JPS6015243B2 - Optical splitter coupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides data buses and C
The present invention relates to an optical branching coupler that is effective when configuring an ATV system or the like.

For example, a data bus system, as seen in the diagram of FIG.
In some cases, one female point belonging to one group can exchange information with all points belonging to one other group.

That is, this corresponds to a case where point 101 in group 1 exchanges information with point #2 201, 202, 203, . . . belonging to group 20. In the figure, 1
If we pay attention to the 82 points in the group, transmission lines 150, 151, etc. from this point to all the points in the other groups.
It is not economical as it would require installing... Therefore, as shown in FIG. 2, if an optical branching coupler 30 is used which has the function of equally distributing a signal from a certain point in one group to each point in another group, the transmission path can be significantly simplified. I understand that. As an element with such a function,
A so-called star coupler has been proposed, in which multiple optical fibers with the same Sekiguchi angle as the optical fibers used in the transmission line are closely assembled, and a fiber rod with a core diameter approximately equal to the aggregate outer diameter is used as a mixer. has been done. However, this type of star coupler inherently suffers from high insertion losses. It is also theoretically possible to construct such an optical branching coupler by combining a large number of semi-transparent mirrors, but this requires the use of a large number of lenses and semi-transparent mirrors. Position adjustment is very difficult, and certain light rays have to pass through several semi-transparent mirrors, which are functionally unreliable, resulting in a large loss of light. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an optical branching coupler suitable for multi-branching, which has less insertion loss than optical branching couplers obtained by conventional techniques.

A second object of the present invention is to provide an economical optical branching coupler with a small number of basic elements, easy assembly and adjustment, and a 4-inch type.

According to the present invention, the refractive index distribution in a plane perpendicular to the optical axis has a parabolic distribution with a maximum on the optical axis, and the length is equal to or slightly smaller than Xn pitch (n is a positive integer). a first total reflection surface that partially includes the optical axis in the length direction, and an angle between the first total reflection surface centered on the optical fiber, and a long one. m number of east-focusing optical transmission bodies (m=1, 2, 3
・・・・・・・・・・・・・・・・) An optical branching coupler formed by cascade connection is obtained.

Next, examples of the present invention will be described in detail with reference to the drawings.

First, FIG. 3 is a diagram illustrating the general structure of an optical element used in this device and its basic principle, in order to help understand the operating principle of the optical branching coupler according to the present invention. As seen in the side cross-sectional view in Figure a, this element is a glass cylinder called an east-focusing optical transmitter, and the distance y from the optical axis in a plane perpendicular to the optical axis AA' and the refraction The relationship with the index n is as shown in Figure b, with the maximum refractive index on the optical axis and decreasing parabolically with y. The shaded area in FIG. a shows the light transmission mode when the length 1 of the optical transmission body 40 is a so-called 1/2 pitch. The light beam emitted while spreading from the optical fiber 50 arranged parallel to the optical fiber AA' travels along the path and spread angle as shown, and enters the optical fiber 60. This east-focusing optical transmission body has a focusing effect and has a beam waist at the emission point, so it is characterized in that it does not require any other lens for coupling with the optical fiber.
FIG. 4 shows the first embodiment of the present invention, and in FIG.
This is a double-pitch optical fiber transmission body, and the difference from that shown in FIG. 3 is that there are total reflection films 701 on two sides including optical axes that are in a relative positional relationship perpendicular to each other on the left and right with half the length as the boundary. and 702.

