JP2589765Y2 - Coupling structure between optical waveguide and optical fiber - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coupling structure between an optical waveguide and an optical fiber, and more particularly, to an optical waveguide chip formed with an optical waveguide and an optical waveguide using an optical fiber array holding the optical fiber. The present invention relates to a coupling structure with an optical fiber.

[0002]

2. Description of the Related Art FIG. 3 is an exploded perspective view for explaining a conventional coupling structure between an optical waveguide and an optical fiber.

In this conventional coupling structure between an optical waveguide and an optical fiber, an optical waveguide 13 and an optical fiber 35 are optically coupled to each other using an optical waveguide chip 10 and an optical fiber array 30.

An optical waveguide 1 is provided on the upper surface of a LiNbO ₃ substrate 11.
3, the optical waveguide chip 10 is formed.

A V-shaped groove 33 having a V-shaped cross section is formed on the upper surface of the ceramic substrate 31.
The optical fiber array 30 is formed by holding the optical fiber 35 in the V groove 33 with the ceramic substrate 31 and the ceramic lid 37 in a state where 5 is placed.

After optically polishing both the end face 15 of the optical waveguide chip 10 and the end face 45 of the optical fiber array 30,
With the optical waveguide chip 10 and the optical fiber array 30 positioned so that the optical axis of the optical waveguide 13 and the optical axis of the optical fiber 35 are aligned, the end surface 15 of the optical waveguide chip 10 and the end surface 45 of the optical fiber array 30 And these end surfaces 15 and 45 were joined with an adhesive resin.

[0007]

However, when a bonded body of the optical waveguide chip 10 and the optical fiber array 30 thus bonded is subjected to a thermal cycle test at, for example, -40 ° C to 100 ° C. In addition, there is a problem that the joint between the end face 15 and the end face 45 is damaged, resulting in poor mechanical reliability.

Accordingly, it is an object of the present invention to provide a coupling structure between an optical waveguide and an optical fiber that provides excellent mechanical reliability.

[0009]

According to the present invention, an optical waveguide is formed, an optical waveguide chip having a first end face at which one end of the optical waveguide is exposed, and an optical fiber is held. An optical fiber array having a second end face exposed at one end, wherein the optical waveguide exposed at the first end face and the optical fiber exposed at the second end face are optically coupled with each other. In the coupling structure of an optical waveguide and an optical fiber, wherein a first end face and the second end face are joined by an adhesive resin, a part of the first end face having a Ra of 0.1 μm or more. Is provided, a second rough surface having Ra of 0.1 μm or more is provided on a part of the second end surface, and the first rough surface and the second rough surface are opposed to each other, The first end face and the second end face are joined by an adhesive resin Thus, a coupling structure between the optical waveguide and the optical fiber is obtained.

[0010] Here, Ra means "center line average roughness" defined in the JIS standard, and the roughness curve f
When a portion of the measurement length L is extracted from (x) in the direction of the center line, and the center line of the extracted portion is the X axis and the direction of the vertical magnification is the Y axis, the following equation is obtained.

[0011]

(Equation 1)

The value obtained by the above is expressed in μm.

[0013]

The end face of the optical waveguide and the end face of the optical fiber array are optically polished with extremely small surface roughness in order to prevent scattering of light at these end faces of the optical waveguide and the optical fiber formed or held thereon. Is given. However, such an optically polished surface
The present inventor has found that the adhesion to the adhesive resin is poor and the strength at the joint interface is low.

As in the present invention, Ra is 0.1 μm on a part of the first end face of the optical waveguide chip where one end of the optical waveguide is exposed.
m is provided on a part of the second end face of the optical fiber array where one end of the optical fiber is exposed.
A second rough surface portion of 1 μm or more is provided, and the first rough surface portion
When the first end face and the second end face are joined by an adhesive resin with the rough surfaces facing each other, the adhesive strength at the interface between the first rough surface and the second rough surface and the adhesive resin is obtained. And the mechanical reliability is improved.

As a substrate material for the optical waveguide chip, an oxide material such as LiNbO ₃ or LiTaO ₃ , a semiconductor, glass, or the like can be used, and a substrate on which a V-groove for an optical fiber array is formed is used. , A Si substrate, a ceramic substrate, or the like can be used. As the adhesive resin, an epoxy resin, an acrylic resin, or the like can be used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view for explaining a coupling structure between an optical waveguide and an optical fiber according to an embodiment of the present invention, and FIG. 2 is an optical waveguide and an optical fiber according to an embodiment of the present invention. FIG. 4 is a perspective view for explaining a coupling structure with the device.

In the coupling structure between the optical waveguide and the optical fiber according to the present embodiment, the optical waveguide 13 and the optical fiber 35 are optically coupled by using the optical waveguide chip 10 and the optical fiber array 30.

As shown in FIG. 1, the thickness is 1 mm and the width is 5 m
An optical waveguide 13 was formed on an upper surface of a LiNbO ₃ substrate 11 having a length of 30 mm and a length of 30 mm, thereby forming an optical waveguide chip 10 serving as a Mach-tuenda type modulator. Then 1mm x 5
mm end faces (one end face of which is end face 15)
Optical polishing was performed on the entire surface.

Next, the optically polished optical waveguide chip 10
Of the end face 15 having a width of about 0.
Each of the end face region 17 having a width of 5 mm and the widths of both end portions is approximately 0.5 mm.
The portions excluding the 5 mm end face regions 19 and 21 were polished using abrasive grains to form rough surface portions 23 and 25.

