JP2016184107A - Ferrule with optical fiber and optical connector system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrule with an optical fiber that: provides a configuration preventing optical loss without providing the ferrule with a lens; and facilitates filling work of a refractive index matching agent in the configuration.SOLUTION: A ferrule with an optical fiber includes: a ferrule 10 having a positioning hole, a plurality of fiber holes 15, and an end surface 11 perpendicular to an axis direction of the fiber holes 15; a lensed fiber 1 in which a tip of an optical fiber 2 is fusion-spliced to a GRIN lens 3; and a flat plate 30 that can transmit light propagating in the optical fiber 2, that is mounted on the end surface 11 of the ferrule 10, and against which an end surface of the lensed fiber 1 inserted into the fiber hole 15 is butted. The ferrule 10 is formed with a recess recessed from the end surface 11 of the ferrule 10, and a space surrounded by the flat plate 30 and the recess is filled with a refractive index matching agent.SELECTED DRAWING: Figure 1

Description

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

  A ferrule defined in JIS C 5981 (F12 type multi-core optical fiber connector: MT connector) is known as a pin fitting positioning type resin ferrule having guide pin holes on both sides of a plurality of optical fiber holes arranged side by side. ing. In this type of ferrule, the connection end faces of the opposed ferrules are brought into contact with each other, whereby the end face of the optical fiber at the connection end face is physically connected (Physical Contact). In JIS C 5982 (F13 type multi-core optical fiber connector: MPO connector), the connection end face of the ferrule is polished obliquely. For example, also in FIG. 6 of Patent Document 1, the connection end face of the ferrule is obliquely polished. When the connection end face of the ferrule is obliquely polished, the end face of the optical fiber is also obliquely polished, and the return loss characteristics are improved.

  In Patent Document 2, it is described that an axial deviation of the optical fiber occurs when the connection end surfaces polished obliquely are brought into contact with each other. In order to suppress an increase in optical loss due to such an optical axis shift of the optical fiber, Patent Document 3 describes that a collimator lens is formed on the ferrule.

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

  Since the ferrule described in Patent Document 3 requires a lens, resin molding is difficult and manufacturing costs are increased. On the other hand, when the MFD (Mode Field Diameter) is small without forming a lens on the ferrule, if the optical fiber is misaligned, the optical loss increases and the optical loss due to dust adhering to the end face of the optical fiber also occurs. Cheap. In addition, even when the connection end face of the ferrule and the end face of the optical fiber are not obliquely polished, there is a problem that light loss is likely to increase under the condition that the MFD (Mode Field Diameter) is small without forming a lens on the ferrule. Can occur.

  An object of this invention is to suppress optical loss, without providing a lens in a ferrule.

  The main invention for achieving the above object is that a GRIN lens is fusion spliced to the tip of an optical fiber, a ferrule having a positioning hole, a plurality of fiber holes, and an end face perpendicular to the axial direction of the fiber hole. A lensed fiber, and a flat plate capable of transmitting light propagating through the optical fiber, the flat plate being attached to the end face of the ferrule and against which the end face of the lensed fiber inserted into the fiber hole is abutted The ferrule has a recess recessed from the end surface of the ferrule, and a space surrounded by the flat plate and the recess is filled with a refractive index matching agent. This is a ferrule with a fiber.

  Other characteristics of the present invention will be made clear by the description and drawings described later.

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

FIG. 1 is an explanatory diagram of an end face (first end face 11A) of the lensed fiber 1 and the ferrule 10. 2A and 2B are perspective views of the ferrule 10 of the first embodiment. FIG. 2B is a perspective view of a state where the flat plate of FIG. 2A is removed. FIG. 3 is an explanatory diagram of the ferrule of the first embodiment. FIG. 4 is an explanatory diagram of a state during optical connection. FIG. 5 is a flowchart of a method for manufacturing the ferrule 10 with an optical fiber. FIG. 6 is a perspective view of the ferrule 10 of the second embodiment. FIG. 7 is an explanatory diagram of the ferrule 10 of the second embodiment. FIG. 8A and FIG. 8B are explanatory diagrams of a state at the time of optical connection according to the second embodiment. FIG. 8A is an explanatory diagram of the optical connector system 20 in which the optical connector 21 having the ferrule 10 with an optical fiber is inserted from both sides of the adapter 22. FIG. 8B is an explanatory diagram of the positional relationship of the ferrule 10 within the adapter 22. FIG. 9 is a flowchart of a method for manufacturing the ferrule 10 with an optical fiber in the third embodiment. FIG. 10 is an explanatory diagram of the relationship between the hardness and thickness of the sheet of the solid refractive index matching material. FIG. 11 is an explanatory diagram of the end surface 11 of the lensed fiber 1 and the ferrule 10 of the fourth embodiment. FIG. 12A is an explanatory diagram of the ferrule 10 of the fourth embodiment. FIG. 12B is an explanatory diagram of a state when the ferrule 10 of the fourth embodiment is optically connected.

  At least the following matters will be apparent from the description and drawings described below.

  A ferrule having a positioning hole, a plurality of fiber holes, and an end surface perpendicular to the axial direction of the fiber hole, a lensed fiber having a GRIN lens fusion-bonded to the tip of the optical fiber, and propagating through the optical fiber A flat plate capable of transmitting light, the flat plate being attached to the end face of the ferrule and against which the end face of the lensed fiber inserted into the fiber hole is abutted. A concave ferrule is formed from the end face of the ferrule, and a ferrule with a fiber is characterized in that a space surrounded by the flat plate and the concave is filled with a refractive index matching agent. According to such a ferrule with a fiber, the optical loss can be suppressed without providing a lens in the ferrule, and the filling operation of the refractive index matching agent can be facilitated in the configuration.

