JPS6383706A - Optical star coupler - Google Patents

Abstract

PURPOSE:To distribute light in two ways by arranging a unidirectional refraction factor distribution type slab-like lens A with a comparatively large aperture angle and a lens B with a comparatively small aperture angle so that their directions of the distributions of their refraction factors coincide. CONSTITUTION:A fiber array 4 composed of plural fibers with large aperture angles and a fiber array 5 composed of plural fibers with small aperture angles are abutted and provided on the one and other ends of a pair of unidirectional refraction factor distribution type slab-like lenses 6 and 7, respectively, so that said arrays can be arranged perpendicular to the direction of the refraction factor distributions of the slab-like lenses. In the lenses 6 and 7, their lengths are about 1/4 pitch, their widths are almost the same as array widths of the fiber arrays 4 and 5, and their aperture angles are the same as those of the fiber arrays 4 and 5. The lenses 6 and 7 are jointed so that their directions of the refraction factor distributions can coincide. Thus light can be uniformly distributed in two ways with a little light losses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an optical star coupler for distributing light from one optical fiber to a plurality of optical fibers.

[Conventional technology 1] With the performance improvement of optical fibers and semiconductor lasers,
Optical communication is reaching the stage of practical application. Among these devices, the optical signal divider is an important element in terms of the system configuration for the in-office equipment. As a conventional optical star/coupler, as shown in FIGS. 1 and 2, a combination of a unidirectional refractive index gradient slab lens 1 and fiber arrays 2 and 3 is known. It is being Here, a unidirectional refractive index gradient type slab-like lens has a maximum refractive index n on the central axis plane, that is, the X-Z axis plane, and the refractive index increases only in the y-axis direction toward the periphery. Gradually, n (y
l = n02 (1-ao2y2) [qo changes according to the equation of a constant q, and has a -like 1 refraction index for the X direction and the 7 directions, which are perpendicular to the y axis. Therefore, as shown in Fig. 1 and Fig. 2, on both end surfaces of the slab-like lens 1 with a large I pitch of 130.5, [Note: Here, 1 bit is the length of the light propagating in a meandering manner through the lens. This refers to one cycle. perpendicular to the refractive index distribution direction of the lens (i.e. 5
, parallel to the X-axis direction), the output α from each fiber of fiber array 2 is
The ray of light that is 1 is bent toward the central axis plane while passing through the slab-like lens 1 in the y direction, that is, the refractive index distribution direction of the lens, and is condensed at the exit end surface (Fig. In the X direction, the split light beam is repeatedly reflected on the side surface of the slab lens 1 according to the exit angle, and is emitted from the exit end face at a certain aperture angle (Fig. 2).
The light beams incident from each fiber are uniformly distributed to each fiber of the fiber array 3. Further, if this configuration is adopted, the optical signal from the fiber array 3 can be distributed to each fiber of the fiber array 2.

However, even with this conventional optical star coupler, it is necessary that fiber arrays 2 and 3 have the same aperture angle. However, in the future, the three fields of optical communication
When transmitting optical information from a long-distance trunk line and optical information from a short distance area to each other, fiber arrays with different aperture angles may be used. In this case, with conventional optical star couplers, light from a fiber with a low aperture angle can be efficiently distributed to a fiber with a high aperture angle; , cannot be fully inserted into fibers with large aperture angles. As can be seen from Figure 1, this
In order to efficiently condense light rays emitted from a fiber with a high aperture angle in the y direction (the refractive index distribution direction of the lens), it is necessary to increase the aperture angle of the slab lens. This is because if the angle is made too large, the angle of the condensed light becomes too large, and a fiber with a low aperture angle cannot receive sufficient light.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical star coupler that overcomes these conventional drawbacks and enables bidirectional light distribution between a fiber array with a high aperture angle and a fiber array with a low aperture angle.

[Means for determining the problem with VR] In order to achieve the above object, in this invention, the refractive index decreases in one direction in proportion to approximately the square of the distance from the optical axis plane, and the refractive index distribution is changed. Comparison of a unidirectional refractive index distribution type slab lens △, which has a relatively large aperture angle to the right in terms of direction, and a similar unidirectional refractive index distribution type I1 type slab lens in terms of the direction of the refractive index distribution. Lenses B and the like, each having a small aperture angle, are brought into contact with each other at their end surfaces so that each has an odd number multiple of approximately 1/4 pitch, and the directions of their refractive indices match, forming a lens pair. A fiber array formed by arranging several fibers with a high aperture angle is brought into contact with the end face of the lens pair having a high aperture angle, and on the other hand, the end face of the lens pair having a low aperture angle A fiber array consisting of a plurality of fibers having a low aperture angle is brought into contact with the end face of the optical star coupler to form an optical star coupler.

