JP2005258017A - Structure for preventing wrong insertion of ferrule - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for preventing wrong insertion of a ferrule to perform favorable optical communication. <P>SOLUTION: When expressing an outside diameter of a tip side cylindrical part 22 of the ferrule 13 by D1; an outside diameter of a flange 23 formed continuous with the tip side cylindrical part 22 of the outside diameter D1 by D2; an outside diameter of an tip side cylindrical part 25 of the ferrule 14 by D3; an outside diameter of a flange 26 formed continuous with the tip side cylindrical part 25 of the outside diameter D3 by D4; an inside diameter of a smaller diameter part 35 of a ferrule insertion hole 32 for inserting the ferrule 13 therein by D5; an inside diameter of a larger diameter part formed continuous with the smaller diameter part 35 of the inside diameter D5 by D6; an inside diameter of a smaller diameter part 37 of a ferrule insertion hole 33 for inserting the ferrule 14 therein by D7; and an inside diameter of a larger diameter part 38 formed continuous with the smaller diameter part 37 of the inside diameter D7 by D8, each part is formed so as to satisfy the respective relations of the following; D1 < D3, D4 < D2, D5 < D7, and D8 < D6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ferrule erroneous insertion prevention structure for arranging a ferrule provided at an end of an optical fiber so as to face a corresponding FOT (Fiber Optic Transceiver).

  In recent years, a system has been adopted in which a part of the wire harness is replaced with an optical fiber, for example, each node is connected with an optical fiber. As such a system, for example, an optical module disclosed in Patent Document 1 below is used. In FIG. 9, reference numeral 1 denotes a conventional optical module. The optical module 1 is a pigtail type optical module, and includes a printed circuit board 2, an optical transceiver 3 mounted on the printed circuit board 2, and a pair of optical connectors 4 and 4 provided at the end of the printed circuit board 2. And a pair of optical fibers 5 and 5 for optically coupling the optical transceiver 3 and the optical connectors 4 and 4.

The optical fibers 5 and 5 have extra length portions 6 and 6, respectively. For example, the optical fibers 5 and 5 are gathered in an annular shape as shown in the figure and stored in the extra length absorption area 7 between the optical transceiver 3 and the optical connectors 4 and 4. Have been placed. A ferrule is attached to each end of the optical fibers 5 and 5 although not particularly shown.
JP 2003-149515 A (Page 3, FIG. 3-4)

  By the way, in the above prior art, if the optical coupling of the optical fibers 5 and 5 to the optical transceiver 3 is mistaken during assembly, that is, one optical fiber 5 and the other optical fiber 5 are connected to the optical transceiver 3. On the other hand, there is a problem in that the optical communication is hindered if they are coupled in reverse.

  This invention is made | formed in view of the situation mentioned above, and makes it a subject to provide the erroneous insertion prevention structure of a ferrule for performing optical communication favorably.

  The structure for preventing erroneous insertion of a ferrule according to claim 1 of the present invention, which has been made to solve the above-mentioned problem, is a FOT (Fiber Optic Transceiver), an optical fiber, a ferrule provided at a terminal of the optical fiber, and the ferrule as described above. A structure for preventing erroneous insertion of the ferrule with respect to the ferrule insertion hole when a pair of optical coupling portions having a ferrule insertion hole guided toward the FOT is present in a pair, and the tip side tube of one of the ferrules D1 is the outer diameter of the portion, D2 is the outer diameter of the flange portion that is coupled to the tip-side cylinder portion of the outer diameter D1, D3 is the outer diameter of the tip-side cylinder portion of the other ferrule, and the tip side of the outer diameter D3 The outer diameter of the flange portion coupled to the cylindrical portion is D4, the inner diameter of the small diameter portion of one ferrule insertion hole into which the one ferrule is inserted is D5, and the large diameter is coupled to the small diameter portion of the inner diameter D5. If the inner diameter is D6, the smaller diameter inner diameter of the other ferrule insertion hole is D7, and the larger diameter inner diameter coupled to the smaller diameter portion of the inner diameter D7 is D8, D1 <D3, D4 <D2, D5 <D7, And each relationship of D8 <D6 is materialized.

