JP2843417B2 - Method for manufacturing fiber coupling pipe used in optical coupling circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a fiber-coupling pipe used in a small-size, simple-structure, low-loss collimating optical coupling circuit.

<Problems to be Solved by Conventional Techniques and Inventions> An optical fiber outgoing beam is expanded and converted into a parallel light beam to connect between the two fibers, or to an expanded parallel light portion, such as a prism, a mirror, and an interference film filter. When configuring a so-called micro-optics optical circuit component that realizes functions such as optical branching, optical switching, and wavelength selection by arranging elements, usually, a collimating lens and a condensing lens near an end face of an input / output fiber are arranged. Thus, a collimated light coupling circuit is formed between the opposing optical fibers.

6 (a) and 6 (b) show a conventional collimating light coupling circuit. FIG. 6 (a) shows an example in which a converging rod lens 2A is arranged near the end face of the optical fiber 1A on the incident side and the exit side, respectively, and the substantially parallel light beam 3A formed between the converging rod lenses 2A. Is used to couple the two optical fibers 1A. FIG. 6 (b) uses a spherical lens 2B instead of the converging rod lens 2A, and connects both optical fibers 1B by a substantially parallel light beam 3B formed between the spherical lenses 2B. . Fig. 7 shows an example of an optical connector using these lens coupling systems (A.NCIA, ELECTRONI
CS LETTERS, VOL. 14, No. 16, PP. 511 to 512, 1978), the optical fiber 1C on the incident side and the output side, and the spherical lens 2C close to these are disposed in the optical connector housing 4C. It is. Then, the light beam emitted from the fiber is expanded by the spherical lens 2C and converted into a substantially parallel light beam 3C, and detachable connector connection is performed via the expanded substantially parallel light beam 3C. By configuring such a beam conversion circuit, the increase in connection loss due to misalignment in the optical axis direction between the connectors and in the vertical direction of the optical axis is greatly reduced, and even when minute dust enters between the connectors. Good connection can be obtained without causing loss reduction. FIG. 8 shows another application example, for example, two sets of optical fibers 1D-1, 1D-2 and a focusing rod lens 2D-1,
2D-2 is arranged and these focusing rod lenses 2D-1, 2D-
This is an optical switch in which a parallelogram prism 6D housed in a prism holder 5D is arranged between the optical fiber 2 and a converging rod lens 2D provided in the vicinity of the optical fiber 1D. The light beam is switched by moving the parallelogram prism 6D into and out of the parallel light beam 3D formed between the converging rod lenses 2D and 2D-1 and 2D-2 (for example, T. AOYAMA et. al. 4th ECQC PP.383-391, 1978).

Various other types of micro-optics optical circuit components of this type have been proposed, but all use a converging rod lens or a spherical lens, and thus are restricted in reducing the size and cost of the optical circuit. Also, since the above-mentioned lens coupling system is a one-to-one optical coupling system, the increase in insertion loss with respect to the optical axis deviation between the lenses is gradual, but the optical axis between the fiber and the lens disposed near the tip thereof is small. Strict dimensional accuracy is required at the time of alignment and sometimes when a single mode fiber is used, and a high-precision processing member is required, and a component assembling operation becomes complicated.

In order to reduce the size and cost of the optical coupling system in place of these individual lens coupling systems, an attempt has recently been made to enlarge the beam with only an optical fiber and to make the beam emitted from the fiber closer to a parallel light beam. . Figures 9 to 12
Figure shows examples of these proposals. As is well known, in the connection of single mode fibers, by increasing the output beam spot size of these fibers, it is possible to suppress an increase in connection loss due to axis deviation in the optical axis direction and in the direction perpendicular to the optical axis.

FIG. 9 shows a proposal in which the single mode fiber 11 is locally heated to several hundreds of degrees to diffuse the Ge dopant in the core portion of the fiber from the core center to the cladding direction to increase the spot size of the fiber (Shiraishi et al. 1989, IEICE Spring National Convention C-451, Kawakami, IEICE OCS88-1). As shown in FIG. 3A, the Ge dopant is diffused from the center of the core toward the outer periphery of the clad in the core portion of the single mode fiber 11 by heating to form a dope diffusion region 12, and the propagating light beam is continuously emitted. It is enlarged. This beam expansion makes it possible to configure a low-loss optical circuit component even if an optical element such as the isolator magneto-optical element 13 is arranged in the gap between the opposing fibers. FIG. 4B shows the dopant distribution and the spot size measurement of a single mode fiber by using the heat treatment process conditions (temperature and heating time) for the Ge dopant diffusion by the inventors as parameters. In this proposal, the spot size of a normal single-mode fiber can be diffused by about three times by heating the fiber at several hundreds of degrees Celsius for several hours to ten hours. This is difficult to apply to a fiber core wire having a protective resin layer, and is inferior in workability. In addition, there is a concern that the reliability of the fiber may be degraded by such a high-temperature and long-time heat treatment.

