JP2006293195A - Optical fiber connecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a core from projecting due to a difference in a thermal expansion coefficient between the core and a clad. <P>SOLUTION: An optical fiber 12 is located by insertion in almost a cylindrical ferrule 22 in which the optical fiber 12 is locatable by insertion. A glass core 13 is exposed at a tip part of the optical fiber 12, and the exposed glass core 13 is bonded to the inner peripheral part of the tip part of the ferrule 22 via an adhesive 16. The adhesive 16 has a smaller refractive index than the glass core 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for connecting optical fibers or optical fibers and optical elements.

  In recent years, the use of an optical fiber having a glass core has been developed and studied for an optical communication system for automobiles.

  As an optical fiber having a glass core, there are those called GOF (Glass Optical Fiber) in which a glass core is coated with a glass clad and PCS (Plastic Clad Silica) in which a glass core is coated with a resin clad. For an optical communication system for automobiles, it is generally appropriate to use PCS having a large core diameter.

  When such an optical cable containing PCS is fixed with a ferrule of an optical connector or the like, the resin clad and the inner peripheral surface of the ferrule are bonded with an adhesive at the tip of the ferrule, and further, the resin around the PCS at the middle of the ferrule The coating and the inner peripheral surface of the ferrule are bonded with an adhesive or the like.

  A technique for fixing the optical fiber together with the clad to the optical fiber fixing portion with a resin is disclosed in Patent Document 1, for example.

JP 2004-85613 A

  However, in the PCS as described above, the adhesion between the glass core and the resin clad is poor, and the difference in thermal expansion coefficient between the two is large. For this reason, in the configuration in which the optical cable including the PCS is fixed to the ferrule as described above, when a thermal shock is applied to the PCS, the resin cladding and the surrounding resin coating are shrunk in a state where the glass core and the resin cladding are separated. End up. As a result, the glass core that is not fixed to the ferrule is projected from the tip of the ferrule. In this case, there is a possibility that the glass core hits a photoelectric converter or the like facing the ferrule and hinders optical coupling.

  Accordingly, an object of the present invention is to prevent the core from protruding in an optical fiber including the core.

  An optical fiber connecting device according to the present invention includes an optical fiber having a core and a clad covering the core, and a fiber fixing member having a fiber fixing surface for fixing the optical fiber at a fixed position and posture. The core is exposed at the tip of the optical fiber, and the exposed core is bonded to the fiber fixing surface via an adhesive.

  The fiber fixing member is a member formed in a substantially cylindrical shape into which the optical fiber can be inserted and disposed, and the core exposed at the tip of the optical fiber is attached to the inner peripheral portion of the fiber fixing member. It may be bonded via.

  Furthermore, the adhesive may have a refractive index smaller than that of the core.

  According to the optical fiber connecting device of the present invention, an optical fiber having a core and a clad covering the core, a fiber fixing member having a fiber fixing surface for fixing the optical fiber at a fixed position and posture, Since the core is exposed at the tip of the optical fiber and the exposed core is bonded to the fiber fixing surface via an adhesive, the core itself is at a fixed position and a fixed posture with respect to the fiber fixing member. Retained. For this reason, even when the core and the surrounding clad are peeled off by thermal shock or the like and the clad is shrunk, the core can be effectively prevented from protruding.

  In this case, the fiber fixing member is a member formed in a substantially cylindrical shape into which the optical fiber can be inserted and disposed, and the core exposed at the tip of the optical fiber is an inner peripheral portion of the fiber fixing member. If the adhesive is adhered to the optical fiber, the optical fiber can be effectively prevented from protruding from the ferrule tip.

  In this case, if the adhesive has a refractive index smaller than the refractive index of the core, leakage of light at the bonded portion can be effectively prevented.

  Hereinafter, an optical connector according to an embodiment of the present invention will be described. FIG. 1 is an explanatory view showing an optical connector.

  The optical connector 20 optically couples the optical fiber 12 to the optical element 18 by being connected to the optical connector 30 on the other side while holding the end portion of the optical fiber cord 10. This optical connector 20 is typically used in an optical communication system such as a vehicle where the thermal environment is severe.

