JP2011017926A - Optical fiber end face structure, optical fiber connecting structure, optical connector, and mechanical splice - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a connection loss when optical fibers are connected to each other via a refractive index matching agent, and to suppress axial deviation between the optical fibers and sticking of dust.SOLUTION: In the end face 26B at the tip end in the axial direction of an optical fiber 26 which is incorporated in the fiber fixing part of an optical connector, a refractive index matching agent 30 is stuck to an area including a core part 27A and excluding the edge of the end face 26B. The refractive index matching agent 30 is formed in the shape of a convex surface and is composed of a half-solid material, and silicone resin is used. When the end face 40C of the optical fiber 40 is abutted on the end face 26B of the optical fiber 26 via the refractive index matching agent 30, the agent 30 is less likely to protrude over the outer periphery of the optical fibers 26, 40 from a space between the end face 26B of the optical fiber 26 and the end face 40C of the optical fiber 40. Also, a distance between the end face 26B of the optical fiber 26 and the end face 40C of the optical fiber 40 is reduced.

Description

  The present invention relates to an optical fiber end face structure, an optical fiber connection structure, an optical connector, and a mechanical splice.

  Conventionally, when connecting optical fibers, a refractive index matching body is often interposed between the end face of one optical fiber and the end face of the other optical fiber.

  In the following Patent Document 1, the sheet-like adhesive connecting member is moved in the axial direction of the optical fiber while the end face of the optical fiber is pressed and brought into close contact with the sheet-like adhesive connecting member (refractive index matching body). A structure is disclosed in which a part of a sticky adhesive connecting member is cut off in a state where it adheres to the end face, and then an optical fiber having the adhesive connecting member attached to the end face is joined to another optical fiber.

  In the following Patent Document 2, the end face of the optical fiber is charged and brought close to the liquid surface of the liquid refractive index matching body, and the liquid refractive index matching body is adsorbed on the end face of the optical fiber and then adsorbed. A method is disclosed in which a solvent of a liquid refractive index matching body is volatilized and solidified, and the refractive index matching body of the optical fiber is butted against another optical fiber.

JP 2005-274839 A JP 2007-183383 A

  However, in the case of Patent Document 1, the adhesive connecting member protrudes to the outer peripheral surface side of the optical fiber when the optical fibers are joined to each other, which causes a shaft misalignment or adhesion of dust.

  In the case of Patent Document 2, the liquid refractive index matching body is adsorbed and solidified on the entire end face of the optical fiber, and is connected to another optical fiber. Therefore, the distance between the end faces of the optical fibers to be connected is increased. Connection loss may increase. Further, when connecting the optical fibers, the refractive index matching body protrudes to the outer peripheral surface side of the optical fiber, which causes an axis deviation and dust adhesion.

  In consideration of the above facts, the present invention reduces an optical fiber end face structure, an optical fiber connection structure, an optical connector, and a mechanical splice that can reduce connection loss when optical fibers are connected to each other, and can suppress misalignment and adhesion of dust. Is the purpose.

  In order to achieve the above object, an end face structure of an optical fiber according to the invention of claim 1 is an end face structure of an optical fiber in which an end face of a second optical fiber is connected to an end face of the first optical fiber. A refractive index matching agent is attached to a region including the core portion of the end face of one optical fiber and excluding the edge of the end face.

  According to the present invention, the refractive index matching agent is attached to a region including the core portion of the end face of the first optical fiber and excluding the edge of the end face, and the refractive index matching agent is attached to the end face of the first optical fiber. The end face of the second optical fiber is abutted and connected via the connector. At this time, the refractive index matching agent is attached to the region excluding the edge of the end face of the first optical fiber, so that the refractive index matching agent can be applied between the end face of the first optical fiber and the end face of the second optical fiber. It is difficult to protrude from the gap to the outer peripheral surface of the first optical fiber or the second optical fiber. Further, when the end face of the second optical fiber is connected to the end face of the first optical fiber via the refractive index matching agent, the gap between the end face of the first optical fiber and the end face of the second optical fiber is The distance is reduced and the connection loss (transmission loss) is reduced. Furthermore, it is suppressed that the refractive index matching agent protrudes from the outer peripheral surface of the first optical fiber or the second optical fiber and a force is applied to the first optical fiber or the second optical fiber. Occurrence of misalignment during connection with the second optical fiber is suppressed. Further, since the refractive index matching agent is difficult to protrude from the outer peripheral surface of the first optical fiber or the second optical fiber, the adhesion of dust is suppressed.

  In order to achieve the above object, an optical fiber end face structure according to a second aspect of the present invention is the optical fiber end face structure according to the first aspect of the present invention, wherein the second end face of the first optical fiber is secondly inserted through the refractive index matching agent. When the end face of each of the optical fibers is abutted and connected, the refractive index matching agent is inserted between the end face of the first optical fiber and the end face of the second optical fiber. 2 is attached so as not to protrude from the outer peripheral surface of the optical fiber.

  According to the present invention, when the end face of the second optical fiber is abutted against and connected to the end face of the first optical fiber via the refractive index matching agent, the refractive index matching agent is connected to the end face of the first optical fiber. It does not protrude from the end surface of the second optical fiber to the outer peripheral surface of the first optical fiber or the second optical fiber. In addition, when the first optical fiber and the second optical fiber are connected, the distance between the end face of the first optical fiber and the end face of the second optical fiber is reduced, and the connection loss (transmission loss) is more sure. Reduced to Furthermore, when the refractive index matching agent protrudes from the outer peripheral surface of the first optical fiber or the second optical fiber, it is prevented that a force is applied to the first optical fiber or the second optical fiber. Occurrence of an axial deviation at the time of connection between the first optical fiber and the second optical fiber is more reliably suppressed, and adhesion of dust is more reliably suppressed.

