JPH01287505A - Optical fiber and multicore optical fiber - Google Patents

Abstract

PURPOSE:To suppress the light loss in optical switching and to enhance the adaptability to conventional optical parts such as optical connectors by forming at least one flat sides having an approximately plane shape to the clad in parallel with the axial direction. CONSTITUTION:The core 2 of the optical fiber having the core 2 for guiding light and the clad 3 enclosing the same is positioned at nearly the center of the circumcircle 6 of the clad 3 and at least one of the flat sides 5a to 5c having approximately the plane shape are formed to the clad 3 in parallel with the axial direction. Namely, the flat sides 5a to 5c are formed to the clad 3 and, therefore, the distances between the cores 2 are decreased by disposing the fiber with the other optical fibers in the parts of the flat sides 5a to 5c. The length of the switching optical path is, therefore, shortened. The light loss is thereby decreased and the optical fiber having the excellent adaptability to the conventional optical parts and the good connectability to the conventional optical fibers is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber and a multicore optical fiber used in optical communication systems, optical sensor systems, and the like.

[Conventional technology]

As shown in FIG. 6(a), a conventional optical fiber 1 is composed of a core 2 for guiding light and a cladding 3 surrounding it, and the circumscribed circle of the cladding 3 has a substantially circular cross section. There is. Here, the core 2 has a higher refractive index than the cladding 3, and using this refractive index difference, light is confined in the core 2,
and guided in a fixed direction. In a typical single mode optical fiber, the diameter of the core 2 is about 10 μm, and the outer diameter of the cladding 3 is about 125 μm. Note that the core 2 is formed so as to substantially coincide with the center of the outer diameter of the cladding 3, and the amount of eccentricity is about 1 μm or less.

Switching of optical communication between the optical fibers 1 is performed, for example, as shown in FIGS. 6(b) and 6(c).

FIG. 6(b) schematically shows an example of the so-called axial direction switching type. That is, optical fiber 1a and optical fiber 1b
The optical fiber 1c to be switched is placed adjacent to the optical fiber 1b to be switched when optical communication is being performed between the two. Then, the optical fiber 1a is quickly moved in the direction of arrow A in the figure, and the optical fiber 1c and optical fiber la (l
a') Switch to optical communication. Here, the minimum value of the distance to which the optical fiber 1a is moved during switching is the sum g of the radius of the optical fiber 1b and the radius of the optical fiber 1c,
Specifically, it is about ji-125 μm.

FIG. 6(c) shows an example of the so-called radial direction switching type.

That is, the optical fiber 1b and the optical fiber 1c are placed adjacent to each other, and a reflecting mirror 4 (which may be a prism or the like) is placed on the end face thereof. Then, the light emitted from the optical fiber 1b is reflected twice by the reflecting mirror 4, and then enters the optical fiber 1c. Here, when switching, the light is transferred to the optical fiber lb.

The minimum value of the optical path length extending outside the IC (switching optical path length) is the sum of the above radii g and the optical fiber lb.

Determined from the distance between 1c and the reflecting mirror 4, N +2
It becomes L.

[Problem to be solved by the invention]

However, when switching as shown in FIGS. 6(b) and 6(c) is performed, there is a problem in that optical loss becomes large. That is, in the example shown in FIG. 6(b), the moving distance of the optical fiber 1a is the optical fiber lb.

Since g cannot be made smaller than the sum of the radii of the optical fibers 1c, the optical communication will be interrupted even momentarily during the travel time of the optical fiber 1a. In addition, in the example shown in FIG. 6(C), no matter how small the distance between the optical fibers lb, lc and the reflecting mirror 4 is, the switching optical path length in which the light exits to the outside of the optical fibers 1b, 1c is cannot be made smaller than the sum p of the radii of the optical fibers lb and lc, and therefore a part of the light emitted from the optical fiber 1b is no longer incident on the core 2 of the optical fiber 1c.

In order to solve these problems, it may be possible to reduce the outer diameter of the cladding 3 itself, but this would require other optical components such as optical connectors to have special specifications. , the entire system becomes expensive. In addition, in this way, the optical fiber 1
If the diameter of the optical fibers 1 is reduced, the connection loss caused by the difference in the structural parameters of the optical fibers 1 increases when connecting optical fibers 1 having different core diameters, which becomes a practical obstacle.

