JPH07128545A - How to connect optical waveguide and optical fiber - Google Patents

Abstract

(57) [Summary] [Object] To provide a method of connecting an optical waveguide and an optical fiber, which is easy to connect, has a small number of steps, and does not deteriorate the performance of the optical fiber. In a connection method for optically coupling a plurality of optical waveguides 27, 28 and a plurality of optical fibers 20, 23 juxtaposed on a waveguide substrate 26, the optical fibers 20, 23 are fused together and fused. Cut at the attachment to form the end surface,
On the other hand, the optical waveguides 27 and 28 are fused with the optical fiber 20,
It is characterized in that the cores 21 and 25 of 23 are formed to have the same spacing at the connection interface, and the optical end face of the fused portion is optically coupled to the end face of the optical waveguide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting method for optically coupling a plurality of optical waveguides and a plurality of optical fibers arranged side by side on a waveguide substrate.

[0002]

2. Description of the Related Art As shown in FIG. 4, when two optical waveguides 2 and 3 arranged side by side on a waveguide substrate 1 and two optical fibers 4 and 5 are optically coupled, a V groove 6 is formed on the surface. , 7 are formed on the silicon substrate 8 and the two optical fibers 4 and 5 whose coatings have been removed in advance are placed on the silicon substrate 8 and then fixed with resin to form an optical fiber array, and the core of the optical fiber 4 (5) is formed. The waveguide substrate 1 and the silicon substrate 8 are connected so that the optical waveguide 2 and the optical waveguide 2 (3) are optically coupled.

[0003]

However, in order to fabricate an optical fiber array by arranging the optical fibers 4 and 5 side by side at the connection portion having the structure shown in FIG. 4, the optical waveguides 2 and 3 are formed on the silicon substrate 8. Since it is necessary to form the V-grooves 6 and 7 in accordance with the intervals, the optical fibers 4 and 5 are arranged in the V-grooves 6 and 7, and further the end faces have to be formed, it is difficult to reduce the cost because three steps are required. Is.

That is, V-groove processing is performed on a plurality of fibers 4,
V-grooves 6 and 7 are individually formed in the silicon substrate 8 to align 5
Since the optical fibers 4 and 5 are processed, the depths in which the optical fibers 4 and 5 are embedded in the V grooves 6 and 7 are likely to be uneven. Since the V-grooves 6 and 7 are almost sharply cut, dust is difficult to remove, and this dust greatly affects the positional accuracy. Further, since resin is used to fix the optical fibers 4 and 5, reliability, particularly temperature characteristics, deteriorates. Further, the optical fibers 4,
In order to match the distance between the cores of the optical fibers 4 and 5 with the distance between the V-grooves 6 and 7 when arranging 5, the flat plate 9 is arranged so that the outer circumferences of the optical fibers 4 and 5 are in contact with the two sides of the V-grooves 6 and 7. The optical fibers 4 and 5 are fixed while being pressed into the V-grooves 6 and 7 from above using the above. At this time, the optical fibers 4, 5
May break due to the removal of the coating, and when the optical fibers 4 and 5 are polarization-maintaining optical fibers, the apparent principal axis of birefringence is There is a problem in that the product is rotated from the position of (1), polarization crosstalk is deteriorated, and the yield is reduced.

Further, in connecting the slab type optical waveguide 10 and the optical fiber array 11 as shown in FIG. 5, if the distance between the optical waveguides 10a and 10b and the core portions 11a and 11b is deviated, the propagating light is propagated. The loss will increase. For example, if an elliptic core type fiber is used as the optical fiber, the core diameter has a major axis of 5 μm and a minor axis of only 1 μm, and further positional accuracy is required for optical connection.

Therefore, an object of the present invention is to solve the above problems and provide a method for connecting an optical waveguide and an optical fiber, which is easy to connect, has a small number of steps, and does not deteriorate the performance of the optical fiber. It is in.

[0007]

In order to achieve the above object, the present invention provides a connection method for optically coupling a plurality of optical waveguides and a plurality of optical fibers juxtaposed on a waveguide substrate. Along with fusing, the end face is formed by cutting at the fusing part, while the optical waveguide is formed so as to have the same spacing at the connection interface as the core of the fused optical fiber, and the end face of the optical waveguide is fused. The optical end faces of the attachment portion are optically coupled.

