JPS6131842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical circuit for optical fiber communication, and more particularly to an optical splitter for distributing a light beam from one optical fiber to a plurality of optical fibers.

Optical fiber communication is expected to be a promising transmission system with a wide range of applications, and development for practical use is progressing. One of the effective application areas of optical fiber communication is communication lines within factories, plants, etc., and communication lines connecting computers.
In these lines, signals are often sent from a central control unit to a large number of terminal devices. Therefore, in order to apply optical fiber communication to these lines, an optical splitter that branches a light beam from one optical fiber into multiple optical fibers is required. Conventionally, in order to achieve this function, multiple optical fibers were bundled and heated and drawn to form a tapered joint, but this method involved processing small-sized optical fibers, so it did not meet the requirements. The processing precision required is very strict, and it is quite difficult to equalize or set the distribution ratio to a large number of optical fibers at an arbitrary ratio, making it difficult to manufacture. On the other hand, in order to eliminate this drawback, a one-dimensional convergent optical transmitter with a refractive index distribution approximated by a square function in only one direction and a plurality of curved surfaces are combined to create a one-dimensional convergent optical transmitter. An optical splitter has been devised that splits and focuses a light beam that spreads in a direction perpendicular to the focusing direction using multiple curved surfaces arranged to have a focusing effect in this direction. Because it utilizes the refraction of light, it is forced to have a structure in which curved surfaces are exposed, and its characteristics tend to deteriorate due to dust, moisture, dirt, etc., which poses problems in terms of reliability.

An object of the present invention is to provide an optical splitter for optical fiber communication that is easy to manufacture and has high reliability.

According to the present invention, there is provided a one-dimensional convergent optical transmitter having a refractive index distribution that decreases in a direction perpendicular to a central plane in approximately proportion to the square of the distance from the plane, and a plurality of two-dimensional curved surfaces. A reflective optical distributor including a reflective surface and three or more optical fibers is obtained.

In this invention, by using reflection instead of refraction on a curved surface in an optical distributor that combines a conventional one-dimensional focusing optical transmitter and a curved surface, the number of component parts is reduced, manufacturing is easy, and reliability is improved. is increasing. That is, a light beam emitted from one optical fiber is guided to a one-dimensional convergent light transmission body, and the diameter of the light beam is expanded in a direction perpendicular to the direction of convergence of the light. A plurality of reflecting surfaces consisting of two-dimensional curved surfaces are placed there, and the expanding light beam is split and focused while being returned back into the original one-dimensional focusing optical transmitter. The optical beam distribution function is realized by coupling the optical fibers separately to each other. In this invention, each optical element is bonded to each other on a plane, so manufacturing is easy. However, since the refraction of the light beam on the surface of the optical element is not used, there is no deterioration in characteristics due to dust, moisture, dirt, etc., and the reliability is high.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a perspective view of a first embodiment of the present invention, and FIGS. 2 and 3 are a plan view and a sectional view, respectively, showing how the light beam is focused. Define the x, y, and z axes as shown. In this embodiment, an input optical fiber 21 is connected to an input end surface 11 of a one-dimensional convergent optical transmission body 1 having a refractive index distribution that decreases in proportion to the square of the distance from the center to the periphery only in the y direction.
and first to fourth output optical fibers 22 to 25
The first to fourth partial cylinders 3 to 6 are adhesively fixed to the output end surface 12 so that their central axes are parallel to the y-axis, and gold is deposited on the surface to create a two-dimensional structure. A reflective film 60 having a curved surface is formed. The one-dimensional focusing optical transmitter 1 is a flat glass plate with a desired refractive index distribution using the well-known ion exchange method, and its length in the z-axis direction is the same as the y-direction of the different-axis incident light beam. It is selected to be approximately 1/4 of the meandering pitch.

