JP2015034939A - Optical fiber terminal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber terminal structure which enables assembling process simplification, failure prevention, component cost reduction, and lossless optical transmission by not using adhesives in assembling thereof.SOLUTION: An optical fiber terminal structure has: an optically functional ferrule 11 having a lens surface 21 formed at a front end thereof and a through hole 24 which is formed along an axial direction with an opening on a rear end side and into which an optical fiber 2 is inserted; and a coil spring 10 which presses the optical fiber 2 toward the front end side. The coil spring 10 is fixed to the optical fiber 2 and is held by the ferrule 11, and the optical fiber 2 is pressed in contact with a butting surface 25 of the through hole 24 by pressing force of the coil spring 10.

Description

  The present invention relates to an optical fiber terminal structure in which a ferrule having an optical function is provided at the tip of an optical fiber.

  An optical fiber consisting of a convex lens surface formed at the tip of a ferrule, by inserting an optical fiber into an insertion hole of a ferrule with an optical function formed from a transparent optical material, and bonding and fixing it. There is known a technique in which light is emitted in the form of parallel light on the functional surface (see, for example, Patent Document 1).

JP 2003-344702 A

  Patent Document 1 describes a structure in which an optical fiber is inserted and connected to an insertion hole of a ferrule having an optical function. For this reason, it is possible to simplify the alignment, reduce the influence of dust and dirt on the tip of the optical fiber, reduce the number of parts, and facilitate the assembly work. .

  By the way, in a terminal structure in which a ferrule having an optical function is provided at an end of an optical fiber, a structure in which the optical fiber is fixed to the ferrule with an adhesive as in the technique of Patent Document 1 is general. However, in the terminal structure in which the optical fiber is fixed to the ferrule with an adhesive, deterioration of the adhesive or poor adhesion is one of the failure factors. Further, since the adhesive requires time for curing, it takes time to assemble the ferrule and the optical fiber. In addition, since the pot life of the adhesive is limited and it hardens and deteriorates with the passage of time, handling is required, and the bonding process is often separated from all processes, resulting in a decrease in productivity. In addition, when filling the adhesive, care must be taken so that optical characteristics do not deteriorate due to bubbles entering between the bottom surface of the insertion hole and the end surface of the optical fiber.

  In addition, in the terminal structure in which the ferrule having an optical function is provided at the end of the optical fiber, in addition to the above problems when using the adhesive, the linear expansion coefficient of the ferrule and the optical fiber is different. There is a problem that a phenomenon called pistoning in which the tip of the optical fiber is separated from the innermost part of the insertion hole of the ferrule due to the change occurs. Then, a space is formed between the tip of the optical fiber and the bottom surface of the insertion hole, and Fresnel reflection loss occurs.

  The present invention has been made in view of the above-mentioned circumstances, and its purpose is to use an adhesive for assembly in a terminal structure in which a ferrule having an optical function is provided at the end of an optical fiber. An object of the present invention is to provide an optical fiber terminal structure capable of simplifying, preventing failure, reducing component costs, and the like and capable of optical transmission without loss.

In order to achieve the above-described object, the terminal structure of the optical fiber according to the present invention is characterized by the following (1) to (8).
(1) optical fiber;
A bottomed cylindrical ferrule having an insertion hole into which the optical fiber is inserted;
An elastic member held by the ferrule;
With
The ferrule is formed with an optical function portion at the bottom, and the insertion hole is formed at the tube portion,
The elastic member is fixed to the optical fiber and urges the optical fiber along an axial direction.
The optical fiber is pressed against the bottom of the ferrule by the biasing force of the elastic member.
(2) An optical fiber terminal structure configured as described in (1) above,
The bottom surface of the ferrule is formed in a spherical shape in which the abutting surface pressed and contacted by the tip of the optical fiber protrudes toward the end surface side of the optical fiber.
(3) An optical fiber terminal structure configured as described in (1) or (2) above,
The elastic member has a front end locked to the optical fiber,
The ferrule has a spring stopper for locking a rear end portion of the elastic member.
(4) An optical fiber terminal structure configured as described in (3) above,
The ferrule includes a ferrule body and the spring stopper, and the spring stopper is detachable from the ferrule body.
The spring stopper has a cutout portion through which the optical fiber is inserted, and the cutout portion is attached to the ferrule body while being inserted through the optical fiber.
(5) An optical fiber terminal structure having the configuration of (1) or (2) above,
The elastic member is a helical coil spring through which the optical fiber is inserted,
The coil spring has a front end locked to the optical fiber and a rear end locked to the ferrule.
(6) An optical fiber terminal structure configured as described in (5) above,
The front end of the coil spring is fixed by being crimped to the optical fiber.
(7) An optical fiber terminal structure configured as described in (6) above,
In the coil spring, the inner surface of the front end portion crimped to the optical fiber is roughened.
(8) An optical connector configured as described in (5) above,
The front end of the coil spring is locked to the optical fiber by an annular flange fixed to the optical fiber.