FIG. 10 shows the tip of the single-mode fiber 21 expanded in a tapered shape over about 15 mm, thereby continuously expanding the beam and finally expanding the spot size to about 50 μmφ (HMPresby et.al., APPLIED OPTI
CS, VOL. 27, No. 15, 1 August, pp. 3121-3123, 1988), and the production of the tapered portion 22 is performed by stretching a fiber preform (preform). FIG. 1 shows an example in which an optical connector is configured using the tapered fiber at the tip, reference numeral 23 denotes a collimated light beam, and reference numeral 24 denotes a sleeve connecting the tapered portions 22 together. In the proposed example, since the tapered portion is formed by stretching the preform, mass production is difficult, and the tapered portion becomes as long as several tens of mm, which limits the miniaturization of the optical circuit. Further, since a large-diameter fiber of about 2.5 mmφ is formed at the end of the 125 μmφ fiber, the fiber is likely to be damaged at the time of assembling a connector or the like, which is expected to be inferior in handling.

FIG. 11 is different from the above two examples of the propagating beam expanding method.
Instead of the converging rod lens used in FIG. 8A and FIG. 8, a graded index (hereinafter abbreviated as GI) type multimode fiber piece having a predetermined length is attached to the tip of the single mode fiber 31. The same effect as the above lens is given by fusion splicing 32 (WILLIAM.EMKEY
et.al., IEEE JOURNAL OF LIGHT WAVE TECHNOLOGY, VOL.L
N-5, No. 9, PP1156-1164, 1978). Fig. 12 (a)-
(C) shows a manufacturing process of the single mode fiber with the tip multimode fiber piece. First, after the single mode fiber 31 and the multimode fiber 32a are fusion-spliced by the fusion discharge electrode 33 as shown in FIG. 1A, the multimode fiber 32a is fixed by a fiber cutter 34 as shown in FIG. (C). In order to expand the light beam emitted from the single mode fiber 31 and make it closer to a parallel light beam, the length l of the GI type multimode fiber piece 32 which is connected and fixed to the tip of the fiber by thermal fusion is adjusted by the focusing rod. Like the lens, the light beam pitch P (P = 2π) determined by the convergence constant g of the multimode fiber
/ g) or an odd multiple thereof. here,
The focusing constant g is GI type multimode fiber as shown in the following equation.
It characterizes the refractive index distribution of the 32 core portions.

n (r) = n ₀ (1−g ² r ² ) ^{1/2 If} the convergence constant g is 1.36, the length 1 of the 1/4 pitch becomes short at 1.155 mm, and the cutting operation is difficult. Because of the difficulty, the document proposes a method of cutting out to an odd multiple of 1/4 pitch length.

According to the optical coupling circuit according to this proposal, an expensive converging rod lens is not necessary and the optical circuit can be downsized. Since this is a manufacturing method of cutting a fiber to a predetermined length with high precision, it is complicated to cut out a multi-mode fiber piece with good yield while maintaining dimensional accuracy, which is inferior in mass productivity. Also, in connection with a multimode fiber, since the core diameter is greatly different, for example, Ge
It is expected that the melting temperature of both fiber cores will differ due to the difference in the dopant content, and it will be difficult to achieve good fusion splicing with good hold. Furthermore, when the optical axes of the two fibers are aligned by monitoring the output light output from the multimode fiber during fusion splicing, the influence of the cladding mode specific to the multimode fiber during the optical axis alignment between the two fibers. Accordingly, it is expected that accurate optical axis alignment will be difficult. Further, in order to improve the return loss between the opposing fibers, it is necessary to form an antireflection film on the emission side of the multimode fiber piece. It is also inferior in workability to arrange a large number of these in a vacuum deposition apparatus for film formation.

As described above, conventionally, there is no optical coupling circuit which is small in size and excellent in mass productivity, and its appearance is expected.

In view of such circumstances, an object of the present invention is to provide a method for manufacturing a fiber coupling pipe used in an optical coupling circuit which is small and excellent in mass productivity.

<Means for Solving the Problems> A method for producing a fiber coupling pipe used in an optical coupling circuit according to the present invention to achieve the above object comprises a thin metal pipe having an inner diameter substantially equal to the outer diameter of the cladding of the optical fiber. In producing a fiber coupling pipe for connecting and fixing optical fibers together, over a predetermined length to the outer periphery of an optical fiber or a metal cylindrical rod having an outer diameter substantially the same as or slightly larger than the cladding diameter, the optical fiber or A metal layer made of a metal that does not dissolve in a solution capable of dissolving the metal cylinder is formed to a predetermined thickness, and the optical fiber or the metal cylinder formed with the metal layer is cut into a predetermined length. The optical fiber or the metal cylinder is immersed in a solution capable of dissolving only the optical fiber or the metal cylinder, and only the optical fiber or the metal cylinder is dissolved and removed.

<Operation> For example, there is provided a collimating light coupling circuit for coupling input / output single mode optical fibers via a parallel light beam swinging a beam spot size larger than a beam spot size inherent to the single mode optical fiber. At each end on the coupling side of the single mode optical fiber, a fiber engaging pipe made of a thin metal pipe having an inner diameter substantially equal to the outer diameter of the clad of the single mode optical fiber and having a predetermined length is fitted. In the fiber coupling and pipe, the cladding diameter is larger than that of the T-mode optical fiber at the T, and the refractive index of the core decreases from the core center to the cladding boundary in a substantially square distribution according to the radial distance. One end face of the multimode fiber piece having a predetermined length and the end face of the single mode optical fiber are connected and fixed, and the other end of the multimode fiber piece is fixed. In the optical coupling circuit in which the two end faces are arranged to face each other at a predetermined distance, light from the single-mode optical fiber on the incident side is transmitted to the multi-mode fiber piece connected and fixed to the single-mode optical fiber. When the length is set to a predetermined value, it expands in the radial direction in the multimode fiber piece, and becomes substantially parallel light beam when emitted. Then, when this substantially parallel light beam is incident on the multimode fiber pieces arranged opposite to each other, it is reduced in the radial direction and guided to the single mode fiber on the emission side.

Here, the length l of the multimode fiber piece is a convergence constant g that determines the refractive index distribution of the core portion of the multimode fiber piece.
1 / of the period of the light propagating in the multimode fiber piece determined from
It is desirable that the value be an odd multiple of 4, that is, the following expression holds.

Further, the optical coupling circuit having the above-described configuration is small in size and excellent in mass productivity by connecting and fixing the single mode optical fiber and the multimode optical fiber via the fiber coupling pipe.

That is, by using the specific fiber coupling pipe, the optical coupling circuit can be downsized and mass-produced.

Further, by providing a cut-out part in which a part in the circumferential direction is cut out along the longitudinal direction of the fiber coupling pipe, the workability of connection and fixing is further improved.

The fiber coupling pipe used in the optical coupling circuit requires not only the inner diameter but also the outer diameter to have high precision. Adopt it. That is,
A metal layer made of a specific metal is formed at a predetermined thickness on the outer periphery of an optical fiber or a metal cylindrical rod having a predetermined dimension, and after cutting this into a predetermined length, only the inner optical fiber or the metal cylindrical rod is melted. Thus, a high-precision optical fiber coupling pipe can be easily manufactured with a high yield.

<Examples> Hereinafter, the present invention will be described based on examples.

FIG. 1 conceptually shows an optical coupling circuit. As shown in the figure, GI-type multimode fiber pieces 102 are connected and fixed to the tips of the single-mode fibers 101 on the incident side and the output side, respectively, from which all the protective resin layers have been removed, via fiber coupling pipes 103. ing.

Here, the single mode fiber 101 and the GI type multimode fiber piece 102 have the same clad outer diameter, and the GI type multimode fiber piece 102 has a predetermined length 1 that satisfies the following equation. I have.

In other words, l is set to an odd multiple of 1/4 of the period of the light propagating in the GI multimode fiber piece 102, which is determined by the convergence constant g that determines the refractive index distribution of the core portion of the fiber piece 102. The GI-type multimode fiber piece 102 is manufactured by simultaneously cutting and polishing a large number of bare multimode fibers from which the protective resin layer has been completely removed.

On the other hand, the fiber coupling pipe 103 is made of a thin metal pipe having an inner diameter substantially equal to the outer diameter of the cladding of the single mode fiber 101 and the GI type multimode fiber piece 102, and is manufactured with high accuracy and high yield. It is preferable to adopt a method described later.

Single mode fiber 101 and GI type multimode fiber piece 102
In order to fix the connection inside the fiber coupling pipe 103, it is preferable to use an ultraviolet curable resin having excellent translucency and having a refractive index substantially equal to that of the optical fiber core. This allows
This is because a low-loss connection can be realized in a short time. In addition,
In the figure, reference numeral 104 denotes such an adhesive fixing layer.

The single mode fiber 1 of the GI type multimode fiber piece 102 thus fixedly connected to the single mode fiber 101
The end faces on the reflection side are arranged opposite to each other at a predetermined interval with respect to 01, and constitute a collimated light coupling circuit. Note that an antireflection film 105 is formed on the facing surface of the GI-type multimode fiber piece 102, whereby a good return loss can be obtained.

In such an optical coupling circuit, for example, when light propagating in the core 101a of the single-mode fiber 101 on the incident side (left side in the figure) enters the core 102a of the GI multimode fiber piece 102, the propagation area Gradually expands in the radial direction, and at the time of emission, becomes a parallel light flux 106 having a beam size larger than the beam spot size inherent to the single mode fiber. This parallel light beam 106 enters the core portion 102a of the other opposing GI-type multimode fiber piece 102, and then gradually contracts in the radial direction to converge, thereby forming the single-mode fiber 101 on the output side (right side in the figure). It couples to the core part 101a.

FIG. 2 shows another example of the fiber coupling pipe. That is, the fiber coupling pipe 107 of this example
Is a so-called split pipe having a cutout portion 107a formed by cutting out a part in the circumferential direction over the longitudinal direction. This further facilitates the work of connecting and fixing the two fibers. In the drawing, reference numeral 101 denotes a single mode fiber, 102 denotes a GI type multimode fiber piece as in FIG. 1, and 101b denotes a fiber protective resin layer of the single mode fiber 101. .

By the way, when the spot size of the enlarged light beam is calculated from the convergence constant of a normal multimode fiber, it is about 30 μm. 1 dB loss
The optical axis deviation (perpendicular to the optical axis) required to suppress the following is about ± 5 μm. Therefore, the outer diameter of the fiber coupling pipe for connecting and fixing the two fibers also requires such accuracy.

As a method for manufacturing such a fiber-coupling pipe, it is conceivable to draw a metal pipe or the like. However, it is difficult to expect a high yield by the same manufacturing method in order to keep ± 5 μm or less.

Here, a method for producing the fiber coupling pipe used in the optical coupling circuit according to the present invention for producing the fiber coupling pipes 104 and 107 with high accuracy and high yield will be described.

For example, it does not dissolve in a solution capable of dissolving a metal cylindrical rod serving as a mandrel to the outer periphery of a metal cylindrical rod having an outer diameter about 1 μm larger than the cladding outer diameter of the single mode fiber 101 or the GI type multimode fiber 102. A metal layer made of metal is formed by plating at a predetermined thickness over a predetermined length, and then the metal rod is dissolved and removed with a predetermined etching solution to form a fiber coupling pipe made of a thin metal film. Make it. More specifically, when the mandrel is made of copper, a copper alloy (for example, brass) or an iron-based alloy, and the thin metal layer is made of, for example, gold, the mandrel can be used as a ferrous chloride solution. Thus, a fiber connecting pipe composed of a thin metal pipe can be obtained.

Further, as another method, a solution capable of dissolving the above-mentioned glass fiber serving as a mandrel to the outer peripheral surface of a multimode fiber piece to be connected or a glass fiber having an outer diameter about 1 μm larger than the outer diameter of the cladding of a single mode fiber. Then, a metal layer that does not melt is formed by plating with a predetermined thickness over a predetermined length, and then the metal-coated fiber is cut into a predetermined length, and the glass fiber portion of the mandrel is treated with a hydrofluoric acid-based solution. There is a method of obtaining a fiber-coupling pipe made of a thin-walled pipe by etching away. According to this method, as will be described later, it is possible to produce a fiber-coupling pipe made of a magnetic film, which has an effect of facilitating opposing connection arrangement work of single-mode fibers with multimode fiber pieces.

