JP2013125195A - Method for producing optical fiber end structure and optical fiber end structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an optical fiber end structure facilitating an insertion of tip ends of a plurality of single-core optical fibers into a ferrule hole.SOLUTION: The method for producing an optical fiber end structure 1A for optically coupling a multi-core optical fiber with a plurality of single-core optical fibers 12 mutually includes an end aggregation step of bundling the ends of the plurality of single-core optical fibers 12 into an optical fiber bundle 10, interposing liquid in clearances between the plurality of single-core optical fibers 12, and aggregating the ends of the plurality of single-core optical fibers 12 by surface tension of the liquid; an insertion step of inserting the optical fiber bundle 10 into an optical fiber insertion hole 22 of a ferrule 20; and a fixation step of pouring an adhesive 25 in the optical fiber insertion hole 22 and fixing the optical fiber bundle 10 in the optical fiber insertion hole 22.

Description

  The present invention relates to an optical fiber end structure manufacturing method and an optical fiber end structure.

  Patent Document 1 describes an optical coupler for a multi-core optical fiber. In Patent Document 1, a multi-core optical fiber including one core and six cores arranged at intervals of 60 ° around the one core and seven single-core optical fibers are optically coupled to each other. As a method, first, a V-groove having an angle of 60 ° is prepared, ten single-core optical fibers are arranged in the V-groove, and seven single-core optical fibers located near the center of the ten single-core optical fibers are arranged. Optical coupling between a fiber and the multi-core optical fiber is described.

JP 58-14108 A

  In general, optical coupling between optical fibers is performed by abutting ferrules attached to the tip of each optical fiber. Even when each core of a multi-core optical fiber having N cores (N is an integer of 2 or more) and N single-core optical fibers are optically coupled to each other, the tips of the N single-core optical fibers It is desirable that the ferrule attached together and the ferrule attached to the tip of the multi-core optical fiber abut each other.

  However, in order to collect the tip portions of a plurality of single-core optical fibers and attach a ferrule thereto, it is necessary to solve the following problems. Usually, the diameter of the uncoated single core optical fiber is about 40 μm to 50 μm and is extremely thin. Therefore, even if each of the plurality of single core optical fibers is individually inserted into the hole of the ferrule, the single core optical fiber is weak in elasticity, so that insertion is extremely difficult, and there is a high possibility that disconnection will occur during the insertion process. Moreover, in order to relieve such difficulty in insertion, it is necessary to increase the inner diameter of the hole of the ferrule. If the inner diameter of the ferrule hole is large, a large gap is generated between the plurality of single-core optical fibers and the inner surface of the hole. Optical loss between each core of the optical fiber and the plurality of single core optical fibers becomes large.

  The present invention has been made in view of such a problem, and is used to produce an end structure of a plurality of single-core optical fibers for optically coupling a multi-core optical fiber and a plurality of single-core optical fibers to each other. Another object of the present invention is to provide an optical fiber end structure manufacturing method and an optical fiber end structure capable of easily inserting the tip ends of a plurality of single-core optical fibers into ferrule holes.

  In order to solve the above-mentioned problems, a method for producing an optical fiber end structure according to the present invention is a method for producing an optical fiber end structure for optically coupling a multi-core optical fiber and a plurality of single-core optical fibers to each other. The ends of a plurality of single-core optical fibers are bundled to form an optical fiber bundle, and liquid is interposed in the gaps between the plurality of single-core optical fibers, and the ends of the plurality of single-core optical fibers are brought together by the surface tension of the liquid. An end aggregating step for aggregating the optical fiber, an inserting step for inserting the optical fiber bundle into the optical fiber insertion hole of the ferrule, a first adhesive is poured into the optical fiber insertion hole, and the optical fiber bundle is fixed to the optical fiber insertion hole And a fixing step.

  In this optical fiber end structure manufacturing method, before inserting a plurality of single core optical fibers into the optical fiber insertion hole of the ferrule, the ends of the plurality of single core optical fibers are bundled together. By interposing a liquid in the gap, the ends of the plurality of single core optical fibers are aggregated by the surface tension of the liquid. At this time, the ends of the plurality of single-core optical fibers are brought into close contact with each other by the surface tension of the liquid, so that they have the thinnest outer diameter corresponding to the number of single-core optical fibers and are compared with individual single-core optical fibers Thus, an optical fiber bundle having high elasticity can be obtained. Therefore, when this optical fiber bundle is inserted into the optical fiber insertion hole of the ferrule, it can be inserted very easily as compared with the case where a plurality of single core optical fibers are inserted individually. Moreover, since the internal diameter of the optical fiber insertion hole of a ferrule can be made small by this, the clearance gap between an optical fiber bundle and the inner surface of an optical fiber insertion hole can be made small. Therefore, it is possible to suppress the deviation of the plurality of single-core optical fibers with respect to the central axis of the ferrule, and to reduce the optical loss between each core of the multi-core optical fiber and the plurality of single-core optical fibers.

