JP2009157146A - Ferrule for optical terminator and method of manufacturing the same, and optical terminator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a ferrule for an optical terminator, which secures a reflection attenuation amount without using special members and without special processing techniques and can be easily manufactured at low cost; a method of manufacturing the same; and an optical terminator having the ferrule. <P>SOLUTION: In the ferrule for the optical terminator which has a clad formed outside an optical fiber core through-hole where an optical fiber core is formed, a transparent resin having a refractive index equal to that of the optical fiber core is heaped up convexly on an end surface for connection junction to be charged in the optical fiber through-hole halfway or wholly from the end surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ferrule for an optical terminator that prevents reflection of signal light at an end face of an unconnected optical fiber connector, a manufacturing method thereof, and an optical terminator.

  In recent years, with the spread of the Internet, optical broadband services using optical fibers have been rapidly introduced. The current mainstream system is called PON (Passive Optical Network). In order to save on-site equipment and optical fiber, fiber 1 from the in-house optical transmission equipment (OLT: Optical Line Terminal) is used. You can communicate with up to 32 users with your heart. In this wiring, an optical splitter for branching the optical fiber is inserted in the middle of the transmission path. In Japan, it is generally placed in two places, inside and outside, with four branches inside and eight branches outside.

  These optical splitters are rarely used at the same time for all terminals, and are usually used gradually as the number of users increases. The unused terminal of this optical splitter has an optical connector plug attached in the office. In addition, from the viewpoint of workability, it is expected that the conventional core wire cut end will shift to the connector outside the office. At the end face of the ferrule of the optical connector plug that is not connected, the signal light transmitted through the optical fiber is reflected by the difference in refractive index between the optical fiber and air. In order to prevent this reflection, an optical terminator is required. The products that are currently on sale are difficult to apply because the price is as high as several thousand yen. The characteristics of the optical terminator are affected by the quality of the connector ferrule to be terminated, but commercially available products usually guarantee a return loss of 40 dB or more.

  Conventional optical terminators include a plug type and a receptacle type. (The receptacle type is sometimes called a jack type or an adapter type.) The plug type is more general, and the present invention belongs to this type. The plug type has a plug structure with a built-in ferrule, and is joined to the target empty connector plug via an adapter. Typical examples of the ferrule in the optical terminator include a method of diffusing light by applying a glass rod having no core, and a method of scattering and absorbing light by applying an optical fiber containing a dopant. This plug-type optical terminator is expensive because it incorporates special optical parts and high-precision parts equivalent to ferrules, end face polishing is essential, and many parts and assembly work are required. In Patent Document 1, a metal dopant is put into an optical fiber core to absorb light. The structure is described.

  As an example of a conventional plug type optical terminator, there is one having a structure described in Patent Document 2. In this example, the capillaries inserted into the zirconia ferrule end face of the optical terminator and the rear end of the zirconia ferrule are polished. In particular, the rear end portion of the zirconia ferrule is characterized by having a polished surface inclined at a predetermined angle or more in order to prevent reflection. For this reason, a polishing process is indispensable. In particular, the rear end portion of the ferrule needs to be managed up to the finished angle of the polished surface, and there is a problem that the manufacturing process increases. Patent Document 3 and Patent Document 4 propose a structure characterized in that a coreless fiber is accommodated in a fine hole of an optical terminator ferrule. In this structure, the light is diffused by the coreless fiber and the non-reflective termination of the light is performed by the light absorption layer around the core. As a problem of this structure, it is indispensable to house and fix the coreless fiber in the ferrule, and the ferrule end face needs to be polished. Therefore, there is a problem of an increase in costs due to an increase in material costs and manufacturing processes.

  Patent Document 5 describes that an end face mounting member is used as an optical terminator having a simple structure, and that the end face mounting member is an adhesive having a refractive index substantially the same as the refractive index of the optical fiber core. ing. However, an end surface mounting member is used.

JP-A-8-334649 JP-A-5-100128 JP 2000-121846 A JP 2003-43264 A JP 2007-279443 A

  As described above, since these conventional optical terminators require special fiber members and many work processes, there is a problem that it is difficult to reduce the cost. Further, polishing of the ferrule end face of the optical terminator is indispensable, which makes it difficult to reduce the price.