On the other hand, thickness 1 mm, width 5 mm, length 5 mm
V-shaped groove 3 having a V-shaped cross section on the upper surface of ceramic substrate 31
The optical fiber 35 is placed in the V-groove 33, and a transparent ceramic lid 37 having a thickness of 1 mm, a width of 5 mm, and a length of 5 mm is put thereon. Then, an adhesive resin was poured in between them, and the ceramic substrate 31, the optical fiber 35 and the lid 37 were fixed and integrated to form the optical fiber array 30. Thereafter, optical polishing was performed on the entire end face 45 of the optical fiber array 30 where the optical fiber 35 was exposed. The end face 45 of the optical fiber array 30 includes an end face 41 of the ceramic substrate 31 from which the optical fiber 35 is exposed and an end face 43 of the lid 37.

Next, similarly to the case of the optical waveguide chip 10, the end face 45 of the optically polished optical fiber array 30 is formed.
Of the parts, the end face area 51 having a width of about 0.5 mm around the optical fiber 35 and the end face areas 53 and 55 having widths of about 0.5 mm at both ends are removed using abrasive grains. By polishing, rough surface portions 57 and 59 were formed.

Thereafter, as shown in FIG.
The optical axis of the optical fiber 35 and the optical axis of the optical fiber 35 are aligned, and the rough surface 57 and the rough surface 23 and the rough surface 59 and the rough surface 25 face each other. With the distance between the end face 45 of the optical fiber array 30 and the end face 45 being 5 μm, and the optical waveguide chip 10 and the optical fiber array 30 are positioned, an ultraviolet curing epoxy resin is poured, and the epoxy resin is cured by applying ultraviolet rays. Then, the optical waveguide chip 10 and the optical fiber array 30 were fixed, and an assembly 100 of the optical waveguide chip 10 and the optical fiber array 30 was formed.

The optical waveguide chip 1 thus produced
0 and an optical fiber array 30 assembly 100,
A heat cycle test was performed in a temperature range of -20 to 80 ° C. That is, it is kept at −20 ° C. for 10 minutes,
The temperature was raised from −20 ° C. to 80 ° C. at a rate of 20 ° C./min, and the temperature was maintained at 80 ° C. for 10 minutes.
The temperature was decreased to 20 ° C. at a rate of 20 ° C./min as one cycle, and this cycle was repeated 2000 times to perform a thermal cycle test.

The rough surface portions 23 and 2 of the optical waveguide chip 10
5 and rough portions 57 and 59 of optical fiber array 30
Has an optically polished surface, Ra: 0.05 μm, R
a: 0.1 μm, Ra: 0.3 μm and Ra: 1 μm
The five types of assemblies 100 were prepared for each roughness, and the above-mentioned thermal cycle test was performed.

Table 1 shows the results of the heat cycle test. The reliability is improved by providing the rough surface portions 23, 25, 57 and 59, and the reliability is improved under the condition that Ra is 0.1 μm or more. It can be seen that the improvement is remarkable.

[0027]

[Table 1]

In this embodiment, the rough surface portion 57,
Although 59 is provided on both the end surface 41 of the ceramic substrate 31 and the end surface 43 of the lid 37, when the height of the upper surface of the ceramic substrate 31 and the upper surface of the LiNbO ₃ substrate 11 are substantially equal, for example, The rough surface portions 57 and 59 may be provided only on the end surface 41.

[0029]

According to the present invention, a first roughened surface having a Ra of 0.1 μm or more is provided on a part of a first end face of an optical waveguide chip in which one end of an optical waveguide is exposed, and an optical fiber array in which one end of an optical fiber is exposed. A second rough surface having Ra of 0.1 μm or more is provided on a part of the second end surface, the first rough surface and the second rough surface are opposed to each other, and the first end surface and the second end surface are provided. Is bonded with an adhesive resin to provide a coupling structure between an optical waveguide and an optical fiber that provides excellent mechanical reliability.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view for explaining a coupling structure between an optical waveguide and an optical fiber according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a coupling structure between an optical waveguide and an optical fiber according to an embodiment of the present invention;

FIG. 3 is an exploded perspective view for explaining a conventional coupling structure between an optical waveguide and an optical fiber.

[Explanation of symbols]

10: optical waveguide chip, 11: LiNbO ₃ substrate, 13
... optical waveguide, 15 ... end surface, 17 ... end surface region, 19 ... end surface region, 21 ... end surface region, 23 ... rough surface portion, 25 ... rough surface portion,
30 ... optical fiber array, 31 ... ceramic substrate, 3
3 V-groove, 35 optical fiber, 37 lid, 41 end face,
43 ... end face, 45 ... end face, 51 ... end face area, 53 ... end face area, 55 ... end face area, 57 ... rough surface part, 59 ... rough surface part,
100 ... assembly

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 6/30

Claims (1)

(57) [Scope of request for utility model registration] 1. An optical waveguide chip having an optical waveguide formed and having a first end face at which one end of the optical waveguide is exposed, and a second optical chip holding an optical fiber and exposing one end of the optical fiber.
An optical fiber array having an end face of the first end face and the first end face to optically couple the optical waveguide exposed to the first end face and the optical fiber exposed to the second end face. In a coupling structure of an optical waveguide and an optical fiber, wherein a second end face is joined by an adhesive resin, a first rough surface portion having Ra of 0.1 μm or more is provided on a part of the first end face; Ra is 0.1 μm on a part of the second end face.
m and a second roughened surface are provided, and the first roughened surface and the second roughened surface are opposed to each other, and the first end face and the second end face are joined by an adhesive resin. A coupling structure between an optical waveguide and an optical fiber.