  Here, the optical fiber cord 10 is obtained by coating an optical fiber 12 with an opaque resin coating portion 11. The optical fiber 12 is obtained by coating a glass core 13 with a transparent resin clad 14 and is called a so-called PCS (Plastic Clad Silica). Of course, like a general optical fiber, the refractive index of the resin cladding 14 is smaller than the refractive index of the glass core 13.

  The counterpart optical connector 30 includes a connector housing 32 having an element housing portion 34 that holds the optical element 18, and a sleeve portion 36 that guides the ferrule 22 toward the optical element 18.

  In the element accommodating portion 34, the optical element 18 such as a light emitting element or a light receiving element is accommodated and held in a predetermined posture. Then, in a state where the optical connector 30 is mounted and fixed on a predetermined circuit board 38, the terminal portions 18b of the optical element 18 are electrically connected to a wiring pattern formed on the circuit board 38 by appropriate soldering or the like.

  The sleeve portion 36 is formed so as to extend forward from the optical coupling surface 18 a that is the light emitting surface or the light receiving surface of the optical element 18. Then, by inserting the ferrule 22 into the sleeve portion 36, the distal end surface of the glass core 13 and the optical coupling surface 18a at the distal end portion of the sleeve portion 36 are arranged to face each other. As a result, the optical fiber 12 and the optical element 18 are optically coupled.

  The optical connector 20 includes a ferrule 22 as a fiber fixing member and a connector housing 26. The ferrule 22 holds the end of the optical fiber 12. The connector housing 26 is made of resin or the like, and has a function of, for example, maintaining a connection state with the counterpart optical connector 20.

  The ferrule 22 and the connector housing 26 may be integrally formed, or the ferrule 22 and the connector housing 26 are formed separately, and the ferrule 22 is axially disposed with respect to the connector housing 26. It is also possible to have a configuration in which the movable member is movable within a predetermined range along and is held in a state of being biased toward the optical connector 30 on the other side.

  More specifically, the ferrule 22 is formed of resin, metal, or the like, and is formed in a substantially cylindrical shape into which the optical fiber 12 can be inserted and arranged. A small-diameter portion 23a is formed in the end portion of the ferrule 22 on the side inserted into the sleeve portion 36, and a large-diameter portion 23c is formed in the end portion on the opposite side. The large-diameter portion 23c is formed to have a diameter that allows the resin-coated portion 11 to be inserted and disposed, and the small-diameter portion 23a has a smaller diameter than the large-diameter portion 23c and has a diameter that allows the optical fiber 12 to be inserted and disposed. . A tapered portion 23b is interposed between the large diameter portion 23c and the small diameter portion 23a, and the diameter is gradually reduced from the large diameter portion 23c toward the small diameter portion 23a.

  The optical fiber cord 10 is fixedly held to the ferrule 22 with the following configuration.

  That is, the resin coating portion 11 is peeled over a predetermined length at the end of the optical fiber cord 10 and the resin cladding 14 is exposed. Further, the exposed end portion of the resin clad 14 is further peeled over a predetermined length, so that the glass core 13 is exposed at the tip end portion of the optical fiber 12. In addition, it is preferable that the exposed length of the glass core 13 is as short as possible within a range in which the fixing strength of the glass core 13 can be sufficiently secured.

  The end portion of the optical fiber cord 10 is inserted into the ferrule 22 from the large diameter portion 23c side, and the exposed glass core 13 portion and the exposed resin clad 14 portion are inserted and disposed in the small diameter portion 23a. The covering portion 11 is inserted into the large diameter portion 23c.

  In such an insertion arrangement state, the glass core 13 exposed at the tip is bonded to the inner peripheral portion of the small diameter portion 23a through the adhesive 16. The adhesive 16 may be applied to the glass core 13 or the small diameter portion 23a before the optical fiber cord 10 is inserted, or after the optical fiber cord 10 is inserted, the small diameter portion 23a and the glass core 13 may be applied. It may be filled in between.