  It is desirable that an antireflection film is formed on the outer surface of the flat plate. Thereby, the return loss can be suppressed.

  The ferrule is preferably a contact end surface that comes into contact with a mating ferrule, and has an end surface to which the flat plate is attached and a contact end surface that protrudes to the mating ferrule side with respect to the flat plate. Thereby, it is not necessary to arrange another member such as a spacer between the opposite ferrule.

  The recess is formed with a fiber hole opening surface facing the inner surface of the flat plate, and a plurality of the fiber holes are opened, projecting from the fiber hole opening surface to the flat plate side, It is desirable to form a protrusion that contacts the edge. Thereby, distortion of a flat plate can be suppressed.

  It is desirable that a solid refractive index matching material whose surface is deformed when the end surface of the lensed fiber is abutted is disposed on the inner surface of the flat plate. This makes it difficult for bubbles to be formed on the end face of the lensed fiber.

  It is desirable that both surfaces of the solid refractive index matching material have adhesiveness. This makes it difficult for the solid refractive index matching material to peel from the end surfaces of the flat plate and the lensed fiber.

  The shore A hardness and thickness of the solid refractive index matching material are as follows: Shore A hardness is 0, thickness is 30 μm, Shore A hardness is 70, thickness is 30 μm, Shore A hardness is 70, thickness is It is desirable to be within a range surrounded by four points of a 50 μm point, a Shore A hardness of 0, and a thickness of 150 μm. Thereby, it becomes difficult for bubbles to be formed on the end face of the lensed fiber abutted against the solid refractive index matching material.

    An optical connector system for optically connecting two optical connectors, each optical connector including a positioning hole, a plurality of fiber holes, and a ferrule having an end surface perpendicular to the axial direction of the fiber hole, and an optical fiber A lensed fiber to which a GRIN lens is fused and connected, and a flat plate capable of transmitting light propagating through the optical fiber, attached to the end face of the ferrule, and inserted into the fiber hole. A flat plate against which an end surface of the lensed fiber is abutted, and the ferrule has a recess recessed from the end surface of the ferrule, and a refractive index in a space surrounded by the flat plate and the recess. An optical connector system is characterized in that it is filled with a matching agent and the flat plates of the optical connector are arranged to face each other at a predetermined interval. . According to such an optical connector system, the optical loss can be suppressed without providing a lens in the ferrule, and the filling operation of the refractive index matching agent can be facilitated in the configuration.

  The ferrule is a contact end surface that comes into contact with a mating ferrule, the end surface to which the flat plate is attached, and a contact end surface that protrudes to the mating ferrule side from the flat plate, and the ferrule It is desirable that the flat plates are arranged to face each other at a predetermined interval by contacting the contact end surface with the contact end surface of the counterpart ferrule. Thereby, it is not necessary to arrange another member such as a spacer between the opposite ferrule.

  It is desirable that the flat plates are arranged to face each other at a predetermined interval when the ferrule contacts the spacer. Thereby, a ferrule can be made to oppose at a predetermined space | interval.

  A ferrule having a positioning hole, a plurality of fiber holes, and an end surface perpendicular to the axial direction of the fiber hole, a lensed fiber having a GRIN lens fusion-bonded to the tip of the optical fiber, and propagating through the optical fiber A flat plate capable of transmitting light, an antireflection film is formed on the outer surface, and the inner surface of the ferrule is arranged to face the end surface of the lensed fiber inserted into the fiber hole. A ferrule with a fiber characterized by having a flat plate attached to the end face is revealed. According to such a ferrule with a fiber, light loss can be suppressed without providing a lens on the ferrule.

  It is desirable that a coreless fiber is fused and connected to the tip of the GRIN lens, and the flat plate is attached to the end face after the end of the lensed fiber protruding from the fiber hole is polished. As a result, since the gap between the end surface of the lensed fiber and the flat plate can be made minute, when the refractive index matching agent is filled between the end surface of the lensed fiber and the flat plate, bubbles are formed on the end surface of the lensed fiber. It becomes difficult to form.

=== First Embodiment ===
<End faces of lensed fiber 1 and ferrule 10>
FIG. 1 is an explanatory diagram of an end face (first end face 11A) of the lensed fiber 1 and the ferrule 10. Note that the dimensions and angles are exaggerated for easy understanding.

  The lensed fiber 1 is an optical fiber that includes a single mode optical fiber 2 and a GRIN lens 3, and the GRIN lens 3 is fused and connected 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. Since the refractive index of the graded index optical fiber gradually decreases from the central axis toward the outer periphery, a graded index optical fiber can be used as the GRIN lens 3. The GRIN lens 3 has a predetermined length so as to function as a collimator lens. Specifically, the GRIN lens 3 has a length (2n + 1) / 4 times the length of the standing wave for one cycle (where n is an integer equal to or greater than 0), Then, the length of the GRIN lens 3 is, for example, 590 μm. As a result, 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. On the contrary, the 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 arranged at the tip of the GRIN lens. The flat plate 30 is disposed perpendicular to the optical axis of the lensed fiber 1 with the end face of the lensed fiber 1 being abutted against it. Since the end surface (first end surface 11A) of the ferrule 10 is perpendicular to the optical axis of the lensed fiber 1, the flat plate 30 is disposed on the first end surface 11A of the ferrule 10 so that the flat plate 30 becomes the optical axis of the lensed fiber 1. Will be arranged vertically.