  In view of the above problems, the present invention provides a ferrule for an optical terminator that can guarantee an amount of return loss and can be manufactured easily and inexpensively without using a special member or a special processing technique, a manufacturing method thereof, and the ferrule. It is providing the optical terminator provided with.

  The present invention provides a filling portion that is applied to the ferrule end face, spreads by wetting of a resin, especially transparent resin, is formed in a convex shape on the front end surface by surface tension, and is also integrated with an optical fiber core through hole provided in the ferrule by wetting And providing an optical terminator ferrule formed by this method.

  The present invention forms a meniscus interface formed of resin in the fiber core through hole. And the structure which combined this interface and convex shape of the front end surface is provided.

  Specifically, in the ferrule for an optical terminator in which a clad is formed outside an optical fiber core through-hole in which an optical fiber core is formed, a resin having a refractive index equivalent to that of the optical fiber core is used for connector joining. Provided is a ferrule for an optical terminator characterized in that it is convexly formed on an end face and is filled in the middle or all of the optical fiber core through hole from the end face.

  The present invention also provides a ferrule for an optical terminator characterized in that the resin is formed in a convex spherical shape on an end surface for connector connection.

  In the ferrule for an optical terminator in which a clad is formed outside the optical fiber core through-hole in which the optical fiber core is formed, the resin having a refractive index equivalent to that of the optical fiber core is wetted by the optical fiber core through-hole. There is provided a ferrule for an optical terminator having a filling portion formed by filling, and a surface of the filling portion in contact with an air layer in the through hole of the fiber core has a meniscus interface.

  The present invention also provides a ferrule for an optical terminator, wherein the resin is a transparent resin.

  The present invention provides a method for manufacturing an optical terminator ferrule in which a cladding is formed outside an optical fiber core through-hole in which an optical fiber core is formed, and the optical terminator ferrule is held vertically with the end face facing up, A resin having a refractive index equivalent to that of the optical fiber core toward the end surface, a predetermined amount of uncured resin is dropped, and a part of the uncured resin forms a convex shape on the end surface for connector connection, A method for producing a ferrule for an optical terminator is provided, wherein the remaining uncured resin is filled in the middle or all of the optical fiber through hole, and then the uncured resin is cured.

  The present invention provides a method for manufacturing an optical terminator ferrule in which a cladding is formed outside an optical fiber core through-hole in which an optical fiber core is formed, and the optical terminator ferrule is held vertically with the end face down, A resin having a refractive index equivalent to that of the optical fiber core toward the optical fiber core through-hole that opens in the end surface opposite to the end surface, and a predetermined amount of uncured resin is dropped to partially uncured The resin forms a convex shape on the end surface for connector connection through the optical fiber core through hole, and fills the optical fiber through hole with the remaining uncured resin, and then cures the uncured resin. A method for manufacturing a ferrule for an optical terminator is provided.

  The present invention also provides a method for producing a ferrule for an optical terminator, wherein the ferrule for an optical terminator is made of a glass material, and a UV curable resin is used as the resin.

  The present invention also provides a ferrule for an optical terminator manufactured by the above manufacturing method.

  The present invention also provides an optical terminator comprising the ferrule for an optical terminator and a plug housing for accommodating the ferrule.

  As described above, the present invention makes it possible to easily form the ferrule tip surface into a convex shape and a convex spherical shape by utilizing the wetting and surface tension of the uncured resin, and using the optical fiber core through hole. It is possible to easily fill the part of the resin and form an integrated resin end face mounting part, thus guaranteeing the return loss without using special parts or special processing technology, and easy It is possible to provide a ferrule for an optical terminator that can be manufactured inexpensively, a manufacturing method thereof, and an optical terminator provided with the ferrule.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view of a ferrule for an optical terminator showing an embodiment of the present invention. 1, the ferrule 1 for an optical terminator is configured by forming a clad 10 on the outer side of an optical fiber core through-hole 11 in which an optical fiber core is formed, and providing a flange 12.

