JPS63173007A - Optical tap device - Google Patents

Abstract

PURPOSE:To execute optical branch from an optical fiber and optical coupling to the optical fiber with high efficiency, by bending the optical fiber at a prescribed bending angle and with a prescribed radius by an optical fiber holding means, and allowing the optical fiber to cross an optical axis of a lens-like medium of an optical member, and positioning and detaining it. CONSTITUTION:An optical fiber 7 is positioned along bending surfaces 5, 6, by a groove 8 formed on the convex binding surface 6 of the second optical member. That is to say, when the convex bending surface 6 is brought into contact closely with the concave bending surface 5 of the first optical member 3, the optical fiber 7 is bent at a prescribed bending angle theta and with a prescribed bending radius R along these bending surfaces 5, 6. An optical signal 10 which is made incident on an end face 9 of the first optical member 3 is propagated while being focused in a lens-like medium 1 along an optical axis A-B. Also, a direction and a position where the optical fiber 7 is made incident on a bending part 71, or an NA value of an incident light are set as prescribed, and the optical signal 10 is radiated to the bending part 71. In such a way, the optical signal 10 is brought to optical coupling to the optical fiber 7, and propagated in the direction of C along an optical axis C-C' of the optical fiber 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical tap device that transmits and receives optical signals to and from an optical fiber.

[Conventional technology]

An optical branching coupler (hereinafter referred to as an optical coupler) is an important component that constitutes an optical local area network (optical LAN), an optical transmission line, and the like.

Conventionally, this type of optical coupler has been constructed by fusing the sides of two optical fibers together, forming an optical waveguide in a Y-shape, or using a minute half mirror. The work of connecting these optical couplers to an optical fiber has been performed by cutting the optical fiber and connecting the optical coupler to the cut portion. For this reason,
Connection loss occurs when an optical coupler is inserted into a trunk optical fiber. Further, there are drawbacks such as difficulty in disconnecting the trunk line and subsequent connection of the optical coupler.

In response to this, a device called an optical tap device has been proposed. This optical tap device is an optical coupler that can send and receive optical signals to and from optical fibers without cutting them, and is based on the Institute of Electronics and Communication Engineers Technical Research Report 0QE-86-104.
An example of this is also shown. According to this, an optical tap device is composed of an optical fiber bent at a predetermined bending angle and bending radius, an optical branching path connected to the bent part of the optical fiber via a bonding material, and an optical coupling path. . For example, by setting the bend angle of the optical fiber to 10 degrees and the bend radius to 5 degrees, the insertion loss can be suppressed to about 0.1 dB.
It is predicted that optical coupling and optical branching can be performed with low loss, which is not possible with conventional optical couplers.

(Problems to be Solved by the Invention) However, the above conventional optical tap device has the following two problems.
There are two problems.

The first problem is that since it is not possible to arrange the optical member close to the bent portion of the optical fiber, it is not possible to efficiently send and receive optical signals to and from the optical fiber.

The first problem will be explained in more detail with reference to FIG. FIG. 5 is an explanatory diagram showing a configuration for exchanging optical signals with an optical fiber according to the prior art.

According to the configuration shown in FIG. 9A, a part of the light incident from the input-side straight portion 21 of the optical fiber 2 is emitted from the bent portion 22 having the bending angle θ, and is condensed through the lens 90. It will be detected by an optical communication photodiode (hereinafter referred to as PD) 91.

According to the configuration shown in FIG. However, the lens diameter of the commonly available lens 90 is usually 2 m or more. Therefore, when the bending angle of the optical fiber 2 is set to 10', the lens 90 and the optical fiber 2 In order to avoid contact with the lens 90 and the bent portion 22, the distance is 5.78 mm.
It has to be more than that. Therefore, the diameter of the light beam incident on the lens 90 increases to about 1.2 m.

On the other hand, since the PD 91 is required to be high-speed, the light-receiving diameter of the light-receiving area is usually set to 200 μm or less.

As a result, although the lens 91 is required to have high light condensing properties, it is generally strongly affected by aberrations, and therefore cannot couple the light emitted from the bending portion 22 to the PD 91 with high efficiency.

FIG. 5(B) shows a configuration in which an optical fiber 93 serving as an optical branch path is directly connected to the bent portion 22 of the optical fiber 2 by a bonding material 92. In this case, a lens is not required, but the light emitted from the bent portion 22 is not condensed at all. Therefore, the coupling efficiency from the optical fiber 2 to the optical fiber 93 becomes poor.

