JPH02278210A - Optical coupler - Google Patents

Abstract

PURPOSE:To sufficiently fix the optical coupler by soldering, etc., by using a hemispherical lens or a one-end spherical rod lens whose refractive index is uniform as a first lens of a second lens, and using a 'selfoc(R)' microlens as a second lens. CONSTITUTION:A light beam from a semiconductor laser, etc., is converted to parallel beams by a first lens 2 of a second lens split type confocal composite lens system, and subsequently, condensed to an optical fiber 5 brought into contact and fixed to an end face of a 'selfoc(R)' microlens by a hemispherical lens 3 or a one-end spherical rod lens whose refractive index is uniform being a first lens for constituting a second lens, and the 'selfoc(R)' microlens 4 being a second lens, and made incident. In this case, by using the hemispherical lens or the one-end spherical rod lens whose refractive index is uniform as a first lens in a second lens, length of the lens can be selected freely. In such a way, the optical coupler can be fixed by soldering.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical coupler such as a semiconductor laser diode used for optical communication.

(Prior Art) In the field of optical communications, optical couplers are used to efficiently make light emitted by a semiconductor laser (hereinafter referred to as LD) or the like enter an optical fiber via a lens.

As one of these optical couplers, an optical coupler using a confocal compound lens system with a split second lens is known (for example, Japanese Patent Application Laid-Open No. 63-20392), and an example thereof is shown in Fig. 2. show.

In Fig. 2, the light emitted by the LDJ is converted into a parallel beam by the pole lens 2, which is the first lens of the second lens segmented confocal compound lens system, and then sent to the selfoc micro lenses 7 and 4, which are the second lenses. The light is then focused on the end face of the SELFOC microlens 4. The focused light enters the single mode optical fiber 5 that is fixed in contact with the end face and propagates therein (hereinafter, the optical fiber 5 that is fixed in contact with the SELFOC microlens 4 is referred to as a virtual fiber). ).

The SELFOC microlens 7.4 is provided so that the entire length including the gap is 0.25 pitch, and the length of the SELFOC microlens 4 is equal to the axis of the partial fiber 6. It is determined by taking into consideration the sensitivity of misalignment and angular misalignment, the precision with which the lens is fixed during assembly, etc. The sensitivity of the partial fiber 6 to axial misalignment and angular misalignment, that is, the rate of change in light coupling efficiency with respect to axial misalignment and angular misalignment, is as shown in Figure 3. However, as the SELFOC microlens 4 becomes longer, the angle becomes larger, and as the SELFOC microlens 4 becomes longer, the angular deviation becomes smaller, showing the opposite tendency.

Therefore, it is necessary to consider the assembly and fixing precision of the optical coupler and select the length of the SELFOC microlens 4 so that the rate of change in coupling efficiency with respect to both axial deviation and angular deviation is small. When fixing lenses by YAG laser welding, which is commonly used today, the length of SELFOC microlens 7 is usually set to o or os pitch, and the length of SELFOC microlens 4 is set to 0.18 pitch. .

(Problem to be Solved by the Invention) However, in the optical coupler having the above configuration, since the length of the SELFOC microlens 7 is as short as 0.06 pitches, that is, about 1 pitch, there is a problem that it cannot be fixed sufficiently by welding. was there. In other words, with the current metallization technology, the metallization on the outer periphery of the lens does not have adhesion for 0.5 m from the cut end, so even if you try to fix the lens by soldering with a selfoc micro lens of one length, it will eventually be fixed sufficiently. That was difficult.

Furthermore, when the length is 1 ms, there is a problem that handling itself is inconvenient.

The present invention has been made in view of the above problems, and its purpose is to provide an optical coupler using a lens that can be sufficiently fixed by soldering etc. and is not inconvenient to handle. It is about providing.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an optical coupler for a second lens split type confocal compound lens system, in which the first lens of the second lens has a uniform refractive index. The lens is a hemispherical lens or a one-end spherical rod lens, and the twelfth (7) lens is a selfoc microlens.