  An optical fiber end face structure according to a third aspect of the present invention is the optical fiber end face structure according to the first or second aspect, wherein the end face of the first optical fiber has a protruding surface that includes the core portion. The refractive index matching agent is attached to the protruding surface.

  According to the present invention, the refractive index matching agent is attached to the protruding surface including the core portion of the end face of the first optical fiber, and the refractive index matching agent is applied to the protruding face of the end face of the first optical fiber. The end face of the second optical fiber is abutted and connected via the via. Since the refractive index matching agent is attached to the projecting surface of the end face of the first optical fiber, the refractive index matching agent escapes to the outside of the projecting surface, and the outer peripheral surface of the first optical fiber or the second optical fiber. Hard to protrude. As a result, when the first optical fiber and the second optical fiber are connected, the distance between the protruding surface of the end face of the first optical fiber and the end face of the second optical fiber is reduced, and the connection loss (transmission loss) is reduced. ) Is further reduced, and the occurrence of misalignment and adhesion of dust when the first optical fiber and the second optical fiber are connected are further suppressed.

  The optical fiber end face structure according to a fourth aspect of the present invention is the optical fiber end face structure according to the second or third aspect, wherein the region where the refractive index matching agent is attached includes the core portion of the first optical fiber. And 34% to 71% of the area of the end face.

  According to the present invention, the region to which the refractive index matching agent is attached includes the core portion of the first optical fiber, and is 34% to 71% of the area of the end face. At the time of connection with the second optical fiber, the refractive index matching agent is provided between the end face of the first optical fiber and the end face of the second optical fiber while ensuring the refractive index matching of the core portion. Alternatively, the second optical fiber can be reliably prevented from protruding. At the same time, the amount of the refractive index matching agent can be reduced, and the distance between the end face of the first optical fiber and the end face of the second optical fiber at the time of connection can be reduced. Accordingly, the connection loss (transmission loss) is more reliably reduced, and the occurrence of axial misalignment and the adhesion of dust during the connection between the first optical fiber and the second optical fiber are more reliably suppressed.

  An optical fiber end face structure according to a fifth aspect of the present invention is the optical fiber end face structure according to any one of the first to fourth aspects, wherein the refractive index matching agent is attached in a convex curve shape.

  According to the present invention, the refractive index matching agent on the end face of the first optical fiber is attached in a convex curved shape, and the end face of the second optical fiber is connected when the end faces of the second optical fiber are butted together. Is hit from the top of the convex-curved refractive index matching agent, and it is difficult for air bubbles to be involved. For this reason, connection loss can be further reduced.

  An optical fiber end face structure according to a sixth aspect of the present invention is the optical fiber end face structure according to any one of the first to fifth aspects, wherein the surface of the refractive index matching agent is non-adhesive and partially cut. The surface layer provided with is formed.

  According to the present invention, a cut is provided in a part of the non-adhesive surface layer formed on the surface of the refractive index matching agent, and the end face of the second optical fiber is abutted against the end face of the first optical fiber. The refractive index matching agent is crushed and the refractive index matching agent is exposed from the cut of the surface layer, and the end face of the first optical fiber and the end face of the second optical fiber are interposed via the refractive index matching agent. Connected. Moreover, since the refractive index matching agent is protected by the surface layer, the adhesion of dust to the refractive index matching agent is suppressed.

  An optical fiber end face structure according to a seventh aspect of the present invention is the optical fiber end face structure according to the sixth aspect, wherein the surface layer is made of a fluororesin.

  According to the present invention, since the surface layer of the refractive index matching agent is made of a fluororesin, it is possible to suppress the adhesion of dust to the refractive index matching agent.

  An optical fiber end face structure according to an eighth aspect of the present invention is the optical fiber end face structure according to the sixth or seventh aspect, wherein the surface layer is non-light transmissive.

  According to the present invention, the surface layer is non-light-transmitting, and only when the first optical fiber and the second optical fiber are connected, the surface layer breaks, the refractive index matching agent is exposed, and light passes through. A shutter function can be provided.

  An optical fiber end face structure according to an invention of claim 9 is the invention according to claim 6 or 8, wherein the surface layer is a metal thin film.

  According to the present invention, the surface layer is a metal thin film, and can protect the refractive index matching agent and have a shutter function.

  An optical fiber end face structure according to a tenth aspect of the present invention is the optical fiber end face structure according to any one of the first to ninth aspects, wherein the refractive index matching agent is semi-solid.

  According to the present invention, the refractive index matching agent is semi-solid (so-called gel), includes the core portion of the end face of the first optical fiber, and stabilizes the refractive index matching agent in a region excluding the edge of the end face. Can be attached.

  An optical fiber end face structure according to an invention of claim 11 is the optical fiber end face structure according to any one of claims 1 to 10, wherein the refractive index matching agent is a silicone resin.

  According to the present invention, the refractive index matching agent is a silicone resin, and the first refractive index matching agent is interposed between the end face of the first optical fiber and the end face of the second optical fiber. Air is suppressed from entering between the end face of the optical fiber and the end face of the second optical fiber, and the connection loss is reduced.

  On the other hand, in order to achieve the above object, an optical fiber connection structure according to a twelfth aspect of the present invention is a first light having the optical fiber end face structure according to any one of the first to eleventh aspects. A second optical fiber is connected to the fiber.

  According to the present invention, the second optical fiber is connected to the first optical fiber having the optical fiber end surface structure according to any one of claims 1 to 11, and the refractive index matching is performed. The agent is difficult to protrude from the outer peripheral surface of the first optical fiber or the second optical fiber. For this reason, the distance between the end face of the first optical fiber and the end face of the second optical fiber is reduced, the connection loss (transmission loss) is reduced, and the first optical fiber and the second optical fiber are reduced. Axis misalignment and dust adhesion when connected to the

  An optical fiber end face structure according to a thirteenth aspect of the present invention is the optical fiber end face structure according to the twelfth aspect of the present invention, wherein holes are formed in the second optical fiber.

