JPS6020722B2 - light distributor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to, for example, an optical splitter in optical fiber communication.

[Prior art]

A conventional device of this type is shown in FIG.

In the figure, 1, 2, 3 are step type fibers, la,
2a and 3a are the core portions, lb, 2b, and 3b are the cladding portions, and 4 is a beam splitter layer that transmits a portion of light and reflects a portion of the light. Next, its operation will be explained.

For example, when light enters an optical fiber, part of the light is transmitted by the beam splitter layer 4 at the part where it is joined to the optical fibers 2 and 3, and part is reflected. 45o to the central axis of 1
Since the reflected light has an angle of 90 degrees, the direction of the light is changed by 90 degrees and enters the optical fiber 3. Further, the transmitted light goes straight as it is and enters the optical fiber 2. Therefore, the light propagating through the core portion la of the optical fiber 1 is distributed to the core portions 2a and 3a of the optical fibers 2 and 3 at a certain distribution ratio by the beam splitter layer 4. Since the conventional optical distributor is constructed as described above, the tip of the optical fiber must be polished obliquely, the optical fiber is easily broken, and the dimensional accuracy is strict, making processing difficult. Therefore, the yield rate also deteriorates. Another drawback is that the mode distribution of light propagating through the optical fiber also affects the distribution ratio. [Summary of the Invention] This invention was made in order to eliminate the drawbacks of the conventional ones as described above.The distribution ratio can be easily varied, and the distribution ratio can be easily varied depending on the mode distribution of light propagating in the optical fiber. The object of the present invention is to provide an optical distributor in which the distribution ratio is hardly affected.

[Embodiments of the invention]

Embodiments of the invention will now be described with reference to the drawings.

In Figs. 2, 3, and 4, 1, 2, and 3 are stepped optical fibers, la, 2a, and 3a are their core parts, and lb
, 2b and 3b are the cladding parts. 5 and 6 are gradient index lenses with a period length of 1'4 (medium/2); 7
4 is the common optical axis of the lenses 5 and 6, and 4 is a branch comprising a fan-shaped total reflection layer 8 on the end face of the lens 5 or 6, which is divided into fan shapes with the optical axis of each lens 5 and 6 as the apex. - At the coupling portion, only the light incident on the fan-shaped total reflection layer 81 is totally reflected, and the other light incident thereon is transmitted.

The fan-shaped total reflection layer 8 is formed as a thin film by vapor deposition or the like of gold or silver, which has an extremely high reflectance for visible light. In general, soot has a distribution in which the refractive index decreases in proportion to the square of the radius from the central axis of the lens toward the outer diameter, and as in normal optical lenses, it forms an image. It has an effect.

The relationship between the geometrical characteristics within the gradient index lens will be explained below.

Here, for the sake of simplicity, a two-dimensional lenticular soot material is considered and its refractive index distribution is expressed by the following equation. n=ratio (・-Kyoa〆) ...{11 Here, the ratio is the refractive index at the central axis, a is the refractive index distribution constant,
x is the distance from the central axis.

It is known that the ray in this medium can be described by the following ray determinant (2) using paraxial ray approximation. ...
(2, where x represents the position of the ray from the central axis of the lens, the inclination of the ray with respect to the female axis of the scale lens, Z' represents the direction of the central axis of the lens, and 1 represents the length of the lens.

Next, the operation of an embodiment of the present invention shown in FIGS. 2, 3, and 4 will be explained.

First, the light emitted from optical fiber 1 has length stroke/2 (= no al
) into the gradient index lens 5. The light that has entered this lens 5 is incident on the branching/coupling section 4 , and the light that has entered the fan-shaped total reflection layer 8 of this branching/coupling section 4 is totally reflected, and the light is reflected again by the lens 5 onto the end face of the optical fiber 3 . is incident as a convergent ray. Also, the fan-shaped total reflection layer 8 of the branching/coupling portion 4
The light incident on the other portions is transmitted and is incident on the end face of the optical fiber 2 by the lens 6 as a convergent light beam. Therefore, the proportion of the fan-shaped total reflection layer 8 that occupies the light irradiation surface of the branching/coupling section 4 can be set to an arbitrary distribution ratio by changing the central angle of the sector.

