JPH05232356A - Optical coupler between semiconductor laser and optical fiber - Google Patents

Abstract

PURPOSE:To realize an optical coupler where the recoupling of reflected light caused on the incident end face of an optical fiber with a semiconductor laser is reduced and whose optical coupling to the optical fiber is high as for a two- lens type optical coupler. CONSTITUTION:Two lenses 4 and 5 are arranged between the semiconductor laser 1 and an obliquely ground fiber 3 whose incident end face 2 is obliquely ground, and the center axes of the two lenses 4 and 5 are arranged to be deviated from each other. The center line of the lens 4 on the laser 1 side out of the two lenses 4 and 5 is aligned with the optical axis of the laser 1 and the center axis of the lens on the fiber 3 side is arranged to be deviated from the optical axis.

Description

Detailed Description of the Invention

[0001]

The optical coupler of the present invention for a semiconductor laser and a fiber is used in the fields of optical communication, optical measurement, optical information and the like.

[0002]

2. Description of the Related Art In order to efficiently enter light emitted from an optical semiconductor element such as a laser diode into an optical fiber, an optical semiconductor element A and an optical fiber B as shown in FIGS.
There is an optical coupler in which the lens C is inserted between and and fixed by soldering or spot welding. The lens C used here is various such as a spherical lens and an aspherical lens.

Further, in order to improve the optical coupling efficiency between the optical fiber B and the optical semiconductor element A, not only an optical coupler (one lens system) using one lens C as shown in FIG.
There is also an optical coupler (two lens system) using two lenses C and D as described above.

If the incident end surface E of the optical fiber B is perpendicular to the optical axis of the optical semiconductor element A (flat polished fiber) as shown in FIG. 6, the optical semiconductor element A, the lenses C and D, and the optical fiber B are High optical coupling efficiency can be obtained simply by arranging the central axes on the same optical axis. In this case, 2 rather than 1 lens system
The lens system provides higher coupling efficiency.

If the incident end face E is an optical fiber (obliquely-polished fiber) B which is obliquely polished with respect to a plane perpendicular to the optical axis as shown in FIG. 5, the light emitted from the optical semiconductor element A is the optical fiber B. It is characterized in that the adverse effect of being reflected by the incident end surface E of and returning to the optical semiconductor element A is eliminated.

In the one-lens system of the optical coupler using the obliquely polishing fiber B, one lens C is arranged between the obliquely polishing fiber B and the optical semiconductor element A as shown in FIG. Moreover, the central axes of the optical semiconductor element A and the lens C are offset from each other. In this case, the light from the optical semiconductor element A is incident on the oblique polishing fiber B at an angle determined by this positional shift amount. The optimum value of the optical coupling efficiency at this time depends on the angle formed by the central axis of the obliquely polished fiber B and the incident end surface E of the fiber B. In order to obtain a high optical coupling efficiency, it is necessary to calculate the optimum position shift amount.

[0007]

In the one-lens system of the optical coupler using the obliquely polished fiber, the reflected return light from the incident end surface E of the optical fiber B does not enter the semiconductor element A, so that the optical coupling efficiency is improved. Although two advantages of reducing reflected return light can be obtained, the coupling efficiency is low due to the one-lens system.

In order to reduce the reflected return light and achieve high coupling efficiency, the obliquely polished fiber B is used, and 2
A lens system may be used, but in that case, it has not yet been clarified how to arrange the optical semiconductor element A, the two lenses C and D, and the central axis of the optical fiber B. For this reason, in the optical coupler using the semiconductor laser A, it is necessary to prevent the recombination of the reflected light generated at the incident end surface E of the optical fiber B to the semiconductor laser A and to obtain a high optical coupling. This is the supreme proposition above.

An object of the present invention is to provide a two-lens system optical coupler in which re-coupling of reflected light generated at the incident end face of the optical fiber to the semiconductor laser is favorably small and high optical coupling to the optical fiber can be obtained. It is to realize an optical coupler that can be used.

[0010]

[Means for Solving the Problems] Therefore, the present inventors
The present invention has been completed through repeated studies on an optical coupler using an obliquely polished fiber in a lens system and an optimum optical coupling degree at that time.

An optical coupler of a semiconductor laser and a fiber according to claim 1 of the present invention is, as shown in FIG. 1, an obliquely polished fiber 3 in which a semiconductor laser 1 and an incident end face 2 are obliquely polished.
Two lenses between (1st lens 4 and 2nd lens 5)
Are arranged and the central axes of the two lenses 4 and 5 are displaced from each other.

An optical coupler of a semiconductor laser and a fiber according to a second aspect of the present invention is an obliquely polished fiber 3 in which a semiconductor laser 1 and an incident end face 2 are obliquely polished as shown in FIG.
The first lens 4 and the second lens 5 are arranged between
Of the two lenses 4 and 5, the center line of the first lens 4 on the semiconductor laser 1 side is aligned with the optical axis of the semiconductor laser 1, and the center axis of the second lens 5 on the oblique polishing fiber 3 side is displaced from the optical axis. It was done.