  In addition, the method for manufacturing the optical fiber end structure includes a step of curing the second adhesive by using a second adhesive of the same type or different from the first adhesive as a liquid during the end aggregation process. It may be further characterized in that it is further included between the end aggregation process and the insertion process. In this method, since the optical fiber bundle is fixed by the second adhesive and then inserted into the optical fiber insertion hole, the optical fiber bundle can be further easily inserted into the optical fiber insertion hole. Note that “curing” in this step means that the viscosity of the second adhesive becomes relatively high before and after the step.

  Moreover, the manufacturing method of the optical fiber end structure may be characterized in that the surfaces of the plurality of single-core optical fibers are made of glass, and the second adhesive contains an aqueous sodium silicate solution. Sodium silicate aqueous solution (so-called water glass) has relatively low wettability to glass. Therefore, when the surface of the single core optical fiber is made of glass, the use of the sodium silicate aqueous solution as the second adhesive makes it difficult for the second adhesive to remain on the surface of the optical fiber bundle. It is possible to easily insert the optical fiber bundle.

  In addition, in the method of manufacturing the optical fiber end structure, the relative position between the optical fiber bundle and the ferrule is set so that the central axis of the optical fiber bundle approaches the central axis of the ferrule in a plane intersecting the longitudinal direction of the optical fiber bundle. An alignment process for adjustment may be further included after the insertion process. By further including such a process, the deviation of the plurality of single-core optical fibers with respect to the central axis of the ferrule is more effectively suppressed, and the optical loss between each core of the multi-core optical fiber and the plurality of single-core optical fibers is reduced. Further reduction can be achieved. Further, by further including such a step, there is almost no problem of optical loss even if the inner diameter of the optical fiber insertion hole is increased. Therefore, the optical fiber with respect to the optical fiber insertion hole is increased by increasing the inner diameter of the optical fiber insertion hole. The ease of inserting the bundle can be further enhanced.

  Further, the method for manufacturing the optical fiber end structure may further include a step of drying the liquid between the insertion step and the fixing step. In this way, by drying the liquid after inserting the optical fiber bundle into the optical fiber insertion hole, the first adhesive is poured into the gap between the single core optical fibers in the subsequent fixing step, and the single core optical fibers are connected to each other. Can be fixed. In this case, the liquid may be volatile, or may contain water or alcohol.

  In addition, in the method of manufacturing the optical fiber end structure, in the end aggregation step, seven single core optical fibers having the same outer diameter are bundled to form an optical fiber bundle, and the seven single core optical fibers are formed. One of them may be arranged at the center of the optical fiber bundle. Such an arrangement of the single core optical fibers is an arrangement in which the ratio (density) of the optical fibers in the cross-sectional area of the optical fiber bundle is extremely high, and is preferably realized by the above-described end aggregation process. By providing the optical fiber bundle with such a configuration, an optical fiber end structure capable of optical coupling with a multi-core optical fiber in which six cores are arranged at equal intervals around the central core is provided. it can.

  The method for producing an optical fiber end structure is characterized in that an optical fiber bundle is configured so as to include one or a plurality of unit structures in which three single core optical fibers are in contact with each other during the end aggregation process. It is good. Such an arrangement of the single core optical fibers is an arrangement in which the ratio (density) of the optical fibers in the cross-sectional area of the optical fiber bundle is extremely high, and is preferably realized by the above-described end aggregation process. Since the optical fiber bundle has such a configuration, the outer diameter of the optical fiber bundle is reduced, so that the optical fiber bundle can be easily inserted into the optical fiber insertion hole.

  An optical fiber end structure according to the present invention is an optical fiber end structure manufactured by any one of the above methods, and an optical fiber bundle formed by aggregating the ends of a plurality of single core optical fibers, and an optical fiber And a ferrule having an optical fiber insertion hole into which the fiber bundle is inserted and fixed, and the difference between the outer diameter of the optical fiber bundle and the inner diameter of the optical fiber insertion hole is greater than 0 μm and less than 5 μm. According to the knowledge of the present inventor, for example, when a plurality of single core optical fibers having a diameter of 40 μm to 50 μm are individually inserted into the optical fiber insertion hole, the inner diameter of the optical fiber insertion hole needs to be at least 5 μm (for example, about 6 μm). It becomes. On the other hand, according to the manufacturing method of the optical fiber end structure described above, a plurality of single core optical fibers can be easily inserted into the optical fiber insertion hole even if the inner diameter of the optical fiber insertion hole is less than 5 μm. .

  In the optical fiber end structure, the gap between the plurality of single-core optical fibers is filled with the second adhesive, and the gap between the optical fiber bundle and the ferrule is different from the second adhesive. It may be filled with an adhesive.

  According to an optical fiber end structure manufacturing method and an optical fiber end structure according to the present invention, an end structure of a plurality of single core optical fibers for optically coupling a multicore optical fiber and a plurality of single core optical fibers to each other is provided. When manufacturing, the tip portions of a plurality of single core optical fibers can be easily inserted into the holes of the ferrule.

FIG. 1 is a perspective view showing an appearance of an optical fiber end structure manufactured by a manufacturing method according to an embodiment of the present invention. FIG. 2 is an enlarged view of a cross section taken along line II-II of the optical fiber end structure shown in FIG. FIG. 3A is a diagram showing a configuration in which three single-core optical fibers are arranged so as to contact each other. FIG. 3B is a diagram showing a form in which four single-core optical fibers are arranged in a diamond shape. FIG. 3C is a diagram showing a form in which 12 optical fibers are further arranged around 7 single-core optical fibers. FIG. 4 is a perspective view showing a state where seven single-core optical fibers and multi-core optical fibers are optically coupled to each other. FIG. 5 is a flowchart showing a method of manufacturing the optical fiber end structure according to the first method. Fig.6 (a) is a figure which shows an example of an edge part aggregation process and a hardening process roughly. FIG. 6B and FIG. 6C are diagrams showing examples of the shape of the holes of the jig. FIG. 7 is a diagram schematically showing another example of the end aggregation process. FIG. 8 is a flowchart showing a method of manufacturing the optical fiber end structure according to the second method. FIG. 9 is a flowchart showing a method of manufacturing the optical fiber end structure according to the third method. FIG. 10 is a diagram schematically showing the state of the alignment process.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical fiber end structure manufacturing method and an optical fiber end structure embodiment according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective view showing an appearance of an optical fiber end structure 1A manufactured by a manufacturing method according to an embodiment of the present invention. 2 is an enlarged view of a cross section taken along line II-II of the optical fiber end structure 1A shown in FIG. As shown in FIGS. 1 and 2, the optical fiber end structure 1 </ b> A of the present embodiment is an optical fiber configured by bundling the end portions of a plurality (seven in this embodiment) of single-core optical fibers 12. A bundle 10 and a ferrule 20 attached to the optical fiber bundle 10 are provided.

  The optical fiber bundle 10 is formed by aggregating and adhering a plurality of single-core optical fibers 12 each having a single core 12a and a cladding 12b provided around the core 12a. As the single-core optical fiber 12, a configuration such as a plastic optical fiber made of plastic in addition to a glass fiber made of quartz glass can be adopted. Specifically, one of the seven single-core optical fibers 12 having the same outer diameter is disposed in the central portion, and the remaining six single-core optical fibers 12 are disposed around the single-core optical fiber in the central portion. It arrange | positions so that the optical fiber 12 may be touched and it may mutually contact. Such an arrangement is such that the ratio of the single-core optical fiber 12 to the cross-sectional area of the optical fiber bundle 10 (the existence density of the optical fiber bundle 10) is highest in a cross section perpendicular to the longitudinal direction of the optical fiber bundle 10. (Closest arrangement). The close-packed arrangement of the plurality of single-core optical fibers 12 is not limited to such a form, and for example, a form in which three single-core optical fibers 12 are arranged so as to contact each other as shown in FIG. Alternatively, as shown in FIG. 3 (b), four single-core optical fibers 12 are arranged in a diamond shape, or around the seven single-core optical fibers 12 as shown in FIG. 3 (c). Further, a configuration in which 12 optical fibers are further arranged is included in the close-packed arrangement. That is, the close-packed arrangement mentioned here is an arrangement including one or a plurality of unit structures 14 in which three single-core optical fibers 12 are in contact with each other. For example, in the form shown in FIG. 3B includes two unit structures 14, and the form shown in FIG. 2 includes six unit structures 14 (FIG. 2). And FIG. 4 shows only one unit structure 14).

  Please refer to FIG. 1 and FIG. 2 again. The ferrule 20 is a substantially cylindrical member made of, for example, zirconia or metal, and has an optical fiber insertion hole 22 extending along the central axis thereof. The optical fiber insertion hole 22 penetrates from one end surface 20a of the ferrule 20 to the other end surface 20b, and a cross section perpendicular to the penetrating direction is circular. The optical fiber bundle 10 described above is inserted into the optical fiber insertion hole 22 and is fixed by an adhesive 25. The end face of the optical fiber bundle 10 is disposed so as to be flush with one end face 20a of the ferrule 20, and the plurality of single core optical fibers 12 extend rearward from the other end face 20b. In a certain form, the difference between the inner diameter D1 of the optical fiber insertion hole 22 and the outer diameter D2 of the optical fiber bundle 10 (that is, the width of the gap between the inner surface of the optical fiber insertion hole 22 and the surface of the optical fiber bundle 10) is , Larger than 0 μm and smaller than 5 μm. The outer diameter D2 of the optical fiber bundle 10 composed of the seven single core optical fibers 12 is equal to the sum of the outer diameters of the three single core optical fibers 12.

  When the plurality of single-core optical fibers 12 and the multi-core optical fiber are optically coupled, one end face 20a of the ferrule 20 described above and the end face of another ferrule attached to the tip of the multi-core optical fiber come into contact with each other. . Here, FIG. 4 is a perspective view showing a state in which the seven single-core optical fibers 12 and the multi-core optical fiber 30 are optically coupled to each other. In FIG. 4, there are gaps between the seven single-core optical fibers 12 and the multi-core optical fibers 30 for easy understanding, but actually, the single-core optical fibers 12 and the multi-core optical fibers 30 Are preferably close to each other.

  As shown in FIG. 4, the optical fiber bundle 10 composed of the ends of seven single-core optical fibers 12 is preferably optically coupled to a multi-core optical fiber 30 having seven cores. The multi-core optical fiber 30 has one central core 30a and six peripheral cores 30b arranged at equal intervals on the circumference centered on the central core. The distance between the center of the central core 30 a and the center of the peripheral core 30 b and the distance between the centers of the adjacent peripheral cores 30 b are equal to the outer diameter of the single core optical fiber 12. The central core 30 a is optically coupled to the core of one single core optical fiber 12 disposed at the center of the optical fiber bundle 10, and the peripheral core 30 b is the other six cores excluding the single core optical fiber 12. The single core optical fiber 12 is optically coupled to each core.

  Hereinafter, a method of manufacturing the optical fiber end structure 1A having such a configuration will be described. In the present embodiment, there are three methods for producing the optical fiber end structure 1A, which are referred to as a first method, a second method, and a third method, respectively.

<First method>
FIG. 5 is a flowchart showing a manufacturing method of the optical fiber end structure 1A according to the first method. In this first method, first, end portions of a plurality of single-core optical fibers 12 are bundled to form an optical fiber bundle 10, and an adhesive is interposed in a gap between the plurality of single-core optical fibers 12, and the surface of the adhesive The ends of the plurality of single core optical fibers 12 are aggregated by tension (end aggregation step S11). The adhesive used at this time is the second adhesive in the present embodiment. When the surfaces of the plurality of single core optical fibers 12 are made of quartz glass (typically, the plurality of single core optical fibers 12 are This adhesive is, for example, an aqueous sodium silicate solution (water glass).

  Various types of adhesives are applied as the adhesive for aggregating the ends of the plurality of single core optical fibers 12, and in addition to the above-mentioned sodium silicate aqueous solution (water glass), acrylic, epoxy, silicone A system adhesive may be used. In addition, the adhesive preferably has a relatively low viscosity, and particularly preferably 100 cP (centipoise) or less.

  Subsequently, the adhesive disposed in the gap between the plurality of single core optical fibers 12 is cured (curing step S12). “Curing” in this step means that the viscosity of the adhesive after the step is relatively higher than that before the step, and is a concept including a state where the adhesive is not completely hardened. At this time, the optical fiber bundle 10 is preferably held by a jig in a state in which ends of the plurality of single core optical fibers 12 are aggregated.

  Specific examples of the end aggregation step S11 and the curing step S12 include the following methods. Fig.6 (a) is a figure which shows roughly an example of edge part aggregation process S11 and hardening process S12. In the method shown in FIG. 6A, a plurality of single core optical fibers 12 are bundled and arranged on a jig 50 having a flat surface, and a covering portion 12c of the plurality of single core optical fibers 12 is provided. Individually insert (or clamp) the holes in the jig 52. FIG. 6B and FIG. 6C are cross-sectional views illustrating examples of the shape of the holes included in the jig 52. As shown in FIG. 6B, the cross-sectional shape of the hole 52a of the jig 52 is a shape corresponding to the cross-sectional shape of the optical fiber bundle 10 (for example, when the number of single-core optical fibers 12 is seven). Hexagon) is preferred. Or as FIG.6 (c) shows, the hole 52b of the jig | tool 52 may be formed in multiple places according to the number and arrangement | positioning of the single core optical fiber 12. FIG. By using such a jig 52, the end portions of the plurality of single core optical fibers 12 can be easily aggregated with a desired arrangement.

  FIG. 7 is a diagram schematically showing another example of the end portion aggregating step S11. In the method shown in FIG. 7, first, as shown in FIG. 7A which is a side sectional view and FIG. 7B which shows the III-III section, it is more than the optical fiber insertion hole 22 of the ferrule 20. A jig 60 having a sufficiently wide hole 62 is prepared, and the end portions of the plurality of single core optical fibers 12 are individually inserted into the holes 62 of the jig 60. Then, a low viscosity adhesive 64 is applied to the plurality of single core optical fibers 12. Then, as shown in FIG. 7C and FIG. 7D showing the IV-IV cross section, the adhesive 64 spreads into the hole 62 due to capillary action, and a plurality of the tensions due to the surface tension of the adhesive 64. The ends of the single core optical fiber 12 are aggregated. Thereafter, the plurality of single core optical fibers 12 are pulled out from the holes 62. As shown in FIG. 7 (e) and FIG. 7 (f) showing the VV cross section, the end portions of the plurality of single-core optical fibers 12 maintain the aggregated state even after being pulled out from the hole 62, and remain as they are. The optical fiber bundle 10 is formed by curing the adhesive.

  Refer to FIG. 5 again. Subsequently, the optical fiber bundle 10 is inserted into the optical fiber insertion hole 22 of the ferrule 20 (insertion step S13). Since the optical fiber bundle 10 is fixed with the minimum outer diameter by the end aggregation step S11 and the curing step S12, the light having only a gap of about 0 to 5 μm between the outer peripheral surface of the optical fiber bundle 10 The optical fiber bundle 10 can also be easily inserted into the fiber insertion hole 22.

  Subsequently, an adhesive is poured into the optical fiber insertion hole 22 to fix the optical fiber bundle 10 to the optical fiber insertion hole 22 (adhering step S14). Since another adhesive has already been interposed in the gap between the plurality of single-core optical fibers 12 constituting the optical fiber bundle 10 by the end aggregation process S11, the adhesive used in this process is mainly It flows between the outer peripheral surface of the optical fiber bundle 10 and the inner surface of the optical fiber insertion hole 22.

  The adhesive used in the fixing step S14 is the first adhesive in the present embodiment, and may be the same type (or the same) as the adhesive used in the end aggregation step S11. Different types may be used. As the adhesive in this step, for example, an acrylic, epoxy, or silicone adhesive is preferably used. Through the above steps, the optical fiber end structure 1A according to the present embodiment is manufactured.

<Second method>
FIG. 8 is a flowchart showing a manufacturing method of the optical fiber end structure 1A according to the second method. In this second method, first, the ends of a plurality of single core optical fibers 12 are bundled to form an optical fiber bundle 10, and a liquid (different from the adhesive) is interposed in the gap between the plurality of single core optical fibers 12. Thus, the ends of the single core optical fibers 12 are aggregated by the surface tension of the liquid (end aggregation process S21). As an example of a specific method, a jig 60 having a hole 62 sufficiently wider than the optical fiber insertion hole 22 of the ferrule 20 is prepared in the same manner as the method shown in FIG. The end portions of the plurality of single core optical fibers 12 are individually inserted into 62. And after pouring the said liquid in this hole 62, it is good to pull out the edge part of the several single core optical fiber 12 from this hole 62. FIG. The cross-sectional shape of the hole 62 of the jig 60 is preferably circular or hexagonal (when the number of single core optical fibers 12 is seven). For example, the end portions of the plurality of single core optical fibers 12 can be suitably aggregated by such a method.

  As the liquid for aggregating the ends of the plurality of single core optical fibers 12, those having relatively low viscosity are preferable, and various kinds of liquids are applied. Examples of the liquid used in this step include water, liquids containing alcohol solvents, volatile liquids (hydrocarbon solvents, ester solvents, ketone solvents, ether solvents, etc.), and these Mixtures are preferred. Water and alcohol solvents have the advantage of high surface tension while taking a long time for the drying process. Moreover, if a volatile liquid is used, a drying process can be shortened. That is, the type of liquid and the mixing ratio may be changed as appropriate according to the manufacturing process.

  Examples of the alcohol solvent include methanol, ethanol, butanol, IPA (isopropyl alcohol), normal propyl alcohol, butanol, isobutanol, TBA (tertiary butanol), butanediol, ethylhexanol, and benzyl alcohol. Examples of ester solvents include ethyl acetate, methyl acetate, butyl acetate, methoxybutyl acetate, cellosolve acetate, amyl acetate, normal propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, and butyl lactate. Examples of the hydrocarbon solvent include toluene, xylene, solvent naphtha, normal hexane, isohexane, cyclohexane, methylcyclohexane, normal heptane, isooctane, and normal decane. Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, DIBK (diisobutyl ketone), cyclohexanone, and DAA (diacetone alcohol). Examples of the ether solvent include methyl cellosolve, cellosolve, butyl cellosolve, dioxane, MTBE (methyl tertiary butyl ether), and butyl carbitol.

  Subsequently, the optical fiber bundle 10 is inserted into the optical fiber insertion hole 22 of the ferrule 20 (insertion step S22). Since the optical fiber bundle 10 is gathered with the minimum outer diameter by the above-described end aggregation step S21, the optical fiber insertion hole 22 having a gap of about 0 to 5 μm between the optical fiber bundle 10 and the outer peripheral surface. In contrast, the optical fiber bundle 10 can be easily inserted.