  According to the present invention, a refractive index matching agent is interposed between the end face of the first optical fiber and the end face of the second optical fiber even when holes are formed in the end face of the second optical fiber. Can be connected.

  On the other hand, in order to achieve the above object, an optical connector according to the invention of claim 14 is a first optical fiber in which the optical fiber end face structure according to any one of claims 1 to 11 is formed. Is a built-in optical fiber built in the ferrule, and the built-in optical fiber and the second optical fiber are connected to each other.

  According to the present invention, the first optical fiber in which the optical fiber end surface structure according to any one of claims 1 to 11 is formed is a built-in optical fiber built in a ferrule, and the built-in optical fiber The end face of the second optical fiber is abutted against the end face of the first optical fiber via a refractive index matching agent. At that time, the refractive index matching agent is difficult to protrude from the outer peripheral surface of the built-in optical fiber or the second optical fiber. For this reason, the distance between the end face of the built-in optical fiber and the end face of the second optical fiber is reduced, connection loss (transmission loss) is reduced, and at the time of connection between the built-in optical fiber and the second optical fiber. This prevents the occurrence of misalignment and the adhesion of dust.

  On the other hand, in order to achieve the above object, a mechanical splice according to the invention of claim 15 is a first in which the optical fiber end face structure according to any one of claims 1 to 11 is formed on both end faces. These optical fibers are built in, and second optical fibers are respectively connected to both end faces of the first optical fiber.

  According to this invention, the 1st optical fiber by which the optical fiber end surface structure of any one of Claim 1 to 11 was formed in both end surfaces is incorporated, and both end surfaces of the 1st optical fiber Are connected by abutting the end face of the second optical fiber via a refractive index matching agent. At this time, the refractive index matching agent is unlikely to protrude from the outer peripheral surface of the first optical fiber or the second optical fiber. For this reason, the distance between the end face of the first optical fiber and the end face of the second optical fiber is reduced, the connection loss (transmission loss) is reduced, and the first optical fiber and the second optical fiber are reduced. Axis misalignment and dust adhesion when connected to the

  ADVANTAGE OF THE INVENTION According to this invention, the connection loss at the time of connecting optical fibers can be reduced, and generation | occurrence | production of an axial shift and adhesion of refuse can be suppressed.

It is sectional drawing which shows the optical connector to which the optical fiber end surface structure which concerns on 1st Embodiment of this invention was applied. It is a partial expansion perspective view which shows the end surface vicinity of the optical fiber incorporated in the optical connector shown to FIG. 1A. 1B is a partially enlarged perspective view showing a process of connecting an optical fiber built in the optical connector shown in FIG. 1A to another optical fiber. FIG. It is a partial expanded side view which shows the process of connecting the optical fiber incorporated in the optical connector shown to FIG. 1A to another optical fiber. It is a partial expanded side view which shows the state which connected the optical fiber incorporated in the optical connector shown to FIG. 1A to another optical fiber. It is a partial expansion perspective view which shows the process of connecting the built-in optical fiber of a comparative example to another optical fiber. It is a partial expanded side view which shows the process of connecting the built-in optical fiber of a comparative example to another optical fiber. It is a partial expanded side view which shows the state which connected the built-in optical fiber of the comparative example to the other optical fiber. It is a front view which shows the end surface of the optical fiber incorporated in the optical connector to which the optical fiber end surface structure concerning 2nd Embodiment of this invention was applied. FIG. 5 is a partially enlarged side view showing a process of connecting the optical fiber shown in FIG. 4 to another optical fiber. FIG. 5 is a partially enlarged side view showing a state where the optical fiber shown in FIG. 4 is connected to another optical fiber. It is a disassembled perspective view which shows the mechanical splice to which the optical fiber end surface structure concerning 3rd Embodiment of this invention was applied. It is a perspective view which shows the process of connecting another optical fiber to the both sides of the optical fiber incorporated in the mechanical splice shown in FIG. FIG. 7 is a partially enlarged side view showing a process of connecting another optical fiber to both sides of the optical fiber built in the mechanical splice shown in FIG. 6. It is a disassembled perspective view which shows the state which connected the other optical fiber to the both sides of the optical fiber incorporated in the mechanical splice shown in FIG. It is the elements on larger scale which show the state which connected the other optical fiber to the both sides of the optical fiber incorporated in the mechanical splice shown in FIG. It is a perspective view which shows the state which connected the other optical fiber to the both sides of the optical fiber incorporated in the mechanical splice shown in FIG. It is a partial expanded side view which shows the process of connecting the optical fiber incorporated in the optical connector to which the optical fiber end surface structure concerning 4th Embodiment of this invention was applied to another optical fiber. It is a partial expanded side view which shows the state which connected the optical fiber incorporated in the optical connector to which the optical fiber end surface structure concerning 4th Embodiment of this invention was applied to another optical fiber. It is a partial expanded side view which shows the process of connecting the optical fiber incorporated in the optical connector with which the optical fiber end surface structure concerning 5th Embodiment of this invention was applied to another optical fiber. It is a partial expanded side view which shows the state which connected the optical fiber incorporated in the optical connector with which the optical fiber end surface structure concerning 5th Embodiment of this invention was applied to another optical fiber. It is a figure for demonstrating the preferable range of the area ratio of the area | region which apply | coats the refractive index matching agent with respect to the area of the end surface of an optical fiber.

  Hereinafter, a first embodiment of an optical connector to which the optical fiber end face structure of the present invention is applied will be described with reference to FIGS. 1 and 2.

  FIG. 1A shows the overall configuration of the field assembly type optical connector 10. FIG. 1B is a perspective view showing the vicinity of the end face of the optical fiber built in the optical connector 10. 2A to 2C show a process of connecting another optical fiber to the optical fiber built in the optical connector 10. As shown in FIG. 1A, an optical connector 10 includes a fiber fixing portion 20 for positioning and fixing an optical fiber 40 as a second optical fiber, a lid member 14 that covers the upper side of the fiber fixing portion 20, and a lid. And a clamp member 16 that presses the member 14 toward the fiber fixing portion 20 by a spring force.

