JPH0268505A - Method of coupling diffused light and optical fiber - Google Patents

Abstract

PURPOSE:To easily and efficiently couple diffused light such as laser light emitted from a light source and an optical fiber by heating the part of a bar-shaped transparent body near the cut end face thereof to form a spherical lens integrated with the bar-shaped transparent body and using this spherical lens. CONSTITUTION:The cut end face of the bar-shaped transparent body 10 is partially heated to melt by arc electrodes 11a, 11b, etc. The transparent body made into a liquid state is then spherodized by surface tension to form a lens 10. The arbitrary central axis of this spherical lens 10b orthogonal with the bar-shaped transparent body 10 is aligned to the prescribed position on the optical axis connecting the light source 2 such as laser diode and the core 6 end face of the optical fiber. The formation of the spherical lens 10b to the smaller diameter is then possible by controlling the rate of heating and melting the bar-shaped transparent body 10. The efficient optical coupling effect is thus obtd. and the alignment such as optical axis alignment by holding the bar-shaped body part continuous with the spherical lens 10b is facilitated.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for coupling diffused light and an optical fiber in an optical transmission system in the field of optical communication, the present invention relates to a method for coupling diffused light such as a laser beam emitted from a light source to an optical fiber easily and efficiently. In an optical system that couples diffused light emitted from a light source to the core end surface of an optical fiber, the vicinity of the cut end surface of a rod-shaped transparent body is heated to integrate the rod-shaped transparent body in the vicinity of the cut end surface. After the spherical lens is formed, an arbitrary central axis of the spherical lens perpendicular to the rod-shaped transparent body is aligned with a predetermined position on the optical axis connecting the light source and the core end surface of the optical fiber.

(Industrial Application Field) The present invention relates to an optical transmission system in the field of optical communication, and in particular to a method for easily and efficiently coupling diffused light such as a laser beam emitted from a light source with an optical fiber. Concerning the joining method.

[Conventional technology]

FIG. 2 is a diagram showing an example of a conventional optical coupling method, in which (A) is a block diagram and (B) is a graph explaining coupling efficiency.

In Figure (A), 1 is a light source stand, 2 is a laser diode as a light source placed on the light source stand 1, 3 is a ball lens molded, for example, from optical glass, and 4 is a cladding 5 and a core 6. Each shows an optical fiber made up of .

In the case of an optical coupling system having such a configuration, the laser light emitted from the laser diode (hereinafter referred to as LD) 2 as a light source is normally emitted at an angle where the optical power is 1/e2 of the power on the central axis, that is, 20 to 40 degrees. With the spread angle of
Diffuse and emit from D.

Therefore, the laser beam is converged by a ball lens 3 which is placed on the central optical axis of the laser beam and has a radius R1 in the range of about 250 to 1000 μm, and further a radius R2 is applied to the tip of the opposing end face on the opposite side of the ball lens 3. The light beam is configured to be incident on a core 6 in which a hemispherical lens of about 100 μm is formed.

In this case, in order to minimize the coupling loss of light in the optical coupling system and achieve efficient optical coupling, the optical axis of the ball lens 3 should be perfectly aligned with the optical axis center line connecting the LD 2 and the core 6. It is necessary to make the radius R of the spherical lens 3
1, it is necessary to increase the maximum value φ of the emission angle of the laser beam that can be coupled to the core 6, and to decrease the distance D2 from the LD 2 to the tip of the core 6.

Radius R1 of the spherical lens 3 and L of the light component that can be coupled to the core 6
A graph (B) showing the relationship between the maximum value φmax of the exit angle from D2, where the horizontal axis represents the distance D1 from LD2 to the closest point of the ball lens 3, and the vertical axis represents the distance D1 from LD2 to the closest point of the core 6. The distance D2 is taken in units of μm.

In this case, L of the light component that can be coupled to the core 6 when the tip radius R2 of the core 6 in Figure (A) is fixed to 100 μm.
The maximum value ψmax of the exit angle from D2 is, if the radius R1 of the ball lens 3 is smaller than the conventional example, for example 125 μm, the area A surrounded by the broken line shows the maximum value 20°, and the radius R1 of the ball lens 3 is It has been theoretically confirmed that when the thickness is set to 62.5 μm, the region B surrounded by the solid line exhibits a maximum value of 30'.

- Therefore, it is advantageous to make the radius R1 of the ball lens 3 as small as possible to increase the above-mentioned φmax and to reduce the distance D2 from the LD 2 to the tip of the core 6, thereby improving the optical coupling characteristics.

However, since the spherical lens 3 is molded by a mechanical polishing method, the radius R1 is 250 mm in order to mold it with good productivity.
The limit is around μm.