The optical fibers 501 to 504 and 601 to 604 are arranged substantially parallel to the optical axis and equidistant from the optical axis in a plane having an angle of 45° with respect to the two total reflection surfaces. In the application shown in FIG. 2, optical fibers 501 to 50
4 shows the points 111, 112, 113 and 11 of group 11.
4 are connected to the optical fibers 601 to 604, respectively, and the points 21 1, 212, 213, 214 of the group 21 are connected to the optical fibers 601 to 604, respectively.
is connected. FIG.
, 602, 603, 604, and shows the operation mode when the light beam (
After the light rays indicated by diagonal lines downward to the right are reflected by the total reflection film 701, half of them are immediately reflected again by the total reflection film 702 and enter the optical fiber 601, and the other half are completely reflected by the total reflection film 702. The light does not enter the reflective film 702 but enters the optical fiber 602 . In addition, half of the remaining light rays, that is, the light rays indicated by diagonal lines on the upper right, are reflected by the total reflection film 702 and enter the optical fiber 604, and the remaining half of the light rays are reflected not only by the total reflection film 701 but also by 702. The light enters the optical fiber 603 without being transmitted. The above description has been made for one of the optical fibers 501 on the input side, but the same applies to the optical fibers 502, 503, and 504, and since they are bilaterally symmetrical, for example, light enters from the optical fiber 601. works the same way. Therefore, in the optical branching coupler configured as shown in FIG.
.
02, 503, and 504. In the above description, the optical fibers 501 to 5
04 and 601 to 604 were arranged approximately parallel to the optical axis and equidistantly in a plane of 45o with respect to two orthogonal total reflection surfaces. That is, the optical fibers 501 to 504 and 601 to 604 were arranged so as to be located at each point of a square on both end surfaces of the east concentrating optical transmission body 401. However, as shown in the diagram of the arrangement of optical fibers seen through in the optical axis direction in FIG.
Even if 8 and 605 to 608 are arranged at the vertices of two congruent rectangles, each side of these two rectangles is parallel or perpendicular to the total reflection films 701 and 702. By arranging the two rectangles so as to overlap in the light direction, the same function as described above can be achieved. Furthermore, in the above embodiment,
Although the two total reflection films 701 and 702 are arranged at right angles to each other including the optical axis, there is no problem even if these total reflection films are positioned around the light bag at a non-perpendicular position. This is done with reference to FIG. 4d, which shows perspective from the optical axis direction. In the figure, two total reflection films 703 and 70
4 make any angle 0 with respect to the optical axis other than oo and 90o. In this case, if one optical fiber 509 is placed on one of the total reflection surfaces, for example, a surface 801 that is perpendicular to 703 and includes the optical axis, the other optical fibers that transmit and receive light beams can be connected to each other as shown in the figure. As shown in FIG. As a special example, the angle 0=4 in d in the same figure
In the case of 5o, the above rectangle becomes a square. However, in the case of 8 sheep and 9 pins, equal light power will not separate them. For example, a
When the light ray enters from the optical fiber 509 at =4y,
The ratio of optical power incident on the optical fibers 609, 610, 611, 612 is 3:1:1:3. The property of being able to change the branching ratio in this way means that, for example, when the lengths of the optical transmission lines connected to this optical splitter/coupler differ (that is, the transmission loss differs), it is possible to It can be used when selecting the branching ratio. FIG. 5 shows an embodiment in which two optical branching couplers with a pitch length of 1/2 are connected in cascade.

Figure a shows optical branching couplers 402 and 403 of the same structure as shown in FIG.
As shown in Figure b, the total reflection film 707 included in the pine.
The structure is shown cascaded to form an angle of 50°. In FIG. b, the light beam that enters the optical branching coupler 402 from the optical fiber 513 within the plane 802 that forms an angle 45o with the total reflection plane 705 and includes the optical axis is transmitted to the optical branching coupler 402 from the optical fiber 513.
At the point of incidence from 02 to 403, as shown in Figure c when looking at the 403 side from the connection surface, the focal points 613, 614, 61
The light is divided into 5,616 equal parts and focused. Figure d shows that the light rays enter the optical splitter coupler 403 from the above-mentioned condensing points 613, 614, 615, and 616, and are split by the total reflection films 707 and 708, and are imaged on the output end face of the optical splitter coupler. The location is shown transparently. That is, in figure d, 6
The light rays incident from 13 are directed to points 617, 618, 619 on the output surface in exactly the same way as explained in FIG. 4c above.
, 620', and the ray incident from 614 is focused on point 62.
1,622, 623, 624, the rays incident from 615 are focused on points 617, 618, 619, 620', and the rays incident from 616 are focused on points 621, 622, 6.
23,624. That is, the optical fiber 5 in Figure b
Assuming that the optical power entering the optical branching coupler 402 from 13 is 1, the focusing power at each of the focusing points 613, 614, 615, and 616 is 0 if the scattering absorption loss of the light transmission soot is 0. It is .25. Furthermore, a focal point 617 on the output surface,
……………, the light gathering power at 624 is 0.125. Moreover, these condensing points are arranged at intervals of 45 degrees around the optical axis, as is clear from Figure d. Therefore, eight optical fibers are installed parallel to the optical axes of the optical branching couplers 402 and 403, and at equal distances from the optical axes, so that the input side and the output side are symmetrical every 450 degrees around the optical axis. In addition, one of them is in contact with the first total reflection surface that is in contact with the input surface, as shown by the input point 513.
By arranging them within the plane indicated by 802 forming an angle of 5o, an eight-terminal optical branching coupler can be constructed. The above embodiments have explained 4-terminal and 8-terminal optical branching couplers, but these can function as a 4-terminal and 8-terminal, respectively, if the number of optical fibers on the input side is limited to one. That should be obvious.

Similarly, m pieces of 1/2 pitch optical branching coupler (m 1,
2, 3, ・・・・・・・・・・・・・・・) By cascade connection, it is possible to realize an optical branching coupler with 4×m terminals, and at the same time, it is possible to realize an optical branching coupler with 4×m terminals. realizable. Also,
It has been explained that the total reflection film inside the east-focusing optical transmission body is selected to have a length of 1/4 pitch in the optical axis direction, but for example, the light of the total reflection films 701 and 702 in FIG. The lengths in the axial direction do not necessarily have to be equal, and there may be a portion without a total reflection film inside. Such an optical branching/coupling device results in changing the branching ratio and has the same function as the method described in FIG. 4d. Furthermore, the arrangement of optical fibers 501 to 504 shown in FIG. 4a and the arrangement of optical fibers 505 to 508 shown in FIG. If done simultaneously within a plane, a two-circuit four-terminal optical branching coupler can be realized, and a circle having a radius different from the radius of the circle centered on the optical axis to which the eight optical fibers belong shown in Fig. 5d can be realized. On the circumference, one of the other eight optical fibers is attached to the surface 80 of FIG. 5b.
By arranging them at equal angles as shown in FIG. 2, an optical branching coupler with approximately 8 terminals can be realized.

As is clear from the above description, according to the present invention,
Compared to the conventional technology, the number of elements is small and the configuration is simple, so it is easy to assemble and adjust, is small in size, and is economical. Furthermore, it is suitable for optical multi-branching of optical fiber transmission lines. Great effects can be obtained when used in data bus systems and CATV systems.

[Brief explanation of drawings]

Figure 1 shows one of the systems in a conventional data bus system.
FIG. 2 is a diagram showing an example of a system in a data bus system to which the optical branching coupler according to the present invention is applied;
Figures 3a and 3b are diagrams explaining the configuration and characteristics of a general optical fiber transmission body, and Figures 4a to d are side views, operation mode explanatory diagrams, and end faces of the optical branching coupler according to the present invention. FIGS. 5A to 5D show a side view and an end view, respectively, when two optical branching couplers according to the present invention are connected vertically. In addition, in the figure, 501 to 513, 601 to 612, 6
17 to 624 are optical fibers, 613 to 616 are beams for focusing spots, 401 to 403 are optical branching couplers according to the present invention, and 701 to 708 are total reflection films. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 The refractive index distribution in the plane perpendicular to the optical axis has a parabolic distribution with a maximum on the optical axis, and the length is 1/2 × n pitch (n is a positive integer) or slightly shorter than that. The selected surface has an angle between the first total reflection surface partially including the optical axis in the internal length direction and the first total reflection surface centered on the optical axis, and has a length. There are m convergent light transmission bodies (m=1, 2, 3, ...
…) Optical branching couplers connected in cascade.