  A refractive index matching agent is filled between the flat plate 30 and the end face of the lensed fiber 1. This is because a gap may be formed between the end face of the lensed fiber 1 and the flat plate 30. 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 (the 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. For this reason, Fresnel reflection can be suppressed by filling the refractive index matching agent.

  Next, the path of the optical signal propagating through the two lensed fibers 1 will be described. Here, it is assumed that the 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 from the outer surface of the flat plate 30 toward the right side through the refractive index matching agent and the flat plate 30. The optical signal propagated in the air enters the right flat plate 30. The optical signal incident on the right flat plate 30 propagates through the right lensed fiber 1 via the flat plate 30 and the refractive index matching agent.

  An optical signal propagating in the air is not completely parallel light, but a beam waist is formed at the center of the optical path so that the diameter is narrow in the optical path. In such a case, it is desirable to set the interval between the end faces of the lensed fiber 1 to a predetermined interval. In the following description, an interval between the first end surfaces 11A of the ferrule 10 for optically connecting the left and right lensed fibers 1 (interval in the optical axis direction of the lensed fiber 1) is L.

  In this embodiment, since it is not necessary to form a lens on the ferrule 10, 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 shift of the lensed fiber 1 is somewhat caused, and it is attached to the end face of the lensed fiber 1 Light loss due to dust can also be suppressed. Further, the first end surfaces 11A of the ferrule 10 need not be brought into contact with each other, and the end surfaces of the lensed fiber 1 are not in direct contact with each other, so that the first end surface 11A of the ferrule 10 is compared with the PC connection between normal MT ferrules. There is also an advantage that the end face of the lensed fiber 1 is hardly damaged. Further, since the flat plates 30 are not in direct contact with each other, there is an advantage that the coating of the anti-reflection processed flat plate 30 is hardly damaged.

<About Ferrule 10>
2A and 2B are perspective views of the ferrule 10 of the first embodiment. FIG. 2B is a perspective view of a state where the flat plate of FIG. 2A is removed. FIG. 3 is an explanatory diagram of the ferrule of the first embodiment. In FIG. 3, for the sake of explanation, the ferrule 10 in the side view is shown with a partial cross section, and the lensed fiber 1 is inserted into the fiber hole 15.

  In the following description, the direction in which the two positioning holes 13 are arranged is referred to as “left-right direction”. In addition, the axial direction of the positioning hole 13 is “front-rear direction”, the side facing the counterpart ferrule 10 is “front”, and the opposite side is “rear”. Further, a direction perpendicular to the left-right direction and the front-rear direction is referred to as “up-down direction”, the side on which the adhesive filling window 16 is provided is “upper”, and the opposite side is “lower”.

  The ferrule 10 is a member that holds the end of the lensed fiber 1. On the rear side of the ferrule 10, a flange 12 is formed. The collar portion 12 is a portion protruding outward from the outer peripheral surface. The ferrule 10 including the flange portion 12 is integrally formed of resin. The ends of the plurality of lensed fibers 1 are held inside the ferrule 10. The ferrule 10 of the present embodiment has substantially the same configuration as the ferrule defined by JIS C 5982 (F13 type multi-core optical fiber connector: MPO connector), and the dimensions and positions of the positioning hole 13, the fiber hole 15 and the like. The relationship is as defined in the standard. However, the ferrule 10 has a spacer portion 111 and a recess 17 which will be described later.

  The ferrule 10 has two positioning holes 13, a plurality of fiber holes 15, and an adhesive filling window 16. Moreover, the ferrule 10 has the flat plate 30 attached to 11 A of 1st end surfaces. Further, the ferrule 10 has a second end surface 11B (an end surface of the spacer portion 111) that protrudes in front of the first end surface 11A and the flat plate 30 (the other ferrule side). Further, a recess is formed in the first end surface 11 </ b> A of the ferrule 10. Hereinafter, each component will be described.

  The positioning hole 13 is a hole for inserting the positioning pin 14 (see FIG. 4). The positioning hole 13 and the positioning pin 14 serve as a positioning portion that positions the ferrule 10. The ferrules 10 are aligned with each other by inserting the positioning pins 14 into the positioning holes 13. 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 penetrates between the front end surface of the ferrule 10 (here, the fiber hole opening surface 17A) and the adhesive filling window 16. The fiber hole 15 is formed parallel to the front-rear direction. Here, a plurality of fiber holes 15 are arranged in the two-dimensional drop. Specifically, twelve rows of fiber holes 15 arranged in the left-right direction are arranged in four rows in the up-down direction. However, the plurality of fiber holes 15 may be arranged in one row side by side in the left-right direction. The fiber hole 15 is a part that forms 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 surface of the ferrule 10. The lensed fiber 1 inserted from the fiber insertion port has an adhesive filling window 16. It will be inserted into the fiber hole 15 across. By filling the adhesive from the adhesive filling window 16, the lensed fiber 1 is fixed to the ferrule 10.

  A flat plate 30 is attached to the first end surface 11 </ b> A on the front side of the ferrule 10. The opening of the fiber hole 15 faces the flat plate 30.

  The first end surface 11 </ b> A on the front side of the ferrule 10 is perpendicular to the axial direction of the fiber hole 15. For this reason, the first end surface 11 </ b> A on the front side of the ferrule 10 is also perpendicular to the optical axis of the lensed fiber 1 inserted into the fiber hole 15. Thereby, it becomes easy to arrange the flat plate 30 perpendicularly to the optical axis of the lensed fiber 1. Since the end face of the lensed fiber 1 is perpendicular to the optical axis, the first end face 11A on the front side of the ferrule 10 is parallel to the end face of the lensed fiber 1 inserted into the fiber hole 15.