  The substrate 12 includes a fiber fixing portion 20 against which the optical fiber 40 is pressed by the lid member 14, a substantially cylindrical ferrule 24 inserted into a cylindrical flange portion 22 fixed to one end side of the fiber fixing portion 20, and It has. The fiber fixing portion 20 has a substantially rectangular cross section in a direction orthogonal to the longitudinal direction, and includes a planar upper surface portion 20A along the longitudinal direction. In the upper surface portion 20A, a shallow groove portion 20B and a groove portion 20C that is deeper and wider than the groove portion 20B are formed continuously along the longitudinal direction. The grooves 20B and 20C have a substantially V-shaped cross section in a direction orthogonal to the longitudinal direction.

  An optical fiber 26 as a first optical fiber is built in the core portion of the ferrule 24, and an end portion 26 </ b> A of the optical fiber 26 protrudes from the flange portion 22 side of the ferrule 24. The optical fiber 26 protruding from the flange portion 22 side is inserted into the groove portion 20 </ b> B of the fiber fixing portion 20.

  The optical fiber 40 includes a coating portion 40B in which the periphery of the bare optical fiber 40A is covered with a resin or the like on the rear end side in the longitudinal direction of the bare optical fiber 40A. The bare optical fiber 40 </ b> A of the optical fiber 40 is held in the groove portion 20 </ b> B of the fiber fixing portion 20, and the covering portion 40 </ b> B of the optical fiber 40 is held in the groove portion 20 </ b> C of the fiber fixing portion 20.

  The lid member 14 holds the optical fiber 40 inserted into the groove portions 20B and 20C of the fiber fixing portion 20. The lid member 14 has a substantially rectangular cross section in a direction orthogonal to the longitudinal direction, and a planar lower surface portion 14A is formed along the longitudinal direction. It arrange | positions so that 14 A of lower surface parts of the cover member 14 and 20 A of upper surface parts of the fiber fixing | fixed part 20 may face | abut.

  The clamp member 16 has a substantially U-shaped cross section in a direction perpendicular to the longitudinal direction. The clamp member 16 sandwiches the lid member 14 and the fiber fixing portion 20, whereby the lid member 14 is fixed to the fiber fixing portion 20. It is the structure which presses by spring force toward.

  As shown in FIGS. 1B, 2A, and 2B, the optical fiber 26 is formed in a substantially cylindrical shape, and includes an axial core portion 27A and a cladding 27B around the core portion 27A. . A refractive index matching agent 30 is applied (attached) to a region including the core portion 27A and excluding the edge of the end surface 26B on the end surface 26B at the tip end in the axial direction of the optical fiber 26. That is, the refractive index matching agent 30 is applied only to the central portion including the core portion 27A of the end surface 26B of the optical fiber 26, and the region applied to the end surface 26B has a substantially circular shape.

  The bare optical fiber 40A of the optical fiber 40 is formed in a substantially cylindrical shape, and includes an axial core part 41A and a clad 41B around the core part 41A. A refractive index matching agent is not applied to the end face 40C at the tip in the axial direction of the bare optical fiber 40A of the optical fiber 40.

  The refractive index matching agent 30 is interposed between the end face 26B of the optical fiber 26 and the end face 40C of the optical fiber 40 when the optical fiber 26 and the optical fiber 40 are connected, so that the end face 26B of the optical fiber 26 and the optical fiber 40 are interposed. Fresnel reflection that occurs when air enters between the end face 40C and the connection loss (transmission loss) is reduced.

  The refractive index matching agent 30 is made of a semi-solid (so-called gel) material, and a silicone resin is used in this embodiment. The refractive index matching agent 30 may use an acrylate resin or a polyurethane resin instead of the silicone resin. Further, a refractive index adjusting agent such as fluorine may be added for adjusting the refractive index. The refractive index matching agent 30 is formed in a convex curved surface at the center portion including the core portion 27 </ b> A of the end surface 26 </ b> B of the optical fiber 26. In the present embodiment, by using a precision dispenser, the refractive index matching agent 30 is applied in a precise shape to the center portion (region excluding the edge of the end surface 26B) including the core portion 27A of the end surface 26B of the optical fiber 26. Yes. As a precision dispenser, for example, NANO MASTER series manufactured by Musashi Engineering Co., Ltd. is used.

  Further, the fluororesin may be coated in a ring shape around the center part including the core part 27A of the end face 26B of the optical fiber 26 (parts other than the part where the refractive index matching agent 30 is applied). As a result, the portion coated with the fluororesin repels the refractive index matching agent 30, so that the refractive index matching agent 30 can be applied at a precise position as shown in FIGS. 1B and 2A.

  At this time, the region where the refractive index matching agent 30 is applied is the end face of the optical fiber 26 in consideration of compression deformation at the time of optical fiber connection such as a refractive index matching agent resin generally used in the art. It is preferably set to 34% to 71% of the area of 26B (or the cross-sectional area of the optical fiber near the end face). Further, since the minimum amount of resin is required, it is preferably 34% to 50% of the area of the end face 26B, and more preferably 34% to 40% of the area of the end face 26B.

Here, the grounds for setting the region to which the refractive index matching agent 30 is applied to 34% to 71% of the area of the end face 26B of the optical fiber 26 will be described.
As shown in FIG. 12, the droplet radius when applying the droplet as the refractive index matching agent 30 is R, the core radius of the optical fiber 26 is Rc, the error when applying the droplet is Ea, and the optical fiber. When the radius is Rf and the width of the edge where no droplet is applied is Rr, the minimum droplet radius Rmin and the maximum droplet radius Rmax are expressed by Equation (1) and Equation (2), respectively.