Therefore, the present invention aims to provide an optical fiber and a multicore optical fiber that can suppress optical loss during optical switching, are compatible with conventional optical components such as optical connectors, and are highly practical. purpose.

[Means to solve the problem]

The optical fiber according to the present invention is an optical fiber having a core for guiding light and a cladding surrounding the core,
The core is located approximately at the center of the circumscribed circle of the cladding, and the cladding is characterized in that at least one substantially planar flat side is formed parallel to the axial direction.

Furthermore, in the multi-core optical fiber according to the present invention, a plurality of optical fibers as described above are arranged in parallel, and when these are integrated by a coating part, the optical fibers are arranged so that the flat sides form a constant arrangement form. It is characterized by its placement. In addition, in this multicore optical fiber, the optical fibers may be arranged on one plane to form a tape shape so that the flat sides of each pair of optical fibers are opposite to each other.

[Effect]

According to the configuration of the present invention, since flat sides are formed in the cladding of the optical fiber, the distance between the mutual cores can be significantly reduced by making the optical fibers adjacent to other optical fibers at the flat sides. . Therefore, the switching optical path length can be shortened. Further, since the circumscribed circle of the cladding does not change at all even after the flat sides are formed, it has excellent compatibility with conventional optical components and has good connection characteristics between optical fibers. Furthermore, if such optical fibers are multi-core in a certain arrangement, the orientation of the flat sides can be easily recognized, making handling easier. An embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view of an optical fiber according to an embodiment of the present invention. In the example shown in FIG. 3(a), one flat side 5 of the cladding 3 is formed parallel to the axial direction of the optical fiber,
In the example shown in FIG. 3(b), there are two flat sides 5 on the cladding 3.
a and 5b are formed. In the example shown in FIG. 3C, the cladding 3 is also provided with two flat sides 5a and 5b, which are parallel to each other. In the example shown in FIG. 3(d), the cladding 3 has three flat sides 5a.

5b and 5c are provided, and the cross-sectional shape is a substantially equilateral triangle. In the example shown in FIG. 5(e), there are two parallel flat sides 5a, similar to the example shown in FIG. 10(c).

5b is formed, but this flat side 5a.

5b is sufficiently large, so that the optical fiber 1 is extremely thin. In addition, in any of the examples shown in FIGS. 1(a) to 1(e) above, the core 2 is arranged approximately at the center of the circumscribed circle 6 of the cladding 3.

The size of this circumscribed circle 6 is generally 125μ
It goes without saying that the thickness may be approximately 70 μm or 140 μm.

In addition, the diameter of the core 2 is generally about 10 μm in a single-moat optical fiber, but it is not limited to this, and the amount of eccentricity of the core 2 from the center of the circumscribed circle 6 is also limited. It is not something that will be done.

Since the optical fiber of the embodiment shown in FIG. 1 is configured as described above, it not only facilitates optical coupling (optical connection) with conventional optical fibers, but also enables easy switching optical path length during optical switching. It is also possible to shorten the length. This situation will be explained below with reference to FIGS. 2 to 4.

First, regarding the optical connector 8 having the circular optical fiber guide hole 7, the optical fiber 1 of the present invention is shown in FIG.
) is applied as follows. FIG. 5(a) is a view of the optical fiber 1 viewed from the end surface direction, and the cladding 3 is located approximately at the center of the circumscribed circle 6 of the core 2. Therefore, as shown in the figure, the core 2 is located approximately at the center of the circumscribed circle 6 of the optical fiber 1. It will be located in the center. On the other hand, the conventional ordinary optical fiber 1 is as shown in FIG. 2B, and in this case as well, the core 2 of the optical fiber 1 is located approximately at the center of the optical fiber guide hole 7. Therefore, if the circumscribed circle 6 of the optical fiber 1 according to the present invention shown in FIG. This can be done extremely easily by using the optical connector 8 as is.

Note that FIG. 3 is a schematic perspective view showing the state of optical coupling, and it goes without saying that the application of the present invention is not limited to this.

Next, the optical connector 8 having the V-shaped groove 9 is applied as shown in FIG. 2(C).