  The flat plate 30 is, for example, a glass plate that can transmit light propagating through the optical fiber 2. The inner (rear) surface of the flat plate 30 faces the end surface of the lensed fiber 1, and the outer (front) surface of the flat plate 30 is a flat plate attached to the first end surface 11 </ b> A of the counterpart ferrule 10. 30.

  The shape of the flat plate 30 is a plate shape that is long in the left-right direction. However, the shape of the flat plate 30 is not limited to this shape, and may be other shapes such as a trapezoidal shape and a rhombus shape when viewed from the front-rear direction. The dimension in the left-right direction of the flat plate 30 is long enough to face the openings of the plurality of fiber holes 15 arranged in the left-right direction.

  The outer (front) surface of the flat plate 30 is coated with an antireflection film. For example, the antireflection film is an AR coating film in which two types of thin films having different refractive indexes are stacked. By forming an antireflection film on the flat plate 30, transmission loss and reflection attenuation can be reduced. Although the volume that can be processed at one time by the film forming apparatus is limited, since the object of the film forming process is a single flat plate 30, it is possible to set a large number of flat plates 30 in the film forming apparatus, and the cost is low. Thus, an antireflection film can be formed on the flat plate 30. Note that if the AR coating process is performed on the end face of the lensed fiber 1 or the AR coated process is performed on the lensed fiber 1 attached to the ferrule, the throughput of the film forming apparatus is reduced. The coating of the protective film is costly.

A spacer part 111 is formed on the front side of the ferrule 10. The spacer portion 111 is a portion protruding to the front side (the ferrule side on the other side) from the first end face 11A and the flat plate 30. The spacer portion 111 is a part that makes the first end faces 11A of the ferrule 10 face each other at a predetermined interval L and contacts the flat plates 30 at a predetermined interval by contacting the ferrule 10 on the other side.
A pair of spacer portions 111 are formed to protrude from the left and right sides of the ferrule 10 to the front side. The pair of spacer portions 111 are arranged so as to sandwich the first end surface 11A and the flat plate 30 from the left and right.

  The front end surface (second end surface 11B) of the spacer 111 is a contact end surface that comes into contact with the mating ferrule. The second end surface 11B protrudes more forward than the first end surface 11A and the flat plate 30 (the other ferrule side). For this reason, when the 2nd end surface 11B of the two ferrules 10 is made to contact and it is made to oppose, flat plates 30 can be made non-contact.

  A positioning hole 13 is opened in the second end face 11B. For this reason, the 2nd end surface 11B used as the contact end surface which contacts with the other party ferrule is provided in the vicinity of the positioning part (the positioning hole 13 and the positioning pin 14). The second end surface 11B is perpendicular to the axial direction of the positioning hole 13.

  A recess 17 is formed in the first end surface 11 </ b> A of the ferrule 10. The concave portion 17 is a portion that is recessed from the first end surface 11A on the front side, and is a portion that forms 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 located on the rear side with respect to the first end surface 11 </ b> A of the ferrule 10. The fiber hole opening surface 17A is a surface facing the inner surface of the flat plate 30, and a plurality of fiber holes 15 are opened in the fiber opening surface.

  A protrusion 17D is further formed in the recess 17. The protruding portion 17D is a portion that protrudes from the upper edge of the fiber hole opening surface 17A to the front side (the flat plate 30 side), and is a portion that contacts 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 first end surface 11A of the ferrule 10, and the upper edge of the flat plate 30 is in contact with the protruding portion 17D. Thereby, distortion of the flat plate 30 by shrinkage | contraction of the adhesive agent with which the recess 17 was filled can be suppressed. In particular, when the plurality of fiber holes 15 are two-dimensionally arranged as in the present embodiment, since the recess 17 is formed deeply, the influence on the flat plate 30 due to the shrinkage of the adhesive is increased. It is particularly effective to form the protrusion 17D. However, the protrusion 17D may not be provided in the recess 17.

  FIG. 4 is an explanatory diagram of a state during optical connection. The optical connector system 20 includes two optical connectors 21 each having the ferrule 10 with an optical fiber, and an adapter 22 into which the two optical connectors 21 can be inserted from both sides.

  By inserting the optical connector 21 from both sides of the adapter 22, the first end surfaces 11 </ b> A of the ferrule 10 of the optical connector 21 are arranged to face each other, and the flat plates 30 attached to the first end surface 11 </ b> A are opposed to each other. Arranged. Positioning pins 14 protrude from the ferrule 10 of the male optical connector 21, and the positioning pins 14 are inserted into the positioning holes 13 of the ferrule 10 of the female optical connector 21, thereby positioning the ferrules 10 within the adapter 22. Positioning is performed in a direction perpendicular to the pin 14 (left and right direction and up and down direction).

  Further, when the second end surfaces 11B of the ferrule 10 of the optical connector 21 are in contact with each other, the first end surfaces 11A of the ferrule 10 are arranged to face each other at a predetermined interval L and attached to the first end surface 11A. The flat plates 30 are arranged to face each other at a predetermined interval. That is, when the second end surfaces 11B of the ferrule 10 are in contact with each other 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. In order to perform alignment in the front-rear direction in this way, the second end surface 11B is positioned on the front side with respect to the first end surface 11A by about half of the interval L between the first end surfaces 11A of the ferrule 10 described above ( (See FIG. 3).