[0008]

According to the above construction, the optical fibers arranged side by side are fused together, and the end faces are formed by cutting at the fused portion, so that an optical fiber array with a stable core interval is formed. In forming this optical fiber array, the step of fixing the optical fiber in the V groove with resin or the like and the step of fixing the optical fiber in the V groove with a flat plate are unnecessary,
The man-hour is reduced. Further, since it is not necessary to press the core against the V-groove with a flat plate or the like, stress of the flat plate is not applied to the core, damage to the optical fiber is prevented, deterioration of polarization crosstalk is less likely to occur, and yield and reliability are improved. To do. Furthermore, the optical waveguide is formed so that it has the same spacing as the core of the fused optical fiber at the connection interface, and the optical end face of the fused part is optically coupled to the end face of the optical waveguide to facilitate alignment. Becomes

[0009]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of an embodiment of a connecting portion to which the method for connecting an optical waveguide and an optical fiber according to the present invention is applied.

In the figure, 20 is an elliptic core type polarization-maintaining optical fiber consisting of a core 21 and a clad 22,
Reference numeral 23 is also an elliptic core type polarization-maintaining single-mode optical fiber composed of a core 25 and a clad 24, and the outer circumference thereof is covered with a coating (not shown) but removed.

The claddings 22 and 24 on one end side (center of the figure) of the optical fibers 20 and 23 are fused to each other, and the end faces of the optical fibers 20 and 23 are connected to a lithium niobate substrate 26. Lithium niobate substrate 26
Two optical waveguides 27 and 28 are arranged side by side. The optical waveguides 27 and 28 are formed so that the distance between them is substantially equal to the outer diameters of the clads 22 and 24 of the optical fibers 20 and 23, and the optical fibers 20 and 23 include the cores 21 and 25 and the optical waveguides 27 and 28. Are fused so that they have the same spacing. The core 21 of the optical fiber 20 and the optical waveguide 27 are optically coupled, and the core 25 of the optical fiber 23 and the optical waveguide 28 are optically coupled.

FIG. 1 shows a method of connecting such a connecting portion.
2 and FIG. 2. Note that FIG. 2 is a schematic view of an optical fiber fusion jig used to form the connection portion shown in FIG.

The two optical fibers 20 and 23, of which the coating is partially removed, are arranged in parallel, and the optical fiber fusion jig 29 is used.
Hold with ~ 32. When the parallel portion 33 of the optical fibers 20 and 23 is heated by arc discharge, the glass on the surface is melted and fixed (fused) to each other. At this time, if the heating is insufficient, the optical fibers 20 and 23 are not fixed, and if excessively heated, the loss of light becomes large, or one light leaks into the other, so care must be taken. .

After the fusion of the optical fibers 20 and 23 is completed, the fused portions are cut vertically to form two sets of optical fiber arrays.

On the other hand, the optical waveguides 27 and 28 are previously
The distance between the claddings 22 and 24 of the optical fibers 20 and 23
Lithium niobate substrate 26 to be approximately equal to the outer diameter of
To be formed. The optical fibers 20 and 23 are the core 2
1, 25 are fused so as to be almost the same distance as the distance between the optical waveguides 27, 28 (so that the connection loss is within an allowable range), and one of the two sets formed by cutting is fused. The connection portion is formed by connecting the end face of the optical fiber array to the end face of the lithium niobate substrate 26 so that the core 21 and the optical waveguide 27 and the core 25 and the optical waveguide 28 are coupled.

Next, the operation will be described.

The portions of the two juxtaposed optical fibers 20 and 23 from which the coating has been removed are fused by arc discharge and cut at the fused portions to form the end faces.
Two sets of optical fiber arrays with stable intervals of 25 are formed. In forming this optical fiber array, the step of fixing the optical fibers to the V-grooves 6 and 7 with resin or the like, and the flat plate 9
Since the step of fixing the optical fiber to the V-grooves 6 and 7 by using the above is unnecessary (FIG. 4), the number of steps is reduced. Also flat plate 9
Since stress due to is not applied to the cores 21 and 25, damage to the optical fiber is prevented, yield and reliability are improved, and a highly accurate connection portion is formed. Further, the optical waveguide is formed at the same interval as the core of the fused optical fiber, and the optical end face of the fused portion is optically coupled to the end face of the optical waveguide, which facilitates the alignment.

FIGS. 3A to 3C are conceptual views of another embodiment of the present invention.

The difference from the embodiment shown in FIG. 1 is that the fused portion of the optical fiber is cut to be inclined with respect to the optical fiber, and the end face of the optical waveguide is also formed to be inclined with respect to the optical waveguide. These inclination angles are set so as to satisfy Snell's law at the connection interface.

The two optical fibers 52 and 53 from which the coatings 50 and 51 have been partially removed are arranged in parallel, and the pressing jig 34 is used.
Hold with ~ 37. Then, when the parallel portion 39 of the optical fibers 32 and 33 is heated by the gas burner 38, the glass on the surface is melted and fused to each other (FIG. 3A).