  According to the present invention having such a feature, in the case of erroneous insertion, since the distal end side cylinder portion of the other ferrule cannot be inserted into the small diameter portion of one ferrule insertion hole, erroneous insertion of the ferrule occurs. Easy to understand. Further, since the flange portion of one ferrule cannot be inserted into the large-diameter portion of the other ferrule insertion hole, it can be easily understood that the ferrule is erroneously inserted.

  According to a second aspect of the present invention, there is provided a structure for preventing erroneous insertion of a ferrule according to the present invention, wherein the optical fiber and the ferrule provided at the end of the optical fiber are provided with the ferrule. A structure for preventing erroneous insertion of the ferrule into the ferrule insertion hole when a pair of optical coupling portions having a ferrule insertion hole for guiding toward the FOT is present, and a flange is formed from the tip of one of the ferrules L1 is the length to the front of the part, L2 is the length from the tip of the other ferrule to the front of the flange part, L3 is the length of the small diameter part of the one ferrule insertion hole into which the one ferrule is inserted, and the other If the length of the small-diameter portion of the ferrule insertion hole is L4, the relationships of L1> L2 and L3> L4 are established, and the force in the removal direction And a spacer having one slip-off preventing portion with which the rear surface of the flange portion of one ferrule abuts and the other slip-off preventing portion with which the rear surface of the flange portion of the other ferrule abuts. It is characterized by having a structure capable of.

  According to the present invention having such characteristics, in the case of erroneous insertion, the other ferrule is inserted into one ferrule insertion hole, and one ferrule is inserted into the other ferrule insertion hole. However, since it is impossible to attach the spacer, it is easy to know that the ferrule is erroneously inserted.

  A structure for preventing erroneous insertion of a ferrule according to a third aspect of the present invention is the structure for preventing erroneous insertion of a ferrule according to the first or second aspect, wherein the ferrule is a metal cutting product. According to the present invention having such characteristics, the dimensional accuracy of the ferrule is improved.

  According to the present invention described in claims 1 and 2, erroneous insertion of a ferrule can be eliminated. Therefore, there is an effect that optical communication can be performed satisfactorily.

  According to the third aspect of the present invention, it is possible to improve the dimensional accuracy of the erroneous insertion prevention structure and to stabilize the optical coupling with the FOT.

Hereinafter, description will be given with reference to the drawings.
FIG. 1 is an exploded perspective view showing an embodiment of an optical module having a ferrule erroneous insertion preventing structure according to the present invention. 2 is a cross-sectional view of the optical module of FIG. 1, and FIG. 3 is an explanatory diagram regarding a structure for preventing erroneous insertion of a ferrule.

  In FIG. 1 to FIG. 3, reference numeral 11 indicates an optical module provided with a structure for preventing erroneous insertion of a ferrule according to the present invention. The optical module 11 is a pigtail optical module, and is mounted on a pair of optical fibers 12 and 12, ferrules 13 and 14 provided at the ends of the optical fibers 12 and 12, and a known circuit board (not shown). FOT (Fiber Optic Transceiver) 15, 16, FOT case 19 having FOT mounting portion 17 and ferrule insertion portion 18, spacer 20 fitted to ferrule insertion portion 18, FOT mounting portion 17 and FOT 15, 16. And a shield case 21 attached thereto. Hereinafter, each component will be described in detail.

  One of the optical fibers 12, 12 is prepared for transmission and the other is prepared for reception. The optical fibers 12 and 12 in this embodiment are the same, and POF (Plastic Optical Fiber) is adopted. The optical fibers 12 and 12 include a core, a clad provided on the core, a primary sheath provided on the clad, and a secondary sheath provided on the primary sheath (this embodiment). Then, a known optical fiber is referred to as an optical fiber 12). Each end of the optical fibers 12 and 12 is in a peeled state in which the primary sheath and the secondary sheath are removed by appropriate lengths.