<Method for Manufacturing Ferrule 10 with Optical Fiber>
FIG. 5 is a flowchart of a method for manufacturing the ferrule 10 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, and the fused graded index optical fiber is cut to a predetermined length, and the tip of the single mode optical fiber 2 is cut. A GRIN lens 3 is formed. At this time, the end surface (cut surface) of the GRIN lens 3 is perpendicular to the optical axis of the lensed fiber 1. Note that the fusion splicing is performed so that the outer diameter of the fusion spliced portion can be inserted into the fiber hole 15 (the fiber hole 15 having the inner diameter defined by the standard). A plurality of such lensed fibers 1 are prepared.

  Next, the operator prepares the ferrule 10 described above, and places the flat plate 30 on the first end surface 11A of the ferrule 10 (S102). When the flat plate 30 is pressed and brought into contact with the first end surface 11 </ b> A of the ferrule 10, the flat plate 30 is disposed perpendicular to the axial direction of the fiber hole 15 of the ferrule 10.

  Next, the operator adheres the lensed fiber 1 and the flat plate 30 to the ferrule 10 with the end face of the lensed fiber 1 abutted against the flat plate 30 (S103). At this time, the operator 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 a space surrounded by the flat plate 30, the fiber hole opening surface 17A, the bottom surface 17B, and the side surface 17C. Thereby, a refractive index matching agent (adhesive) is filled between the flat plate 30 and the end face of the lensed fiber 1. When the adhesive is cured, the end face of the lensed fiber 1 is bonded to the flat plate 30. When the recess 17 is filled with the adhesive, the adhesive penetrates between the first end surface 11A of the ferrule 10 and the flat plate 30, so that the flat plate 30 is bonded to the first end surface 11A. Here, an ultraviolet curable adhesive is used as a refractive index matching agent. When the ultraviolet ray is irradiated through the flat plate 30 after filling the adhesive, the adhesive is cured and the end face of the lensed fiber 1 is bonded to the flat plate 30. The Further, since the ultraviolet curable adhesive penetrates also between the first end surface 11A of the ferrule 10 and the flat plate 30, when the ultraviolet light is irradiated through the flat plate 30, the flat plate 30 adheres to the first end surface 11A of the ferrule 10. Is done. A thermosetting adhesive may be used instead of the ultraviolet curable adhesive. In addition, the operator fixes the lensed fiber 1 to the ferrule 10 by filling the ferrule 10 with an adhesive from the adhesive filling window 16.

  The ferrule 10 with an optical fiber is manufactured by the above operation. In addition, when the ferrule 10 with an optical fiber manufactured as described above is optically connected by being opposed to each other as shown in FIG. 1, 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. 4) of the first embodiment described above, the two ferrules 10 are arranged to face each other, and the second end faces 11B of the ferrule 10 come into contact with each other so that the flat plates 30 are predetermined. Are arranged at intervals of. Thereby, even if another member such as a spacer is not disposed between the ferrules, the flat plates 30 are aligned in the front-rear direction and the lensed fibers 1 of the two ferrules 10 are optically connected as shown in FIG. Can do. Since the GRIN lens 3 has a large MFD (Mode Field Diameter) of the optical signal, it is possible to suppress optical loss, and it is not necessary to form a lens on the ferrule 10, so that the ferrule 10 can be easily manufactured. Further, since the recess is formed in the ferrule 10, if the recess 17 is filled with an adhesive serving as a refractive index matching agent, the refractive index matching agent (adhesion) is formed between the flat plate 30 and the end face of the lensed fiber 1. Agent).

=== Second Embodiment ===
In the first embodiment described above, the spacer portion 111 is formed on the front side of the ferrule 10. However, the ferrule 10 may not include the spacer portion 111.

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

  Also in the second embodiment, the ferrule 10 has two positioning holes 13, a plurality of fiber holes 15, and an adhesive filling window 16. In the second embodiment, the spacer portion 111 is not formed, and the flat plate 30 is attached to the front end face 11 of the ferrule 10 (corresponding to the first end face 11A described above). On the front end face 11 of the ferrule 10, a positioning hole 13 is opened. Since the positioning hole 13 is not blocked 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 disposed to face the flat plate 30. The horizontal dimension of the flat plate 30 is such that the positioning hole 13 is not blocked while facing the openings of the plurality of fiber holes 15 arranged in the left-right direction. That is, when the ferrule 10 is viewed from the front, the left and right edges of the flat plate 30 are located between the fiber hole 15 located at the end and the positioning hole 13 (see FIG. 7).

  Also in the second embodiment, a recess 17 is formed in the end surface 11 of the ferrule 10. Also in the second embodiment, a refractive index matching agent is provided between the flat plate 30 and the end face of the lensed fiber 1 by filling the space surrounded by the flat plate 30 and the recess 17 with an adhesive serving as a refractive index matching agent. (Adhesive) will be filled. If the adhesive is cured, the end face of the lensed fiber 1 is bonded to the flat plate 30. Moreover, since the adhesive permeates between the first end surface 11A of the ferrule 10 and the flat plate 30 when the recess 17 is filled with the adhesive, the flat plate 30 is bonded to the first end surface 11A.

  Also in the second embodiment, the protrusion 17 </ b> D is formed in the recess 17. When the upper edge of the flat plate 30 is in contact with the protrusion 17D, distortion of the flat plate 30 due to shrinkage of the adhesive filled in the recess 17 can be suppressed.

  FIG. 8A and FIG. 8B are explanatory diagrams of a state at the time of optical connection according to the second embodiment. FIG. 8A is an explanatory diagram of the optical connector system 20 in which the optical connector 21 having the ferrule 10 with an optical fiber is inserted from both sides of the adapter 22. FIG. 8B is an explanatory diagram of the positional relationship of the ferrule 10 within the adapter 22.