  The adhesive 16 used here is an optical adhesive that is transparent at least in a solidified state. Such an optical adhesive is conventionally known as a material for joining light transmission paths or forming a light transmission path, unlike the use in the present invention. In order to reflect light at the interface between the glass core 13 and the adhesive 16, the refractive index of the adhesive 16 (after curing) is preferably smaller than the refractive index of the glass core 13. In order to obtain an equivalent light propagation characteristic between the adhesive portion and other portions of the adhesive 16, the refractive index (after curing) of the adhesive 16 is substantially the same as the refractive index of the resin cladding 14. preferable.

  Further, the resin coating portion 11 of the optical fiber cord 10 is appropriately bonded to the inner peripheral portion of the large diameter portion 23c with an adhesive 17 or the like. This adhesive 17 is a general adhesive for resin bonding. However, the adhesive 17 may be omitted.

  Then, in the state where the optical fiber cord 10 is fixed to the ferrule 22 as described above, end processing by polishing or the like is performed on the end surface of the glass core 13 at the tip of the ferrule 22.

  When thermal shock or the like due to heat is applied from the surrounding environment to the optical connector 20 configured in this way, the glass core 13 and the resin cladding 14 are peeled off, and the resin cladding 14 is greatly contracted with respect to the glass core 13. It can happen that the Even in that case, since the glass core 13 itself is adhered to the inner peripheral portion of the small-diameter portion 23 a of the ferrule 22 with the adhesive 16, it is possible to effectively prevent the glass core 13 from protruding from the tip of the ferrule 22. Can be prevented. In this case, it is preferable that the resin clad 14 is not bonded to the inner peripheral portion of the small diameter portion 13a so that the resin clad 14 can be freely contracted in the ferrule 22.

  Furthermore, since the adhesive 16 has a refractive index smaller than the refractive index of the glass core 13, it is possible to effectively prevent light leakage at the bonded portion and to reduce the loss of the optical signal as much as possible. be able to.

  In the present embodiment, the case where the fiber fixing member is the substantially cylindrical ferrule 22 has been described. However, the application example of the present invention is not necessarily limited thereto. Even if the optical fiber 12 is fixed in a groove formed in a substantially semi-cylindrical member or the optical fiber 12 is fixed on a plate-like member, the present invention can be applied to the end of the optical fiber 12. The glass core 13 is exposed at the part, and this can be applied as a configuration in which the glass core 13 is adhered to the inner peripheral surface of the groove or the upper surface of the plate-like member via an adhesive.

  In short, in the present invention, when the optical fiber 12 is fixed to a fiber fixing member having a fiber fixing surface for fixing the optical fiber 12 at a fixed position and posture, the glass core 13 is formed at the tip of the optical fiber 12. It includes all configurations that are exposed and that the exposed glass core 13 is bonded to the fiber fixing surface via an adhesive 16.

  Furthermore, in the present embodiment, the optical connector connection structure has been described as a configuration in which an optical fiber and an optical element are detachably optically connected. However, a connector for connecting optical fibers to each other, and other optical connectors The present invention can be applied to various fiber connection devices that fix and optically connect fibers or optical fibers and optical elements.

  Further, the present invention is not limited to the configuration in which the resin cladding 14 is formed on the outer periphery of the glass core 13, and the present invention is applicable to all configurations in which a predetermined core is coated with the cladding and the thermal expansion coefficients of the core and the cladding are different. Is applicable.

It is explanatory drawing which shows the optical connector which concerns on embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical fiber cord 11 Resin coating part 12 Optical fiber 13 Glass core 14 Resin clad 16 Adhesive 18 Optical element 20 Optical connector 22 Ferrule 23a Small diameter part 30 Optical connector

Claims (3)

An optical fiber having a core and a cladding covering the core;
A fiber fixing member having a fiber fixing surface for fixing the optical fiber at a fixed position and posture;
An optical fiber connecting device, wherein the core is exposed at a tip portion of the optical fiber, and the exposed core is bonded to the fiber fixing surface via an adhesive. The optical fiber connection device according to claim 1,
The fiber fixing member is a member formed in a substantially cylindrical shape into which the optical fiber can be inserted and arranged, and a core exposed at a tip portion of the optical fiber is inserted into the inner peripheral portion of the fiber fixing member via the adhesive. Optical fiber connection device that is bonded together. The optical fiber connection device according to claim 1 or 2,
The optical fiber connecting device, wherein the adhesive has a refractive index smaller than that of the core.

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