After the fusion of the optical fibers 52 and 53 is completed, the fusion portion 39a is cut at an angle of about 15 ° to form two sets of optical fiber arrays. The end face is inclined in order to suppress the reflected return light, and at the same time, to obtain the angle at which Snell's law is satisfied for the light wave propagating through the optical fibers 52 and 53 and the optical waveguide. . For this reason, other angles may be used as long as they are effective in suppressing reflected return light and Snell's law holds (FIG. 3).
(B)).

On the other hand, the optical waveguides 40 and 41 are previously
The fused optical fibers 52, 53 are formed on the substrate 42 so as to have the same spacing as the core spacing and the connection interface, and the end faces of the optical array are guided so that the cores are coupled with the optical waveguides 40, 41. A connection portion is formed by connecting to the end face of the waveguide substrate (FIG. 3 (c)).

In the embodiments shown in FIGS. 1 and 3, the optical fibers are fused and the end faces are formed by cutting the optical fibers at the fusion portion, while the optical waveguide is fused to the core of the fused optical fiber. Since the optical end face of the fused portion is optically coupled to the end face of the optical waveguide, it is easy to connect, the number of steps is small, and the performance of the optical fiber is deteriorated. It is possible to realize a method of connecting an optical waveguide and an optical fiber which does not exist.

The optical waveguides are not limited to the above-mentioned embodiments, and the optical waveguides may be juxtaposed (laminated) in the depth direction of the substrate, and the proton exchange optical waveguide and tantalum formed on the lithium niobate substrate. A proton exchange optical waveguide, a zinc diffusion optical waveguide, a silica glass optical waveguide, a multi-component glass optical waveguide, a semiconductor optical waveguide, or an organic optical waveguide formed on a lithium oxyacid substrate may be used. The number of optical waveguides juxtaposed may be three or more, and the number of optical fibers to be fused is three.
It may be more than a book. The optical fiber includes polarization-maintaining optical fiber, single mode optical fiber, multimode optical fiber,
Either plastic optical fiber may be used. Further, the end face of the optical fiber and the end face of the optical waveguide may be fixed by using an adhesive other than the ultraviolet curing type, and the end faces may be fused or fused with quartz glass, low melting point glass, multi-component glass, plastic, etc. It may be attached to the periphery and fixed. In order to enhance the mechanical strength of the connecting portion, a holding member may be arranged around the optical fiber and connected and fixed. A method other than a gas burner or arc discharge may be used for fusing the optical fibers together, for example, a heater, a laser beam, or the like, and quartz glass, low melting point glass, multi-component glass, plastic, or the like is attached around the optical fibers. May be fused together.

[0026]

In summary, according to the present invention, the following excellent effects are exhibited.

The optical fibers are fused and cut at the fused portion to form an end face, while the optical waveguide is formed at the same interval as the core of the fused optical fiber, and the end face of the optical waveguide is fused. Since the optical end faces of the attachment portion are optically coupled, it is possible to realize a method of connecting an optical waveguide and an optical fiber that facilitates connection, has a small number of steps, and does not deteriorate the performance of the optical fiber.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an embodiment of a connecting portion to which a method for connecting an optical waveguide and an optical fiber according to the present invention is applied.

FIG. 2 is a schematic view of an optical fiber fusing jig used to form the connection part shown in FIG.

3 (a) to (c) are conceptual diagrams of another embodiment of the present invention.

FIG. 4 is a diagram showing a conventional example of a method of connecting an optical waveguide and an optical fiber.

FIG. 5 is a diagram showing another conventional example of a method for connecting an optical waveguide and an optical fiber.

[Explanation of symbols]

 20, 23 Optical fiber 21, 25 Core 26 Waveguide substrate (lithium niobate substrate) 27, 28 Optical waveguide

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Iizuka 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable Co., Ltd. Hidaka Plant

Claims (3)

[Claims] 1. A connection method for optically coupling a plurality of optical waveguides and a plurality of optical fibers arranged side by side on a waveguide substrate, wherein the optical fibers are fused and cut at a fused portion to form an end face. On the other hand, the optical waveguide is formed so as to have the same spacing as the core and the connection interface of the fused optical fiber, and the optical end face of the fused portion is optically coupled to the end face of the optical waveguide. A characteristic method of connecting an optical waveguide and an optical fiber. 2. The optical waveguide according to claim 1, wherein the fusion-bonded portion of the optical fiber is cut while being inclined with respect to the optical fiber, and the cut end face is coupled to the optical waveguide. Connection method with optical fiber. 3. The method for connecting an optical waveguide and an optical fiber according to claim 1, wherein the optical waveguide is formed in a multi-layer slab type.