  As shown in FIG. 8A, when the optical connector 21 is inserted from both sides of the adapter 22, the end surfaces 11 of the ferrule 10 of the optical connector 21 are arranged to face each other, and the flat plates 30 attached to the end surface 11 Are arranged opposite to each other. Positioning pins 14 protrude from the ferrule 10 of the male optical connector 21, and the positioning pins 14 are inserted into the positioning holes 13 of the ferrule 10 of the female optical connector 21, thereby positioning the ferrules 10 within the adapter 22. Positioning is performed in a direction perpendicular to the pin 14 (left and right direction and up and down direction).

  A spacer 23 that protrudes inward is formed inside the adapter 22. The dimension of the spacer 23 in the front-rear direction corresponds to the distance L between the end faces 11 of the ferrule 10 shown in FIG. When the ferrule 10 contacts the spacer 23, as shown in FIG. 8B, the end faces 11 of the ferrule 10 are arranged to face each other at a predetermined interval L, and the flat plates 30 attached to the end face 11 are fixed to each other. Opposed at intervals. 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 front end surface 11 of the ferrule 10 is in contact with the spacer 23, but the end surface 11 of the ferrule 10 is opposed to the spacer 23 at a predetermined interval L when the flange portion 12 of the ferrule 10 is in contact with the spacer 23. Also good.

  Also in the second embodiment, 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. Since the GRIN lens 3 has a large MFD (Mode Field Diameter) of the optical signal, it is possible to suppress optical loss, and it is not necessary to form a lens on the ferrule 10, so that the ferrule 10 can be easily manufactured. Further, since the recess is formed in the ferrule 10, if the recess 17 is filled with an adhesive serving as a refractive index matching agent, the refractive index matching agent (adhesion) is formed between the flat plate 30 and the end face of the lensed fiber 1. Agent).

=== Third Embodiment ===
If only the recess 17 is filled with a fluid refractive index matching agent (adhesive), bubbles may be formed on the end face of the lensed fiber 1. On the other hand, in the third embodiment, a 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 to thereby form a lens. The formation of bubbles on the end face of the fiber 1 is suppressed.

  FIG. 9 is a flowchart of a method for manufacturing the ferrule 10 with an optical fiber in the third embodiment.

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

  Next, an operator arrange | positions a 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 almost the same as that of the above-mentioned adhesive (refractive index matching agent). Examples of materials for the solid refractive index matching material include acrylic, epoxy, vinyl, silicone, rubber, urethane, methacrylic, nylon, bisphenol, diol, polyimide, fluorinated epoxy, and fluorine. And polymer materials such as fluorinated acrylics.

  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 against which the lensed fiber 1 is abutted. Specifically, a sheet-like (film-like) solid refractive index matching material is attached to a region facing the fiber hole 15 on the surface of the flat plate 30 in FIG. 2A (or FIG. 6) facing the recess 17. The solid refractive index matching material is arranged on the flat plate 30 by solidifying after applying a liquid refractive index matching agent to the flat plate 30 instead of sticking 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 against it. Thereby, it is possible to suppress the formation of bubbles on the end face of the lensed fiber 1.

  FIG. 10 is an explanatory diagram 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 the solid refractive index matching material, those in the region RD in the figure can be suitably used. Note that the region RC and the region RD in the figure are separated by a straight line connecting the point P1 (HSA 70, thickness 50 μm) and the point P2 (HSA0, thickness 150 μm).

  In the region RA (region where the Shore A hardness is greater than 70), the hardness is too high, and the followability of the surface of the solid refractive index matching material when the lensed fiber 1 is abutted is low. For this reason, a gap (bubble) is likely to be generated on the end face of the lensed fiber 1. However, even when the solid refractive index matching material in the region RA is used, bubbles on the end face of the lensed fiber 1 can be suppressed as compared with the case where there is no solid refractive index matching material.

  In the region RB (the region where the Shore A hardness is 70 or less and the thickness is smaller than 30 μm), since the solid refractive index matching material is too thin, the end surface of the lensed fiber 1 is rough, or a plurality of lensed fibers. If the end faces of 1 are not aligned, gaps (bubbles) are likely to be generated on the end face of the lensed fiber 1. However, even when the solid refractive index matching material in the region RB is used, bubbles at the end face of the lensed fiber 1 can be suppressed as compared with the case where there is no solid refractive index matching material.

  In the region RC (the region where the Shore A hardness is 70 or less and the thickness is larger than the straight line connecting the points P1 and P2), the distance between the end surface of the lensed fiber 1 and the surface 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 at the end face of the lensed fiber 1 can be suppressed as compared with the case where there is no solid refractive index matching material.

  As described above, the region RD (the region having a Shore A hardness of 70 or less and a thickness of 30 μm or more, including a straight line connecting the points P1 and P2 and having a smaller thickness than the straight line) is appropriate. It becomes an area. That is, as a solid refractive index matching material, a range surrounded by four points (HSA0, thickness 30 μm), (HSA70, thickness 30 μm), (HSA70, thickness 50 μm), and (HSA0, thickness 150 μm) in the figure. It is desirable to use what is inside.

