JPS58208722A - Branch coupler of optical fiber - Google Patents

Abstract

PURPOSE:To reduce the loss of the titled device by separating one end of plural optical fibers for branch coupling, arranging these optical fibers closely in parallel on the other end part so that respective core parts are opposed and arranging the end surface of these fibers on a common plane at their coupling part. CONSTITUTION:The titled coupler is constituted by optical fibers 8 for branch coupling, an optical fiber 9 to be coupled, the core 10 of the optical fiber 9, the cores 11 of the optical fibers 8, and a coupling part 12. Although the core 10 of the optical fiber 9 to be coupled is located on the center axial position similarly to normal optical fibers, the cores 11 of the optical fibers 8 for branch coupling are deflected up to the position contacting with the external circumference. In addition, two optical fibers 8 for branch coupling are arranged in parallel so that their cores 11 are closely opposed each other.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical component for efficiently branching and coupling optical signals to an optical fiber with a simple configuration, and particularly relates to a type in which the branching and coupling section is entirely composed of optical fibers. It is something.

Conventional components of this type can be roughly divided into two types: one type uses a prism □ or a semi-reflective mirror to split and combine light into a spatial beam, and the other type uses a lens to couple this to an optical fiber to be coupled. There is a type in which the entire section is made of optical fiber.

Since the structure and principle of the former are completely different from those of the parts of the present invention, a description thereof will be omitted, and only the prior art related to the latter, which is related to the present invention, will be described here.

FIGS. 1(a) to 1(d) are structural explanatory diagrams of an optical fiber branching coupler constructed using only conventional optical fibers. Here, an example is shown in which there are two branches, and in FIG. 2(a), 1 is an optical fiber for branching and coupling, 2 is an optical fiber to be coupled, and 3 is a coupling part.

Figures (b), (C), and (d) show the branching and coupling optical fibers 1. Joint part 6. A cross section of a coupled optical fiber 2 is shown. Here, 4 is the core and 5 is the cladding. In order to increase the coupling efficiency in the coupling section 6, two branching and coupling optical fibers 1 are arranged in parallel and then integrated by fusion. During fusion, surface tension acts, so the cross-sectional outline after integration is a circle and a hole, as shown in (C), and the core part also has two semi-cylindrical shapes lined up accordingly.

Here, let us consider the case where the optical fiber is a graded multimode fiber, which is commonly used.

Xl-Yl of the cross section shown in Figures 1(C) and (d),
If we look at the refractive index distribution overflowing X2-Y2, we will see 6 and 7 in Fig. 2, respectively. As can be seen from the figure, there is a large difference between the two refractive index distributions, which causes a decrease in coupling efficiency. That is, when light is transmitted from the branching/coupling optical fiber 1 to the coupled optical fiber 2, a loss occurs due to the part 1 (mismatched part) in FIG. When light is transmitted to the branching/coupling optical fiber 1, loss occurs due to the portion (mismatched portion) marked with ■ in FIG.

One possible way to reduce the loss is to eliminate the cladding of the optical fiber 1 for branching and coupling, but even in this case, the insertion loss remains, and furthermore, the loss of the optical fiber 1 itself for branching and coupling is expected to increase. As the diameter becomes smaller, manufacturing becomes more difficult.

As described above, the conventional optical fiber branching coupler constructed only of optical fibers has the drawbacks of high insertion loss and difficulty in manufacturing.

In order to eliminate these drawbacks, the present invention uses an optical fiber having a structure in which the core portion is in contact with the side surface as an optical fiber for branching and coupling, and will be described in detail below with reference to Examples.