Here, an example of the fiber coupling pipe will be described with reference to FIGS. FIG. 2A shows a step of forming a vapor-deposited thin film on the surface of a bare fiber. That is, in a step of disposing a bare fiber 112 having both ends fixed to the frame 111 in a vacuum deposition apparatus, and forming a predetermined deposited metal thin film on the outer peripheral surface of the bare fiber 112 while rotating the frame 111 as shown in the figure. is there. In the figure, reference numeral 113 denotes a vapor deposition metal source. Next, FIG.
Shows a step of forming a metal layer on the outer peripheral surface of the deposited metal thin film-formed optical fiber by an electroplating method. Note that the metal layer used here does not dissolve in the solution used in the etching step shown in FIG. In the figure, 114 is a plating solution 115
, An electroplating anode 116 disposed in a plating bath 114, an electroplating cathode 117 disposed above a plating solution 115, and an anode 116 and a cathode 117.
The optical fiber 119 formed with the deposited metal thin film obtained in the step (a) is attached to the electroplating cathode 117, and most of the optical fiber 119 is immersed in the plating solution 115. I have. By performing electroplating in this state,
A metal film having a thickness of several μm to several tens μm is formed on the surface of the optical fiber 119 on which the deposited metal thin film is formed. Then, FIG.
Shows a step of etching and removing only the glass fiber portion while leaving the metal film thus formed. In the figure, 120
Denotes a glass fiber portion, and 121 denotes a metal film formed in the step (b). After the step (b) is completed, the glass film cut to a predetermined length can remove only the glass fiber portion 121. By immersing the glass fiber portion 121 in the solution for a predetermined time, only the glass fiber portion 121 is gradually removed by etching, and a fiber coupling pipe 122 made of a thin pipe is manufactured.

Specifically, for example, as the bare glass fiber 112, a fiber that is about 1 μm thicker than the connected single mode fiber and multimode fiber (cladding diameter 125 μmφ) is used, and Ti, NiCr
And the like are further deposited by several thousand Å (Step (a)), and then an Au film is formed to a thickness of about 20 μm by electroplating (Step (b)). The coated optical fiber is cut to a length of several mm and immersed in a hydrofluoric acid solution to produce a fiber coupling pipe made of an AU thin metal pipe (step (c)). Observation of the cross section of the fiber coupling pipe formed in this way revealed that when the glass fiber portion was etched with the hydrofluoric acid solution, the deposited layer of Ti or NiCr, which is the metal deposited on the underlayer, was also etched away. Was. In addition, the clearance between the cladding outer diameter of the single-mode fiber and the multi-mode fiber inserted into the pipe was within about 1 μm, and it was confirmed that the fiber could be smoothly inserted into the pipe. .

In order to manufacture the fiber coupling pipe 107 having the cutout portion 107a as shown in FIG.
In the step of FIG. 7A, the frame 111 on which the bare fiber 112 is fixed may be vapor-deposited without rotating, so that a portion to which the vapor-deposited metal does not adhere may be formed. That is, the metal film is not formed in the portion where the deposited metal does not adhere even in the step (b), and this portion becomes the cutout portion 107a shown in FIG.

When comparing the glass fiber used for the mandrel with the metal cylindrical rod, the glass fiber is more eccentric and has better surface accuracy. And the inner wall dimensional accuracy is excellent.

Next, as another example of the optical coupling circuit, an example in which an optical connector for connecting a multi-core single-mode fiber is realized will be described with reference to FIG.

As shown in the figure, each single mode fiber 101 and G
The I-type multimode fiber piece 102 is connected and fixed by an ultraviolet curable resin in a fiber coupling pipe 107 having a cutout portion 107a, and the single mode fiber with the multimode fiber piece is formed of an optical connector housing 131A, 131B. It is fixed to a fiber insertion hole (not shown). Here, the length l of the multimode fiber piece 102 is a length that almost satisfies the following equation.

The optical axis alignment of each fiber when connecting both optical connector housings 131A and 131B is performed by the optical connector housing 13A.
This is performed by fitting the guide pins 133 with the guide pin holes 132 arranged at both ends of the opposing surface of 1A and 131B. At this time, the end faces of the multimode fiber pieces 102 face each other with a predetermined gap therebetween, and the beam expansion effect of the multimode fiber pieces 102 causes the optical axis shift between the opposing fibers (vertical / horizontal direction). The increase in the connection loss for (1) is mitigated, whereby the loss unevenness at each connection portion of the multi-core fiber is also remarkably improved. In addition, in FIG.
Reference numeral 106 denotes a single mode fiber protection resin portion.