In the terminal structure of the optical fiber having the configuration (1), an elastic member is fixed to the optical fiber, and the elastic member is held by a ferrule with an optical function. That is, the optical fiber is held on the ferrule without using an adhesive. Therefore, as compared with the structure in which the optical fiber is fixed to the ferrule with the adhesive, the assembly can be simplified and the reliability can be improved. That is, failure due to deterioration of the adhesive or poor adhesion can be prevented, and productivity can be increased by omitting the adhesion process. In addition, it is possible to eliminate the problem that the optical characteristics deteriorate due to bubbles entering between the end face and the abutting face of the optical fiber due to poor filling of the adhesive.
In addition, the end of the optical fiber is pushed back into contact with the abutting surface by the urging force of the elastic member. Can be compensated by pressing to This prevents gaps between the tip of the optical fiber and the abutting surface and prevents Fresnel reflection loss caused by the formation of a space between the tip of the optical fiber and the abutting surface. can do.
In the end structure of the optical fiber configured as described in (2) above, the abutting surface is formed in a spherical shape protruding toward the end surface side of the optical fiber inserted into the insertion hole, so that the tip of the optical fiber is moved by the urging force of the elastic member. It is possible to make a good and reliable pressing contact with the abutting surface.
In the end structure of the optical fiber having the configuration (3) above, by attaching a spring stopper to the ferrule, it is possible to easily apply the elastic force to the optical fiber by locking the rear end portion of the elastic member. can do.
In the end structure of the optical fiber configured as described in (4) above, the spring stopper can be easily attached to the ferrule by passing the optical fiber through the notch portion of the spring stopper, and the assembly work can be facilitated. it can.
In the terminal structure of the optical fiber having the configuration (5), an elastic force can be reliably applied to the optical fiber at low cost by using a coil spring as the elastic member.
In the end structure of the optical fiber having the configuration (6), since the front end portion of the coil spring is fixed to the optical fiber by crimping, the cost can be reduced by simplifying the structure. Further, since the coil spring can be fastened and fixed to the optical fiber in a short time, the time for assembling the optical fiber to the ferrule can be shortened.
In the end structure of the optical fiber having the configuration (7), the inner surface of the front end portion that is crimped to the optical fiber of the coil spring can be securely fixed to the optical fiber by roughening the inner surface.
In the optical connector configured as described in (8) above, by using the flange, the coil spring can be locked to the optical fiber and elastic force can be applied to the optical fiber without processing the coil spring.

  According to the present invention, in a terminal structure in which a ferrule having an optical function is provided at an end portion of an optical fiber, the use of an adhesive for the assembly simplifies assembly, prevents failure, and reduces component costs. Moreover, it is possible to provide an optical fiber terminal structure capable of optical transmission without loss.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is a cross-sectional view of an optical fiber terminal portion showing an optical fiber terminal structure according to an embodiment of the present invention. FIG. 2 is a perspective view of the ferrule and spring stopper. FIG. 3 is a perspective view of the spring stopper. FIG. 4 is a perspective view of a spring stopper having another shape. FIG. 5A to FIG. 5D are views for explaining how to assemble the optical fiber terminal, and are sectional views. FIG. 6A and FIG. 6B are views showing the connection state of the optical fiber end portions in the optical connector, and are sectional views, respectively. FIG. 7 is a cross-sectional view of an optical module including an optical fiber terminal portion. FIG. 8 is a cross-sectional view of an optical fiber terminal portion showing an optical fiber terminal structure according to a modification. FIG. 9 is a cross-sectional view of an optical fiber terminal portion showing an optical fiber terminal structure according to a modification. FIG. 10 is a cross-sectional view of an optical fiber terminal portion showing an optical fiber terminal structure according to a modification.

Hereinafter, an example of an embodiment according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of an optical fiber terminal portion showing an optical fiber terminal structure according to an embodiment of the present invention. FIG. 2 is a perspective view of the ferrule and spring stopper. FIG. 3 is a perspective view of the spring stopper. FIG. 4 is a perspective view of a spring stopper having another shape.

  As shown in FIG. 1, the optical fiber terminal portion 1 generally has a ferrule 11 provided at the tip of an optical fiber 2. The optical connector includes a plug-side optical connector and a receptacle-side optical connector (not shown), but the optical fiber terminal portion 1 is accommodated in the respective housings of the plug-side optical connector and the receptacle-side optical connector. By engaging the housings of the plug-side optical connector and the receptacle-side optical connector, the tips of the optical fiber end portions 1 accommodated in these housings come into contact with each other, and the end faces of the two optical fibers 2 are abutted. . Thus, the two optical fibers 2 are optically connected. Further, the optical module engages the housings of the plug-side optical connector and the receptacle-side optical connector so that the optical fiber 2 of the optical fiber terminal portion 1 accommodated in one housing and the receiving provided in the other housing. The light emitting element approaches and the end face of the optical fiber 2 faces the light emitting / receiving element. Thus, the optical fiber 2 and the light emitting / receiving element are optically connected.