From the above formulas (1) and (2), the droplet radius R is expressed by formula (3).

When the area of the end surface 26B of the optical fiber 26 is Si and the area of the droplet is Sf, the ratio of the area of the droplet to the area of the end surface 26B of the optical fiber 26 (Sf / Si) is expressed by Equation (4). .

  A recent quantitative dispenser has a positional accuracy of 5 μm or less (Ea ≦ 5 μm), and in the case of a refractive index matching agent used for optical fiber connection, an edge width Rr of about 10 μm is sufficient. Accordingly, in the case of a single mode with a core diameter of 10 μm (Rc = 5 μm) in the most widely used optical fiber with an outer diameter of 125 μm (Rf = 62.5 μm), the adhesion area is 2.5% to 71%. In the case of multimode with a diameter of 50 μm (Rc = 25 μm), it is convenient to set the adhesion area to 23% to 71%, and in the case of multimode with a core diameter of 62.5 μm (Rc = 31.25 μm) It is convenient to set between 34% and 71%. Therefore, in order to correspond to any optical fiber, the adhesion area of the refractive index matching agent 30 is preferably set to 34% to 71%.

  In addition, the adhesion area of the refractive index matching agent 30 is experimentally obtained from an adhesion apparatus (adhesion condition), an adhesion material (and an adhesion amount), and an adhesion target fiber. In addition, the adhesion area actually used is to reduce the contact end face interval by using the vicinity of the lower limit when importance is attached to the junction loss, and to use the vicinity of the upper limit value when importance is attached to the stability of the joint. Set to earn.

  Next, operations and effects of the optical connector 10 to which the optical fiber end face structure of the present embodiment is applied will be described.

  As shown in FIG. 1A, when the optical connector 10 is attached to the optical fiber 40, the optical fiber 40 is inserted into the grooves 20B and 20C of the fiber fixing portion 20 along the axial direction from the bare optical fiber 40A side. The bare optical fiber 40A of the fiber 40 is inserted until it hits the optical fiber 26 arranged in the groove 20B.

  At this time, as shown in FIGS. 2A and 2B, the end face 26B of the optical fiber 26 is coated with the refractive index matching agent 30 in the region including the core portion 27A and excluding the edge of the end face 26B. As shown in FIG. 2C, when the end face 40C of the bare optical fiber 40A of the optical fiber 40 is abutted against the end face 26B of the optical fiber 26 via the refractive index matching agent 30, the refractive index matching agent 30 is removed from the optical fiber. 26 to the outer peripheral surface of the optical fiber 26 and the optical fiber 40 from between the end surface 26B of the optical fiber 26 and the end surface 40C of the optical fiber 40. Here, “when abutting” is intended to abut one optical fiber with the optical fiber to be connected with a pressing force that does not bend the optical fiber. Therefore, the region excluding the edge is set in consideration of the spread of the refractive index matching agent 30 at the time of the abutment. Further, since the refractive index matching agent 30 is applied to the region excluding the edge of the end face 26B of the optical fiber 26, the end face 26B of the optical fiber 26 and the optical fiber 40 are connected when the optical fiber 26 and the optical fiber 40 are connected. The distance to the end face 40C is reduced, and the connection loss (transmission loss) can be reduced. Further, it is prevented that the refractive index matching agent 30 protrudes from the outer peripheral surface of the optical fiber 26 and the optical fiber 40 and a force is applied to the optical fiber 26 or the optical fiber 40, so that an axial misalignment between the optical fiber 26 and the optical fiber 40 occurs. Can be suppressed. Further, since the refractive index matching agent 30 is difficult to protrude from the outer peripheral surfaces of the optical fiber 26 and the optical fiber 40, it is possible to suppress the adhesion of dust.

  Further, since the region where the refractive index matching agent 30 is applied is set to 34% to 71% of the area of the end face 26B of the optical fiber 26, the refractive index matching agent 30 is applied to the entire end face 26B of the optical fiber 26. The amount of the refractive index matching agent 30 is reduced as compared with the case where the optical fiber 26 is applied, and the distance between the optical fiber 26 and the optical fiber 40 can be reduced. It can suppress more reliably that it protrudes into the outer peripheral surface of the optical fiber 26 and the optical fiber 40 from between the end surface 26B and the end surface 40C of the optical fiber 40.

  Further, the refractive index matching agent 30 on the end surface 26B of the optical fiber 26 is formed in a convex curved shape, the end surface 40C of the optical fiber 40 hits from the top of the refractive index matching agent 30, and the refractive index matching agent 30 spreads outward. So it is hard to get air bubbles involved. For this reason, connection loss can be further reduced.

  On the other hand, as shown in FIGS. 3A and 3B, when the refractive index matching agent 30 is applied in a convex curved surface over almost the entire end surface 200A of the optical fiber 200, the refractive index is applied to the end surface 200A of the optical fiber 200. When the end face 202 </ b> A of the optical fiber 202 is abutted through the matching agent 30, the refractive index matching agent 30 is between the end face 200 </ b> A of the optical fiber 200 and the end face 202 </ b> A of the optical fiber 202. Protrude to the side. At that time, since a lot of gel-like refractive index matching agent 30 exists between the end faces of the optical fiber, the distance between the end face 200A of the optical fiber 200 and the end face 202A of the optical fiber 202 becomes large, and the connection loss (transmission loss). ) May be large. Further, when the refractive index matching agent 30 protrudes to the outer peripheral surface side of the optical fiber 200 and the optical fiber 202, a force is applied to the optical fiber 200 or the optical fiber 202, and an axial deviation between the optical fiber 200 and the optical fiber 202 is likely to occur. . Furthermore, there is a possibility that dust will be taken in when the refractive index matching agent 30 protrudes. In this case, the connection loss may increase due to the dust taken in when the optical fiber is reconnected.