Further, another example of the optical coupling circuit will be described with reference to FIG. As shown in the figure, in this example, a fiber coupling pipe 141 for connecting and fixing the single mode fiber 101 and the GI type multimode fiber piece 102 is formed of a magnetic alloy film such as FeNi or NiCo. In addition, the opposing connection arrangement work of the single mode fibers with the multimode fiber pieces becomes very easy as follows. That is, if the permanent magnet 145 is arranged in a recess directly below the V-groove portion 144 of the housing member 143 in which the space portion 142 in which the collimated light beam is formed is formed in the middle, the single-mode fiber with the multimode fiber piece can be converted into the V-groove portion Fiber connection pipe 141
Is attracted to the permanent magnet 145, so that the fibers on both sides are automatically arranged to face each other. Then, after the arrangement of both fibers is completed, each fiber is fixed to the V-groove portion 144 by an ultraviolet curable resin or a metal brazing material. In this case, it is preferable to use a non-magnetic material for the material of the housing member 143, and also from the viewpoint of forming a high-precision V-groove.
It is particularly preferable to use a Si single crystal substrate. In addition, by arranging a desired optical element such as an interference film filter or a magneto-optical element in the space 142, various optical circuit components can be easily configured.

In the above-described embodiment, an example in which the fiber coupling pipe is used for the collimating optical coupling circuit has been described. However, the application of the fiber coupling pipe is not limited to this. Useful as a connection.

<Effects of the Invention> As described above, according to the method of manufacturing a fiber coupling pipe used in an optical coupling circuit according to the present invention, a light pipe made of a thin metal pipe having an inner diameter substantially equal to the outer diameter of the cladding of the optical fiber is used. In producing a fiber coupling pipe for connecting and fixing fibers together, over a predetermined length around the outer circumference of an optical fiber or a metal cylindrical rod having an outer diameter substantially the same as or slightly larger than the clad diameter, the optical fiber or A metal layer made of a metal that does not dissolve in a solution capable of dissolving the metal cylinder is formed to a predetermined thickness, and the optical fiber or the metal cylinder formed with the metal layer is cut into a predetermined length. Since only the optical fiber or the metal cylindrical rod is immersed in a solution that can dissolve the optical fiber or the metal cylindrical rod, only the optical fiber or the metal cylindrical rod is dissolved and removed. Can be manufactured with high precision and high yield.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an optical coupling circuit, FIG. 2 is an explanatory view showing another example of a fiber coupling pipe, FIG. 3 is a process diagram of fabricating a fiber coupling pipe, and FIGS. 6 to 8 are explanatory diagrams showing a collimated optical coupling circuit using an individual lens according to the prior art and an application example thereof, and FIGS. 9 to 12 are individual diagrams. It is explanatory drawing which shows the prior art which comprises a beam expansion and a collimating light coupling circuit only with an optical fiber instead of a lens coupling system. In the drawing, 101 is a single mode fiber, 102 is a GI type multimode fiber, 103 is a fiber coupling pipe, 104 is an adhesive layer, 105 is an antireflection film, 106 is a parallel light beam, 107 is a fiber coupling pipe, 107a Is a cutout portion, 111 is a frame, 112 is a bare fiber, 113 is a vapor deposition metal source, 114 is a plating bath, 115 is a plating solution, 116 is an electroplating anode, 117 is an electroplating cathode, and 119 is a deposited metal thin film forming optical fiber. , 120 is a glass fiber part, 121 is a metal film, 122 is a fiber coupling pipe, 131A and 131B are multi-core connector housings, 132 is a guide pin hole, 133 is a guide pin, 141 is a fiber coupling pipe (magnetic film pipe ), 142 denotes a collimated light beam forming space portion, 144 denotes a V groove portion, and 145 denotes a permanent magnet.

Claims (1)

(57) [Claims] In producing a fiber coupling pipe made of a thin metal pipe having an inner diameter substantially equal to the outer diameter of the cladding of an optical fiber, the outer diameter is substantially the same as or slightly larger than the cladding diameter. Forming a metal layer made of a metal that does not dissolve in a solution capable of dissolving the optical fiber or the metal cylindrical rod to a predetermined thickness over a predetermined length around the outer periphery of the optical fiber or the metal cylindrical rod having After cutting the optical fiber or the metal cylindrical rod having the metal layer formed into a predetermined length, the optical fiber or the metal cylindrical rod is immersed in a solution capable of dissolving only the optical fiber or the metal cylindrical rod, and only the optical fiber or the metal cylindrical rod is dissolved and removed. A method for producing a fiber coupling pipe for use in an optical coupling circuit.