterized in that a protrusion which protrudes from the fiber hole opening surface to the side of the flat plate and contacts the edge of the flat plate is formed. A ferrule with a fiber according to claim 1 or 2, wherein
The end face of the ferrule is formed with a groove formed to pass through the upper part of the openings of the plurality of fiber holes,
A ferrule with a fiber, wherein at least a part of an inner wall surface constituting the groove is located above the fiber hole. It is a ferrule with a fiber according to any one of claims 1 to 6 ,
A ferrule with a fiber, wherein both surfaces of the solid refractive index matching material have adhesiveness. It is a ferrule with a fiber according to any one of claims 1 to 7 , wherein
The Shore A hardness and thickness of the solid refractive index matching material are
Shore A hardness 0, thickness 30 μm,
70 A Shore A hardness, 30 μm thick,
70 A Shore A hardness, 50 μm thickness,
A ferrule with a fiber characterized in that it has a Shore A hardness of 0 and a thickness of 150 μm within a range enclosed by four points. An optical connector system comprising an adapter and two optical connectors inserted on both sides of the adapter,
Each of the optical connectors is
A ferrule having a plurality of fiber holes,
A lensed fiber in which a GRIN lens is fusion spliced to the end of the optical fiber,
A flat plate capable of transmitting light propagating through the optical fiber, the flat plate being attached to an end face of the ferrule ;
A deformable solid refractive index matching material disposed on the inner surface of the flat plate;
Have
The end face of the ferrule and the flat plate are inclined with respect to a plane perpendicular to the optical axis of the lensed fiber inserted into the fiber hole;
The end face of the lensed fiber inserted into the fiber hole is abutted against the solid refractive index matching material, the surface of the solid refractive index matching material is deformed, and the end face of the lensed fiber and the flat plate The solid refractive index matching material is filled in the gap,
The adapter has an inwardly projecting spacer,
The optical connector system characterized in that the end faces of the ferrules are arranged to face each other at a predetermined interval by the ferrule being in contact with the spacer inside the adapter.

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