  The front end of the clad 10 is a ferrule front end surface 13. In this example, the peripheral surface 13A is chamfered and the central surface 13B is substantially flat (flat) so that the entire surface is convex and the resin can be easily applied. It is said. The ferrule tip surface 13 can be a spherical surface. It may not be a spherical surface but may be a flat surface or another curved surface. The rear end of the clad 10 is a ferrule rear end surface 14, which is a flat surface in this example. The ferrule rear end surface 14 may be an inclined surface.

  The optical fiber core through hole 11 is formed as a through hole reaching the ferrule rear end surface 14 from the ferrule front end surface 13. The entrance to the ferrule tip end face 13 of the optical fiber core through-hole 11 is referred to as a tip end entrance 15 and the entrance at the ferrule rear end face 14 is referred to as a rear end entrance.

  In the configuration as described above, in this example, a resin having a refractive index equivalent to that of the optical fiber core is convexly formed on the end surface for connector connection, that is, on a part of the ferrule tip surface 13, Filled from the end surface to the middle of the optical fiber through hole 11 from the optical fiber inlet 15, an integrated resin end surface mounting portion 17 is formed. The resin end face mounting portion 17 is composed of a convex raised portion 18 formed on the ferrule tip end surface 13 and a filling portion 19 that is integrated therewith and reaches the middle of the optical fiber core through hole 11. The portion 18 functions as a reflection attenuation function, and the filling portion 19 is fitted into the optical fiber core through hole 11 and functions as a holding function. Therefore, the optical fiber core through hole 11 functions as a fitting hole. In this example, as shown in FIG. 1, the convex raised portion 18 is formed on a part of the ferrule tip surface 13, but may be formed on the entire ferrule tip surface. As a particularly good shape, it is recommended to have a convex spherical shape. The filling portion 19 functions as a holding function, and it is sufficient that the filling portion 19 is filled up to the middle of the optical fiber through hole 11. However, the filling portion 19 may be filled in the entire optical fiber through hole 11.

  In order to form the resin end face mounting portion 17, a resin having a refractive index equivalent to that of the optical fiber core is used.

  For example, at normal temperature (23 ± 2 ° C.), the refractive index of the resin is preferably within a range of ± 0.05 of the refractive index of the optical fiber core 12. This is because if the optical fiber core 12 is out of the range of ± 0.05, the return loss will be 35 dB or less. If the difference in refractive index is ± 0.03, the return loss can be 40 dB or more. More preferably, the refractive index of the resin is within ± 0.01 of the refractive index of the optical fiber core 12.

In consideration of the influence of the use environment temperature on the return loss, the change in the refractive index of the resin in the temperature range of −40 to 70 ° C. is preferably within ± 0.03.
The resin used for the end face mounting portion 17 has an appropriate tack property and needs to be in close contact with the end face of the optical fiber or the ferrule end face. It is assumed that this adhesive does not cause cohesive failure when the optical fiber or ferrule is pulled apart.

  As such a resin, for example, an acrylic, epoxy, vinyl, ethylene, silicone, urethane, polyamide, fluorine, an adhesive coating solution that has been crosslinked and cured with heat, light, moisture, electron beam, etc. Polyptadiene-based and polycarbonate-based pressure-sensitive adhesives can be applied, and the refractive index, adhesive strength, and wettability can be adjusted, so that it can be optimized according to the material of the counterpart optical fiber or ferrule.

  For example, as the silicone-based pressure-sensitive adhesive, an addition-type silicone pressure-sensitive adhesive coating solution (SD4590, SD4590 / BY24-741 / SRX212 / toluene (blending ratio 100 / 1.0 / 0.9 / 50 (parts by weight)) is used. BY24-741 and SRX212 are those obtained by crosslinking and curing Toray Dow Corning Co., Ltd., and acrylic adhesives include n-butyl acrylate / methyl acrylate / acrylic acid / 2-hydroxyethyl methacrylate. To 100 parts by weight of a 50% ethyl acetate solution of an acrylic resin composed of a polymer (blending ratio = 82/15 / 2.7 / 0.3 (parts by weight)), a crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name) Coronate L) An acrylic adhesive coating solution obtained by mixing 1.0 part by weight is preferably crosslinked and cured. .