[0013]

In the optical coupler of the present invention, the improvement of the optical coupling efficiency can be achieved by the two-lens system, and the reduction of the reflected return light can be achieved by the obliquely polished fiber. That is, the two lenses 4,
By shifting the central axes of 5 from each other, light can be emitted at an angle that is best coupled to the oblique polishing fiber 3, and the reflected return light at the incident end face 2 of the oblique polishing fiber 3 is deflected from the semiconductor laser 1. The reflected return light can be reduced.

In the conventional one-lens system optical coupler (FIG. 5), the central axes of the semiconductor laser A and the lens C are displaced, and therefore, if the displacement is increased, the optical coupling amount is decreased, and therefore the optical coupling amount can be increased. Inevitably, it becomes small (it was about 40 μm in our examples). However, in the optical coupler of the present invention (FIG. 1), since the axes of the first lens 4 and the second lens 4 are displaced, the amount of positional deviation can be made large (150 μm in the embodiment). For this reason, the influence of the positional deviations of the semiconductor laser 1, the first lens 4, the second lens 5, and the obliquely polished fiber 3 which are accidentally generated at the time of assembling are relatively small, and variations in optical coupling are also small.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the optical coupler of the present invention aligns the optical axis of a laser diode 1 which is an optical semiconductor element with the central axis of an aspherical lens (first lens) 4 and With respect to the spherical lens (second lens) 5, the central axis of the spherical lens (5) is shifted, and the light emitted at an angle determined by the amount of positional deviation is incident on the incident end face 2 of the obliquely polishing fiber 3 with the highest coupling efficiency. It is arranged as follows. In the embodiment of FIG. 1, the second lens 5 is displaced by about 150 μm with respect to the optical axis in order to realize the optimum incident angle of 2.4 degrees of the obliquely polished fiber 3.

The oblique direction of the incident end surface 2 of the obliquely polished fiber 3 is such that the light reflected by the incident end surface 2 is the semiconductor laser 1.
It was fixed so that it would not recombine.

[0017]

COMPARATIVE EXAMPLE For comparison with the optical coupler of the present invention, the central axes of the first lens (aspherical lens) 4 and the second lens (spherical lens) 5 are aligned as shown in FIG. Was combined with the obliquely polished fiber 3 by displacing with the optical axis of the laser diode 1 (comparative example).

In the optical coupler of the comparative example of FIG. 2, the first lens 4 is used.
The amount of positional deviation between the optical semiconductor element 1 and the optical semiconductor element 1 is as small as 11 μm due to the structure, and the eccentricity of the lens holder for accommodating the lenses 4 and 5 is usually several + μm. Therefore, in the optical coupler of FIG. Is significantly larger than that of the present invention.

In order to show the good optical coupling efficiency of the optical coupler of the present invention, the optical coupling efficiency of the optical coupler using the one-lens system of FIG. 5 and using the obliquely polished fiber is shown in FIG. The optical coupling efficiency of the optical coupler of the invention is shown in FIG. From these figures, it can be seen that not only the optical coupling efficiency of the optical coupler of the present invention is high, but also the high coupling efficiency can be stably obtained. The optical coupling efficiency of the optical coupler of the present invention was 30% or more higher than that of the optical coupler of the comparative example shown in FIG.

Although the second lens 5 in FIG. 1 is a spherical lens, the same effect can be obtained by using an aspherical lens as the second lens 5 in the present invention.

[0021]

The optical coupler of the present invention can obtain a high and stable optical coupling efficiency which is not obtained by the conventional one-lens system optical coupler using the obliquely polished fiber, and the incidence of the optical fiber. The recombination of the reflected light generated at the end face with the semiconductor laser is also small.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of an optical coupler of the present invention.

FIG. 2 is an explanatory diagram of an optical coupler according to a comparative example with the present invention.

FIG. 3 is an explanatory diagram showing the measurement result of the optical coupling efficiency of an optical coupler using a one-lens system and using an obliquely polished fiber.

FIG. 4 is an explanatory diagram showing measurement results of optical coupling efficiency of the optical coupler of the present invention.

FIG. 5 is an explanatory view of a conventional optical coupler using a one-lens system and an obliquely polished fiber.

FIG. 6 is an explanatory view of a conventional optical coupler using a two-lens system and an obliquely polished fiber.

[Explanation of symbols]

 1 Semiconductor Laser 2 Incident End Face 3 Oblique Polished Fiber 4, 5 Lens

Claims (2)

[Claims] 1. Two lenses 4, between a semiconductor laser 1 and an obliquely polished fiber 3 whose incident end face 2 is obliquely polished,
5. An optical coupler between a semiconductor laser and a fiber, characterized in that the central axes of the two lenses 4 and 5 are displaced from each other. 2. Two lenses 4, between a semiconductor laser 1 and an obliquely polished fiber 3 whose incident end face 2 is obliquely polished,
5 are arranged, the center line of the lens 4 on the semiconductor laser 1 side of the two lenses 4 and 5 is aligned with the optical axis of the semiconductor laser 1, and the central axis of the lens 5 on the oblique polishing fiber 3 side is the optical axis. An optical coupler between a semiconductor laser and a fiber, which is arranged so as to be offset from each other.