[Means to solve the problem]

The above problem is that in an optical system that couples diffused light emitted from a light source to the core end surface of an optical fiber, the vicinity of the cut end surface of a rod-shaped transparent body is heated, and a spherical shape integrated with the rod-shaped transparent body is heated near the cut end surface of the rod-shaped transparent body. After the lens is formed, the problem is solved by a method of coupling diffused light and an optical fiber, in which an arbitrary central axis perpendicular to the rod-shaped transparent body of the spherical lens is aligned with a predetermined position on the optical axis connecting the light source and the core end surface of the optical fiber. Ru.

[Problem that the invention sought to solve]

Conventional configurations have the problem that efficient optical coupling characteristics cannot be obtained due to restrictions on the size of the ball lens, and the distance between the light source and the core becomes long, which tends to increase light transmission loss. there were.

Furthermore, since a single ball lens is used, it is a light source.

There was a problem in that a large number of man-hours were required to align the optical axes between the ball lens and the core-equivalent components of the optical fiber.

[For production]

When the cut end surface of the rod-shaped transparent body is partially heated and melted in the vicinity thereof, the transparent body becomes liquid and becomes spherical due to surface tension to form a lens.

In the present invention, the conventional spherical lens is replaced with a minute spherical lens formed on the cut end surface of a rod-shaped transparent body.

Therefore, by controlling the amount of heating and melting of the rod-shaped transparent body, it is possible to miniaturize the spherical lens and obtain an efficient light coupling effect. Alignment such as optical axis alignment can be easily achieved.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention, and (^) shows the process of forming a spherical lens. FIG. 1(B) is a diagram showing an example of the overall configuration.

In (A) of Figure (A), 10 is a rod-shaped transparent body made of, for example, high-purity transparent quartz and has a diameter of about 10 μm.
a is a cut end surface of the rod-shaped transparent body 10.

Here, as shown in (b), the cut end surface 1 of the rod-shaped transparent body 10
Arc electrodes 11a are located several tens of μm apart from 0a along the rod-shaped transparent body 10 and are closely opposed to each other in the diametrical direction.
llb is placed and a discharge is caused between the electrodes.

At this time, the rod-shaped transparent body 10 melts from the vicinity of the discharge position to its tip and becomes liquid, and due to surface tension, only the tip portion forms a spherical lens 10b having a diameter of about 10 μm as shown in FIG.

Therefore, the rod-shaped transparent body 10 of the arc electrodes 11a, llb
The size of the spherical lens 10b can be made to a predetermined size by appropriately setting the arrangement position relative to the spherical lens 10b.

It has been experimentally confirmed that better results can be obtained if the diameter of the rod-shaped transparent body 10 is about 10 to 20% smaller than the diameter of the required spherical lens 10b.

In the diagram (B) showing an example of the overall configuration, the spherical lens t in FIG. 1(A) is replaced with the spherical lens 3 in FIG. 2(A).
ab has been replaced with a light source stand of 1° and a laser diode of 2. Optical fiber 4. The cladding 5 and the core 6 are all similar to those shown in FIG.

In the case of such a configuration, since the diameter of the spherical lens 10b can be changed as described above, for example, the radius of the spherical lens 10h can be changed to 62.5 μm (as explained in FIG. 2).
125 μm in diameter), and the spherical lens 10 of the core 6
If the radius of the spherical end face facing b is 100 μm, the maximum value φ of the output angle from the LD of the light component that can be coupled to the core 6
max can be coupled up to 30°.

Reference numeral 12 in the figure shows a holder that holds the rod-shaped body part connected to the spherical lens 10b, and by fixing the holder 12 to a mechanical part (not shown), such as a precision three-dimensional moving table, the spherical lens 105 part It is extremely easy to align the center line between the optical axes of the LD 2 and the core 6.

11a and llb are arc electrodes, 12 is a holder; respectively.

〔Effect of the invention〕

As described above, the present invention can provide a method for coupling diffused light and an optical fiber, which can efficiently and easily couple diffused light emitted from a light source to an optical fiber.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a conventional optical coupling method. In the figure, ■ is a light source stand, 2 is a laser diode, 4 is an optical fiber, 5 is a cladding, 6 is a core, 10 is a rod-shaped transparent body, 10a is a cut end surface, 10b & is a spherical lens, (A) (Ol hull Honbe e month's laughter completion example quality,

Claims (2)

[Claims] (1) In an optical system that couples diffused light emitted from a light source to the core end surface of an optical fiber, the vicinity of the cut end surface (10a) of the rod-shaped transparent body (10) is heated to cause the rod-shaped transparent body (10) to be heated near the cut end surface (10a). Transparent body (10)
After forming a spherical lens (10b) integrated with the spherical lens (10b), an arbitrary central axis perpendicular to the rod-shaped transparent body (10) of the spherical lens (10b) is aligned with the light source (2) and the core (
6) A method for coupling diffused light to an optical fiber, characterized by matching the end faces to a predetermined position on the optical axis. (2) The method for coupling diffused light and an optical fiber according to claim 1, wherein heating of the vicinity of the cut end surface of the rod-shaped transparent body is performed by arc discharge.