JPH01270011A - Spherically tapered optical fiber, its manufacture, and optical coupling system using same - Google Patents

Abstract

PURPOSE:To obtain such a spherically tapered optical fiber that light projected by the spherically tapered optical fiber is reflected by a photodetection surface and does not enter the optical fiber again by making the tapered tip sphere part which decrease in diameter continuously from the main body part eccentric with the center part of the main body part. CONSTITUTION:The tapered tip spherical part 6 which decreases in diameter continuously from the main body part 4 is eccentric with the center line 5 of the main body part 4, and consequently the light projected from the tapered tip sphere part 6 travels in a different direction from the center line. Therefore, light which is reflected by the photodetection surface 10 of the photodetecting element 8 having the photodetection surface 10 at right angles to the center line 5 of the main body part 4 is prevented from entering the spherically tapered optical fiber (THF). The taper tip sphere part 6 is supported slantingly to the perpendicular direction of the optical fiber, drawn while heated partially between support parts, and separated at its drawn part to make the taper tip sphere part 6 eccentric with the center line 5 of the main body part by gravitation.

Description

[Detailed Description of the Invention] Overview Regarding a tapered optical fiber used for optical coupling with an optical semiconductor element, light emitted from the tapered optical fiber is reflected by a light receiving surface, etc., and the tapered optical fiber is reflected again into a tapered optical fiber. In a tapered optical fiber with a tapered spherical tip whose diameter continuously decreases from the main body, the tapered spherical portion is aligned with respect to the center line of the main body. Construct eccentrically.

INDUSTRIAL APPLICATION FIELD The present invention relates to a tapered optical fiber used for optical coupling with an optical semiconductor element, a manufacturing method thereof, and an optical coupling method using the same.

The end of the optical fiber is tapered into a tapered shape, and the tip is processed into a hemispherical shape.
It is sometimes called. ) is widely used as a device that provides high optical coupling efficiency in optical coupling with optical semiconductor elements such as light emitting elements and light receiving elements. Of course, the shape of this type of THF is optimized to increase the optical coupling efficiency, and especially when used for optical coupling with a light receiving element, the light reflected on the light receiving surface is returned to the THE. It is necessary to prevent this from being introduced into the light emitting device and having an adverse effect on the light emitting element.

BACKGROUND OF THE INVENTION FIG. 5 is a diagram for explaining optical coupling between a conventional THF and a light receiving element. The THF 32 has a tapered spherical portion 36 whose diameter continuously decreases from a main body portion 34 made of an optical fiber, and the light receiving element 38 is arranged such that its light receiving surface 40 faces the tapered spherical portion 36. has been done. Note that the light-receiving surface 40 is arranged perpendicularly to the center line of the main body portion 34 so that the apparent upper light-receiving diameter is maximized. Since the tip of the tapered spherical part 36 has a smooth curvature, the light that has traveled inside the main body 34 is focused when exiting from the tapered spherical part 36, thereby achieving high optical coupling efficiency. is now possible.

Problem to be Solved by the Invention With the structure shown in Figure 5, the light receiving surface is generally flat and has an appropriate reflectance, so that the light emitted from the tapered spherical portion is not received. It may be reflected by the surface and a portion of it may return from the tapered ball portion into the THF. When such reflected feedback light occurs, the operation of a light emitting element such as an LD (semiconductor laser) (not shown) provided at the other end of the optical transmission line becomes unstable, increasing noise, and preventing deterioration of transmission quality. I can't. In order to avoid this problem, it may be proposed to apply an anti-reflection coating to the tapered tip sphere, insert an optical isolator between the tapered tip sphere and the light receiving surface, etc. Due to the shortage, reflected feedback light cannot be completely eliminated. Therefore, a first object of the present invention is to provide THF in which the light emitted from THF is not reflected by a light receiving surface or the like and reintroduced into THF.

By the way, as shown in FIG. 6, the light receiving surface 4 of the light receiving element 38
0 obliquely to the THF 32 is a simple but effective method for suppressing reflected light returning to the THF 32, since the optical axis of incidence on the light receiving surface 40 and the optical axis of reflection are different. be.

According to experiments, it has been found that if the light receiving surface 40 is inclined by 6 degrees or more with respect to a plane perpendicular to the center line of the main body 34, reflected feedback light can be almost completely eliminated. However, when fixing the THF and the light receiving element in such a positional relationship, it is impossible to avoid increasing the size and complexity of the fixing part. In particular, when a large number of light receiving elements are bent to form an array, this problem becomes more serious.

Therefore, a second object of the present invention is to simplify the configuration when optically coupling THF and a light receiving element.

Means for Solving the Problems In order to achieve the above first object, in a tapered spherical optical fiber having a tapered spherical portion whose diameter continuously decreases from the main body, the tapered spherical portion is connected to the main body. A tapered optical fiber is provided which is eccentric with respect to the center line of the optical fiber.

This tapered optical fiber is manufactured by supporting an optical fiber diagonally with respect to the vertical direction, stretching the optical fiber while partially heating it between supporting parts, and separating it at the stretched part. be able to.

Furthermore, in order to achieve the second object, a light receiving element is disposed on the output optical axis when light is emitted from the tapered spherical part of the tapered spherical optical fiber, and the light receiving surface of the light receiving element is There is provided an optical coupling system characterized in that the main body is arranged perpendicularly to the center line of the main body.

The reason why the tapered spherical portion is eccentric with respect to the center line of the main body is to prevent the optical axis of the emitted light from coinciding with the center line. That is, in the conventional configuration, the optical axis of the emitted light and the center line coincided, so reflected feedback light was introduced into the THF, but with the configuration of the present invention, the main body For a light-receiving element having a light-receiving surface perpendicular to the center line of
It is prevented from being introduced into the HF.

