JP5254296B2 - Capillary - Google Patents

Description

  The present invention relates to a capillary, and more particularly to a capillary for connecting an optical fiber.

As a general method of connecting an optical fiber to the end face of a PLC, there is a method of connecting an optical fiber formed into a V-groove block to a PLC end face to which a reinforcing glass plate is attached (see FIG. 5 of Patent Document 1). An example is shown in FIG. A reinforcing glass plate 112 is attached to the upper surface of the PLC 111 so that the end surfaces are aligned. The optical fiber 121 is fixed to the V-groove fiber block 122. Then, the optical fiber 121 and the optical waveguide of the PLC 111 are aligned and connected. Here, “PLC” refers to a quartz lightwave circuit in which an optical waveguide mainly composed of SiO ₂ glass is formed on a Si substrate.

  However, the connection using the V-groove fiber block causes an increase in the size of the optical component due to the size of the V-groove fiber block. In FIG. 1, the numerical value of each part was illustrated. Therefore, it is conceivable to use a capillary instead of the V-groove fiber block. An example is shown in FIG. A reinforcing glass plate 212 is attached to the upper surface of the PLC 211 so that the end surfaces are aligned. A capillary 222 through which an optical fiber 221 is passed is fixed to the end face of the PLC 211. Alignment is performed by adjusting the position of the optical fiber 221 inside the capillary 222.

JP 9-318840 A

  However, both the prior arts of FIGS. 1 and 2 have a problem resulting from the necessity of a reinforced glass plate. One is a chip size problem. The reinforced glass plate is attached in order to increase the connection cross-sectional area and increase the strength in connection with the optical fiber. The size of the chip in which the optical fiber is connected to the PLC is increased only in order to secure a region for attaching the reinforced glass plate that is unnecessary from the functional side. In the thickness direction of the chip, the size is increased by the thickness of the reinforcing glass plate (for example, 1 mm). In the length direction of the chip, it is impossible to produce a lightwave circuit having functionality in the area of the PLC covered by the reinforcing glass plate, so the size is increased by the length of the reinforcing glass plate (for example, 2 mm). . The other is a troublesome problem. It is necessary to attach one end surface of the reinforced glass so as to coincide with the end surface of the PLC. Since the end face of the PLC requires optical polishing, it is possible to make the same surface as the reinforced glass plate in the polishing. However, in order to shorten the polishing time, for example, reinforced glass with a certain degree of accuracy such as 0.5 mm in advance is used. A plate must be attached, and alignment work is required.

  The above problems are not limited to the PLC, but various such as an LN waveguide in which an optical waveguide is formed on a lithium niobate (LN) substrate using titanium (Ti) diffusion, an optical waveguide is formed on a polymer substrate, and the like. This also occurs with respect to such a waveguide type optical element.

  The present invention has been made in view of such problems, and an object thereof is to provide a capillary for connecting an optical fiber to the end face of a waveguide type optical element without using a reinforced glass plate. It is in.

In order to achieve such an object, a first aspect of the present invention is a capillary for connecting an optical fiber to an end face of a waveguide type optical element, and at one end, a protrusion is formed on a part of the outer periphery. And when the waveguide type optical element and the projection are connected to engage the end face and the upper surface of the waveguide type optical element at the one end where the projection is formed, A movable margin between the inner periphery of the capillary and the outer periphery of the optical fiber for aligning the core of the optical fiber at the center of the core of the optical waveguide included in the element is secured, and the movable margin is It is characterized by being larger than the distance from the upper surface of the waveguide type optical element to the core center of the optical waveguide .

  According to a second aspect of the present invention, in the first aspect, the protrusion extends to the inside of the inner diameter of the capillary.

  According to a third aspect of the present invention, in the first aspect, the protrusion is present between an inner diameter and an outer diameter of the capillary.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the protrusion has a length of 0.5 mm to 1.5 mm and a height of 0.3 mm to 0.6 mm. It is characterized by the following.

  According to the present invention, a capillary is provided for connecting an optical fiber to an end face of a waveguide type optical element without using a reinforced glass plate by providing a protrusion on a part of the outer periphery at one end of the capillary. be able to.

It is a figure which shows the connection method of the optical fiber by the conventional V-groove fiber block. It is a figure which shows the connection method of the optical fiber by the conventional capillary. It is a figure which shows the connection method of the optical fiber by embodiment of this invention. FIG. 4 is a side view of the capillary of FIG. 3 as viewed from a fixed end surface 302A. It is a figure which shows the deformation | transformation form of the capillary concerning this invention. It is a figure which shows the deformation | transformation form of the capillary concerning this invention. It is a figure which shows the deformation | transformation form of the capillary concerning this invention. It is a figure for demonstrating the dimension of the capillary which concerns on this invention. It is a figure for demonstrating the especially preferable dimension of the capillary which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is a diagram illustrating an optical fiber connection method according to an embodiment of the present invention. A capillary 302 is fixed to the end face of the PLC 301. A significant difference from the prior art of FIG. 2 is that a ridged protrusion 302B is provided on the fixed end surface 302A of the capillary instead of using a reinforced glass plate in order to increase the contact cross-sectional area. For example, the capillary 302 can be manufactured by scraping the capillary 302 in the length direction while leaving a part of the circumference on the fixed end surface 302A of the capillary 302. A part of the remaining circumference becomes the protrusion 302B. FIG. 4 shows a side view seen from the fixed end face 302A.