(Function) Light from a semiconductor laser, etc. is converted into a collimated beam by the first lens of the second lens segmented confocal compound lens system, and then converted into a collimated beam by the first lens constituting the second lens, which has a refractive index. By means of a uniform hemispherical lens or one end spherical rod lens and a second lens, a Selfoc microlens, the light is focused and incident on an optical fiber that is fixed in contact with the end surface of the Selfoc microlens. . The first lens is a hemispherical lens with a uniform refractive index or a one-sided spherical rod lens whose length is independent of the length of the Selfoc microlens by making the incident side of the parallel beam a flat surface. can be freely selected. Therefore, by making the length appropriate, metallization with sufficient adhesion can be achieved, and the difficulty in handling can also be solved.

(Example) FIG. 1 is a block diagram showing an embodiment of the present invention.

In this embodiment, as shown in FIG. 1, a confocal compound lens system with a split second lens is adopted, and the SELFOC microlens 7 in the conventional optical coupler shown in FIG. It has been replaced with . Here, 1
is an LD; 2 is a goal lens which is the second lens of the second lens segmented confocal compound lens system; 3 is a hemispherical lens with a uniform refractive index which is the first lens of the second lens of the lens system; 4 The SELFOC microlens 15, which is the second lens of the second lens of the lens system, is a range of Langer mode optical fibers that are fixed in contact with the end surface of the SELFOC microlens 4 (hereinafter referred to as SELFOC microlens). The optical fiber 5 that is fixed in contact with the optical fiber 4 is called a optical fiber.

The light emitted by the LDI is converted into a parallel beam by the goal lens 2. The parallel beam is focused on the end face of the optical fiber 5 by the hemispherical lens 3 and the selfoc microlens 4. The focused light enters the optical fiber 5 and propagates.

By the way, as mentioned above, this embodiment uses a self-locking microlens 7 whose length is 0.06 pitch in FIG.
is replaced with a hemispherical lens 3 as shown in Fig. 1, but in order to make both optically almost equivalent, the radius of the hemispherical surface of the hemispherical lens 3 is set to approximately 2.5 fl. are doing. However, the length of the hemispherical lens 3 can be freely selected since the end face on which the parallel beam from the sol lens 2 is incident is made 7 rat. Therefore, the length of the hemispherical lens 3 can be selected to a value that provides sufficient adhesion for metallizing the outer periphery of the lens and does not cause any inconvenience in handling.

The hemispherical lens 3 is made of BK-7 material, and the portion through which light does not pass is shaped like a rond to ensure secure fixation.

In addition, the hemispherical lens 3 with a uniform refractive index in this embodiment
Even if a single-end spherical rod lens with a uniform refractive index is used instead, the same effect as described above can be obtained.

(Effects of the Invention) As described above in detail, according to the present invention, the first lens of the second lens segmented confocal compound lens system
Since the second lens is made of a hemispherical lens or one-sided spherical rod lens with a uniform refractive index, the lens length can be freely selected.

Therefore, by appropriately selecting the lens length, metallization with sufficient adhesion can be obtained, and fixation by soldering is possible. Difficulty can also be eliminated.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional optical coupler, and FIG. 3 is a diagram showing coupling efficiency characteristics of a virtual fiber lens. 1... LD, 2... Sol lens, 3... Hemispherical lens, 4, 7... Selfoc micro lens, 5
...Optical fiber, 6...Virtual Fiha Patent Applicant Oki Electric Industry Co., Ltd. Tomomizunri of the present invention Fig. 1 (a) 1-ton light valve also passed Fig. 2-4, 0-2,002,0 Kakui de > hl (O) (b) 4.0 Harnayarfuhii Ginseng's bracket 4 I loved A1 Saba 5 Note 3

Claims (1)

[Claims] 1. In an optical coupler of a confocal compound lens system with a split second lens, the first lens of the second lens is a hemispherical lens with a uniform refractive index or a one-sided spherical rod lens; An optical coupler characterized in that the second lens is a SELFOC microlens. 2. The optical coupler according to claim 1, wherein BK-7 material is used for the first lens.