JPS5916888Y2 - optical coupling device - Google Patents

Description

[Detailed description of the invention] This invention prevents the reflected light from returning to the semiconductor laser by preventing reflection from occurring at the light-receiving end face of the optical fiber when the emitted light from the semiconductor laser is introduced into the optical fiber. The present invention relates to an optical coupling device.

When introducing light emitted from a semiconductor laser into an optical fiber, an optical coupling device as shown in FIG. 1 has conventionally been used.

Explaining FIG. 1 below, the emitted light from the semiconductor laser 1 is partially reflected at the end surface A of the lenticular convergence medium 2, and the emitted light from the lenticular convergence medium 2 passes through the air gap and enters the holding metal fitting 3. A portion of the light is also reflected at the end face B of the optical fiber 4 located at .

The former reflected light at the end surface A of the lenticular medium 2 does not return to the semiconductor laser 1, but the latter reflected light at the end surface B of the optical fiber 4 passes through the optical path opposite to the emitted light and returns to the semiconductor laser 1. This becomes a problem.

In other words, in conventional optical coupling devices, the reflected light at the end face of the optical fiber returns to the semiconductor laser, causing an increase in semiconductor laser noise and periodic fluctuations in the semiconductor laser light output, which affect the characteristics of the semiconductor laser. There were some drawbacks that could have a negative impact.

Furthermore, the conventional optical coupling device has the drawback that the position of the optical image formed on the end face of the optical fiber shifts each time it is attached or detached, so that the noise level fluctuates.

SUMMARY OF THE INVENTION In order to solve these drawbacks, it is an object of the present invention to provide an optical coupling device having a structure that does not cause reflection at the end face of an optical fiber.

Describing the configuration of the present invention, the present invention provides an optical coupling device for introducing emitted light from a semiconductor laser into an optical path, in which a semiconductor laser is placed at a distance from the semiconductor laser and their optical axes coincide with each other. the first and second optical imaging means, and the semiconductor laser is positioned such that the incident end surface is at the imaging position of the optical image of the semiconductor laser formed by passing through the first and second optical imaging means. The central axis of the emitted light beam of the semiconductor laser is parallel to the optical axis of the first optical imaging means and is deviated in the radial direction by a distance that prevents reflected light from returning to the semiconductor laser. furthermore, the central axis of the incident light beam of the optical path is parallel to the optical axis of the second optical imaging means and is offset in a direction opposite to the deflection direction by the same distance as the deflection distance. This is an optical coupling device.

Hereinafter, the present invention will be explained by way of examples with reference to the drawings.

2 and 3 both show embodiments of the present invention,
1 is a semiconductor laser, 5 is a non-reflective film, 6 is a first lenticular focusing medium, 7 is a holding fitting, 8 is an optical fiber, 9 is a second lenticular focusing medium, and 10 is a holding fitting.

In the embodiment shown in FIG. 2, the semiconductor laser 1 has a central axis of the emitted light beam parallel to the optical axis of the first lenticular convergence medium 6 having a pitch length (to which the anti-reflection film 5 is attached), and the reflected light is radial. The optical fiber 8 is held by a holding bracket 7 with the center axis of the incident light beam being deviated by a distance that does not return to the semiconductor laser. The optical fiber is held at the end face between the first and second lenticular convergence media 6.9 in complete contact with the holding fitting 10 at a position offset in the opposite direction to the above-mentioned distance at the same distance as above. 8 can be attached and detached.

With such a structure, the light emitted from the semiconductor laser 1 passes through the non-reflection film 5 and the first lens-like convergence medium 6.
, and enters the second lenticular convergence medium 9 as a parallel ray, and the second lenticular convergence medium 9
The light is focused and imaged on the end face of the optical fiber 8.

As shown by the broken line in the figure, the reflected light at the end face C of the first lenticular convergence medium 6 and the end face of the second lenticular convergence medium 9 is relative to the optical axis of the first lenticular convergence medium 6. Since the light is focused through an optical path that is almost symmetrical to the outgoing light,
It does not return to the semiconductor laser 1.

Furthermore, since the optical fiber 8 is in complete contact with the second lenticular focusing medium 9, no reflection occurs at the end face of the optical fiber.

In the embodiment shown in FIG. 3, a matching oil 11 having almost the same refractive index as the optical fiber 8 is sealed between both end surfaces of the optical fiber 8 and the second lenticular focusing medium 9 in the embodiment shown in FIG. It has a structure that eliminates reflection at the end face of the optical fiber, similar to the embodiment shown in FIG.

In the examples shown in FIGS. 2 and 3, the first and second lens-like convergence media have a pitch length of 2, but even if the pitch length is an odd number multiple of the pitch length, reflections at the fiber end face can be similarly removed. can do.

Furthermore, the same function as described above can be achieved by using the first and second normal spherical lenses instead of the first and second lenticular convergence media described above.

FIG. 4 shows experimental data showing that when the emitted light from the semiconductor laser is introduced into the optical fiber, the noise characteristics of the semiconductor laser are improved when the reflected light at the end face of the optical fiber inside the holding fitting is removed.

In FIG. 4, a shows the semiconductor laser noise when there is reflection at the end face of the optical fiber, and b shows the semiconductor laser noise when the reflection at the end face of the optical fiber is removed.

From this experimental data, it is clear that by using the optical coupling device of the present invention, the reflected light at the end face of the optical fiber can be removed, so that the semiconductor laser noise can be significantly reduced.

As explained above, according to the optical coupling device of the present invention,
Since the reflected light returning to the semiconductor laser can be eliminated, for example, if it is used for optical coupling in an analog signal optical transmitter using a semiconductor laser as a light source, the S/N ratio of optical transmission can be improved by reducing the semiconductor laser noise. In addition to this, there is also the advantage that the optical signal output can be kept stable.

[Brief explanation of drawings]

FIG. 1 is a front cross-sectional view of a conventional optical coupling device, FIGS. 2 and 3 are front cross-sectional views of the first and second embodiments of the present invention, respectively, and FIG. 4 is a front cross-sectional view of a conventional optical coupling device. A semiconductor laser noise characteristic diagram is shown to explain the effect caused by this. The symbols used in the drawings indicate the following. 1... Semiconductor laser, 2... Lens-shaped focusing medium, 3... Holding metal fitting, 4... Optical fiber, 5... None Reflective film, 6... First lens-shaped focusing medium, 7... Holding metal fitting, 8...
...Optical fiber, 9...Second lenticular convergence medium, 10...Holding metal fitting, 11...
・Matching oil.

Claims (2)

[Scope of utility model registration request] (1) In an optical coupling device that introduces light emitted from a semiconductor laser into an optical path, the semiconductor laser and first and second optics are spaced apart from the semiconductor laser and whose optical axes coincide with each other. target imaging means and these first
and the optical path placed so that the incident end face is at the imaging position of the optical image of the semiconductor laser transmitted through a second optical imaging means, and the optical path is arranged such that the incident end face is at the imaging position of the optical image of the semiconductor laser that is focused by passing through a second optical imaging means, and a central axis parallel to the optical axis of the first optical imaging means and radially offset by a distance that prevents reflected light from returning to the semiconductor laser; and a central axis of the incident light beam of the optical path; is parallel to the optical axis of the second optical imaging means and is offset by the same distance as the offset distance in a direction opposite to the offset direction. (2) The optical coupling device according to claim 1, wherein the first and second optical imaging means are constituted by a cylindrical rod-shaped convergent medium having a lens function.