According to the optical star coupler having such a configuration, bidirectional light distribution between the high aperture angle fiber and the low aperture angle fiber can be efficiently performed.

[Example] The present invention will be described below based on the drawings. FIGS. 3 and 4 show an embodiment of the present invention. First, to explain the configuration, a fiber array 4 made up of a plurality of fibers having a high aperture angle is arranged on one end face of a lens pair made up of unidirectional gradient index slab lenses 6 and 7, and a fiber array 4 made up of a plurality of fibers having a high aperture angle is disposed on the other end face. A fiber array 5 consisting of a plurality of fibers having a low aperture angle is placed in contact with each other so that the fibers are arranged perpendicularly to the direction of the refractive index distribution of the slab-shaped lens. The length of the slab lens 6 is approximately 1/4 bit, its width is approximately equal to the arrangement width of the fiber array 4, and its aperture angle is also equal to that of the fiber array 4. Similarly to the slab-shaped lens, the width is approximately 1/4 pitch, the width is approximately equal to the arrangement width of the fiber array 5, and the aperture angle is also equal to that of the fiber array 5. The slab lenses 6 and 7 are joined together so that the directions of their respective refractive index distributions match.

Here, the slab-shaped lens 6 can be produced, for example, by the method disclosed in Japanese Patent Application No. 59-146913 by the present applicant, and the slab-shaped lens 7 can be produced, for example, by the method disclosed in Japanese Patent Application No. [Can be made using a method such as that disclosed in No. 758-16109.

In addition, fiber arrays with low aperture angles can be made using quartz fibers made by the CVD method, and fiber arrays with high aperture angles can be made using multicomponent systems made by the ion exchange method or rod-in-tube method. It can be made using fiber.

Next, the action will be explained. Regarding the direction of the refractive index distribution of the slab lens, that is, the light in the y direction, as shown in Figure 3,
Light with a large output angle entering from one of the fiber arrays 4 having a high aperture angle is first converted into parallel light by a slab-like lens 6 having a high aperture angle, and then converted into parallel light by a slab-like lens 7 having a low aperture angle. The light is condensed onto the end face of the lens and efficiently transmitted to the fiber array 5 with a low aperture angle of <1 m. On the other hand, for the X section that is perpendicular to the direction of the refractive index distribution,
As shown in the figure, the light incident from the fiber array 4 is reflected by the side surfaces of the slab lenses 6 and 7 and travels straight through the slab lenses, and due to the difference in aperture angle, the light entering the fiber array 5 is One part (] loss (, L is b's,
It is distributed approximately evenly to each fiber of the fiber array 5.

Then, the slab lenses 6a3 and 7 are arranged on both side surfaces of the lenses in the direction in which they have a -like refractive index, that is, in the example shown in FIG. If the surface is coated with a reflective film, the reflection efficiency will increase and a decrease in light loss can be prevented.

[Effects of the Invention] According to the present invention, as described above, light beams from optical fibers having different aperture angles can be uniformly distributed in both directions with less loss of one optical IC.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams showing the configuration of a conventional star coupler and the traveling state of light rays, and Figures 3 and 4 are explanatory diagrams showing the configuration of a star coupler according to the present invention and the traveling state of light rays. be. 1.6,7: slab lens,

Claims (1)

[Claims] a unidirectional gradient index slab-like lens A whose refractive index decreases in one direction in proportion to approximately the square of the distance from the optical axis plane, and which has a relatively large aperture angle with respect to the direction of the refractive index distribution;
A similar unidirectional refractive index distribution type slab-like lens, which has a relatively small aperture angle in the direction of the refractive index distribution, and lens B are each formed with a length that is an odd number multiple of approximately 1/4 pitch. , and so that the directions of the refractive index distribution match,
A pair of lenses that are in contact with each other at their end faces, a fiber array that has a high aperture angle that is provided in contact with the end face of the lens A side that has a high aperture angle of this lens pair, and a lens B that also has a low aperture angle of the lens pair. An optical star coupler consisting of a fiber array with a low aperture angle provided in contact with the side end face.