Incidentally, in the explanation of FIGS. 5(A> and (B)), we have explained the optical branching from the optical fiber to the optical branching path, but the same problem occurs when optically coupling from the optical coupling path to the optical fiber. ing.

Next, the second problem that the prior art has will be explained.

Generally, when transmitting and receiving optical signals to and from an optical fiber through a bent portion of the optical fiber, the direction of incidence of light, the position of incidence, the NA value of the incident light, etc. must be optimally set. These set values are necessarily determined depending on the refractive index of the optical fiber and its surroundings, the bending shape of the optical fiber, and the like.

However, according to the prior art, the optical fiber is
There is no means for bending at a bending angle and bending radius and maintaining the shape. Therefore, it is difficult to set the bending angle and bending radius of the optical fiber to predetermined values. Therefore, in conventional optical tap devices, optical fibers cannot be positioned and stably held, so optical branching paths and optical coupling paths are arranged while maintaining a predetermined positional relationship with respect to the bending part of the optical fiber. Can not do it.

As a result, coupling loss with the optical fiber cannot be reduced, and bending loss caused by bending the optical fiber cannot be minimized.

As described above, the prior art mainly has the above two problems. As a result, the conventional optical tap device cannot perform optical coupling with an optical fiber or optical branching with low loss, and many of the above-mentioned features of the optical tap device cannot be utilized.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical tap device that can perform optical coupling and branching with an optical fiber with high efficiency and can be easily connected to an optical fiber.

(Means for Solving the Problems) A tap device according to the present invention includes an optical member having a lens-like medium and an optical fiber bent at a predetermined bending angle and bending radius across the optical axis of the optical member. It is characterized by comprising an optical fiber holding means for holding the optical fiber.

[Effect]

According to the present invention, since the optical tap device is configured as described above, the optical fiber holding means bends the optical fiber at a predetermined bending angle and bending radius, positions the optical fiber, and attaches the optical member made of a lens-like medium. The optical fiber acts to radiate a portion of the optical signal from the bend to a lenticular medium and branch the signal to an optical member, or the lenticular medium of the optical member radiates a portion of the optical signal to a lenticular medium. It acts to illuminate the bend in the fiber and couple the signal into the optical fiber.

(Embodiments) Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings FIGS. 1 to 4. In the following description, the same elements are given the same reference numerals to avoid duplication of the description.

FIG. 1 is a perspective view showing the structure of a first embodiment of the present invention.

The optical member is composed of first and second optical members 3 and 4 which are arranged in series with the optical axes AA' and B-8' in common. The first optical member 3 has a concave bent surface 5 that diagonally crosses the optical axis A-8. The second optical member 4 has a corresponding convex curved surface. The first and second optical members 3.4 are arranged such that both curved surfaces 5, 6 are brought into close contact with each other. A groove 8 having a V-shaped cross section is formed in the convex bent portion 6 of the second optical member 4, in which the optical fiber 7 is positioned and disposed on the surface 6 thereof. These optical members 3 and 4 consist of a lenticular medium 1 whose optical axis is A-8 and a cladding 2 around it, and the refractive index of the lenticular medium 1 is 2 whose symmetrical axis is the optical axis A-8. , has a square distribution. These optical members 3 and 4 are made by drawing a graded index type optical fiber base material to a diameter larger than that of a normal optical fiber, and cutting it.

In addition, in FIG. 1, for convenience of understanding, the first and second optical members 3.4 are shown in a separated state, and the bent surfaces 5, 6 are shown in this state. In addition, the common optical axis A-8 is separated as shown in the figure, and the light 'i'fllA-A
', B-8'.

The operation of the first embodiment will be described below with reference to FIGS. 1 and 2.

FIG. 2 is a longitudinal sectional view showing the structure of the tap device shown in FIG. 1. As shown, the optical fiber 7 is positioned along the curved surfaces 5 and 6 by a groove 8 formed in the convex curved surface 6 of the second optical member. That is, when the convex bending surface 6 is brought into close contact with the concave bending surface 5 of the first optical member 3, the optical fiber 7 is bent at a predetermined bending angle θ and bending radius R along these bending surfaces 5 and 6. It can be bent with.