  The ferrule 13 is a cylindrical member attached to the end of the transmission optical fiber 12 in the peeled state. The ferrule 13 is connected to the distal end side cylindrical portion 22 which is the distal end side of the ferrule 13 and the distal end side cylindrical portion 22. It has a flange part 23 formed and a rear end side cylinder part 24 connected to the flange part 23. On the other hand, the ferrule 14 is a cylindrical member attached to the end of the receiving optical fiber 12 in the peeled state, and includes a distal end side cylindrical portion 25 which is a distal end side of the ferrule 14 and a distal end side cylinder. A flange portion 26 coupled to the portion 25 and a rear end side cylindrical portion 27 coupled to the flange portion 26 are provided. Although the ferrules 13 and 14 will be described later, their outer shapes are slightly different. The ferrules 13 and 14 are both formed by cutting a metal (assuming that the dimensional accuracy is sufficiently secured, it may be formed by a synthetic tree material).

  The FOT 15 includes a plurality of lead frames 28 that are electrically connected to the circuit of the circuit board (not shown), a light emitting element (not shown) (for example, LD or LED), and a mold part 29. A light emitting element (not shown) is mounted on one of the plurality of lead frames 28. Further, the light emitting element (not shown) and the remaining lead frame 28 are electrically connected. The mold part 29 is formed so as to cover and protect the light emitting element (not shown) and the electrical connection part. The mold part 29 is molded using a light transmissive synthetic resin. The mold part 29 is formed with a window 29a facing a light emitting element (not shown).

  The FOT 16 includes a plurality of lead frames 30 electrically connected to the circuit of the circuit board (not shown), a light receiving element (for example, PD) (not shown), and a mold part 31. A light receiving element (not shown) is mounted on one of the lead frames 30. The light receiving element (not shown) and the remaining lead frame 30 are electrically connected. The mold part 31 is formed so as to cover and protect a light receiving element (not shown) and the electrical connection part. The mold part 31 is molded using a light transmissive synthetic resin. The mold part 31 is formed with a window 31a facing a light receiving element (not shown).

  The FOT case 19 is a molded product molded using a synthetic resin material, and is formed in a state in which the ferrule insertion portion 18 and the FOT mounting portion 17 are continuous in the front-rear direction as described above. The ferrule insertion part 18 has two ferrule insertion holes 32 and 33 arranged in parallel, and a spacer fitting hole 34 for fitting the spacer 20. The ferrule insertion hole 32 is formed with a small diameter portion 35 and a large diameter portion 36 coupled to the small diameter portion 35. On the other hand, the ferrule insertion hole 33 is similarly formed with a small diameter portion 37 and a large diameter portion 38 coupled to the small diameter portion 37. The ferrule insertion holes 32 and 33 are both holes penetrating in the front-rear direction of the FOT case 19 and are formed in a stepped shape. The small-diameter portion 35 of the ferrule insertion hole 32 and the small-diameter portion 37 of the ferrule insertion hole 33 are formed so that their ends open to the FOT mounting portion 17.

  The FOT mounting portion 17 is a portion to which these can be mounted so as to cover the front sides of the FOTs 15 and 16, and includes a plurality of positioning projections 39 that determine the mounting positions of the FOTs 15 and 16, and lead frames 28 and 30. Guides 40 and 40 for guiding are provided. When the FOTs 15 and 16 are mounted on the FOT mounting part 17, the position of the window 29 a is aligned with the opening of the small diameter part 35 of the ferrule insertion hole 32, and the position of the window 31 a is aligned with the opening of the small diameter part 37 of the ferrule insertion hole 33. It can be adjusted.