First, the configuration and structure of the optical fiber 2 will be described.
The optical fiber 2 includes a resin / glass core / cladding portion 3 that propagates an optical signal, a coating layer 4 that covers the core / cladding portion 3, and a jacket (not shown). The outer cover is removed by a predetermined length and processed so that the covering layer 4 is exposed. The optical fiber 2 is formed in a shape that is circular in cross section. Although the optical fiber 2 in the figure is short, it is actually a little longer.

Next, the configuration and structure of the optical fiber terminal 1 will be described.
The optical fiber terminal 1 includes an optical fiber 2, a coil spring (elastic member) 10, and a ferrule 11.

  A spiral coil spring 10 is attached to the optical fiber 2. The inner diameter of the coil spring 10 is larger than the outer diameter of the coating layer 4. A portion of the coating layer 4 of the optical fiber 2 is inserted into the coil spring 10. The coil spring 10 is fixed to the coating layer 4 portion of the optical fiber 2 by caulking the front end side of the coil spring 10. As the coil spring 10, an elastic material that is easily plastically deformed and has high rigidity is selected so that it can be fixed by crimping to the coating layer 4 of the optical fiber 2. As a material of the coil spring 10, for example, a metal material such as brass, aluminum, or stainless steel is used. As the coil spring 10, for example, a hard steel wire made of carbon steel such as a piano wire is used.

  The coil spring 10 is fixed by caulking to the coating layer 4 of the optical fiber 2. Therefore, as the coating layer 4 of the optical fiber 2, a material and a thickness that do not affect the core portion of the core / cladding portion 3 even when the coil spring 10 is mechanically caulked are selected. As the optical fiber 2, for example, it is preferable to use a plastic optical fiber in which the core portion of the core / cladding portion 3 has a diameter of 100 μm and the covering layer 4 has a diameter of 500 μm.

  The entire ferrule 11 is formed of a synthetic resin material that is transparent. Although it does not specifically limit as a transparent synthetic resin material, For example, a polyimide, an acrylic resin, an alicyclic olefin resin, and an alicyclic acrylic resin are used.

The ferrule 11 includes a bottom part 11a, a cylinder part 11b, and a spring stopper 12.
The ferrule 11 has a bottomed cylindrical shape as a whole, the bottom part 11a is formed as an optical function part, and the cylindrical part is formed as an insertion hole into which the optical fiber is inserted. The bottom portion 11a has a spherical lens surface 21 that protrudes forward (leftward in FIG. 1) on the outer surface thereof. The cylinder portion 11b of the ferrule 11 is formed in a circular shape in cross section. Further, a flange portion 22 is formed in the cylindrical portion 11b of the ferrule 11 at the intermediate portion in the longitudinal direction so as to project outward in the circumferential direction. Further, an engagement piece 23 is formed at the rear end of the ferrule 11 so as to protrude outward in the circumferential direction.

  An insertion hole 24 is formed at the center of the ferrule 11 along the front-rear direction. The insertion hole 24 is closed by the bottom portion 11 a on the front side of the ferrule 11, and the inner surface of the bottom portion 11 a that is continuous with the inner surface that defines the insertion hole 24 serves as an abutting surface 25 on which the optical fiber 2 abuts. ing. The abutting surface 25 is formed in a spherical shape protruding toward the rear side (right side in FIG. 1).

  The optical fiber 2 is inserted into the insertion hole 24. The tip of the optical fiber 2 inserted into the insertion hole 24 comes into contact with the abutting surface 25. The inner diameter of the insertion hole 24 is slightly larger than the outer diameter of the optical fiber 2 so that the optical fiber 2 can be inserted. The rear end side of the insertion hole 24 is a spring accommodating space 27 including a hole portion 26 having a large diameter. The coil spring 10 attached to the optical fiber 2 is inserted into the spring accommodating space 27. The inner diameter of the hole 26 forming the spring accommodating space 27 is slightly larger than the outer diameter of the coil spring 10 so that the coil spring 10 can be inserted. The hole 26 is slightly larger than the maximum outer diameter in a state where the coil spring 10 is compressed and elastically deformed to the maximum. Further, a guide taper portion 28 that gradually narrows forward is formed between the insertion hole 24 and the spring accommodating space 27. The guide taper portion 28 prevents the tip of the optical fiber 2 from being caught when the optical fiber 2 is inserted into the insertion hole 24.

  The spring stopper 12 is attached to the rear end of the cylindrical portion 11b corresponding to the ferrule body. As shown in FIGS. 2 and 3, the spring stopper 12 has a base 45 formed in a disc shape so that the base 45 closes the hole 26 at the rear end of the cylindrical portion 11 b of the ferrule 11. Installed. Engaging claws 41 projecting toward the ferrule 11 are formed on the base 45b so as to oppose each other at two opposing outer edges. These engaging claws 41 are further formed with engaging protrusions 42 protruding inward. The spring stopper 12 is pressed against the rear end of the cylindrical portion 11 b of the ferrule 11, and the engagement protrusion 42 of the engagement claw 41 engages with the engagement piece 23 at the rear end of the ferrule 11, thereby It is kept attached.