The reason why the optical fiber is supported diagonally with respect to the vertical direction in the manufacturing method is to cause eccentricity due to the action of gravity when the support portions of the optical fiber are heated and stretched.

As for the second purpose, since the light-receiving surface of the light-receiving element is arranged perpendicularly to the center line of the main body, the structure is prevented from becoming complicated as in the conventional example shown in FIG.

Example Embodiments of the present invention will be described below based on the drawings.

Figure 1 is a side view (a) of TH-F showing an embodiment of the present invention.
, a bottom view (b) and a front view (C). This THF2
is a tapered tip spherical portion 6 whose diameter continuously decreases from the main body portion 4.
The tip of the tapered spherical portion 6 is formed into a roughly hemispherical shape with a smooth curvature. The tapered spherical portion 6 is eccentric with respect to the center line 5 of the main body portion 4, so that the light emitted from the tapered spherical portion 6 travels in a direction different from the center line 5.

FIG. 2 is a diagram showing a specific example when THF is optically coupled to a light receiving element. At the inner corner of the L-shaped cross-sectional metal block 4'! "HF 2 is fixed, e.g. by adhesive,
Further, the metal block 4 is fixed onto a metal substrate 12 by, for example, laser welding, and a light receiving element 8 is placed opposite the THF 2.
It has been established.

The flat light-receiving surface 10 of the light-receiving element 8 is arranged perpendicularly to the THF 2, allowing for simple construction of the device. That is, when either the metal block 4 or the light receiving element 8 is fixed at an angle relative to the other, the structure of the fixing part becomes complicated, but the structure is simplified by eliminating the need for an inclination. and miniaturization can be achieved.

FIG. 3 is an enlarged side view of the optical coupling section in FIG. 2.

14 is the output optical axis from the tapered spherical portion 6, and 16 is the light receiving surface 1.
The reflected optical axis at 0 is shown.

Since the light-receiving surface 10 is perpendicular to the center line 5 of the main body 4 and the output optical axis 14 and the center line 5 do not coincide with each other, the output optical axis 14 and the reflected optical axis 16 do not coincide with each other. By appropriately setting the degree of eccentricity of the spherical tip portion 6 and the distance between the tip of the tapered spherical portion 6 and the light receiving surface 10, the reflection optical axis 16 can be set in a direction away from the THF 2. Therefore, reflected feedback light is prevented from being introduced into the THF 2, and unstable operation of a light emitting element such as an LD (not shown) connected to the other end of the THF 2 is avoided.

FIG. 4 is a diagram for explaining the THF manufacturing process.

First, the optical fiber 18 such as a single mode optical fiber is placed in the chuck 20.22 so as to be diagonal to the vertical direction.
(b) The optical fiber 18 between the chucks 20 and 22 is partially heated, for example, by arc discharge between the electrodes 24 and 26, and is stretched in the direction of the arrow in the figure (b).
. Then, by performing this heating and stretching, for example, multiple times, the optical fiber 18 is separated at the stretching part, and the tapered spherical part 28 is separated.
a.

Form two THF28.30 each with 30a (C). At this time, the melted and softened optical fiber is subjected to force in a direction different from the center line due to the action of gravity, so
The tapered spherical portion 28a and FOa are eccentric with respect to the center line. Note that the reason why the tip of the tapered spherical portion is formed into a hemispherical shape is that surface tension acts on the tip of the optical fiber that has been melted and softened. In addition to arc discharge, a burner such as an H202 burner can be used as a means for partially heating the optical fiber.

Effects of the Invention As detailed above, according to the present invention, the light receiving surface is treated with THF.
It is possible to prevent the light emitted from the THF from being reflected on the light-receiving surface and being introduced into the THF again without arranging it at an angle with respect to the THF.

[Brief explanation of the drawing]

FIG. 1 is a side view (a) of THF showing an embodiment of the present invention;
Fig. 2 is a perspective view of an optical coupling section showing an embodiment of the present invention, Fig. 3 is an enlarged side view of the main part of Fig. 2, and Fig. 4 is an implementation of the present invention. The THF manufacturing process explanatory diagram showing an example, and FIGS. 5 and 6 are diagrams for explaining the prior art. 2.28.30... THF (Taber tip tapered optical fiber), 4... Main body, 6.28a, 30a... Tapered tip spherical part, 8... Light receiving element, 1o... Light receiving surface. (b) one (C) 4.ゎ4yo. 6: Chi l\° tip ne () ning (″) 7 ≦ 1 i 4 J Figure 1 Figure 8: All-light IJ- 1o: Light receiving surface is sharp Figure 2 Uku Pu〉chi I row Jpu i person Circle Diagram 3 (a) (b) (C) Ue Pu Kajiida JJ ff Epidemic Goji 1J Hi β Mouth Diagram 4

Claims (3)

[Claims] (1) In a tapered optical fiber with a tapered spherical tip whose diameter continuously decreases from the main body, the tapered spherical tip (6) is aligned with respect to the center line (5) of the main body (4). A tapered, spherical optical fiber characterized by being eccentrically formed. (2) The optical fiber (18) is supported obliquely with respect to the vertical direction, and the optical fiber (18) is stretched while being partially heated between the supporting parts, and separated at the stretched part. A method for manufacturing a tapered optical fiber with a spherical tip. (3) A light receiving element (8) is disposed on the output optical axis when light is emitted from the tapered spherical part (6) of the tapered spherical optical fiber according to claim 1, and this light receiving element (8) The light-receiving surface (10) of the main body (4)
) is arranged perpendicularly to the center line (5) of the optical coupling system.