  Subsequently, the liquid is dried in a state where the optical fiber bundle 10 is inserted into the optical fiber insertion hole 22 (drying step S23). In this step, unlike the curing step S12 in the first method, drying is performed to remove the liquid from the gaps between the plurality of single core optical fibers 12. By removing the liquid, gaps between the plurality of single core optical fibers 12 become air gaps. Therefore, the end portions of the plurality of single core optical fibers 12 aggregated in the end portion aggregation step S21 are once separated from each other.

  Subsequently, an adhesive is poured into the optical fiber insertion hole 22 to fix the optical fiber bundle 10 to the optical fiber insertion hole 22 (adhering step S24). Since the gap between the plurality of single-core optical fibers 12 constituting the optical fiber bundle 10 is a gap as described above, the adhesive used in this step is the outer peripheral surface of the optical fiber bundle 10 and the optical fiber insertion hole. The air flows not only between the inner surfaces of the optical fibers 22 but also between the plurality of single-core optical fibers 12. The plurality of single core optical fibers 12 once separated from each other in the drying step S23 are aggregated again by the surface tension of the adhesive. The adhesive used in the fixing step S24 is the first adhesive in the present embodiment, and the same adhesive as the end aggregation step S11 and the fixing step S14 in the first method described above is used. The

<Third method>
FIG. 9 is a flowchart showing a manufacturing method of the optical fiber end structure 1A according to the third method. In the third method, first, the end aggregation step S11, the curing step S12, and the insertion step S13 of the first method described above are performed. However, in the insertion step S13, unlike the first method, the optical fiber bundle 10 is inserted into the optical fiber insertion hole 22 having a gap of 2 μm or more and less than 5 μm between the outer peripheral surface of the optical fiber bundle 10. In this case, the optical fiber bundle 10 can be more easily inserted as compared with the first method.

  Subsequently, the relative position between the optical fiber bundle 10 and the optical fiber insertion hole 22 is adjusted so that the central axis of the optical fiber bundle 10 approaches the central axis of the ferrule 20 in a plane intersecting the longitudinal direction of the optical fiber bundle 10. (Alignment step S31). FIG. 10 is a diagram schematically showing the state of the alignment step S31. Specifically, while checking the relative position of the optical fiber bundle 10 with respect to the ferrule 20 in a plane perpendicular to the longitudinal direction of the optical fiber bundle 10 (that is, the central axis direction of the optical fiber insertion hole 22), The relative position is adjusted by moving the fiber bundle 10 (or ferrule 20) in two axial directions (arrow A in the figure) perpendicular to each other in the plane. Note that FIG. 10 shows a jig 61 for holding the optical fiber bundle 10 and moving it in the biaxial direction.

  In one embodiment, the straight edges P1, P2 of the ferrule 20 shown in FIG. 10 are observed by a camera image or the like to measure the outer diameter of the ferrule 20, and the straight edges P3, P4 of the optical fiber bundle 10 are observed to observe the light. The outer diameter of the fiber bundle 10 is measured. Thereafter, the amount of eccentricity may be obtained by measuring the distance between the straight edge P1 and the straight edge P3 and the distance between the straight edge P2 and the straight edge P4. Alternatively, the amount of eccentricity may be obtained by measuring the distance between the intersection of the straight edges P3 and P5 and the straight edge P1, and the distance between the intersection of the straight edges P4 and P6 and the straight edge P2.

  After the alignment step S31 described above, the fixing step S14 of the first method described above is performed. In the fixing step S14, after pouring the adhesive into the optical fiber insertion hole 22, the relative position between the optical fiber bundle 10 and the optical fiber insertion hole 22 is finely adjusted again, and then the adhesive is cured. Good. Alternatively, after the adhesive is poured into the optical fiber insertion hole 22, the alignment step S31 may be performed, and then the adhesive may be cured.

  The effect obtained by the manufacturing method of the optical fiber end structure 1A according to the present embodiment described above will be described. In the manufacturing method (first to third methods) of the optical fiber end structure 1 </ b> A according to the present embodiment, before the plurality of single core optical fibers 12 are inserted into the optical fiber insertion holes 22 of the ferrule 20, end aggregation is performed. In steps S11 and S21, the ends of the plurality of single-core optical fibers 12 are bundled, and liquid is interposed in the gaps between the plurality of single-core optical fibers 12, and the ends of the plurality of single-core optical fibers 12 are brought together by the surface tension of the liquid. Agglomerate. At this time, the ends of the plurality of single core optical fibers 12 are brought into close contact with each other due to the surface tension of the liquid, and therefore have the thinnest outer diameter corresponding to the number of single core optical fibers 12 and each single core optical fiber 12. As a result, the optical fiber bundle 10 having higher elasticity can be obtained. Therefore, when the optical fiber bundle 10 is inserted into the optical fiber insertion hole 22 of the ferrule 20 in the insertion steps S13 and S22, it is very easily inserted as compared with the case where a plurality of single core optical fibers 12 are individually inserted. be able to. In addition, since the inner diameter of the optical fiber insertion hole 22 of the ferrule 20 can be reduced, the gap between the optical fiber bundle 10 and the inner surface of the optical fiber insertion hole 22 can be reduced. Therefore, the deviation of the central axis of the optical fiber bundle 10 with respect to the central axis of the ferrule 20 is suppressed, and the optical loss between the cores 30a and 30b of the multi-core optical fiber 30 and the cores 12a of the plurality of single-core optical fibers 12 is reduced. be able to.