  On the other hand, in this embodiment, since the amount of the refractive index matching agent 30 used is relatively small compared to that according to the conventional method, the end face 26B of the optical fiber 26 is connected when the optical fiber 26 and the optical fiber 40 are connected. The distance between the optical fiber 40 and the end face 40C of the optical fiber 40 is reduced, so that the connection loss (transmission loss) can be reduced, and the occurrence of axial misalignment between the optical fiber 26 and the optical fiber 40 and the adhesion of dust can be suppressed. .

  Next, an optical connector to which the optical fiber end face structure according to the second embodiment of the present invention is applied will be described. In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  In this embodiment, as shown in FIG. 4 and FIG. 5A, instead of the optical fiber 26 of the first embodiment, the first optical fiber built in the fiber fixing portion (see FIG. 1) of the optical connector, An optical fiber 50 is used. The end face 50A at the tip end in the axial direction of the optical fiber 50 includes a core portion 27A and a semi-solid (so-called gel-like) refractive index matching in a region excluding the edge of the end face 50A (center portion including the core portion 27A). An agent 52 is applied, and a surface layer 54 is formed on the surface of the refractive index matching agent 52. The surface layer 54 is made of a non-adhesive material having a hardness higher than that of the refractive index matching agent 52, and covers the surface of the refractive index matching agent 52. One straight cut 55 is provided at the center of the surface layer 54. In the present embodiment, a fluororesin is used as the surface layer 54. A silicone resin is used for the refractive index matching agent 52 as in the first embodiment. In addition to the fluororesin, an epoxy resin, an acrylate resin, a silicone resin having a higher hardness than the refractive index matching agent 52, a metal thin film, or the like may be used as the surface layer 54.

  In this embodiment, the refractive index matching agent 52 is applied to the end face 50A of the optical fiber 50 in a convex curved surface shape with a precision dispenser (NANO MASTER series manufactured by Musashi Engineering Co., Ltd.) and cured. Further, a surface layer 54 made of a fluororesin thin film is formed by applying a fluororesin solution on the surface of the refractive index matching agent 52 and drying by heating. Here, when adhesion between the fluororesin thin film and the refractive matching agent 52 does not occur, it is not necessary to use a fluororesin solution or other stripping solution or stripping agent. At that time, although not shown, the fluororesin thin film may be formed not only on the surface of the refractive index matching agent 52 but also on the entire end face 50 </ b> A of the optical fiber 50. By making the surface layer 54 a fluororesin, it is possible to make it difficult to get dirt. In addition, by spreading the fluororesin solution on the surface of the surface layer 54, the spread of the cut can be promoted at the time of pressing described later.

  The cut 55 in the surface layer 54 can be formed by laser processing or the like.

  As shown in FIG. 5B, when the end face 40C of the optical fiber 40 (second optical fiber) is abutted against the end face 50A of the optical fiber 50, the refractive index matching agent 52 inside the surface layer 54 is crushed and spread. At the same time, the cut 55 spreads, the refractive index matching agent 52 appears in the core portion 41A of the end face 40C of the optical fiber 40, and the refractive index matching agent 52 and the end face 40C of the optical fiber 40 are brought into close contact with each other. As a result, the end face 50A of the optical fiber 50 and the end face 40C of the optical fiber 40 are connected.

  Since the refractive index matching agent 52 is applied only to the central portion (the region excluding the end surface 50A) including the core portion 27A of the end face 50A of the optical fiber 50, and the refractive index matching agent 52 is covered with the surface layer 54. Further, the refractive index matching agent 52 is prevented from protruding from between the end face 50A of the optical fiber 50 and the end face 40C of the optical fiber 40 to the outer peripheral face of the optical fiber 50 and the optical fiber 40. As a result, the distance between the end face 50A of the optical fiber 50 and the end face 40C of the optical fiber 40 is reduced when the optical fiber 50 and the optical fiber 40 are connected, and the connection loss (transmission loss) can be reduced. And the optical fiber 40 can be prevented from occurring.

  In addition, since the refractive index matching agent 52 is protected by the surface layer 54 in a state where the optical fiber 40 is not connected (unconnected state), there is no adhesion of dirt such as dust, and the optical fiber 40 is connected. Sometimes, a clean surface of the refractive index matching agent 52, which is always free of dirt, appears and is connected to the end face 40C of the optical fiber 40.

  When the optical fiber 40 is removed from the optical connector (see FIG. 1), the optical fiber 40 returns to the unconnected state, so that the refractive index matching agent 52 is protected by the surface layer 54 having high hardness. For this reason, dirt is prevented from adhering to the refractive index matching agent 52, and the optical fiber 40 can be connected repeatedly.

  The surface layer 54 is made of a non-light transmissive material such as a metal thin film, so that a shutter function is provided so that the refractive index matching agent 52 is exposed and light is transmitted only when the optical fiber 40 is connected. You can also.

  In the above embodiment, the cut line 55 is a single straight line, but is not limited to this. For example, the cut line 55 is slightly smaller than the core of the fiber to be connected in order to avoid connection loss due to a cross line or a surface layer. It is good also as a shape with a big circular hole. Further, in order to prevent the surface layer from being peeled off from the end surface 50A during pressing, a resin that improves the adhesion of the end surface 50A to the end surface 50A before the surface layer 54 is formed. Or an adhesive may be applied.

  Next, a mechanical splice to which the optical fiber end face structure of the third embodiment of the present invention is applied will be described. In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment and 2nd Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIGS. 6 and 7A, the mechanical splice 70 includes a rectangular substrate 72 and a rectangular lid member 74. On the upper surface portion 20A of the substrate 72, a shallow groove portion 20B is formed at the center in the longitudinal direction, and a groove portion 20C that is deeper and wider than the groove portion 20B is formed on both sides in the longitudinal direction of the groove portion 20B. A short optical fiber 76 as a first optical fiber is built in an intermediate portion of the groove 20B, and optical fibers 40 as second optical fibers are connected to both sides in the axial direction of the optical fiber 76. It has a configuration. When the optical fiber 40 is connected, the bare optical fiber 40A of the optical fiber 40 is held in the groove portion 20B, and the covering portion 40B is held in the groove portion 20C.