  Further, the base 45 of the spring stopper 12 is formed with a hole 43 at the center thereof that is larger than the outer diameter of the coating layer 4 portion of the optical fiber 2 and smaller than the outer diameter of the coil spring 10. . Then, with the optical fiber 2 inserted in advance into the hole 43 of the spring stopper 12, the spring stopper 12 is attached to the cylindrical portion 11 b of the ferrule 11, whereby the coil spring 10 is locked and the spring of the ferrule 11 is accommodated. The state of being accommodated in the space 27 is maintained.

  As shown in FIG. 4, the spring stopper 12 has a diameter larger than the outer diameter of the coating layer 4 portion of the optical fiber 2 from the center toward the radially outer side, instead of the hole 43, and a coil. A notch 44 having a width smaller than the outer diameter of the spring 10 may be formed. In this case, the notch 44 of the spring stopper 12 is passed through a part of the optical fiber 2 located on the rear side of the coil spring 10, and the spring stopper 12 is attached to the cylindrical portion 11 b of the ferrule 11, thereby The state in which the coil spring 10 is accommodated in the spring accommodating space 27 of the ferrule 11 can be maintained by locking the spring 10. That is, if the notch 44 is formed in the spring stopper 12, it is not necessary to pass the optical fiber 2 through the spring stopper 12, and the operation can be simplified.

  In the ferrule 11 described above, light emitted from the tip of the optical fiber 2 inserted into the insertion hole 24 is emitted as parallel light at the lens surface 21.

Next, how to assemble the optical fiber terminal unit 1 will be described.
FIG. 5A to FIG. 5D are views for explaining how to assemble the optical fiber terminal, and are sectional views.

  First, as shown in FIG. 5A, the end face of the optical fiber 2 is processed to be smooth.

  Next, the optical fiber 2 whose end has been processed is inserted into the coil spring 10.

  Then, the front end side of the coil spring 10 is crimped by the coating layer 4 portion of the optical fiber 2. In this way, the coil spring 10 is fixed to the coating layer 4 of the optical fiber 2. When the coil spring 10 is caulked, the inner diameter of the coil spring 10 is deformed to be, for example, about 5% of the outer diameter of the coating layer 4. Further, in order to prevent the coil spring 10 from coming off from the optical fiber 2, the surface roughness of the inner surface of the coil spring 10 is roughened so that the frictional force between the crimped portion of the coil spring 10 and the coating layer 4 is increased. It is preferable to keep it.

  Next, as shown in FIG. 5C, the optical fiber 2 is inserted from the rear side of the ferrule 11, and the optical fiber 2 is inserted into the insertion hole 24.

  Thereafter, as shown in FIG. 5 (d), the spring stopper 12 is attached from the rear end of the ferrule 11. If it does in this way, the spring stopper 12 will be fixed to the ferrule 11 by the engaging protrusion 42 of the engaging claw 41 of the spring stopper 12 engaging with the engaging piece 23 of the ferrule 11. When the spring stopper 12 is fixedly attached to the ferrule 11, the coil spring 10 is housed and held in the spring housing space 27 while being compressed by being pushed forward by the coil spring stopper 12. In this manner, the spring stopper 12 is securely fixed to the rear end portion of the ferrule 11, so that the coil spring 10 is compressed and the optical fiber 2 is prevented from coming out of the ferrule 11.

  The optical fiber terminal 1 assembled in this way is arranged in a state in which the ferrule 11 is attached to the tip of the optical fiber 2 and the tip of the optical fiber 2 is pressed against and abutted against the abutting surface 25. . Here, the coil spring 10 has a caulking position with respect to the optical fiber 2 so that the optical fiber 2 is pressed with a predetermined pressing force so that the tip of the optical fiber 2 abuts against the abutting surface 25 of the insertion hole 24. Adjusted.

  The optical fiber terminal portion 1 assembled as described above has a structure in which the optical fiber 2 is inserted and connected to the insertion hole 24 of the ferrule 11 having the lens surface 21. It is possible to alleviate the influence of dust and dirt adhering to the tip of the slab, reduce the number of parts, and facilitate assembly work.

  In particular, in the optical fiber terminal portion 1, the abutting surface 25 against which the tip of the optical fiber 2 is abutted is formed in a shape that slightly protrudes on the spherical surface, so that it directly contacts the tip of the optical fiber 2 very well ( Physical contact). Therefore, the Fresnel reflection loss between the end face of the optical fiber 2 is suppressed.

  In addition, by attaching the spring stopper 12, the optical fiber 2 is urged forward by the elastic force of the spring 10, and is pressed in a state where the tip of the optical fiber 2 abuts against the abutting surface 25. For this reason, pistoning is suppressed and a gap does not occur between the tip of the optical fiber 2 and the abutting surface 25. In the present embodiment, the pressing force of the optical fiber 2 against the abutting surface 25 is 0.5N to 1.5N.