Figure (c) is a diagram of the optical fiber 1 according to the present invention viewed from the end face direction, whereas Figure (d) shows the conventional optical fiber 1 set in an optical connector 8 having a V-groove 9. FIG. As is clear from the figure, in this case as well, if the circumscribed circles 6 of the cladding 3 are the same, the optical connector 8 having the V-groove 9 of the same size
By using this, it is possible to accurately position the core 2 at the same position. Therefore, optical coupling can be performed using the conventional optical connector 8 as is, as shown in FIG. 3(b).

When performing optical switching as explained in FIG. 6, an optical connector 8 having grooves as shown in FIGS. 2(e) and 2(f), for example, may be used. That is, the flat sides 5 of the two optical fibers 1 are brought into contact with each other, and these are set in the optical connector 8 having the V-groove 9 or the rectangular groove 10. In this way, the distance i! between the cores 2 of the two end fibers 1! f
iB is smaller than that of the conventional one. That is, it becomes smaller by the sum of 1 minute cut by the flat side 5.

Therefore, it becomes possible to shorten the switching optical path length as shown in FIG. FIGS. 4(a) and (b) correspond to FIGS. 6(b) and (c), respectively. As shown in FIG. 4(a), in the axial switching type, the moving distance of the optical fiber 1a is shortened by the sum of the lengths cut by the flat sides 5, so the optical communication is interrupted by that amount. time can be shortened. In addition, as shown in FIG. 4(b), in the radial switching type, not only the switching optical path length is shortened by the sum of the cuts of the flat sides, but also the optical fiber 1b
, 1c can be brought close to the reflecting mirror 4, so that the switching optical path length can be further shortened in this respect.

As described above, according to the present invention, optical connections can be made using conventional optical connectors and mechanical splices as they are, and the switching optical path length can also be shortened. It becomes possible to achieve a high degree of integration. First, optical switching, optical branching, demultiplexing, multiplexing, etc. can be efficiently performed on the substrate.

For this reason, we have developed a new optical fiber integrated component (OFIC) that has excellent compatibility with conventional optical fibers.
iber Integrated Component
) or optical fiber integrated connector (OFIC;
0ptical Fiber IntegratCd
Connector> ) can be realized.

Next, an embodiment of the multi-core optical fiber according to the present invention will be described with reference to FIG.

FIG. 5 is a sectional view of a tape-shaped optical fiber 13 in which a plurality of optical fibers 1 are arranged in parallel and integrated into a tape shape. As shown in the figure, each of the plurality of optical fibers 1 having a flat side 5 on the cladding 3 is coated with an inner coating material 14 made of UV curable resin or the like, and further formed into a tape shape by an outer coating material 15. .

Here, the flat sides 5 of each optical fiber 1 integrated by the coating portion consisting of the inner coating material 14 and the outer coating material 15 are arranged with a certain regularity. That is, in FIG. 5(a), the flat sides 5 are aligned in one direction, and in FIG. 5(b), the flat sides 5 of adjacent optical fibers 1 are arranged to face each other.

Further, in FIG. 5(C), the optical fiber 1 has two flat sides 5, which are opposed to each other. Furthermore, in the example of FIG. 5(d), the flat sides 5 of the two optical fibers 1 on the left and right sides are opposed to each other, and the flat sides 5 of the two middle optical fibers 1 are oriented in a fixed direction (vertical direction). are arranged.

By arranging the optical fibers 1 with such a certain regularity, practical handling becomes extremely easy. That is, the optical fiber 1 is usually extremely thin, about 125 μm, and therefore it is not easy to visually confirm which direction the flat side 5 is facing. Therefore, if the arrangement of the flat sides 5 is given a certain regularity as shown in FIG. 5, it becomes extremely easy to confirm this arrangement.

Next, a specific example by the present inventor will be described.

Example 1 First, a single mode optical fiber with a cladding circumscribed circle of 125 ± 0.5 μm and a core diameter of 10 μm (within an eccentricity of 0.3 μm) was prepared, and one side of the cladding was removed to create a flat side. Formed. Note that the dimensions of the flat sides were such that when optical fibers of the same shape were faced with their flat sides, the distance between their cores was approximately 50 μm.