  Although not shown, the mechanical splice 70 includes a clamp member that sandwiches the substrate 72 and the lid member 74, and the optical fiber 76 and the optical fiber 40 are pushed into the grooves 20B and 20C by the lid member 74 by the spring force of the clamp member. It is applied and gripped.

  As shown in FIG. 7B, the end faces 76A and 76B on both axial sides of the optical fiber 76 include a core portion 27A and a region excluding the edges of the end faces 76A and 76B (a central portion including the core portion 27A). A refractive index matching agent 30 is applied. The refractive index matching agent 30 is formed in a convex curved surface shape. The refractive index matching agent 30 is made of a semi-solid (so-called gel) material, and a silicone resin is used in this embodiment.

  In this mechanical splice 70, as shown in FIGS. 8A and 8B, the two optical fibers 40 are inserted into the grooves 20B and 20C from both sides in the longitudinal direction of the substrate 72 until they abut against the end faces 76A and 76B of the optical fiber 76.

  When the end face 40C of the optical fiber 40 is abutted against the end faces 76A and 76B of the optical fiber 76 via the refractive index matching agent 30, the refractive index matching agent is provided only in the central portion including the core portion 27A of the end faces 76A and 76B of the optical fiber 76. 30 is applied, it is difficult for the refractive index matching agent 30 to protrude from between the end faces 76A and 76B of the optical fiber 76 and the end face 40C of the optical fiber 40 to the outer peripheral surface of the optical fiber 76 and optical fiber 40.

  In this state where the end face 40C of the optical fiber 40 is abutted against the end faces 76A and 76B of the optical fiber 76 via the refractive index matching agent 30, as shown in FIG. Covering and sandwiching the substrate 72 and the lid member 74 with a clamp member (not shown) allows the optical fiber 76 and the optical fiber 40 to be pressed against and fixed to the grooves 20B and 20C by the lid member 74 by the spring force of the clamp member. The

  In such a mechanical splice 70, when the end face 40C of the optical fiber 40 is connected to the end faces 76A and 76B of the optical fiber 76 via the refractive index matching agent 30, the end faces 76A and 76B of the optical fiber 76 and the optical fiber 40 are connected. The distance from the end face 40C is reduced, so that the connection loss (transmission loss) can be reduced, and the occurrence of misalignment between the optical fiber 76 and the optical fiber 40 and the adhesion of dust can be suppressed.

  For simplification of the connection work, the lid 74 includes a lid for fixing the central portion of the optical fiber 76 for connection, a connection portion of each fiber connected to the short fiber, and a lid for fixing each fiber. A clamp member that clamps each lid individually is prepared. First, the optical fiber 76 may be fixed with the lid and the clamp, and one end of the optical fiber 76 may be connected and fixed with the corresponding lid. .

  Here, an example is shown in which a short fiber for connection is used in the middle, but without using a short fiber for connection, a peripheral portion of one end face to be connected is coated with fluorine, and then refractive index matching is performed. An end face may be immersed in the agent solution to form a gel-like refractive index matching agent on a convex curve adhering to the central portion not coated with fluorine, and connected to the other optical fiber.

  Next, an optical connector to which the optical fiber end face structure according to the fourth embodiment of the present invention is applied will be described. In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment-3rd Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 10A, an optical fiber 90 is used instead of the optical fiber 26 of the first embodiment as the first optical fiber built in the fiber fixing portion (see FIG. 1) of the optical connector. . A protruding portion 92 that protrudes so that the distal end side becomes gradually narrower is provided at the axial end of the optical fiber 90, and a flat protruding surface 92 </ b> A is formed at the end of the protruding portion 92. When the protrusion 92 is viewed from the side, a linear taper portion is formed. In other words, the projecting portion 92 has a shape in which a conical tip portion is notched and a planar projecting surface 92A is formed. When the projecting portion 92 is viewed from the side, a linear taper portion is provided. . The protrusion 92 can also be formed using a tool used in conventional chamfering.

  The refractive index matching agent 94 is applied to almost the entire projecting surface 92A of the projecting portion 92. Thus, the refractive index matching agent 94 includes the core portion 27A of the end face (projecting portion 92) of the optical fiber 90 and a region excluding the edge of the end face (projecting portion 92) of the optical fiber 90, that is, the protrusion 92. It is applied only to the central part including the core part 27A. The refractive index matching agent 94 is formed in a convex curved shape. The refractive index matching agent 94 is made of a semi-solid (so-called gel) material, and a silicone resin is used in this embodiment.

  As shown in FIG. 10B, when the end surface 40C of the optical fiber 40 (second optical fiber) is abutted against the projecting surface 92A of the optical fiber 90 via the refractive index matching agent 94, the refractive index matching agent 94 becomes the optical fiber. The protrusion 92 protrudes from the gap between the protruding surface 92A of 90 and the end surface 40C of the optical fiber 40 to the tapered portion side. At this time, the refractive index matching agent 94 is prevented from protruding to the outer peripheral surfaces of the optical fiber 90 and the optical fiber 40, and no force is applied to the optical fiber 90 or the optical fiber 40. As a result, when the optical fiber 90 and the optical fiber 40 are connected, the distance between the protruding surface 92A of the optical fiber 90 and the end surface 40C of the optical fiber 40 is reduced, so that the connection loss (transmission loss) can be reduced and the optical fiber can be reduced. It is possible to suppress the occurrence of axial misalignment between 90 and the optical fiber 40 and adhesion of dust. In addition, the size of the tapered portion where the protruding portion 92 is cut is set in consideration of the amount of protrusion of the squeezed refractive index matching agent 94.