  In the above assembling procedure, when assembling the optical fiber terminal portion 1, the end face of the optical fiber 2 is processed so as to be smooth, the coil spring 10 is fixed to the optical fiber 2, and the optical fiber 2 is moved to the ferrule 11. Assembled. However, after fixing the coil spring 10 to the optical fiber 2, the optical fiber 2 is cut so that the tip of the optical fiber 2 has a predetermined length against the abutting surface 25, and the end surface is processed to be smooth. Also good. In this case, since the optical fiber 2 is cut after the coil spring 10 is fixed, the length of the optical fiber 2 positioned on the front side of the coil spring 10 can be easily kept constant. Position adjustment of the coil spring 10 with respect to the optical fiber 2 can be facilitated.

Next, an optical connector that connects the two optical fiber terminal portions 1 will be described.
FIG. 6A to FIG. 6B are diagrams showing a connection state of optical fiber terminal portions in the optical connector, and are sectional views.

  As shown in FIG. 6A, the optical connector 50 including the two optical fiber terminal portions 1 is engaged with the first housing 51 and the second housing 52 that accommodate the respective optical fiber terminal portions 1. Connected.

  The first housing 51 is molded from a synthetic resin and includes a first housing front portion 61 and a first housing rear portion 62. The first housing front portion 61 is formed as an engagement portion with the second housing 52. A guide surface 63 is formed on the inner surface of the first housing front portion 61. The guide surface 63 is formed as a surface for guiding a second housing front portion 71 (described later) of the second housing 52. An engagement space 64 is formed in the first housing front portion 61. The second housing front portion 71 is inserted into the engagement space 64. The first housing rear portion 62 is formed with a terminal accommodating portion 65 in which the optical fiber terminal portion 1 is accommodated from behind. Between the first housing front part 61 and the first housing rear part 62, a hole part 66 is formed through which the front end side of the ferrule 11 is inserted until the flange part 22 comes into contact with the bottom surface of the terminal accommodating part 65. The tip of the ferrule 11 of the optical fiber terminal portion 1 housed in the terminal housing portion 65 protrudes from the hole 66 toward the engagement space 64 side of the first housing front portion 61. The first housing 51 is provided with a fixing mechanism (not shown), and the ferrule 11 is fixed to the first housing 51 by this fixing mechanism.

  The second housing 52 is formed from a synthetic resin, and includes a second housing front portion 71 and a second housing rear portion 72. The second housing front portion 71 is formed as an engagement portion with the first housing 51. A guide surface 73 is formed on the outer surface of the second housing front portion 71. The guide surface 73 is formed as a surface that guides the first housing front portion 61 of the first housing 51. The second housing front part 71 is inserted into the engagement space 64 of the first housing front part 61. The second housing rear portion 72 is formed with a terminal accommodating portion 75 in which the optical fiber terminal portion 1 is accommodated from the rear. A sleeve housing space 76 is formed in the second housing 52 from the front end to the front of the second housing rear portion 72, and a cylindrical connection sleeve 77 is housed in the sleeve housing space 76. The distal end portion of the cylindrical ferrule 11 of the optical fiber terminal portion 1 housed in the terminal housing portion 75 is fitted into the connecting sleeve 77. The connecting sleeve 77 fitted with the ferrule 11 of the optical fiber terminal portion 1 fixed to the second housing 52 has a cylindrical ferrule of the optical fiber terminal portion 1 fixed to the first housing 51 on the opposite side. 11 is fitted. As a result, the ferrules 11 of the respective optical fiber terminal portions 1 are connected by being aligned by the connecting sleeve 77 and aligned. The connecting sleeve 77 is a precision sleeve with a high-precision inner diameter into which a split sleeve or a ferrule 11 into which a slit is formed in the axial direction can be inserted. The second housing 52 is provided with a fixing mechanism (not shown), and the ferrule 11 is fixed to the second housing 52 by this fixing mechanism.

  Next, in the optical connector 50 including the first housing 51 and the second housing 52, a case where the optical fibers 2 of the respective optical fiber terminal portions 1 are optically connected will be described.

  In order to optically connect the optical fibers 2 of the respective optical fiber terminal portions 1, the first housing 51 and the second housing 52 that accommodate the respective optical fiber terminal portions 1 are brought close to each other. Then, as shown in FIG. 6A, the second housing front part 71 of the second housing 52 is inserted into the engagement space 64 formed in the first housing front part 61 of the first housing 51, and the first housing 51 and the second housing 52 are positioned.

  In this state, when the first housing 51 and the second housing 52 are further brought closer to each other and the second housing front portion 71 is completely inserted into the engagement space 64, the first housing 51 and the second housing 52 are engaged. . Then, as shown in FIG. 6B, the optical fiber terminal 1 fixed to the second housing 52 is fixed to the first housing 51 on the opposite side of the connection sleeve 77 fitted with the ferrule 11. The ferrule 11 of the optical fiber terminal unit 1 is fitted. Accordingly, the ferrules 11 of the optical fiber terminal portions 1 are aligned by the connecting sleeve 77 and aligned. In this state, the optical connector 50 is in a fitted state in which the first housing 51 and the second housing 52 are completely engaged, and a lock mechanism (not shown) provided in the first housing 51 and the second housing 52 is provided. ) Locks the first housing 51 and the second housing 52 and maintains the fitted state.