  Specifically, it is a UV curable resin that is generally commercially available, and a transparent resin can be employed. Even if it is a resin that is not completely transparent or translucent, or a resin that contains a colored resin or glass filler, as long as light propagates sufficiently and does not generate heat Can be adopted. By using a transparent resin (even if it is translucent), when the light propagates to the resin, the resin can absorb the light and prevent heat generation.

  Quartz glass can be employed as the optical fiber core. A material other than glass such as plastic fiber may be used. When a UV curable resin is used, it is preferable to use a glass material as a material constituting the ferrule. The UV light can be irradiated from the side surface of the ferrule, and the resin inside the ferrule end face and the optical fiber core through hole 11 can be cured by the UV light transmitted through the glass ferrule. Hereinafter, an example using a transparent resin will be described.

  In FIG. 1, the code | symbol 18 is the transparent resin apply | coated to the ferrule front end surface 13, and has a refractive index equivalent to an optical fiber core. A suitable amount of transparent resin is dropped on the ferrule tip surface 13 that is used as the optical connector fitting surface of the ferrule 1 for optical terminator, and the dropped transparent resin is spread on the ferrule tip surface 13 by wetting, and the tip surface is made convex by surface tension. That is, it is a convex spherical shape. The applied transparent resin enters and fills the inside of the optical fiber core through hole 11 by wetting, and the transparent resin forms a meniscus-like interface 20 in the middle of the optical fiber core through-hole 11 by the wetting and spreading process. The meniscus is known as a liquid bridge that can form a minimal gap between objects. When a UV curable resin is used as the transparent resin, the UV resin is used to cure the transparent resin that has reached the interface 20 through the glass ferrule. For this reason, in this embodiment, a glass material that transmits UV light is used for the optical terminator ferrule.

  By curing the transparent resin using UV light in this way, as shown in FIG. 1, the resin end face mounting portion 17 is formed, and the convex raised portion 18 having a convex spherical surface is formed on the ferrule tip surface 13. The optical terminator ferrule 1 is formed which is formed on the ferrule tip end face 13 and is filled into the optical fiber core through hole 11 to form an integrated filling portion 19.

  As described above, when configuring the optical terminal ferrule 1 to be configured, when the transparent resin is dropped and filled on the ferrule tip surface 13 as described above, the transparent resin is filled from the ferrule rear end surface 13, A method of forming a wetting spread on the ferrule tip surface 13 by wetting may be employed.

  In the former case, the optical terminator ferrule 1 is a transparent resin that is held vertically with the ferrule end face 13 facing upward and has a refractive index equivalent to that of the optical fiber core toward the ferrule end face 13, and is an uncured resin. A predetermined amount is dropped, a part of the ineffective resin forms a convex spherical shape on the ferrule tip surface 13 on the end surface for connector connection, and the remaining uncured resin is filled in the middle or all of the optical fiber through hole 11. Then, the ferrule 1 for an optical terminator is configured by a manufacturing method in which the uncured resin is cured thereafter.

  In the latter case, the optical terminator ferrule 1 is held vertically with the ferrule end face 13 down, and toward the optical fiber core through-hole 11 that opens at the end face opposite to the ferrule end face 13. A transparent resin having an equivalent refractive index, in which a predetermined amount of uncured resin is dropped, and a part of the uncured resin protrudes through the optical fiber core through-hole 11 to the ferrule tip surface 13 on the end surface for connector connection. A ferrule 1 for an optical terminator is formed by a manufacturing method in which a spherical shape is formed, the remaining uncured resin is filled into the optical fiber through hole, and then the uncured resin is cured.

  The ferrule 1 for an optical terminator is made of a glass material, and a manufacturing method of an optical termination ferrule using a UV curable resin as a transparent resin can be used.