Next, the two optical fibers were brought into contact with each other with their flat sides and coated with a UV curable resin having a diameter of 250 .mu.m to be integrated.The two optical fibers were attached to a groove connector and the coupling loss between the optical fibers was measured.

Average coupling loss when using refractive index matching agent is 0.25
dB, and it was found that characteristics comparable to those of conventional optical fibers can be obtained.

Example 2 A 16-core tape-shaped optical fiber was produced using an optical fiber having flat sides similar to that of Example 1. and,
Coupling loss between optical fibers was measured using a multi-core optical connector. In this case as well, it was found that the average coupling loss when using the refractive index matching agent was about 0.25 dB, and that characteristics comparable to those of conventional optical fibers could be obtained.

Example 3 Using an optical fiber having the same flat side 5 as in Example 1, experiments were conducted on light branching using a prism, etc. In this case, the distance between the cores is about 50 μm, which is less than half of the conventional case (about 125 μm), and depending on this distance, the branching loss can be suppressed to 1 dB or less. Furthermore, when a tape-shaped optical fiber in which the flat sides of the optical fiber are arranged in a fixed direction is used, handling is extremely easy.

The present invention is not limited to what has been described above, and various modifications are possible.

For example, the number of flat sides can vary depending on the usage situation. In addition, the dimensions of the flat side should be determined as appropriate depending on the physical strength of the optical fiber, optical transmission characteristics, degree of crosstalk, manufacturing conditions, and standards required for optical communication systems and optical sensor systems. It is possible to transform.

〔Effect of the invention〕

As explained in detail above, according to the present invention, the cladding has flat sides, and by making the cladding adjacent to other optical fibers at the flat sides, the distance between the mutual cores can be significantly reduced. Can be made smaller. Therefore, the switching optical path length can be shortened, and therefore optical loss can be reduced. Furthermore, since the circumscribed circle of the cladding does not change even after the flat sides are formed, it has excellent compatibility with conventional optical components and good connectivity with conventional optical fibers.

On the other hand, if the above-mentioned optical fiber is made into a multi-core optical fiber by giving a certain regularity to the arrangement of the flat sides, handling becomes considerably easier. The invention is particularly suitable for application to 0FIC.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an optical fiber according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of positioning of an optical fiber according to an embodiment of the present invention, and FIG. 3 is a diagram showing an example of optical coupling according to the present invention. FIG. 4 is a diagram showing an example of optical switching of an optical fiber according to the present invention,
FIG. 5 is a sectional view of a multi-core optical fiber according to an embodiment of the present invention, and FIG. 6 is a diagram illustrating a conventional optical fiber and optical switching optical path length. 1... Optical fiber, 2... Core, 3... Clad. 5a, 5b, 5c...Flat side, 6...Circumcircle. 7... Optical fiber guide hole, 8... Optical connector. 9... V groove, 10... Rectangular groove, 13... Tape-shaped optical fiber, 14... Inner coating material, 15... Outer coating material. Patent Applicant: Sumitomo Electric Industries, Ltd. Representative Patent Attorney Yoshiki Hase Figure 1 Example of positioning of optical fiber according to the embodiment Figure 2 Figure 3 Example of optical switching of optical fiber Figure 4 13 Tape according to the present invention shaped optical fiber Figure 5

Claims (1)

[Claims] 1. An optical fiber having a core for guiding light and a cladding surrounding the core, wherein the core is located approximately at the center of a circumcircle of the cladding, and the cladding includes at least one An optical fiber characterized in that two substantially planar flat sides are formed parallel to the axial direction. 2. In a multi-core optical fiber in which a plurality of optical fibers each having a core for guiding light and a cladding surrounding the core are arranged in parallel and are integrated by a coating part, the core is a circumscribed part of the cladding. The optical fibers are located approximately at the center of a circle, and the cladding has at least one substantially planar flat side formed parallel to the axial direction, and the optical fibers are arranged so that the flat side forms a certain arrangement. A multi-core optical fiber featuring: 3. The multicore optical fiber according to claim 2, wherein the optical fibers are arranged on one plane and have a tape shape so that the flat sides of each pair of optical fibers are opposed to each other.