  In the optical connectors 50 connected to each other in this way, an optical signal that has propagated through the optical fiber 2 of the optical fiber terminal portion 1 on one side is emitted from the tip. The optical signal emitted from the tip of the one-side optical fiber 2 is converted into parallel light on the lens surface 21 at the tip of the one-side ferrule 11 and emitted toward the optical fiber terminal portion 1 on the other side. The light enters the lens surface 21 at the tip of the ferrule 11 of the optical fiber terminal portion 1. The optical signal incident on the lens surface 21 is condensed on the tip of the other optical fiber 2 on the lens surface 21 and guided to the other optical fiber 2 to propagate.

Next, an optical module including the optical fiber terminal unit 1 will be described.
FIG. 7 is a cross-sectional view of an optical module including an optical fiber terminal portion.

  As shown in FIG. 7, the optical module 80 provided with the optical fiber terminal portion 1 is engaged with an element side housing 81 provided with a light emitting / receiving element 105 described later and a fiber side housing 82 containing the optical fiber terminal portion 1. Connected.

  The element side housing 81 is molded from a synthetic resin and includes an element side housing front portion 91 and an element side housing rear portion 92. The element side housing front portion 91 is formed as an engagement portion with the fiber side housing 82. A guide surface 93 is formed on the inner surface of the element-side housing front portion 91. The guide surface 93 is formed as a surface for guiding a fiber side housing front portion 111 to be described later of the fiber side housing 82. An engagement space 94 is formed in the element-side housing front portion 91. The fiber side housing front portion 111 is inserted into the engagement space 94.

  The element-side housing 81 includes a lens-equipped sleeve 95. The lens-equipped sleeve 95 is formed of a transparent synthetic resin material. Although it does not specifically limit as a transparent synthetic resin material, For example, a polyimide, an acrylic resin, an alicyclic olefin resin, and an alicyclic acrylic resin are used. The lens-equipped sleeve 95 includes a bottomed cylindrical sleeve portion 96, a flange portion 97 projecting outward in the circumferential direction on the rear end side of the sleeve portion 96, and a lens surface 98 provided on the bottom portion of the sleeve portion 96. have. The lens surface 98 is formed in a spherical shape that protrudes toward the distal end side of the sleeve portion 96. An element housing portion 101 is formed in the element side housing rear portion 92. Between the element-side housing front portion 91 and the element-side housing rear portion 92, a hole portion 102 through which the sleeve portion 96 of the lens-equipped sleeve 95 is inserted until the flange portion 97 contacts the bottom surface of the element housing portion 101 is formed. The sleeve portion 96 of the lens-equipped sleeve 95 inserted from the element housing portion 101 side protrudes from the hole portion 102 toward the engagement space 94 side of the element-side housing front portion 91.

  The element side housing 81 has an element package 103. The element package 103 is accommodated in the element accommodating portion 101 of the element-side housing rear portion 92. In the element package 103, a light emitting / receiving element 105 mounted on a substrate 104 is mounted. The light emitting / receiving element 105 is disposed at an opposing position passing through the central axis of the lens-equipped sleeve 95. In addition, by housing the element package 103 in the element-side housing rear portion 92, the lens-equipped sleeve 95 is pressed forward and fixed to the element-side housing 81.

  The fiber side housing 82 is molded from a synthetic resin and includes a fiber side housing front part 111 and a fiber side housing rear part 112. The fiber side housing front part 111 is formed as an engagement part with the element side housing 81. A guide surface 113 is formed on the outer surface of the fiber-side housing front portion 111. The guide surface 113 is formed as a surface for guiding the element side housing front portion 91 of the element side housing 81. The fiber side housing front part 111 is inserted into the engagement space 94 of the element side housing front part 91. A terminal accommodating portion 115 in which the optical fiber terminal portion 1 is accommodated from the rear is formed in the fiber side housing rear portion 112. The fiber side housing 82 is formed with a ferrule accommodation hole 116 penetrating in the front-rear direction, and the optical fiber terminal portion 1 is inserted and accommodated in the ferrule accommodation hole 116 from the rear side of the fiber side housing 82. . The ferrule housing hole 116 has a small diameter from the middle portion to the distal end side, and the sleeve portion 96 of the lens-equipped sleeve 95 provided in the element-side housing 81 is disposed at the distal end side of the ferrule housing hole 116 formed in this small diameter. The inner diameter can be inserted. The fiber side housing 82 is provided with a fixing mechanism (not shown), and the ferrule 11 is fixed to the fiber side housing 82 by this fixing mechanism.

  Next, in the optical module 80 including the element side housing 81 and the fiber side housing 82, a case where the light receiving / emitting element 105 and the optical fiber 2 of the optical fiber terminal portion 1 are optically connected will be described.