  The spacer 20 is a resin molded product for preventing the ferrules 13 and 14 inserted into the ferrule insertion holes 32 and 33 from being removed, and has a fitting portion 41 and ferrule locking portions 42 and 42. . The fitting portion 41 is formed as a portion to be fitted when inserted into the spacer fitting hole 34. Further, the ferrule locking portions 42 and 42 are formed as portions for locking the flange portions 23 and 26 of the ferrules 13 and 14.

  The shield case 21 is a substantially box-like member, and is formed by pressing a conductive metal thin plate. Such a shield case 21 is formed so that the FOTs 15 and 16 can be free from backlash. That is, the shield case 21 is formed with leaf spring-like pressing portions 43 and 43 that press the FOTs 15 and 16 toward the FOT mounting portion 17. The shield case 21 is provided with a plurality of fixing leg portions 44. The fixing leg portion 44 is inserted into a fixing hole of the circuit board (not shown) to be grounded, and contributes to fixing the FOTs 15 and 16.

  In the above configuration, the FOTs 15 and 16 are attached to the FOT attachment part 17 of the FOT case 19, the shield case 21 is attached across the FOT attachment part 17 and the FOTs 15 and 16, and the lead frames 28 and 30 of the FOTs 15 and 16 are further attached. And the fixing leg 44 of the shield case 21 to the circuit board (not shown), the ferrules 13 and 14 of the ends of the optical fibers 12 and 12 can be inserted, that is, the optical coupling is possible. Become.

  Here, the FOT 15, the ferrule insertion hole 32 corresponding to the FOT 15, the ferrule 13 inserted into the ferrule insertion hole 32, and the optical fiber 12 constitute an optical coupling part 45 on the transmission side, and the FOT 16 and the FOT 16 The corresponding ferrule insertion hole 33, the ferrule 14 inserted into the ferrule insertion hole 33, and the optical fiber 12 constitute an optical coupling unit 46 on the receiving side. The optical coupling parts 45 and 46 are the main part of the erroneous insertion prevention structure of the ferrule of the present invention, and the structure will be described below.

  The outer diameter of the distal end side cylindrical portion 22 of the ferrule 13 is D1, the outer diameter of the flange portion 23 coupled to the distal end side cylindrical portion 22 of the outer diameter D1 is D2, and the outer diameter of the distal end side cylindrical portion 25 of the ferrule 14 is the outer diameter. D3, D4 is the outer diameter of the flange portion 26 coupled to the distal end side cylinder portion 25 of the outer diameter D3, D5 is the inner diameter of the small diameter portion 35 of the ferrule insertion hole 32 into which the ferrule 13 is inserted, and the small diameter is the inner diameter D5. The inner diameter of the large diameter portion 36 coupled to the portion 35 is D6, the inner diameter of the small diameter portion 37 of the ferrule insertion hole 33 into which the ferrule 14 is inserted is D7, and the large diameter portion coupled to the small diameter portion 37 of the inner diameter D7. Assuming that the inner diameter of 38 is D8, the respective parts are formed so that the relationships of D1 <D3, D4 <D2, D5 <D7, and D8 <D6 are established.

  According to the erroneous insertion prevention structure of the ferrule of the present invention having such a relationship, when the ferrule is erroneously inserted, the distal end side tubular portion 25 of the ferrule 14 cannot be inserted into the small diameter portion 35 of the ferrule insertion hole 32. Therefore, it can be easily understood that the ferrule 14 is erroneously inserted. Further, since the flange portion 23 of the ferrule 13 cannot be inserted into the large-diameter portion 38 of the ferrule insertion hole 33, in this case also, occurrence of erroneous insertion of the ferrule 13 can be easily understood.

  When the optical coupling portions 45 and 46 are configured without erroneous insertion, the spacer 20 is inserted and fitted into the spacer fitting hole 34, and removal of the ferrules 13 and 14 is prevented, a series of operations is completed.