  In addition, as in the first or third method of the present embodiment, in the end portion aggregation step S11, the same or different adhesive as that used in the fixing step S14 is used, and curing is performed to cure the adhesive. It is preferable to implement process S12 between edge part aggregation process S11 and insertion process S13. In this method, since the optical fiber bundle 10 is hardened with the second adhesive and then inserted into the optical fiber insertion hole 22, the optical fiber bundle 10 can be inserted into the optical fiber insertion hole 22 more easily.

  In order to easily insert the optical fiber bundle 10 into the optical fiber insertion hole 22, it is preferable that no adhesive remains on the surface of the optical fiber bundle 10. This is because the difference between the outer diameter of the optical fiber bundle 10 and the inner diameter of the optical fiber insertion hole 22 can be made closer. From this point of view, the adhesive preferably has low wettability with the surface of the single core optical fiber 12. For example, when the surfaces of the plurality of single core optical fibers 12 are made of glass, the adhesive used in the fixing step S14 is preferably an aqueous solution diluted with water, and includes an aqueous sodium silicate solution (so-called water glass). Is preferred. The adhesive aqueous solution has low wettability with respect to the water used for dilution with respect to glass. Therefore, when the surface of the single core optical fiber 12 is made of glass, the adhesive hardly remains on the surface of the optical fiber bundle 10, The optical fiber bundle 10 can be easily inserted into the optical fiber insertion hole 22. In the case of an aqueous sodium silicate solution, it is preferable that 80% by weight or more of dilution water is contained. By doing so, the gap between the plurality of single core optical fibers is filled with the second adhesive, and the gap between the optical fiber bundle and the ferrule is different from the second adhesive. An optical fiber end structure can be created that is characterized by being filled with an agent.

  Further, as in the third method of the present embodiment, in addition to the end portion aggregation step S11 and the insertion step S13, the alignment step S31 may be further performed. By performing the alignment step S31, the deviation of the center axis of the optical fiber bundle 10 with respect to the center axis of the ferrule 20 is more effectively suppressed, and the cores 30a and 30b of the multi-core optical fiber 30 and the plurality of single-core optical fibers 12 Optical loss between each core 12a can be further reduced. Further, by performing the alignment step S31, there is almost no problem of optical loss even if the inner diameter of the optical fiber insertion hole 22 is increased. Therefore, the inner diameter of the optical fiber insertion hole 22 is increased to the optical fiber insertion hole 22. The ease of insertion of the optical fiber bundle 10 can be further enhanced.

  Moreover, like the 2nd method of this embodiment, when using the liquid which is not an adhesive agent in edge part aggregation process S21, you may further perform drying process S23 which dries the liquid. After the optical fiber bundle 10 is inserted into the optical fiber insertion hole 22, the liquid is dried, and then the adhesive is poured into the gap between the single core optical fibers 12 in the subsequent fixing step S24 to fix the single core optical fibers 12 together. be able to.

  Further, in the manufacturing method of the optical fiber end structure 1A described above, the optical fiber bundle 10 is configured by bundling seven single core optical fibers 12 having the same outer diameter in the end aggregation steps S11 and S21. One of the seven single-core optical fibers 12 may be disposed at the center of the optical fiber bundle 10 (see FIG. 2). Such an arrangement of the single core optical fibers 12 is an arrangement in which the ratio (density) occupied by the single core optical fibers 12 in the cross-sectional area of the optical fiber bundle 10 is extremely high, and is preferably used by the end aggregation processes S11 and S21. Realized. The optical fiber bundle 10 having such a configuration allows the optical fiber end structure 1A capable of optical coupling with the multi-core optical fiber 30 in which six cores 30b are arranged at equal intervals around the central core 30a. Can be provided.

  Further, in the manufacturing method of the optical fiber end structure 1A described above, the light is so contained as to include one or a plurality of unit structures 14 in which the three single core optical fibers 12 are in contact with each other in the end aggregation processes S11 and S21. You may comprise the fiber bundle 10 (refer FIG.2 and FIG.3 (a)-FIG.3 (c)). Such an arrangement of the single core optical fibers 12 is an arrangement in which the ratio (density) occupied by the single core optical fibers 12 in the cross-sectional area of the optical fiber bundle 10 is extremely high, and the end aggregation processes S11 and S21 described above are used. It is suitably realized. Since the optical fiber bundle 10 has such a configuration, the outer diameter of the optical fiber bundle 10 is reduced, so that the optical fiber bundle 10 can be easily inserted into the optical fiber insertion hole 22.