First, considering the y-direction, the incident light beam 31 emitted from the incident optical fiber 21 is focused in the y-direction by the one-dimensional focusing optical transmitter 1 and becomes a light beam substantially parallel to this direction. The light is incident on the reflective film 60 formed on the surfaces of the partial cylinders 3 to 6 of No. 4. Since the reflective film 60 does not have a convergence effect in the y direction, the incident light beam 31 is turned back while remaining almost parallel and enters the original one-dimensional convergent light transmission body 1.
There, it is focused in the y direction and converted into first to fourth distributed light beams 32 to 35, which enter the first to fourth output optical fibers 22 to 25, respectively. Since the light beam passes through the one-dimensional convergent optical transmitter 1 in the z-axis direction for approximately half the length of the meandering pitch in the y-direction, it is separated from the incident light beam 31 at the incident end surface 11 of the one-dimensional convergent optical transmitter 1. y of distributed light beams 32-35
The light beam diameters in both directions are approximately equal. Next, consider the state of the light beam in the x direction.Since the one-dimensional focusing optical transmitter 1 does not have a focusing effect in the
0, where it is split and focused while being turned back and converted into the first to fourth distributed light beams 32 to 35, which are then transmitted to the first to fourth output optical fibers 22 to 2.
It is distributed into 5 parts and enters the field. . As mentioned above, y
In the x direction, the light beam diameter hardly changes, and in the x direction, it is focused separately by the reflective film 60 of each of the partial cylinders 3, 4, 5, and 6, so this optical splitter can reduce insertion loss. . Since the optical element for distribution is placed where the light beam spreads, the shape etc. do not require very strict machining precision, and the distribution ratio can be set to any value. It was hot. That is, by determining the size of the partial cylinders 3 to 6 in consideration of the intensity distribution of the diffused light beam, each distribution optical fiber 22
It was possible to set the distribution ratio to ~25 to a desired value. Because the shape of the distributing optical element is relatively large and the one-dimensional convergent light transmitter 1 and the partial cylinders 3 to 6 can be adhesively fixed to each other on a flat surface, it is possible to manufacture this optical distributor with ease. It was hot. Furthermore, since this optical splitter utilizes reflection by the reflective film 60 instead of refraction of light on the surface of the optical element, the light beam does not go into the air, and the light beam is not affected by surface dirt, moisture, dust, etc. There was no deterioration in characteristics at all, and the reliability was high.

FIG. 4 shows a plan view of a second embodiment of the invention. In this embodiment, the reflective film 60 applied to the surface of the plurality of partial pillars used in the first example is the same as the reflective film 60 applied to the surface of the transparent body 40 having the divided first to fourth curved surfaces 42 to 45. It was replaced in 61. These curved surfaces are such that the locus of the centers of the first to fourth distributed light beams 32 to 35 that are split, focused, and reflected by each curved surface of the reflective film 61 is aligned with the central axis 50.
It was set so that it was almost parallel to. By doing so, the first to fourth output optical fibers 22 to 25 can be arranged parallel to each other, making it easier to manufacture the optical distributor. In addition, by making the angle observed by the second and third curved surfaces 43 and 44 near the central axis 50 smaller than the angle observed by the first and fourth curved surfaces 42 and 45 far from the central axis 50, the incident optical fiber 21 is focused. Even in the case where the angular distribution of the intensity of the light beam in the x-z plane is smaller as the angle is larger, as in the case of a type fiber, the light beam is transmitted to the first to fourth output optical fibers 22 to 25. We were able to make the distribution ratios almost equal. transparent body 4
0 was made by creating a mold with the necessary curved surface, pouring transparent plastic material into it, and letting it solidify. As described above, in this example as well, an optical distributor that was easy to manufacture and had high reliability was obtained.

This invention can be modified in several ways in addition to the preferred embodiments described above. The quadratic curved surface for dividing and focusing the light beam is not limited to a part of a cylindrical surface, but may also be a semi-cylindrical surface, a parabolic cylinder surface that is a curved surface of a paraboloid, or other special curved surfaces. As the one-dimensional focusing light transmitting body, it is possible to use not only glass but also plastic or the like with a refractive index distribution using polymerization diffusion. In the case of a plastic one-dimensional focusing light transmission body, one end surface thereof can be directly formed into a curved surface divided into a plurality of parts. The length of the one-dimensional focusing optical transmitter in the z-axis direction is y
If it is an odd number multiple of 1/4 of the direction meandering pitch, the same effect as this embodiment can be expected. In this case, the longer the length, the greater the spread of the light beam in the x direction, which is convenient when the number of distributions is large. Also, by using an appropriate spacer
It can be made longer or shorter than 1/4 pitch 4. The number of distributions is not limited to 4 as shown in the example,
It's okay to have more or less. A refractive index matching material can be used between the input/output optical fiber and the one-dimensional focusing optical transmission body to reduce reflection loss there.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a first embodiment of this invention, FIG. 2 is a plan view thereof, FIG. 3 is a sectional view thereof, and FIG. 4 is a plan view of a second embodiment of this invention. . In the figure, 1... one-dimensional focusing optical transmission body, 3
~6...Partial cylinder, 11,12...End face, 21~
25...Optical fiber, 31-35...Light beam,
40...Transparent body, 42-45...Curved surface, 50...
Central axis, 60, 61 . . . represent reflective films, respectively.

Claims (1)

[Claims] 1. A one-dimensional lens having a refractive index distribution that decreases in a direction perpendicular to a central plane including the central axis in approximately proportion to the square of the distance from the central plane, and having an entrance end surface and an exit end surface that are approximately perpendicular to the central axis. a convergent light transmitter; a reflective surface made of a plurality of two-dimensional curved surfaces installed close to the output end face thereof and having axes parallel to the perpendicular direction; 1. A reflective optical splitter comprising at least one optical fiber.