  It is desirable that both surfaces of the solid refractive index matching material have adhesiveness. This makes it difficult for the solid refractive index matching material to peel off from the flat plate 30, and after the end surface of the lensed fiber 1 is abutted against the solid refractive index matching material, the solid refractive index matching material and the end surface of the lensed fiber are separated. It becomes difficult to peel. As such a solid refractive index matching material, an adhesive material made of a polymer material in the form of a film can be used. From the standpoint of environmental resistance and adhesiveness, silicone-based and acrylic-based materials are generally used. Can be used.

  Next, the operator bonds the lensed fiber 1 and the flat plate 30 to the ferrule 10 with the end face of the lensed fiber 1 abutted against the flat plate 30 (S203). Also 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. Thereby, even if there is a gap between the end face of the lensed fiber 1 and the solid refractive index matching material, this gap is filled with an adhesive serving as a refractive index matching agent. At this time, the adhesive penetrates between the first end surface 11A of the ferrule 10 and the flat plate 30, and the flat plate 30 is bonded to the first end surface 11A of the ferrule 10. In addition, the operator fixes the lensed fiber 1 to the ferrule 10 by filling the ferrule 10 with an adhesive from the adhesive filling window 16. Thereby, the ferrule 10 with an optical fiber is manufactured.

  According to the third embodiment, by causing the lensed fiber 1 to abut against a soft solid refractive index matching material disposed on the flat plate 30, it is possible to suppress the formation of bubbles on the end surface of the lensed fiber 1.

=== Fourth Embodiment ===
FIG. 11 is an explanatory diagram of the end surface 11 of the lensed fiber 1 and the ferrule 10 of the fourth embodiment. Note that the dimensions and angles are exaggerated for easy understanding.

  The lensed fiber 1 according to the fourth embodiment includes a single mode optical fiber 2, a GRIN lens 3, and a coreless fiber 4, and the GRIN lens 3 is fusion-spliced to the tip of the single mode optical fiber 2. This is an optical fiber in which a coreless fiber 4 is fusion-connected to the tip of the GRIN lens 3. That is, in the lensed fiber 1 of the fourth embodiment, the coreless fiber 4 is provided at the tip of the GRIN lens 3. The parallel light incident on the coreless fiber 4 from the GRIN lens 3 propagates in the coreless fiber 4 as parallel light and is radiated to the outside from the end face of the coreless fiber 4. On the contrary, the parallel light incident on the coreless fiber 4 from the outside propagates through the coreless fiber 4 and enters the GRIN lens 3.

  FIG. 12A is an explanatory diagram of the ferrule 10 of the fourth embodiment. FIG. 12B is an explanatory diagram of a state when the ferrule 10 of the fourth embodiment is optically connected.

  The outer (front) surface of the flat plate 30 is coated with an antireflection film. For example, the antireflection film is an AR coating film in which two types of thin films having different refractive indexes are stacked. The inner (rear) surface of the flat plate 30 faces the end surface of the lensed fiber 1 inserted into the fiber hole 15.

  Also in 4th Embodiment, the end surfaces 11 of the ferrule 10 are arrange | positioned facing each other. By inserting the positioning pin 14 into the positioning hole 13, the ferrules 10 are aligned in a direction perpendicular to the positioning pin 14 (left and right direction and up and down direction) in an adapter (not shown). Also in the fourth embodiment, 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.

  When producing the lensed fiber 1 (see FIG. 11) of the fourth embodiment, first, the graded index optical fiber is fusion-spliced to the single mode optical fiber 2, and the fused graded-index optical fiber is fused. The GRIN lens 3 is formed at the tip of the single mode optical fiber 2 by being cut to a predetermined length. Next, the coreless fiber 4 is fused and connected to the end of the GRIN lens 3, and the fused coreless fiber 4 is cut to a predetermined length. At this time, the end face (cut face) of the coreless fiber 4 is perpendicular to the optical axis of the lensed fiber 1. Note that the fusion splicing is performed so that the outer diameter of the fusion spliced portion can be inserted into the fiber hole 15 (the fiber hole 15 having the inner diameter defined by the standard). Also in the fourth embodiment, since the MFD (Mode Field Diameter) of the optical signal is large by the GRIN lens 3, it is possible to suppress the optical loss, and it is not necessary to form a lens on the ferrule, so that the ferrule 10 can be easily manufactured. .

  While the end face of the lensed fiber 1 is abutted against the flat plate 30 in the above-described embodiment, in the fourth embodiment, the lensed fiber 1 is attached to the fiber hole 15 before the flat plate 30 is disposed on the end face of the ferrule 10. Insert into and glue. At this time, the length of the end portion of the lensed fiber 1 protruding from the end surface 11 of the ferrule 10 may slightly vary. In order to eliminate this variation, in the fourth embodiment, the end surface 11 of the ferrule 10 is polished by polishing the end surface 11 of the ferrule 10 and polishing the end portions of the plurality of lensed fibers 1 protruding from the end surface 11 of the ferrule 10. 11 is aligned with the end face of the lensed fiber 1 (end face of the coreless fiber 4). In the fourth embodiment, since the coreless fiber 4 is provided at the tip of the GRIN lens 3, the length of the GRIN lens 3 does not change even if the end surface of the lensed fiber 1 is polished. When polishing is performed along the end surface 11 of the ferrule 10, the end surface of the lensed fiber 1 (the end surface of the coreless fiber 4) becomes a surface perpendicular to the optical axis. After polishing the end face of the ferrule 10, the flat plate 30 is bonded to the end face 11 of the ferrule 10.

  In the fourth embodiment, since the ferrule 10 does not have the recess 17, the ferrule 10 is applied using a capillary phenomenon by applying an adhesive serving as a refractive index matching agent to the boundary between the end face 11 of the ferrule 10 and the flat plate 30. The refractive index matching agent is permeated between the end face 11 and the flat plate 30, and the refractive index matching agent is filled between the end face of the lensed fiber 1 and the flat plate 30. Compared to the case where the recess 17 is filled with a refractive index matching agent (adhesive) as in the above-described embodiment, the fourth embodiment uses the capillary phenomenon to infiltrate the adhesive. It takes time to fill the refractive index matching agent between the lens and the end face of the lensed fiber 1.

  On the other hand, in the fourth embodiment, since the flat plate 30 is disposed on the end surface 11 of the ferrule 10 after the end of the lensed fiber 1 is polished, the gap between the end surface of the lensed fiber 1 and the flat plate 30 is made minute. it can. For this reason, a refractive index matching agent is infiltrated between the end surface 11 of the ferrule 10 and the flat plate 30 using capillary action, and the refractive index matching agent is filled between the end surface of the lensed fiber 1 and the flat plate 30. There is an advantage that bubbles are hardly formed on the end face of the lensed fiber 1.

=== Others ===
The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be modified and improved without departing from the gist thereof, and it goes without saying that the present invention includes equivalents thereof.

1 lensed fiber,
2 single mode optical fiber,
3 GRIN lens,
10 Ferrule,
11 End face,
11A 1st end surface,
11B 2nd end surface,
111 spacer part,
12 Buttocks,
13 Positioning hole,
14 locating pins,
15 Fiber hole,
16 Adhesive filling window,
17 Recess,
17A Fiber hole opening surface,
17B Bottom,
17C side,
17D protrusion,
20 optical connector system,
21 optical connector,
22 adapter,
23 spacer,
23A recess,
30 flat plate

Claims (12)

A ferrule having a positioning hole, a plurality of fiber holes, and an end surface perpendicular to the axial direction of the fiber hole;
A lensed fiber having a GRIN lens fused and connected to the tip of the optical fiber;
A flat plate capable of transmitting light propagating through the optical fiber, the flat plate being attached to the end face of the ferrule and against which the end face of the lensed fiber inserted into the fiber hole is abutted;
Have
The ferrule has 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 a refractive index matching agent. The ferrule with a fiber according to claim 1,
A ferrule with a fiber, wherein an antireflection film is formed on an outer surface of the flat plate. A ferrule with a fiber according to claim 1 or 2,
The ferrule is a contact end surface that comes into contact with a mating ferrule, the end surface to which the flat plate is attached, and a contact end surface that protrudes toward the mating ferrule side with respect to the flat plate. Ferrule. A ferrule with a fiber according to any one of claims 1 to 3,
The recess is formed with a fiber hole opening surface facing the inner surface of the flat plate, and a plurality of the fiber holes are opened,
A ferrule with a fiber, characterized in that a protruding portion that protrudes from the fiber hole opening surface toward the flat plate and contacts with an edge of the flat plate is formed. A ferrule with a fiber according to any one of claims 1 to 4,
A ferrule with a fiber, characterized in that a solid refractive index matching material whose surface is deformed when an end face of the lensed fiber is abutted against the inner surface of the flat plate. A ferrule with a fiber according to claim 5,
A ferrule with a fiber, wherein both surfaces of the solid refractive index matching material have adhesiveness. The ferrule with a fiber according to claim 5 or 6,
The Shore A hardness and thickness of the solid refractive index matching material are
The point where the Shore A hardness is 0 and the thickness is 30 μm,
A point with a Shore A hardness of 70 and a thickness of 30 μm,
A point with a Shore A hardness of 70 and a thickness of 50 μm,
A ferrule with a fiber, wherein the Shore A hardness is 0 and the thickness is within a range surrounded by four points of 150 μm. An optical connector system for optically connecting two optical connectors,
Each said optical connector is
A ferrule having a positioning hole, a plurality of fiber holes, and an end surface perpendicular to the axial direction of the fiber hole;
A lensed fiber having a GRIN lens fused and connected to the tip of the optical fiber;
A flat plate capable of transmitting light propagating through the optical fiber, the flat plate being attached to the end face of the ferrule and against which the end face of the lensed fiber inserted into the fiber hole is abutted;
Have
The ferrule has a recess recessed from the end face of the ferrule,
A space surrounded by the flat plate and the recess is filled with a refractive index matching agent,
The optical connector system, wherein the flat plates of the optical connector are arranged to face each other at a predetermined interval. The optical connector system according to claim 8,
The ferrule is a contact end surface that comes into contact with a mating ferrule, the end surface to which the flat plate is attached, and a contact end surface that protrudes to the mating ferrule side from the flat plate,
An optical connector system, wherein the flat plates are arranged to face each other at a predetermined interval when the contact end surface of the ferrule contacts the contact end surface of the counterpart ferrule. The optical connector system according to claim 8,
The optical connector system, wherein the flat plates are arranged to face each other at a predetermined interval when the ferrule contacts a spacer. A ferrule having a positioning hole, a plurality of fiber holes, and an end surface perpendicular to the axial direction of the fiber hole;
A lensed fiber having a GRIN lens fused and connected to the tip of the optical fiber;
A flat plate capable of transmitting light propagating through the optical fiber, an antireflection film is formed on the outer surface, and the inner surface faces the end surface of the lensed fiber inserted in the fiber hole. And a flat plate attached to the end face of the ferrule. A ferrule with a fiber according to claim 11,
A coreless fiber is fusion spliced to the tip of the GRIN lens,
The ferrule with a fiber, wherein the flat plate is attached to the end face after the end of the lensed fiber protruding from the fiber hole is polished.

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