  According to the present embodiment, since the ferrule tip end surface 13 that is the optical connector fitting end surface of the optical terminator ferrule 1 is formed in a convex spherical shape, it is possible to sufficiently attenuate the light without polishing the ferrule tip end surface 11. Can do. Furthermore, according to the present embodiment, it is easy to make the resin itself have appropriate elasticity, so that a stable bonded state can be obtained. Further, according to the prior art, it has been proposed to prevent reflection of light by obliquely polishing the rear end face 14 of the ferrule 1 for an optical terminator. However, according to the present embodiment, the inside of the optical fiber core through-hole 11 can be prevented. Since the resin can form the interface 20 in a meniscus shape, the reflected light generated in the filling layer 19 of the meniscus interface 20 and the air layer of the optical fiber core through-hole 11 is incident on the optical fiber core again. The rear end surface 14 of the ferrule 1 for an optical terminator can be formed as a plane perpendicular to the penetration direction of the optical fiber core through-hole 11 (vertical direction in the drawing). It is particularly desirable in terms of attenuation of reflected light to use the meniscus-shaped interface 20 in combination with the convex raised portion 18.

  As described above, according to the present embodiment, the optical termination ferrule 1 can be obtained by guaranteeing a good reflection attenuation without requiring a special member, special processing technique, and ferrule end face polishing work, and greatly reducing the manufacturing cost. Can be provided.

FIG. 2 is a partial cross-sectional view showing a configuration of a non-reflective optical terminator 30 employing the optical termination ferrule shown in FIG.
In FIG. 2, an optical terminator 30 includes the optical terminator ferrule 1 described above, a plug frame 33 which is a part of a standard SC type optical connector, a spring 34, a stop ring 35, a knob 36 and a cap 37. Have. The plug housing 38 is attached to the plug frame 33 that houses the ferrule 1 in the optical terminator, the spring 34 that presses the ferrule 1 in the axial direction, the stop ring 35 that fixes the spring 34, and the plug frame 33. And a cap 37 that is provided at the rear end of the knob 36 and closes the rear end surface.

  When the optical terminator is mounted, the end face of the optical connector ferrule to be terminated is adhered to the resin of the raised portion 18 and also to the end face of the optical fiber at the center of the ferrule. The end face of the optical fiber is substantially at the same position as the end face of the ferrule, but the end face of the optical fiber may be slightly recessed by several microns. Even in this case, since the resin is elastically deformed, the air layer is omitted and the resin covers the end face of the optical fiber, and the light from the optical fiber core is transmitted to the resin side without reflection. While passing through the resin in the filling portion 19 filled in the optical fiber core through hole 11, the light spreads and reaches the interface 20 with the air on the opposite side of the resin. Since some light components are absorbed, scattered, or transmitted by the inner surface of the optical fiber core through-hole 12, the light reaching the interface 20 is attenuated. The interface 20 in the through hole 11 becomes a surface having a large curvature due to the surface tension at the time of liquid and the non-uniformity of flow at the inner surface of the through hole, and does not become a surface perpendicular to the optical axis of the optical fiber core. For this reason, the reflected light there is not reflected on the connector fitting end face side but scattered in the other direction.

樹脂の屈折率ｎ_２をｎ_１に一致できれば、計算の上では反射減衰量Ｒ_ｄＢは無限大になる。（現実にはフェルール端面自体の不完全性により６０ｄＢを超えることは困難である。）ただし、ｎ_２は、光ファイバの素材である石英ガラスと比べて、屈折率が温度によって変わりやすい欠点がある。 FIG. 3 is an explanatory diagram of the characteristics of the return loss. FIG. 3 shows a model. The light that has propagated through the core of the optical fiber is partially reflected by the adhesive surface due to the difference in the refractive index between the optical fiber core and the resin, and propagates backward in the core. The light transmitted through the resin is not a problem because there are many means for attenuating as described above, and the reflection on the adhesive surface essentially determines the characteristics. If the refractive index of the optical fiber core is n ₁ and the refractive index of the resin is n ₂ , the return loss R _dB can be calculated by the following equation.

If the refractive index n _{2 of the} resin can match n ₁ , the return loss R _dB becomes infinite in the calculation. (In reality, it is difficult to exceed 60 dB due to the imperfection of the ferrule end face itself.) However, n ₂ has a defect that the refractive index is easily changed depending on the temperature as compared with quartz glass which is a material of an optical fiber. .

