JPH01292877A - Semiconductor laser and optical fiber coupling circuit - Google Patents

Abstract

PURPOSE:To minimize coupling loss with less parts by slanting the tip of an optical fiber and by mutually shifting the center axis of a semiconductor laser and a lens for coupling. CONSTITUTION:A semiconductor laser 1, a lens 2, and an optical fiber 3 are placed in this order and center axes are shifted mutually. Also, the edge surface of the optical fiber 3 is polished aslant but the polishing surface is directed toward the axial deviation of the optical fiber 3. Then, since the semiconductor laser 1 and the lens 2 are positioned while the axis are deviated, optical beam radiated from the lens 2 is not parallel and slants. By setting this angle to a proper value, beam after inciding from an edge surface 3' becomes parallel to the center axis of the optical fiber 3 and no extra coupling loss is generated. Also, no extra parts and materials such as a glass plate and an adhesive are required, thus enhancing reliability.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semiconductor laser/optical fiber coupling circuit used mainly for the purpose of optical fiber communication, and in particular to a semiconductor laser/optical fiber coupling circuit that is used to prevent light reflected from the end face of an optical fiber from returning to the semiconductor laser. The present invention relates to a coupling circuit that prevents coupling loss and at the same time has small coupling loss.

[Conventional technology]

It is known that when light emitted from a semiconductor laser is coupled to an optical fiber, reflected light from the end face of the fiber returns to the semiconductor laser, making the operating state of the semiconductor laser unstable and causing noise generation. For this reason, several methods are known to prevent the reflected light from the fiber end face from returning to the semiconductor laser.

FIG. 3 is an example of such a conventional reflection countermeasure. In the figure, a light beam emitted from a semiconductor laser l is condensed and focused by a lens 2, and if the end face of an optical fiber 3 is located at the focus, it is converted into a mode that is guided through the optical fiber 3. be done.

At this time, reflected light is generated at the end face 3' of the fiber 3 with a reflectance of about 4%, but since the end face 3' is inclined at an angle of about 9 degrees, the returned light returns to the semiconductor laser l at a large angle. , and is not coupled to the eigenmode of the semiconductor laser l. Therefore, the operating state of the semiconductor laser 1 is not disturbed by the reflected return light. However, end face 3
If ' is tilted, the beam after entering the optical fiber 3 will not be parallel to the central axis of the optical fiber 3, resulting in extra coupling loss.

FIG. 4 is an example of another reflection countermeasure. In the figure, a glass plate 4 is bonded to the end face of the optical fiber 3 with a transparent adhesive, but other parts are the same as in FIG. 3. If the refractive index of the glass plate, adhesive, and optical fiber are the same, no reflection will occur at the end face of the optical fiber 3, and reflected return light will occur only at the end face of the glass plate. 2, the returned light does not form an image on the end face of the semiconductor laser 1. Therefore, in this case as well, the influence of reflected return light is removed, and in this case, the optical fiber 3
Since the light beam incident on the optical fiber 3 is parallel to the central axis of the optical fiber 3, no extra coupling loss occurs. However, in this case, extra parts and materials such as glass plates and adhesives are required.

[Problem to be solved by the invention]

As explained above, conventional coupling circuits have problems such as a large number of components or a large coupling loss.

[Means for Solving the Problems] According to the present invention, in a coupling circuit in which a semiconductor laser, a coupling lens, and an optical fiber are arranged in this order, the tip of the optical fiber is made oblique, and the semiconductor laser and the optical fiber are arranged at an angle. A semiconductor laser/optical fiber coupling circuit is obtained, which is characterized in that the center axes of the coupling lenses are shifted from each other.

[Embodiment 1] FIG. 1 shows a layout diagram of an embodiment of the present invention. In the figure, a semiconductor laser 1. Although the lens 2 and the optical fiber 3 are arranged in this order, their central axes are shifted from each other.

Moreover, the end face of the optical fiber 3 is polished diagonally,
The polishing surface is oriented in the direction of the axis misalignment of the optical fiber 3.

In this case, reflection occurs at the end face 3' of the optical fiber 3, but since the angle of the light returning to the semiconductor laser 1 is large, the influence of reflection is suppressed, as in FIG. 3. However, in the case of FIG. 1, since the semiconductor laser 1 and the lens 2 are arranged with their axes shifted, the light beam emitted from the lens 2 is not parallel to the central axis but is tilted. If this angle of inclination is appropriate, the beam after entering from the end face 3' will be transmitted to the optical fiber 3.
is parallel to the central axis of , so no extra coupling loss occurs. Furthermore, extra parts and materials such as glass plates and adhesives in the case of FIG. 4 are not required, and reliability is increased.

゛ [Example 2] FIG. 2 is a diagram explaining another embodiment.

In the figure, the lens 2 is divided into two parts, but the semiconductor laser 1. The central axes of the two lenses and the optical fiber 3 are shifted from each other. In this case as well, the same effect as in the case of FIG. 1 can be obtained.

〔Effect of the invention〕

As explained above, in the coupling circuit of the present invention, the tip of the optical fiber is a slope polished obliquely to the optical axis, and at the same time, the semiconductor laser and the coupling lens are arranged offset from each other with respect to their central axes, that is, the optical axes. As a result, the number of parts is small, the reliability is excellent, reflected return light can be prevented, and coupling loss can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of an example of a coupling circuit of the present invention, FIG. 2 is a layout diagram of another example of the invention, FIG. 3 is a layout diagram of an example of a conventional coupling circuit, and FIG. 4 is a layout diagram of another example of a conventional coupling circuit. It is a layout diagram of an example. 1... Semiconductor laser, 2... Lens,
3...Optical fiber, 3'...Optical fiber end face, 4...Glass plate agent Patent attorney Uchihara Onhoki 1 figure ¥Lit 4 figures

Claims (1)

[Claims] In a coupling circuit formed by arranging a semiconductor laser, a coupling lens, and an optical fiber in this order, the tip of the optical fiber is oblique, and the center axes of the semiconductor laser and the coupling lens are arranged offset from each other. Features a semiconductor laser/optical fiber coupling circuit.