  In order to optically connect the light emitting / receiving element 105 and the optical fiber 2 of the optical fiber terminal 1, the element side housing 81 and the fiber side housing 82 are brought close to each other. Then, the fiber side housing front part 111 of the fiber side housing 82 is inserted into the engagement space 94 formed in the element side housing front part 91 of the element side housing 81, and the ferrule accommodation hole 116 of the fiber side housing front part 111 is inserted. The sleeve 96 of the lens-equipped sleeve 95 is inserted into the element-side housing 81 and the fiber-side housing 82 are positioned.

  In this state, when the element side housing 81 and the fiber side housing 82 are further brought closer to each other and the fiber side housing front portion 111 is completely inserted into the engagement space 94, the element side housing 81 and the fiber side housing 82 are engaged. . Then, the ferrule 11 of the optical fiber terminal portion 1 fixed to the fiber side housing 82 is fitted into the sleeve portion 96 of the sleeve 95 with lens fixed to the element side housing 81. Thereby, the ferrule 11 of the optical fiber terminal portion 1 is aligned by the sleeve portion 96 and aligned. In this state, the optical module 80 is in a fitting state in which the element-side housing 81 and the fiber-side housing 82 are completely engaged, and a lock mechanism (not shown) provided in the element-side housing 81 and the fiber-side housing 82. ), The element side housing 81 and the fiber side housing 82 are locked, and the fitting state is maintained.

  In the optical module 80 connected in this way, the optical signal that has propagated through the optical fiber 2 of the optical fiber terminal unit 1 is emitted from its tip. The optical signal emitted from the tip of the optical fiber 2 is emitted as parallel light at the lens surface 21 at the tip of the ferrule 11 and is incident on the lens surface 98 of the sleeve 95 with lens. The optical signal incident on the lens surface 98 is condensed on the light receiving / emitting element 105 including the light receiving element on the lens surface 98, and the optical signal is converted into an electrical signal by the light receiving / emitting element 105 and transmitted.

  In the optical module 80, when an electric signal is transmitted to the light emitting / receiving element 105, which is a light emitting element, the light emitting / receiving element 105 converts the electric signal into an optical signal and emits the optical signal. This optical signal is guided to the lens-attached sleeve 95, is emitted as parallel light at the lens surface 98 of the lens-attached sleeve 95, and enters the lens surface 21 at the tip of the ferrule 11 of the optical fiber terminal portion 1. The optical signal incident on the lens surface 21 is condensed on the tip of the optical fiber 2 by the lens surface 21 and guided to the optical fiber 2 to propagate.

  As described above, according to the end structure of the optical fiber according to the present embodiment, the coil spring 10 is fixed to the optical fiber 2, and the coil spring 10 is held by the ferrule 11 with an optical function. That is, the optical fiber 2 is held by the ferrule 11 without using an adhesive. Therefore, as compared with the structure in which the optical fiber 2 is fixed to the ferrule 11 with an adhesive, the assembly can be simplified and the reliability can be improved. That is, failure due to deterioration of the adhesive or poor adhesion can be prevented, and productivity can be increased by omitting the adhesion process. In addition, it is possible to eliminate such a problem that optical characteristics are deteriorated due to bubbles entering between the end face of the optical fiber 2 and the abutting face 25 due to poor filling of the adhesive.

  Further, the tip of the optical fiber 2 is pressed and brought into contact with the abutting surface 25 by the urging force of the coil spring 10, so that even if the pistoning due to temperature change occurs, the amount of the optical fiber 2 that has been pulled backward is reduced. This can be compensated by pressing against the abutment surface 25. As a result, the generation of a gap between the tip of the optical fiber 2 and the abutting surface 25 can be prevented, and the Fresnel generated by forming a space between the tip of the optical fiber 2 and the abutting surface 25. It is possible to prevent reflection loss.

  In addition, since the abutting surface 25 is formed in a spherical shape protruding toward the end surface side of the optical fiber 2 inserted into the insertion hole 24, the tip of the optical fiber 2 is excellently applied to the abutting surface 25 by the biasing force of the coil spring 10. The pressing contact can be ensured.

  Further, by using the coil spring 10 as an elastic member, it is possible to reliably apply an elastic force to the optical fiber 2 at a low cost.

  Furthermore, since the tip of the coil spring 10 is fixed to the optical fiber 2 by caulking the optical fiber 2, the cost can be reduced by simplifying the structure. Further, since the coil spring 10 can be fastened and fixed to the optical fiber 2 in a short time, the time for assembling the optical fiber 2 to the ferrule 11 can be shortened.

  In addition, the coil spring 10 can be securely fixed to the optical fiber 2 by roughening the inner surface of the tip portion of the coil spring 10 that is crimped to the optical fiber 2.

  Further, by attaching the spring stopper 12 to the ferrule 11, the rear end portion of the coil spring 10 can be locked very easily and the elastic force can be applied to the optical fiber 2.

  In particular, if the notch 44 is formed in the spring stopper 12, the spring stopper 12 can be easily attached to the ferrule 11 by passing the optical fiber 2 through the notch 44, thereby facilitating assembly work. be able to.