6(a) to 6(C) are structural explanatory diagrams of one embodiment of the optical fiber branching coupler of the present invention, and FIG. 6(a) is a perspective view.
It is a diagram. 8 is an optical fiber for branching and coupling, 9 is an optical fiber to be coupled, 10 is a core 11 of the optical fiber 9 to be coupled, and 12 is a coupling portion. Also,
Figures (b) and (c) respectively show a cross section of the coupling portion 12 in (a) on the side of the optical fiber 8 for branching and coupling, and a cross section on the side of the coupled optical fiber 9. As can be seen from these figures, in the optical fiber to be coupled 9, the core is located on the central axis as in a normal optical fiber, whereas in the optical fiber for branching and coupling 8, the core is located up to the point where it touches the side surface. Eccentric. Furthermore, the two optical fibers 8 for branching and coupling are arranged close to each other in a row so that the cores 11 face each other. The shape of the branching/coupling optical fiber core 11 shown in FIG. 6(b) is designed in advance so as to substantially match the shape of the coupled optical fiber core 10 shown in FIG. 6(C) when arranged in parallel. Therefore, the refractive index distribution at the coupling portion 12 matches extremely well between the branching/coupling optical fiber 8 side and the coupled optical fiber 9 side. As a result, the insertion loss of the branch coupling portion is significantly reduced compared to the conventional structure shown in FIG. However, as can be seen from FIG. 6(b), since the optical fibers 8 for branching and coupling are arranged so as to be in contact with each other, a gap 13 exists in the core portion, although it is small. Since this gap 16 often causes loss, it is necessary to make the gap as small as possible. One way to reduce this gap is to increase the diameter of the optical fiber 8 for branching and coupling;
As shown in FIG. 4, there is also a method of increasing the contact width of the core 11 by heating and softening the branching/coupling optical fiber 8 from the outside. Reference numeral 14 in FIG. 4 is an auxiliary glass fiber, which is used to prevent the core 11 from being significantly deformed due to the large change in the overall shape during softening.

The above was for the case where there were two optical fibers for branching and coupling, but
The present invention is also applicable to cases where the number of wires is three or more.

FIG. 5 and FIG. 6 are both cross-sectional structural views of an embodiment in which there are six optical fibers for branching and coupling. Fig. 5 shows an arrangement in which optical fibers for branching and coupling are simply arranged in parallel, and Fig. 6 shows an arrangement in which these are further fused.

FIG. 7 is a cross-sectional structural diagram of an embodiment in which the core shapes are different between the branching and coupling optical fibers.

As in the case of optical fiber bidirectional communication, the light from the semiconductor laser in the transmitting section can be coupled with low loss even to an optical fiber with a small core, and when the receiving section wants to collect as much optical power as possible, the transmitting section Optical fiber for branching and coupling 8-1, optical fiber for branching and coupling 8-2 in the receiving section
By using this, the total loss can be reduced.

FIG. 8 is a cross-sectional structural diagram of an embodiment in which the core of one of the two V-branch coupling optical fibers extends over the entire fiber. In such a structure, as in the case of FIG.
-3. By using the optical fiber 8-4 for branching and coupling in the receiving section, it is possible to reduce the total loss. As an extension of this embodiment, both branching and coupling optical fibers 8-3.8. It is also possible to adopt a structure in which the core extends throughout the fiber. Such a structure is effective when simply branching the light of the optical fiber 9 to be coupled.

In the structures shown in FIGS. 7 and 8, there are two optical fibers for branching and coupling, but the present invention is equally applicable to six or more optical fibers.

As explained above, in the present invention, an optical fiber for branching and coupling with a special structural cross section is used. By taking steps in advance, such as making a material in which the core material is placed in an eccentric state, a product having a desired cross-sectional structure when spun can be produced relatively easily. Therefore, the structure of each of the embodiments of the present invention described above can be easily realized and has features such as low loss and low placement, and can be used to create a high-performance bidirectional optical transmission coupler, This has the advantage of being able to create optical mixers, photosynthesizers, etc.