  The optical fiber end structure 1A manufactured by the manufacturing method according to the present embodiment includes the optical fiber bundle 10 and the ferrule 20 having the optical fiber insertion hole 22, and the outer diameter of the optical fiber bundle 10 is The difference from the inner diameter of the optical fiber insertion hole 22 is greater than 0 μm and less than 5 μm. For example, when a plurality of single core optical fibers 12 having a diameter of 40 μm to 50 μm are individually inserted into the optical fiber insertion hole 22, the inner diameter of the optical fiber insertion hole 22 is required to be at least 5 μm (for example, about 6 μm). On the other hand, according to the manufacturing method of the optical fiber end structure 1A according to the present embodiment, even if the inner diameter of the optical fiber insertion hole 22 is less than 5 μm, the plurality of single core optical fibers 12 are used as the optical fiber insertion holes 22. Can be inserted easily.

  Further, in the optical fiber end structure 1A manufactured by the first or third method of the present embodiment, the gaps between the plurality of single core optical fibers 12 are filled with the adhesive, and the optical fiber bundle 10 and the ferrule The gap with 20 may be filled with an adhesive different from the adhesive.

  The manufacturing method of the end structure of a plurality of optical fibers and the end structure of the plurality of optical fibers according to the present invention are not limited to the above-described embodiments, and various other modifications are possible.

  DESCRIPTION OF SYMBOLS 1A ... Optical fiber end structure, 10 ... Optical fiber bundle, 12 ... Single core optical fiber, 12a ... Core, 12b ... Cladding, 12c ... Covering part, 14 ... Unit structure, 20 ... Ferrule, 22 ... Optical fiber insertion hole, 25 ... Adhesive, 30 ... Multi-core optical fiber, 50, 52, 60 ... Jig, 62 ... Hole, 64 ... Adhesive.

Claims (11)

A method of fabricating an optical fiber end structure for optically coupling a multi-core optical fiber and a plurality of single-core optical fibers to each other,
The ends of the plurality of single-core optical fibers are bundled to form an optical fiber bundle, and a liquid is interposed in the gap between the plurality of single-core optical fibers, and the ends of the plurality of single-core optical fibers are caused by surface tension of the liquid. An end aggregating step for aggregating parts,
An insertion step of inserting the optical fiber bundle into an optical fiber insertion hole of a ferrule;
A method for producing an optical fiber end structure, comprising: a fixing step of pouring a first adhesive into the optical fiber insertion hole and fixing the optical fiber bundle to the optical fiber insertion hole. In the end aggregation step, a second adhesive that is the same or different from the first adhesive is used as the liquid,
The method for producing an optical fiber end structure according to claim 1, further comprising a step of curing the second adhesive between the end aggregation step and the insertion step. The surfaces of the plurality of single core optical fibers are made of glass,
The method for producing an optical fiber end structure according to claim 2, wherein the second adhesive contains an aqueous sodium silicate solution.   An alignment step of adjusting a relative position between the optical fiber bundle and the ferrule so that a central axis of the optical fiber bundle in a plane intersecting a longitudinal direction of the optical fiber bundle approaches a central axis of the ferrule; The method for producing an optical fiber end structure according to claim 2, further comprising after the inserting step.   2. The method for producing an optical fiber end structure according to claim 1, further comprising a step of drying the liquid between the insertion step and the fixing step.   6. The method of manufacturing an optical fiber end structure according to claim 5, wherein the liquid is volatile.   The method for producing an optical fiber end structure according to claim 5, wherein the liquid contains water or alcohol.   In the end aggregation step, the seven single core optical fibers having the same outer diameter are bundled to form the optical fiber bundle, and one of the seven single core optical fibers is used as the optical fiber. It arrange | positions in the center of a bundle | flux, The manufacturing method of the optical fiber edge part structure as described in any one of Claims 1-7 characterized by the above-mentioned.   8. The optical fiber bundle according to claim 1, wherein the optical fiber bundle is configured so as to include one or a plurality of unit structures in which the three single-core optical fibers are in contact with each other during the end aggregation step. The manufacturing method of the optical fiber end part structure as described in any one. An optical fiber end structure produced by the method according to any one of claims 1 to 9,
An optical fiber bundle formed by aggregating the ends of a plurality of single-core optical fibers;
A ferrule having an optical fiber insertion hole into which the optical fiber bundle is inserted and fixed;
An optical fiber end structure, wherein a difference between an outer diameter of the optical fiber bundle and an inner diameter of the optical fiber insertion hole is greater than 0 μm and less than 5 μm. A gap between the plurality of single-core optical fibers is filled with a second adhesive;
11. The optical fiber end structure according to claim 10, wherein a gap between the optical fiber bundle and the ferrule is filled with a first adhesive different from the second adhesive.