  In the above manufacturing method, after forming the hole through which the optical fiber passes (that is, forming the capillary), it may be scraped off leaving a part of the circumference, or before forming the hole through which the optical fiber passes. It is also possible to form a hole through which the optical fiber passes after leaving a part of.

  A method of forming a mold from the beginning is also conceivable. A mold in which an eaves-like protrusion 302B is provided on the fixed end face 302A of the capillary may be fabricated in advance, and the shape may be fabricated by pouring the capillary material into the mold, and then a hole through which the optical fiber passes may be formed. However, if the hole through which the optical fiber passes can be formed with a mold from the beginning, that may be sufficient.

  By having the protrusion 302B, the capillary 302 is engaged with the end surface and the upper surface of the PLC 301 at the fixed end surface 302A. By contacting not only the end surface of the PLC 301 but also the upper surface, the contact cross-sectional area can be increased and the strength can be increased without providing a reinforcing glass plate on the upper surface of the PLC 301.

  The outer shape of the capillary 302 shown in FIG. 4 is circular, but it may be square or rectangular (see FIG. 5). When the outer diameter is not circular, the protrusion 302B is provided not on the circumference but on a part of the outer circumference on the fixed end surface 302A of the capillary 302. Moreover, although it is single core in FIG. 4, you may use a multi-core thing (refer FIG. 6). Further, the way of opening the inner diameter is not particularly limited to a circle, and may be, for example, a square (see FIG. 7).

  The material of the capillary 302 may be glass such as quartz glass or borosilicate glass, or ceramic such as zirconia or alumina. When the material is glass, the connection configuration is already the same as that of a conventional reinforced glass plate, and thus there is a feature that connection reliability is high. Moreover, these glass materials transmit UV light. Therefore, it is possible to easily connect the PLC and the optical fiber by using the UV adhesive resin for these connections. On the other hand, zirconia ceramics have already been used in high-accuracy ferrules used in optical fiber connectors, and since these also have the same capillary shape, their connection reliability is high. In addition, since ceramic is sintered to produce its shape, it can be manufactured in large quantities at low cost.

  Furthermore, the material may be plastic. This can also be produced in large quantities at a low cost in mold formation. However, plastics are generally unsuitable for high-accuracy connection reliability for connecting single-mode fibers because of their generally large thermal expansion coefficient. However, its use is possible, though limited, such as applications where connection tolerance is low, such as multimode fiber.

  The general size of a conventional capillary having no protrusion is about 1 to 4 mm in length, 1 to 1.5 mm in outer diameter, and about 0.125 to 0.5 mm in inner diameter. Thus, it is preferable to provide a protrusion 302B having a length of about 0.5 to 1.5 mm and a height of about 0.3 to 0.6 mm. 8 (a) and 8 (b) show an embodiment of the capillary 302 according to the present invention. FIG. 8 (a) shows a case where the protrusion 302B extends to the inside of the inner diameter, and FIG. This is the case outside the inner diameter, that is, between the inner diameter and the outer diameter. The latter has higher connection strength. When the dimensions as described above are taken, the chip can be made smaller than the conventional reinforced glass plate having a thickness of 1 mm and a length of 2 mm.

FIG. 9 is a diagram showing particularly preferred capillary dimensions. In FIG. 9, when the optical fiber strand (diameter 0.127 mm) is inserted by setting the inner diameter of the capillary to 0.3 mm, there is a margin of 0.0865 mm with respect to the inner diameter. Moreover, since the distance from the upper surface of the PLC to the core center of the PLC is usually 0.01 to 0.04 mm by setting the height of the capillary eaves to 0.45 mm, the capillary is simply adhered to the end surface of the PLC. Thus, the core center of the optical fiber comes within 0.05 mm from the center of the capillary. For this reason, it is possible to facilitate the rough alignment of the optical fiber after the capillary is attached to the PLC. For the 0.05 mm alignment, the 0.0865 mm movable margin with respect to the inner diameter is sufficiently secured.

301 PLC
302 Capillary 302A Fixed end face 302B Projection

Claims (4)

A capillary for connecting an optical fiber to an end face of a waveguide type optical element,
At one end, provided with a protrusion on a part of the outer periphery ,
When the waveguide optical element and the protrusion are connected to engage the end face and the upper surface of the waveguide optical element at the one end where the protrusion is formed, the waveguide optical element is A movable margin between the inner periphery of the capillary and the outer periphery of the optical fiber for aligning the core of the optical fiber with the center of the core of the optical waveguide is provided, and the movable margin is the waveguide A capillary having a larger distance from the upper surface of the optical element to the core center of the optical waveguide .
  The capillary according to claim 1, wherein the protrusion extends to the inside of the inner diameter of the capillary.   2. The capillary according to claim 1, wherein the protruding portion exists between an inner diameter and an outer diameter of the capillary.   The capillary according to any one of claims 1 to 3, wherein the protrusion has a length of 0.5 mm to 1.5 mm and a height of 0.3 mm to 0.6 mm.

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