The light reflected or transmitted by the above-mentioned branching/coupling part 4 will each travel m length (zoal) within the lens, and the formula ■ is {
3} can be expressed as the following equation. ．．・・・．・・・． ．．
(3) Therefore, the light emitted from the optical fiber placed at a distance S from the central axis 7 of the lens 5 is transmitted to the input end face of the lens 5 and the output end face of the lens 6, and the optical fiber 1 Images of the same size as at the time of incidence are formed at symmetrical positions.

Furthermore, the spread angle of the light is also kept the same as at the time of incidence. Therefore, we used a precision fine movement table to move the optical fibers 2 and 3 at that position.
If the optical fibers 2 and 3 are arranged and fixed, light with a distribution ratio determined by the transmission/reflectance ratio of the branching/coupling part will be transmitted through the optical fibers 2 and 3.
A highly efficient optical distributor is constructed. Note that the junction between an optical fiber and a gradient index lens, a lens with a beam splitter layer, and another lens has a refractive index close to that of the optical fiber or lens to prevent unnecessary loss. Use adhesive or matching oil with a certain rate. Optical splitters with various distribution ratios can be obtained by appropriately selecting the material and thickness of the beam splitter layer in consideration of the wavelength of the light. Furthermore, the distribution ratio is kept constant almost without depending on the mode power distribution of light propagating in the optical fiber.

The length of each gradient index lens can be as long as 11 (m=o'1'2・●・).

If the optical axes of the two lenses are slightly misaligned, the exit angle of the light coming out of the lens 6 will change.
All you have to do is place it on the central axis.

Although the case of a thin film has been described, a beam splitter plate or a mirror plate may be inserted between the lenses.

FIG. 5 shows still another embodiment of the present invention. In the above embodiment, the case where there is one optical fiber for incidence has been explained, but by adding one optical fiber for incidence 21, four optical fibers for incidence are added. The terminal structure increases the degree of freedom in terminal selection.

FIG. 6 shows still another embodiment of the present invention.

As shown in Fig. 7, a branching/coupling section 4 having a plurality of types of fan-shaped total reflection mirrors formed to have different paths and reflection ratios is attached to a disk 9, and the disk 9 is rotated. By rotating around axis 9c, variable light splitters with several different distribution ratios can be constructed. In each of the above embodiments, the case where a stepped optical fiber was used as the optical waveguide was explained.
It does not matter if it is a concentrated type optical fiber, a single mode optical fiber, or a multimode optical fiber. Further, in the above embodiment, the branching/coupling section 4 is configured by dividing the fan-shaped total reflection layer and the transmitting section into fan shapes, but a part of the light is transmitted through the transmitting section.
It can also be configured with a layer that partially reflects (for example, a semi-transparent mirror). [Effects of the Invention] As explained above, the present invention includes lenses provided at the connection ends of the input and output optical waveguides, and a sector-shaped total reflection layer divided into sectors with the optical axis of the lens as the apex. By exploring a configuration with branching and connecting parts,
The distribution ratio can be changed simply by changing the fan-shaped center angle of the sector-shaped total reflection layer, and changing this distribution ratio does not affect the mode distribution in the optical fiber. This has the effect that it is almost unaffected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional side view showing a subordinate optical distributor, FIG. 2 is a sectional side view showing an optical distributor according to an embodiment of the present invention, and FIG. The cross-sectional views along the m-line, FIGS. 4 to 7, are as follows:
FIG. 7 is a sectional view and a side view showing another embodiment of the invention. 1, 2, 3... Optical fiber, 4... Branching/coupling part, 5, 6... Gradient index lens,
7...The central core of those lenses, 8...
- Fan-shaped total reflection layer. In the figures, the same reference numerals indicate the same or equivalent parts. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. Two gradient index lenses arranged on the same optical axis, and a fan-shaped sector inserted into the connecting part of these lenses and divided into sectors with the optical axis of each lens as the apex. 1. An optical distributor comprising: a branching/coupling section having a total reflection layer; and a plurality of input and output optical waveguides connected to end surfaces of the lenses opposite to the connection section. 2. A fan-shaped total reflection layer in which the branching/coupling portion is divided into fan shapes with the optical axis of each lens as the apex, and a part of the light is transmitted through the fan-shaped total reflection layer other than the fan-shaped divisions, and a part of the light is reflected. 2. The optical distributor according to claim 1, further comprising a layer comprising: