JPS5926005B2 - Optical branching and coupling circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compact and highly efficient optical branching and coupling circuit suitable for optical communication systems.

Recent improvements in the performance of optical semiconductor devices and optical fibers for communications have been remarkable, and research and development for the practical application of optical communication systems is progressing in various places.

One of the optical devices indispensable for the practical application of optical communication systems is an optical branching/coupling circuit. This is used when extracting a part of the optical signal to monitor the state of the main optical signal, when receiving the optical signal, when branching the main optical signal into the first and second main optical signals, or when branching the main optical signal into the first and second main optical signals. It is used when transmitting a second optical signal superimposed on an optical signal, and is required to be small, highly efficient, inexpensive, and highly reliable.

The optical branching/coupling circuit conventionally used for this purpose is a combination of individual parts such as a reflecting mirror (for example, a half mirror) and a lens system (for example, an objective lens), and the individual parts themselves are large in size and weight. In addition to being expensive, they need to be installed accurately, which requires a lot of time and skill, making them even more expensive.

On the other hand, in terms of performance, since it is made up of individual parts, there are many unnecessary interfaces, which leads to increased loss.In addition, performance changes due to changes in the mutual positional relationships of individual parts over time are also a major problem. be.

Therefore, the first object of the present invention is to obtain a small and lightweight optical branching and coupling circuit suitable for optical communication systems, and the second object of the present invention is to obtain optical branching and coupling circuits suitable for optical communication systems, especially simple optical communication systems. The third object of the present invention is to obtain an inexpensive, high-performance, and highly reliable optical branching and coupling circuit with a small number of compatible individual parts. The object of the present invention is to obtain an optical branching/coupling circuit in which the optical axes of incident light, outgoing light, branched light, or combined light are substantially parallel to each other. According to the present invention, the first convergent light is obtained by cutting a transparent body whose refractive index gradually decreases from the center toward the periphery in a cross section perpendicular to the axial direction, along a plane parallel to the axial direction. a transmission body, and a second convergent light transmission body obtained by cutting the transparent body in a plane parallel to the axial direction, and the first and second convergence light transmission bodies are formed of the transparent body. An optical branching/coupling circuit characterized in that the cut surfaces are arranged close to each other is obtained.

Next, the present invention will be explained using the drawings.

Fig. 1 shows an embodiment of the present invention, and 1 and 2 are cross sections perpendicular to the axial direction, and the focusing property is obtained by cutting a transparent body whose refractive index gradually decreases from the center to the periphery along a plane including the axis. In the optical transmission body, 3, 4, 5 and 6 are optical fibers.

Here, the cut surfaces of the convergent light transmitters 1 and 2 are close to each other, and part of the light incident toward the cut surfaces is reflected and part of the light is transmitted. In this configuration, the light emitted from the optical fiber 3 enters the convergent light transmitter 1 and then proceeds toward the convergent light transmitter 2 .

When this light reaches the vicinity of the convergent light transmitters 1 and 2, part of it is reflected and heads towards the optical fiber 4, and part of it is transmitted and heads towards the optical fiber 5. The length of the convergent light transmitting bodies 1 and 2 is n/2 of the pitch (distance until the meandering light propagating inside reaches the original direction and position again) of the transparent body.
If the number is double (n is an integer), the output light will be parallel to the input light.

As in this embodiment, light incident parallel to the length direction of the convergent light transmission body 1 is branched into optical fibers 4 and 5 parallel to it and travels therethrough. Now, when light is further incident on the convergent light transmission member from the optical fiber 6, the light is similarly split into reflected light and transmitted light at the cutting surface and propagated to the optical fibers 4 and 5.

By using the converging light transmitters 1 and 2 that are close to each other in this way, it is possible to split light as well as combine light.

In the above embodiment, when the depth of the seepage wave is close to the distance between the convergent optical transmitters 1 and 2, the convergent optical transmitters 1 and 2
The reflectance and transmittance of the seeping waves in the vicinity of the optical fiber 3 can be changed arbitrarily by changing the interval.
It is clear that the distribution ratio of the light emitted from the optical fibers 4 and 5 to the optical fibers 4 and 5 and the coupling ratio of the light from the optical fibers 3 and 6 to the optical fibers 4 and 5 can be selected to desired values.

Furthermore, in the above embodiment, it is of course possible to change the degree of branching or coupling by filling the gap between the convergent light transmitters 1 and 2 with a substance having a refractive index different from that of the convergent light transmitters 1 and 2. It is. Further, in the above embodiment, convergent light transmitting bodies 1 and 2 obtained by cutting one of the above-mentioned transparent bodies are used.
However, the focusing light transmission bodies 1 and 2 may be obtained by cutting transparent bodies with different characteristics, or they may be cut on a plane that does not include the axis of the transparent body. It is clear that it may be used. Furthermore, in the above embodiment, one set of branching and coupling was explained, but as shown in FIG.
and 2 can be used. Here, 3 in Figure 2
, 4 and 5 indicate optical fiber groups, respectively. Finally, the present invention has features such as small size, light weight, high performance, high reliability, and simplicity because it uses a convergent optical transmission body that has reflection and transmission surfaces inside. Accordingly, it is possible to obtain an optical branching/coupling circuit that is well suited for optical communication systems.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, in which 1 and 2 are convergent optical transmission bodies, and 3, 4, 5, and 6 are optical fibers. FIG. 2 shows another embodiment of the invention, in which 1 and 2 are convergent light transmission bodies, and 3, 4 and 5 are optical fiber groups.

Claims (1)

[Claims] 1. A first focusing light transmitting body obtained by cutting a transparent body whose refractive index gradually decreases from the center toward the periphery in a cross section perpendicular to the axial direction, along a plane parallel to the axial direction; a second converging light transmitting body obtained by cutting a transparent body along a plane parallel to the axial direction, and the first converging light transmitting body and the second converging light transmitting body An optical branching/coupling circuit characterized in that the cut surfaces of the two are arranged close to each other.