  As described above with reference to FIGS. 1 to 3, the optical module 11 includes the ferrule erroneous insertion prevention structure having the above-described relationship, so that erroneous insertion of the ferrules 13 and 14 is reliably eliminated. There is an effect that can be. Therefore, from this, there is an effect that optical communication can be performed satisfactorily.

  Next, another example of the above-described optical module 11 will be described with reference to FIGS. 4 and 5. 4 is an exploded perspective view showing another example, and FIG. 5 is a cross-sectional view of the optical module of FIG.

  4 and 5, the optical module 11 'is further provided with lens sleeves 48, 48 with respect to the above-described embodiment, and the sleeve mounting portion 49 for the lens sleeves 48, 48 is inserted into the ferrule of the FOT case 19'. It differs from the point arrange | positioned between the part 18 and the FOT mounting part 17 (The same code | symbol is attached | subjected the same member and part as the above-mentioned form.). Sleeve mounting holes 49a and 49a are formed in the FOT case 19 ′ so as to be continuous with the ferrule insertion holes 32 and 33.

  The lens sleeve 48 constituting the optical coupling portion 45 ′ on the transmission side has a function of condensing light from a light emitting element (not shown) toward the end face of the optical fiber 12. The lens sleeve 48 constituting the optical coupling portion 46 ′ on the receiving side has a function of condensing light from the end face of the optical fiber 12 toward a light receiving element (not shown).

  Next, another embodiment of the optical module having the ferrule erroneous insertion preventing structure according to the present invention will be described with reference to FIGS. FIG. 6 is an exploded perspective view showing another embodiment, FIG. 7 is a cross-sectional view of the optical module of FIG. 6, and FIG. 8 is an explanatory diagram regarding a structure for preventing erroneous insertion of a ferrule. In addition, the same code | symbol is attached | subjected to the member and part fundamentally the same as the above-mentioned form, and detailed description is abbreviate | omitted.

  6 to 8, reference numeral 51 denotes an optical module provided with the ferrule erroneous insertion prevention structure of the present invention. The optical module 51 is a pigtail type optical module, similar to the above-described embodiment, and includes a pair of optical fibers 12 and 12, ferrules 52 and 53 provided at the ends of the optical fibers 12 and 12, FOT 15, 16, a lens sleeve 48, a FOT case 55 having a ferrule insertion portion 54, a sleeve mounting portion 49, and a FOT mounting portion 17, a spacer 56 fitted to the ferrule insertion portion 54, the FOT mounting portion 17 and the FOT 15. , 16 and a shield case 21 that is attached across the board.

  The ferrule 52 is a cylindrical member that is attached to the end of the optical fiber 12 for transmission, and includes a distal end side cylindrical portion 57 that becomes the distal end side of the ferrule 52 and a flange portion that is coupled to the distal end side cylindrical portion 57. 58 and a rear end side cylinder portion 59 coupled to the flange portion 58. On the other hand, the ferrule 53 is a cylindrical member that is attached to the end of the receiving optical fiber 12, and is coupled to the distal end side cylindrical portion 60 that is the distal end side of the ferrule 53 and the distal end side cylindrical portion 60. And a rear end side cylinder portion 62 coupled to the flange portion 61. The ferrules 52 and 53 have the same diameter, but the arrangement of the flange portions 58 and 61 is slightly different (described later). The ferrules 52 and 53 are both formed by cutting a metal (assuming that the dimensional accuracy is sufficiently secured, it may be formed by a synthetic tree material).