  The ferrule 1 for an optical terminator used as the optical connector described above is for a single-core optical fiber. In addition to this, an MT connector for a multi-fiber ribbon is often used, but this embodiment can also be carried out only by making the shape of the hole into a square of the MT connector ferrule. There has been no optical terminator for MT connector ferrules so far, and in the case where non-reflective treatment of the MT connector ferrule end is necessary in experiments or the like, a convenient means such as attaching a paste-like refractive index matching agent to the end face Has been taken. However, this has a problem that the subsequent cleaning is troublesome and the characteristics are unstable.

  Also, in the APC polished connector ferrule for suppressing reflection at the end face of the optical connector, no optical terminator is conventionally attached. In the future, when it is desired to prevent the influence of reflection on the end face of the APC polished connector ferrule as much as possible, the terminator structure of this embodiment is effective.

  The conventional optical terminator has a possibility that the end face of the connector may be damaged at the time of mating if dust is attached to the end face, but the optical terminator 30 of the present embodiment has an advantage that there is no concern about this. Since the resin on the end face of the terminator has an elastic modulus that is orders of magnitude smaller than that of quartz glass, which is an optical fiber material, or zirconia, which is a connector ferrule material, the deformation of this resin causes contact pressure between dust and the connector end face. Is greatly relaxed.

Cross-sectional explanatory drawing of the ferrule which shows one Embodiment of this invention. The fragmentary sectional view which shows one Embodiment of the non-light termination | terminus device of this invention. The characteristic explanatory view of return loss.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ferrule for optical terminators, 10 ... Cladding, 11 ... Optical fiber core through-hole, 12 ... Flange, 13 ... Ferrule front end surface, 14 ... Ferrule rear end surface, 15 ... Ferrule front end surface inlet, 16 ... Ferrule rear end surface inlet, 17 ... resin end face mounting part, 18 ... convex raised part, 19 ... filling part, 20 ... interface, 30 ... optical terminator.

Claims (9)

In the ferrule for optical terminator in which the cladding is formed outside the optical fiber core through-hole in which the optical fiber core is formed,
A resin having a refractive index equivalent to that of an optical fiber core is formed in a convex shape on an end face for connector connection, and is filled in the middle of or through the optical fiber core through hole from the end face. A dexterous ferrule.   2. The ferrule for an optical terminator according to claim 1, wherein the resin is formed in a convex spherical shape on an end surface for connector connection. In the ferrule for optical terminator in which the cladding is formed outside the optical fiber core through-hole in which the optical fiber core is formed,
A resin having a refractive index equivalent to that of the optical fiber core has a filling portion formed by filling the optical fiber core through-hole by wetting, and a surface of the filling portion in contact with the air layer in the fiber core through-hole A ferrule for an optical terminator characterized by comprising a meniscus interface.   4. The ferrule for an optical terminator according to claim 1, wherein the resin is a transparent resin. In the method of manufacturing a ferrule for an optical terminator in which a clad is formed outside an optical fiber core through-hole in which an optical fiber core is formed,
The optical terminator ferrule is held vertically with the end face up, toward the end face, a resin having a refractive index equivalent to that of the optical fiber core, and a predetermined amount of uncured resin is dropped, The uncured resin forms a convex shape on the end surface for connector connection, the remaining uncured resin is filled in the middle or all of the optical fiber through hole, and then the uncured resin is cured. Manufacturing method of ferrule for optical terminator. In the method of manufacturing a ferrule for an optical terminator in which a clad is formed outside an optical fiber core through-hole in which an optical fiber core is formed,
A resin having a refractive index equivalent to that of the optical fiber core toward the optical fiber core through-hole that holds the optical terminator ferrule vertically with the end face down and opens in the end face opposite to the end face. Then, a prescribed amount of uncured resin is dropped, a part of the uncured resin forms a convex shape on the end surface for connector connection through the optical fiber core through hole, and the remaining uncured resin is disposed on the optical fiber. A method for producing a ferrule for an optical terminator, comprising filling the through hole and then curing the uncured resin.   7. The method of manufacturing a ferrule for an optical terminator according to claim 5, wherein the ferrule for the optical terminator is made of a glass material, and a UV curable resin is used as the resin.   The ferrule for optical terminators manufactured by the manufacturing method in any one of Claim 5 to 7.   An optical terminator comprising the ferrule for an optical terminator according to any one of claims 1 to 4 and a plug housing for accommodating the ferrule.

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