  Next, an optical connector to which the optical fiber end surface structure of the fifth embodiment of the present invention is applied will be described. In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment-4th Embodiment, and the overlapping description is abbreviate | omitted.

  In this embodiment, as shown in FIG. 11A, a central portion including a core portion 27A that is a part of the protruding surface 92A of the protruding portion 92 of the optical fiber 90, instead of the refractive index matching agent 94 of the fourth embodiment. A refractive index matching agent 96 is applied. That is, the refractive index matching agent 96 is applied to a region excluding the edge of the protruding surface 92 </ b> A of the protruding portion 92 of the optical fiber 90. The refractive index matching agent 96 is formed in a convex curved surface shape. The refractive index matching agent 96 is made of a semi-solid (so-called gel) material, and a silicone resin is used in this embodiment.

  As shown in FIG. 11B, when the end face 40C of the optical fiber 40 (second optical fiber) is abutted against the protruding surface 92A of the optical fiber 90 via the refractive index matching agent 96, the refractive index matching agent 96 is projected. By being applied to the central portion of 92A, the refractive index matching agent 96 is unlikely to protrude from between the protruding surface 92A of the optical fiber 90 and the end surface 40C of the optical fiber 40 to the tapered portion side of the protruding portion 92. Thereby, when the optical fiber 90 and the optical fiber 40 are connected, the distance between the protruding surface 92A of the optical fiber 90 and the end surface 40C of the optical fiber 40 is further reduced, and the connection loss (transmission loss) can be reduced. Generation of axial misalignment between the fiber 90 and the optical fiber 40 and adhesion of dust can be suppressed.

  In the fourth and fifth embodiments described above, a substance having a peeling action such as a fluororesin solution is attached to the tapered portion of the end face before the refractive index matching agent is attached, so that other than the tip of the protruding portion. It can be avoided that the refractive index matching agent is attached.

  In addition, although 2nd Embodiment, 4th Embodiment, and 5th Embodiment which were mentioned above are examples of an optical connector, you may apply the structure of the end surface shape and refractive index matching agent of the same optical fiber to mechanical splice. .

  Further, in the above-described fourth and fifth embodiments, the protruding portion 92 has a shape protruding so as to have a linear taper portion, but the shape of the protruding portion 92 is not limited to this, and is an R shape. Alternatively, it may have a spherical shape.

  In the first to fifth embodiments described above, in order to apply the refractive index matching agent only to a region including the core portion of the end face of the first optical fiber and excluding the edge of the end face, Surface treatment of the end face of the optical fiber (primer treatment or surface treatment by plasma discharge) may be performed.

  In the first to fifth embodiments described above, the type of optical fiber 40 having no holes is used as the second optical fiber connected to the first optical fiber. The same effect can be obtained even if the optical fiber formed with is applied to the above embodiment.

10 optical connector 24 ferrule 26 optical fiber (first optical fiber)
26B End face 27A Core portion 30 Refractive index matching agent 40 Optical fiber (second optical fiber)
40C end face 41A core part 50 optical fiber (first optical fiber)
50A End face 52 Refractive index matching agent 54 Surface layer 55 Cut 70 Mechanical splice 76 Optical fiber (first optical fiber)
76A end face 90 optical fiber (first optical fiber)
92A Projecting surface 94 Refractive index matching agent 96 Refractive index matching agent

Claims (15)

An end face structure of an optical fiber in which an end face of a second optical fiber is connected to an end face of the first optical fiber,
An optical fiber end face structure including a core portion of an end face of the first optical fiber and having a refractive index matching agent attached to a region excluding an edge of the end face.   When the end surface of the second optical fiber is abutted against and connected to the end surface of the first optical fiber via the refractive index matching agent, the refractive index matching agent is in contact with the end surface of the first optical fiber and the second optical fiber. 2. The optical fiber end face structure according to claim 1, which is attached so as not to protrude from an outer peripheral face of the first optical fiber or the second optical fiber from between the end faces of the first optical fiber and the second optical fiber.   The end face of the first optical fiber is provided with a protruding surface that protrudes including the core portion, and the refractive index matching agent is attached to the protruding surface. Optical fiber end face structure.   4. The end face of the optical fiber according to claim 2, wherein the region to which the refractive index matching agent is attached includes the core portion of the first optical fiber and is 34% to 71% of the area of the end face. Construction.   The optical fiber end face structure according to any one of claims 1 to 4, wherein the refractive index matching agent is attached in a convex curved surface shape.   The optical fiber end face structure according to any one of claims 1 to 5, wherein a surface layer that is non-adhesive and is partially cut is formed on a surface of the refractive index matching agent.   The optical fiber end face structure according to claim 6, wherein the surface layer is a fluororesin.   The optical fiber end face structure according to claim 6 or 7, wherein the surface layer is non-light transmissive.   The optical fiber end face structure according to claim 6 or 8, wherein the surface layer is a metal thin film.   The optical fiber end face structure according to any one of claims 1 to 9, wherein the refractive index matching agent is semi-solid.   The optical fiber end face structure according to any one of claims 1 to 10, wherein the refractive index matching agent is a silicone resin.   An optical fiber connection structure in which a second optical fiber is connected to a first optical fiber having the optical fiber end face structure according to any one of claims 1 to 11.   The optical fiber connection structure according to claim 12, wherein holes are formed in the second optical fiber.   The first optical fiber in which the optical fiber end surface structure according to any one of claims 1 to 11 is formed is a built-in optical fiber built in a ferrule, and the built-in optical fiber and the second light An optical connector that is connected to a fiber.   A first optical fiber in which the optical fiber end face structure according to any one of claims 1 to 11 is formed on both end faces is built in, and second end faces are respectively provided on both end faces of the first optical fiber. Mechanical splice to which optical fiber is connected.

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