  The FOT case 55 is a molded product molded using a synthetic resin material, and is formed in a state where the ferrule insertion portion 54, the sleeve mounting portion 49, and the FOT mounting portion 17 are continuous in the front-rear direction as described above. ing. The ferrule insertion portion 54 has two ferrule insertion holes 63 and 64 arranged in parallel, and a spacer fitting hole 65 for fitting the spacer 56. The ferrule insertion hole 63 is formed with a small diameter portion 66 coupled to the sleeve mounting hole 49 a and a large diameter portion 67 coupled to the small diameter portion 66. On the other hand, the ferrule insertion hole 64 is similarly formed with a small diameter portion 68 coupled to the sleeve mounting hole 49 a and a large diameter portion 69 coupled to the small diameter portion 68. The ferrule insertion holes 63 and 64 are holes that penetrate through the FOT case 55 in the front-rear direction, and are formed in a stepped shape.

  The spacer 56 is a resin molded product that prevents the ferrules 52 and 53 inserted into the ferrule insertion holes 63 and 64 from coming off and constitutes the erroneous insertion prevention structure of the ferrule of the present invention. It has the latching | locking parts 42 and 42 (detachment | blocking prevention part). The ferrule locking portions 42 and 42 are arranged and formed in a stepped manner in accordance with the arrangement of the flange portions 58 and 61 of the ferrules 52 and 53.

  In the above configuration, the FOTs 15 and 16 are mounted on the FOT mounting part 17 of the FOT case 55, the shield case 21 is mounted across the FOT mounting part 17 and the FOTs 15 and 16, and the lead frames 28 and 30 of the FOTs 15 and 16 are further mounted. And the fixing leg 44 of the shield case 21 to the circuit board (not shown), the ferrules 52 and 53 of the ends of the optical fibers 12 and 12 can be inserted, that is, the optical coupling is possible. Become.

  Here, the FOT 15, the ferrule insertion hole 63 corresponding to the FOT 15, the ferrule 52 inserted into the ferrule insertion hole 63, and the optical fiber 12 constitute an optical coupling unit 70 on the transmission side, and the FOT 16 and the FOT 16 The corresponding ferrule insertion hole 64, the ferrule 53 inserted into the ferrule insertion hole 64, and the optical fiber 12 constitute an optical coupling portion 71 on the reception side. The optical coupling parts 70 and 71 are the main parts of the erroneous insertion prevention structure of the ferrule of the present invention, and the structure will be described below.

  The length from the tip of the ferrule 52 to the front surface of the flange portion 58 is L1, the length from the tip of the ferrule 53 to the front surface of the flange portion 61 is L2, and the length of the small diameter portion 66 of the ferrule insertion hole 63 into which the ferrule 52 is inserted When the length is L3 and the length of the small-diameter portion 68 of the ferrule insertion hole 64 into which the ferrule 53 is inserted is L4, each portion is formed so that the relations L1> L2 and L3> L4 are established.

  According to the erroneous insertion prevention structure of the ferrule of the present invention having such a relationship, in the case of erroneous insertion of the ferrule, the ferrule 53 is inserted into the ferrule insertion hole 63 and the ferrule 52 is inserted into the ferrule insertion hole 64. Is done. However, since the spacer 56 cannot be attached, that is, cannot be fitted, the erroneous insertion of the ferrules 52 and 53 can be easily recognized.

  If the optical coupling portions 70 and 71 are configured without erroneous insertion, the spacer 56 is inserted and fitted into the spacer fitting hole 65, and removal of the ferrules 52 and 53 is prevented, a series of operations is completed.

  As described above with reference to FIGS. 6 to 8, the optical module 51 has the structure for preventing erroneous insertion of ferrules having the above relationship, so that erroneous insertion of the ferrules 52 and 53 can be reliably prevented. There is an effect that can be. Therefore, from this, there is an effect that optical communication can be performed satisfactorily.

  In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention. Of course, the ferrule misinsertion prevention structure of the present invention may be applied to an optical connector that optically couples end faces of optical fibers.