  In the above embodiment, the coil spring 10 is fixedly attached to the optical fiber 2 by caulking the tip of the coil spring 10, but the coil spring 10 is attached to the optical fiber 2 by another mounting structure. Also good.

  For example, as another structure for mounting the coil spring 10 to the optical fiber 2, there is a structure using a flange 120 formed in an annular shape as shown in FIG. In this mounting structure, the end face of the optical fiber 2 that has passed through the coil spring 10 is processed so as to be smooth, and the optical fiber 2 is inserted into a flange 120 that is formed in an annular shape. Next, the flange 120 is caulked and the flange 120 is fixed to the optical fiber 2. Thereafter, the optical fiber 2 is inserted from the rear side of the ferrule 11, the optical fiber 2 is inserted into the insertion hole 24, and the tip of the optical fiber 2 is disposed in contact with the abutting surface 25. A spring stopper 12 is attached from the rear end.

  In this way, the coil spring 10 whose front end is locked by the flange 120 is pressed forward by the spring stopper 12 and compressed. The coil spring 10 is housed and held in the spring housing space 27 in this state. In the optical fiber terminal portion 1 assembled as described above, the optical fiber 2 is urged forward by the elastic force of the coil spring 10, and the optical fiber 2 is pressed in a state where the tip of the optical fiber 2 abuts against the abutting surface 25. Is done.

  As described above, if the flange 120 is used, the coil spring 10 can be locked to the optical fiber 2 and the elastic force can be easily applied to the optical fiber 2 without processing the coil spring 10.

  As the flange 120 that locks the front end side of the coil spring 10, a flange made of the same resin material as that of the coating layer 4 of the optical fiber 2 may be used. As described above, when the flange 120 made of the same resin material as the coating layer 4 of the optical fiber 2 is used, the flange 120 can be welded and fixed to the coating layer 4 of the optical fiber 2. The application of stress to the core / cladding portion 3 of 2 can be reduced.

  Further, in the above embodiment, the engaging claws 41 are formed on the spring stopper 12, and these engaging claws 41 engage with the engaging piece 23 at the rear end of the ferrule 11, so that the spring stopper 12 is attached to the ferrule 11. Although mounted, the mounting structure of the spring stopper 12 to the ferrule 11 is not limited to this structure.

  For example, as another mounting structure of the spring stopper 12 to the ferrule 11, as shown in FIG. 9, a circular spring stopper 12 having an outer diameter larger than the inner diameter of the hole 26 forming the spring accommodating space 27 of the ferrule 11. May be press-fitted into the hole 26 from the rear end of the cylindrical portion 11b of the ferrule 11 and fixed.

  In the above embodiment, the coil spring 10 is used as an elastic member that imparts an elastic force to the optical fiber 2, but the elastic member is not limited to the coil spring 10, and other members having elasticity may be used. good.

  For example, as a structure using another elastic member, as shown in FIG. 10, the optical fiber 2 is inserted into a rubber sleeve 130 in which rubber is formed in a cylindrical shape, and the flange 120 is fixed to the optical fiber 2 by caulking or welding. In some cases, the front end side of the rubber sleeve 130 is locked, and the rear end of the rubber sleeve 130 is locked by a spring stopper 12 press-fitted and fixed from the rear end of the ferrule 11. In this structure, the elastic force from the cylindrical rubber sleeve 130 is applied to the optical fiber 2, and the end surface of the optical fiber 2 is abutted against the abutting surface 25.

  Further, for example, a plate spring may be used as the elastic member, and the elastic force of the plate spring may be applied to the optical fiber 2 so that the end surface of the optical fiber 2 abuts against the abutting surface 25.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimensions, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

2 Optical fiber 10 Coil spring (elastic member)
11 Ferrule 12 Spring stopper 21 Lens surface (optical function part)
24 Insertion hole 25 Abutting surface 44 Notch 120 Flange 130 Rubber sleeve (elastic member)

Claims (4)

Optical fiber,
A bottomed cylindrical ferrule having an insertion hole into which the optical fiber is inserted;
An elastic member held by the ferrule;
With
The ferrule is formed with an optical function portion at the bottom, and the insertion hole is formed at the tube portion,
The elastic member is fixed to the optical fiber and urges the optical fiber along an axial direction.
The optical fiber is pressed against and contacted with the bottom of the ferrule by the urging force of the elastic member. The optical fiber terminal structure according to claim 1,
The end portion of the optical fiber is characterized in that the bottom surface of the ferrule is formed in a spherical shape in which the abutting surface pressed and contacted by the tip of the optical fiber protrudes toward the end surface side of the optical fiber. An optical fiber terminal structure according to claim 1 or 2,
The elastic member has a front end locked to the optical fiber,
The ferrule has a spring stopper for locking a rear end portion of the elastic member. An optical fiber end structure. An optical fiber terminal structure according to claim 3,
The ferrule includes a ferrule body and the spring stopper, and the spring stopper is detachable from the ferrule body.
The end structure of the optical fiber, wherein the spring stopper has a notch portion through which the optical fiber is inserted, and the notch portion is attached to the ferrule body while being inserted through the optical fiber.

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