The optical signal 10 incident on the end surface 9 of the first optical member 3 propagates while converging in the lenticular TS 1 along the optical axis A-8. Then, the direction and position of incidence on the bent portion 71 of the optical fiber 7 or the NA value of the incident light are set to a predetermined value, and the optical signal 10 is irradiated onto the bent portion 71 . As a result, the optical signal 10 is optically coupled to the optical fiber 7 under optimal conditions and propagates in the direction C along the optical axis c-c' of the optical fiber 7.

Thereby, optical coupling to the optical fiber 7 is performed with high efficiency. Note that the optical signal 10 that does not contribute to optical coupling propagates in the direction B in the lens-like medium 1 of the second optical member 4.

In the description of the first embodiment, optical coupling from the optical member 3 to the optical fiber 7 has been described, but optical branching from the optical fiber 7 to the optical member 3 can be performed in the same manner. Optical fiber 7 from direction C along optical axis c-c' of optical fiber 7
The light incident on the bending part 71 of the first optical member 3 has the radiation direction and position of the light at the bending part 71 or the NA value of the emitted light set to a predetermined value depending on the bending shape. radiated inside. As a result, the optical signal is branched from the optical fiber 7 to the first optical member with high efficiency. The remaining optical signal components that are not emitted from the bent portion 71 of the optical fiber 7 are transmitted along the optical axis D- of the optical fiber 7 with bending loss.
It is sent in the D direction along D'.

The inventor conducted the following experiment in order to confirm the usefulness of the first embodiment.

First, the optical fiber 7 was a silica-based optical fiber having a core diameter of 100 μm, a cladding diameter of 140 μm, and a coating diameter of 250 μm. The bending angle of the optical fiber 7 by the optical members 3 and 4 was set to 10°, and the bending radius was set to 5.0 m. and,
When light having a predetermined NA value and beam diameter was incident on the end face 9 of the first optical member 3, the coupling efficiency to the optical fiber 7 was as high as 85%. Furthermore, even when the optical tap device having this configuration was repeatedly disassembled and assembled several times, the coupling efficiency varied within 10% each time.

Regarding the light branching from the optical fiber 7 to the optical member 3, N A 1iI! of the light emitted from the bent portion 71 of the optical fiber 7 to the lenticular medium 1 of the optical member 3! There will be some differences between the two. Therefore, even if optical branching is performed using the same configuration as in the above experimental example, optimal branching may not necessarily be obtained. However, by changing the shape of the curved surface of the optical member 3 and optimally setting the shape and position of the curved portion 71 of the optical fiber 7, the coupling efficiency can be increased to a value as high as about 95%. Incidentally, this coupling efficiency is based on the light receiving diameter of 150 mm when the light obtained from the end surface 9 of the second optical member 3 is
This is achieved by coupling it to a μm photodiode.

Next, a second embodiment will be described with reference to FIG.

FIG. 3 is a perspective view showing the structure of this embodiment.

The configuration of this embodiment is different from the first embodiment shown in FIG.
And, the optical member made of the cladding 2 surrounding it is constituted by a single optical member 31 having the groove 81. The groove 81 is a groove that passes through the optical axis AB and crosses the optical member 31 in the diametrical direction. The cutting depth of the groove 81 is varied in the radial direction of the optical member 31. by this,
The optical fiber 7 inserted into the groove 81 is bent along the groove bottom 82 so as to be positioned on the optical axis of the lenticular medium 1.

Next, the operation of this second embodiment will be explained.

The optical fiber 7 is laid along the groove bottom 82 of the groove 81, and is bent in a predetermined manner in contact with the lenticular medium to form a bent portion 71. At this time, after the optical fiber 7 is inserted into the groove 81, the gap in the groove 81 is filled with a resin having a predetermined refractive index, such as acrylic resin, and polymerized under pressure.

According to this second embodiment, the optical member is composed of a single member. Therefore, the structure of the first embodiment described above can be simplified, and the work of attaching the optical fiber can be facilitated.

Next, a third embodiment will be described with reference to FIG.

FIG. 4 is a perspective view showing the structure of this embodiment.

The structure of this embodiment differs from the structure of the first embodiment or the second embodiment in that the optical member 3 has a concave curved surface on the base 10, and the optical fiber 7 is connected to the curved surface. This is the point where the holding member 41 for positioning is placed. The holding member 41 is a flat plate-like member, and a convex curved surface 61 that closely contacts the concave curved surface of the optical member 3 is formed on its end surface.