It is a disassembled perspective view which shows one Embodiment of the optical module provided with the erroneous insertion prevention structure of the ferrule by this invention. It is a cross-sectional view of the optical module of FIG. It is explanatory drawing regarding the erroneous insertion prevention structure of a ferrule. It is a disassembled perspective view which shows the other example of the optical module of FIG. It is a cross-sectional view of the optical module of FIG. It is a disassembled perspective view which shows other one Embodiment of the optical module provided with the erroneous insertion prevention structure of the ferrule by this invention. It is a cross-sectional view of the optical module of FIG. It is explanatory drawing regarding the erroneous insertion prevention structure of a ferrule. It is a block diagram of the optical module of a prior art example.

Explanation of symbols

11 Optical Module 12 Optical Fiber 13, 14 Ferrule 15, 16 FOT
17 FOT mounting portion 18 Ferrule insertion portion 19 FOT case 20 Spacer 21 Shield case 22, 25 Front end side cylindrical portion 23, 26 Flange portion 24, 27 Rear end side cylindrical portion 28, 30 Lead frame 29, 31 Mold portion 29a, 31a Window 32, 33 Ferrule insertion hole 34 Spacer fitting hole 35, 37 Small diameter part 36, 38 Large diameter part 39 Positioning protrusion 40 Guide 41 Fitting part 42 Ferrule locking part (drop prevention part)
43 Pressing part 44 Fixing leg part 45, 46 Optical coupling part 48 Lens sleeve 49 Sleeve mounting part 51 Optical module 52, 53 Ferrule 54 Ferrule insertion part 55 FOT case 56 Spacer 57, 60 Tip side cylinder part 58, 61 Flange part 59, 62 Rear end side cylindrical portion 63, 64 Ferrule insertion hole 65 Spacer fitting hole 66, 68 Small diameter portion 67, 69 Large diameter portion 70, 71 Optical coupling portion

Claims (3)

When there is a pair of optical coupling parts having FOT (Fiber Optic Transceiver), an optical fiber and a ferrule provided at the end of the optical fiber, and a ferrule insertion hole for guiding the ferrule toward the FOT The erroneous insertion prevention structure for the ferrule insertion hole of the ferrule,
D1 is an outer diameter of the distal end side cylinder portion of one of the ferrules, D2 is an outer diameter of a flange portion coupled to the distal end side cylinder portion of the outer diameter D1, and D3 is an outer diameter of the distal end side cylinder portion of the other ferrule. The outer diameter of the flange portion coupled to the distal end side cylinder portion of the outer diameter D3 is D4, the inner diameter of one of the ferrule insertion holes into which one of the ferrules is inserted is D5, and the smaller diameter portion of the inner diameter D5 D1 <D3, where D6 is the large diameter inner diameter coupled to D6, D7 is the small diameter inner diameter of the other ferrule insertion hole, and D8 is the large diameter inner diameter coupled to the small diameter portion of the inner diameter D7. A structure for preventing erroneous insertion of a ferrule, wherein the relationships of D4 <D2, D5 <D7, and D8 <D6 are established. When there is a pair of optical coupling parts having FOT (Fiber Optic Transceiver), an optical fiber and a ferrule provided at the end of the optical fiber, and a ferrule insertion hole for guiding the ferrule toward the FOT The erroneous insertion prevention structure for the ferrule insertion hole of the ferrule,
The length from the tip of one ferrule to the front surface of the flange portion is L1, the length from the tip of the other ferrule to the front surface of the flange portion is L2, and the small diameter of the one ferrule insertion hole into which the one ferrule is inserted When the length of the portion is L3 and the length of the small diameter portion of the other ferrule insertion hole is L4, the relationships of L1> L2 and L3> L4 are established,
In addition, the spacer further includes one omission prevention portion where the rear surface of the flange portion of one ferrule abuts when the force in the omission direction occurs and the other omission prevention portion where the rear surface of the flange portion of the other ferrule abuts. A structure for preventing erroneous insertion of a ferrule, wherein the spacer can be attached. In the erroneous insertion prevention structure of the ferrule according to claim 1 or claim 2,
A structure for preventing erroneous insertion of a ferrule, wherein the ferrule is a metal cutting product.

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