[Brief explanation of drawings]

Figures 1 (a) to (d) are structural explanatory diagrams of a conventional optical fiber branching coupler, Figure 2 is a diagram showing the refractive index distribution at the coupling part of a conventional optical fiber branching coupler, and Figure 3 (a) ) ~ (C
), FIG. 4 is a structural explanatory diagram of an embodiment of the optical fiber branching coupler of the present invention, FIGS. 5, 6, 7, and 8 all show embodiments of the present invention. FIG. 2 is a cross-sectional structural diagram of a coupling optical fiber. 1... Optical fiber for branching and coupling 2... Optical fiber to be coupled 3... Coupling section 4... Core 5... Clad 8+ 81 +
8-2+ 83+ 84...Optical fiber for branching and coupling 9...Optical fiber to be coupled 10...Core of optical fiber to be coupled 11...Core 12 of optical fiber for branching and coupling...Coupling section 16. ...Gap 14...Glass fiber patent applicant Nippon Telegraph and Telephone Public Corporation's representative patent attorney Junnosuke Nakamura 1 "11 Spear 2 Figure t3 Procedural amendment (voluntary) September 20, 1970 Director General of the Japan Patent Office Display of the case Patent application No. 91257 of 1981 Title of the invention 0 relationship with the optical fiber splitter/coupler correction case Patent application 7, agent
Subject of human amendment: Each column of the detailed description of the invention in the specification, the brief description of the drawings, and the drawings. Contents of correction (1) "Optical mixer, optical combiner J" on page 8, line 5 of the specification is corrected to "optical directional coupler, optical accessor." (2) Insert the following sentence between page 8, line 6 and line 7 of the specification. 9 shows an example of the configuration of an optical directional coupler. This was realized using four sets of optical fiber branch couplers shown in FIG. 3(a). .6.1.7
゜18 indicates an input/output port. Now port 15
Considering the optical input from the port, the optical power is split into two and then becomes the optical output from the port (16.18). No optical output appears at port 17, and port 17 becomes an isolation port in this case. Similar thing is port 16, 17.18
This also applies to optical input. Therefore, the optical circuit shown in FIG. 9 functions as a directional coupler. Although four sets of optical fiber branching couplers are used in Figure 9, a three-port optical branching circuit can also be realized by using three sets of optical fiber branching couplers using the same configuration method. . FIG. 10 shows an example of the configuration of an optical accessor. This is the third
It was realized using two sets of optical fiber branching couplers in Figure (al), and 19, 20, 21, and 22 refer to the input/output ports. Now, an optical signal propagates from port 19 to port 20. Assuming that the optical fiber is connected to the port 19, a part of the light can be branched by the optical fiber branching coupler on the port 19 side and taken out as an output from the port 21.Furthermore, the optical signal incident from the port 22 can be output from the port 20 side. In the optical fiber branching coupler, it is combined with the optical signal propagated from port 19 and appears at port 20.In this way, the 10th
The optical circuit shown in the figure can take out a part of the optical signal propagating through the optical transmission line and conversely insert another optical signal, and functions as an optical accessor. (3) Add the following sentence after "Aru." on page 8, line 15 of the specification. [Figures 9 and 10 are configuration examples of optical circuits that can be realized using the optical fiber branching coupler of the present invention. It is. (4) Explanation of the following symbols shall be added from page 9, line 6 of the specification. r15.16.17.18... Optical directional coupler input/output ports 19, 20. 21, 22... Optical accessor input/output ports" (5) Add drawings FIGS. 9 and 10. The drawings to be added are as attached. that's all

Claims (1)

[Claims] It has an optical fiber to be coupled and a plurality of branching and coupling optical fibers having a structure in which the core portion is in contact with the side surface, and the plurality of branching and coupling optical fibers have one end separated from each other and the other end separated from each other. The respective core portions are arranged in parallel and facing each other in close proximity at the coupling portion, and the end faces of the plurality of branching and coupling optical fibers arranged in parallel are all located within one common plane at the coupling portion, and each core 1. An optical fiber branching coupler, characterized in that the optical fiber branching coupler is constructed by collectively coupling the core of the coupled optical fiber.