JPH0353205A - Optical fiber connecting part - Google Patents

Abstract

PURPOSE:To improve the allowable degree of position accuracy, and also, to obtain a low loss connection of a multi-mode optical fiber and a single mode optical fiber by tapering an end part in a state that a core part is covered with a clad part, and connecting the respective end parts with each side face part of the tapered part. CONSTITUTION:Tapers 13, 13' are formed by heating and drawing each end part of GI type multi-mode optical fibers 12, 12' consisting of a core part 10 and a clad part 11. Subsequently, matching oil whose refractive index is almost the same as that of the clad part 11 is applied by a small quantity to side face parts 14, 14' of the tapered parts 13, 13' a contact part 15 is formed by using its surface tension, and an optical fiber connecting part 15 is constituted. In such a manner, the allowable degree of position accuracy is connecting plural optical fibers can be improved, and also, a low loss connection from the multi- mode optical fiber to a single mode optical fiber is obtained, and the function of demultiplexing/multiplexting can be added at the time of connection.

Description

[Detailed Description of the Invention] Industrial Application Fields The present invention relates to an optical fiber connection section that connects optical fibers together, and which greatly reduces transmission loss while widening the tolerance range of the positional accuracy of the optical fibers to be connected. This is something that has been devised to improve it.

Background Technology> Two common methods for connecting optical fibers are fusion splicing, which is a permanent connection, and optical connectors, which can be connected and disconnected at any time.

The former fusion splicing has the following problems.

■ Optical fibers are light waveguides, so unless the core is connected to the core and the cladding is connected to the cladding, the light will leak or be reflected, resulting in loss. For example, when optical fibers are cut and formed and their t-end faces are connected, a highly accurate positioning device is required because axial misalignment and angular misalignment result in connection loss.

■ In addition, when connecting a multimode optical fiber and a single mode optical fiber, the optical transmission loss from the multimode optical fiber to the single mode optical fiber is determined by the core cross-sectional area ratio of both optical fibers. The diameter is 50 μm and l, respectively.
If it were 0 μm, it would be 14 dB, which was unavoidable.

■Furthermore, it was difficult to add branching and multiplexing functions at the time of connection due to the structure of the connection part.

The present invention was made in view of the above circumstances, and it significantly improves the tolerance of positional accuracy in optical fiber connections, realizes low-loss connections between multimode optical fibers and single mode optical fibers, and provides optical The purpose is to provide an optical fiber connection section that adds branching and multiplexing functions.

Means for Solving the Problems> The configuration of the present invention to achieve the above object is an optical fiber connecting section that connects optical fibers at their respective ends in order to perform optical transmission between the optical fibers. The ends of each of the optical fibers are tapered with the core portion covered with a cladding portion, and each end portion is
It is characterized in that the side surfaces of the tapered portions are connected to each other.

Function> Tapered optical fibers with the core portion at the end of the optical fiber covered with a cladding portion are butted against each other with their tapered side portions and connected by contacting, adhering, or fusion bonding, It is used as an optical fiber connection part. As a result, the light that has been propagated through the core portion of one optical fiber leaks out through the tapered portion, and the light is transmitted to the other core.

Embodiments Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the examples disclosed below are merely illustrative of the present invention, and do not limit the scope of the present invention in any way.

(Example 1) FIG. 1 is a plan view explaining the first example of the present invention, and FIG.
The figure is a sectional view taken along line I-II in FIG.

As shown in these drawings, the core part (core diameter 50 μm)
Each end of a Gl type multimode optical fiber 12 and 12' consisting of a cladding section 10 and a cladding section (cladding diameter 70 .mu.m) 11 is heated and stretched to form tapered sections 13 and 13' with a length of 25 mm and a tip diameter of 1 .mu.m. A small amount of matching oil (d: 1.46) having almost the same refractive index as that of the cladding part 11 is applied to the side surfaces 14 and 14' of the tapered parts 13 and 13', and the surface tension is used to form the contact part 15. , constituted the optical fiber connection section.

In order to form the tapered portions 13, 13', the optical fibers 12, 12' may be drawn while the core portion 10 is completely covered with the cladding portion 11 during heating and drawing. This is because when the end of an optical fiber is formed into a tapered shape (for example, by etching), the core is scraped and the side surfaces of the tapered part of the core become rough. In contrast, the tapered part 13 according to this embodiment is heated and melted and then stretched so that the core part 10 and the cladding part 11 gradually become tapered, so that the core part 10 and the cladding part 11 are stretched. It is possible to form a tapered shape while covering the core part, so that the core part is always protected and the side faces of the tapered part do not become rough.

If the optical connection loss of this connection is determined, the wavelength is 1 3 1 0
A value obtained by inputting light from a nm LED light source into a scrambler, inputting the output light into one optical fiber 12, and measuring the light from the other optical fiber 12' with an optical power meter,
The ratio of the values of the light in the optical fiber 12 measured with an optical power meter was taken.

FIG. 3 is a relationship result showing the relationship between the length d (unit: ■) of the contact portion 15 of the side surface portion 14, 14' and the connection loss (dB).

As is clear from the results shown in Figure 3, it is much faster than the conventional technology that connects the cut end faces of optical fibers. Accuracy tolerance has been significantly improved. Thereby, alignment work when connecting optical fibers can be performed simply and easily.

(Example 2) Next, experiments similar to the configuration using the multimode optical fiber shown in FIG. 1 and rfjJ were conducted using a single mode optical fiber.