A 0-shaped groove 83 for positioning the optical fiber 7 is provided on the end face.

Next, the operation of the third embodiment will be explained.

According to the configuration of this embodiment, the optical fiber 7 is
It is positioned along the end surface of the presser member 41 by the groove 83 of No. 1 . By bringing the holding member 41 and the optical member 3 into close contact with each other, the optical fiber 7 is bent into a predetermined shape and held by the bending surface formed at the boundary between these members 3.41.

According to the third embodiment, the optical member 3 and the holding member 41
Since these members 3 and 41 are placed on the same plane of the base 10, there is an advantage that these members 3 and 41 can be easily assembled. Further, since other optical members such as a light emitting element, a light receiving element, or a lens can be positioned and placed on the base 10, there is an advantage that the optical tap device can be made multi-functional and its operation can be performed stably.

The present invention is not limited to the above embodiments, and various modifications are possible.

For example, in the above explanation, the refractive index distribution of the lenticular medium included in the optical member is assumed to be a square distribution with the optical axis as the object.
Other refractive index distributions are also possible. This results in
It is possible to optimally set the NA value of light emitted from the bent portion of the optical fiber to the lenticular medium, or to optimally set the NA value of the incident light that enters the bent portion of the optical fiber from the lenticular medium. .

Further, although the lenticular medium 1 has been described as being covered with the cladding 2, the present invention is not limited thereto, and a converging rod lens can also be used as the lenticular medium.

Further, the cross-sectional shape of the groove for positioning the optical fiber is not limited to the V-shape or U-shape, but can also be a square groove or a semicircular groove. Instead of these grooves, steps or a combination of steps may be used.

Furthermore, in the description of the embodiments above, the transmission and reception of optical signals between the optical fiber and the optical member is explained as using - pairs of optical fibers and optical members, but the invention is not limited to this. It is also possible to combine optical elements. According to this, it is possible to branch an optical signal from one optical fiber to a large number of optical branch paths, or to optically couple the same optical signal from the same optical member to a plurality of optical fibers.

〔Effect of the invention〕

As described in detail above, according to the present invention, the optical fiber is bent by the optical fiber holding means at a predetermined bending angle and bending radius, and is positioned and held across the optical axis of the lenticular medium of the optical member. This makes it possible to optimally set the light input/output direction and position when transmitting and receiving light through the bent portion of the optical fiber, as well as the NA value of the human-emitted light, and moreover, it can be focused on the bent portion of the optical fiber. Lens-like media with properties can be placed closely together. As a result, loss in transmitting and receiving optical signals between the optical fiber and the optical member can be suppressed to a small level, and optical branching from the optical fiber and optical coupling to the optical fiber can be performed with high efficiency.

Further, according to the present invention, when an optical tap device is attached to an optical transmission line, the operation can be easily performed, and moreover, it is possible to achieve the effect that a large number of terminal connections can be made.

[Brief explanation of the drawing]

1 is a perspective view showing the structure of an optical tap device according to the first embodiment of the present invention, FIG. 2 is a sectional view showing the structure of the optical tap device according to the first embodiment, and FIG. Embodiment 2 is a perspective view showing the configuration of such an optical tap device, FIG. 4 is a perspective view showing the configuration of the optical tap device according to the third embodiment, and FIG. 5 is an explanatory diagram of the prior art. DESCRIPTION OF SYMBOLS 1... Lens-shaped medium, 2... Clad, 3... First optical member, 4... Second optical member, 5, 6...
Bent surface, 7... Optical fiber, 71... Bent part, 8,
81.83...Groove, 10...Base. Patent Applicant: Sumitomo Electric Industries, Ltd. Representative Patent Attorney Yoshi Hase Yoshikimasu Fig. 1 Block diagram of the first embodiment Fig. 4 Block diagram of the third embodiment

Claims (1)

[Claims] 1. An optical member having a lens-like medium and an optical fiber disposed across the optical axis of this optical member are bent at a intersection with the optical axis with a predetermined bending angle and bending radius. An optical tap device comprising an optical fiber holding means for holding an optical fiber. 2. The optical tap device according to claim 1, wherein the optical axis of the optical member is included in a plane formed by the bent optical fiber.