In this example, the optical fiber has a cladding outer diameter of 3
A stepped single mode optical fiber having a core diameter of 0 μm and a core diameter of 8 μm was used, and the optical fiber was heated and stretched to form a tapered portion having a length of 25 m and a tip diameter of 1 μm, and the same operation as in Example 1 was performed.

The measurement of the optical connection loss of this connection Seizo was performed at a wavelength of 1550 nm.
Light from an LD light source was input into one optical fiber, and the output light from the other optical fiber was measured.

Figure 4 is real! It is a measurement result which shows the relationship between the length d (unit: cabinet) of the contact part of the side part of the taper part of one example, and connection loss (dB).

Furthermore, when the side contact portions of the tapered portions were fused and spliced, the splice loss was further improved and the stability of the loss was increased. As is clear from these results, the tolerance for positional accuracy has been significantly improved compared to the conventional technology that connects the cut end faces of optical fibers.

(Example 3) Next, Example "A" which best represents the features of the present invention will be explained. This example shows the connection of an optical fiber between a multimode optical fiber and a single mode optical fiber. It was operated in the same manner as in Example 1.

FIG. 5 is a plan view explaining the third embodiment of the present invention, and FIG.
The figure is a cross-sectional view of the same along ■-M, where 12 is a Gl-type polygonal optical fiber with a cladding outer diameter of 70 μm and a core diameter of 50 μm used in Example 1, and 22L is a cladding outer diameter of 30 μm and a core diameter used in Example 2. 8μm stepped single mode optical fiber, 1o is the core part, 11 is the cladding part, 13j 23
is a length of 25IIT+ formed by heating and stretching an optical fiber.
1. Tapered part with tip diameter of 1 μm, 14 and 24 are taper @1
3. The side surface of 24 and 15 each show a contact portion that is coated with a small amount of matching oil and brought into contact using its surface tension.

The optical connection loss of this connection was measured from a multimode optical fiber to a single mode optical fiber, and from a single mode optical fiber to a multimode optical fiber with input and output reversed.

Figure 7 shows the length d (unit: 2 m) of the contact portion 15 and the connection loss (
dB). Note that the broken line represents the case from a multimode optical fiber to a single mode optical fiber, and the solid line represents the case from a single mode optical fiber to a multimode optical fiber.

Further, FIG. 8 shows the wavelength characteristics of splice loss when the contact length is 15 m+++. The upper solid line is from multimode optical fiber M to single mode optical fiber (Sl (M-, S
), the lower solid line is from the single mode optical fiber fsl to the multimode optical fiber M (S→M).

As is clear from these results, compared to the conventional technology that connects the cut end faces of optical fibers, the tolerance of positional cleanliness is greatly improved, and the process from multimode optical fiber to single mode optical fiber is reduced. A lossy connection was realized.

Further, the wavelength characteristics were flat without much change as shown in FIG.

(Embodiment 4) Branching and multiplexing of optical fibers when using the optical fiber connection section according to the present invention will be described with reference to the following FIGS. 9 and 10.

FIG. 9 is a plan view illustrating the fourth embodiment of the present invention;
Figure 0 is its XX cross-sectional view. In this example, the multimode optical fiber 12 used in Example 1 was used. Repeated explanation will be omitted.

As shown in these drawings, the optical fibers 12b and 12c are in contact with the tapered portion 13a of the optical fiber 12a via matching oil at their respective taper portions 13b and 13c, forming an optical fiber connection portion. ing.

When light was input from the optical fiber 12m, the light was extracted from the optical fibers 1 2 b and 1 2 c.

On the other hand, when light was input from the optical fiber 12b, the light was extracted from the optical fiber 12a, but only a small amount of light could be extracted from the optical fiber 12c.

Further, when lights of different wavelengths were input into the optical fibers 12b and 12c, the combined light could be outputted to the optical fiber 12a.

As is clear from these results, we were able to add optical fiber branching and multiplexing functions, which are difficult to achieve with conventional technology that connects the cut ends of optical fibers.

Effects of the Invention> As explained above, if the optical fiber connection structure of the present invention is adopted, the tolerance of positional accuracy in connection of a plurality of optical fibers can be greatly increased! By improving IIζ, there is no need for a high-precision alignment device, and there is an advantage that low-loss connection from multimode optical fiber to single mode optical fiber can be realized, and branching and multiplexing functions can be added at the time of connection. .

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams showing the structure of the optical fiber connection in the first and second embodiments, Figures 3 and 4 are graphs showing the measurement results, and Figures 5 and 6 are graphs showing the measurement results. The figure is an explanatory diagram showing the structure of the optical fiber connection part according to the third embodiment, FIG.
FIG. 8 is a graph showing the measurement results, and FIGS. 9 and 10 are explanatory diagrams showing the optical fiber connection structure according to the fourth embodiment. In the drawings, 10 is a core part, 11 is a clad part, 12, 12', 12a, 12b, 12. 22 are optical fibers, 13, 13', 23 are tapered parts, 14, 14', 24 are side parts, and 15 is a contact part. Fig. 1 Fig. 2 Fig. 3 Multimode optical fiber splice loss wavelength [nml Fig. 4 Single mode optical fiber splice loss @ length [mm] Fig. 5 Fig. 6 Fig. 12 Fig. A Contact length [mml Fig. 8 Figure multimode/single mode optical fiber O00

Claims (1)

[Scope of Claims] An optical fiber connection section for connecting optical fibers at their respective ends in order to perform optical transmission between the optical fibers, the core section connecting each of the optical fiber ends with a cladding section. The coated state is tapered, and each end is
An optical fiber connection section characterized in that the connection is made by connecting the side surfaces of the tapered sections.