JP2658064B2 - Optical waveguide end forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding a method for forming an end portion of an optical waveguide for connecting an optical fiber, an optical waveguide is formed for the purpose of improving the connection strength and reducing the man-hour for forming the end portion of the optical waveguide to reduce the cost. After adhering a fixed piece of the same material and substantially the same thickness as the optical waveguide substrate on one end surface of the optical waveguide substrate, the fixed piece is attached to at least the fixed piece in a direction perpendicular to the optical waveguide. Using a rotary cutting saw, the end of the optical waveguide is configured to be cut and removed to expose the optical waveguide to a depth obtained by adding the radius of the optical fiber diameter to the thickness.

[Industrial applications]

The present invention relates to a device constituting an optical communication system,
In particular, the present invention relates to a method for forming an end portion of an optical waveguide for connecting an optical fiber.

2. Description of the Related Art As optical communication technology has become widespread, there has been an increasing demand for various components and devices constituting an optical communication system to be improved in reliability, downsized, and inexpensive.

In particular, various means have been taken to connect the optical waveguide and the optical fiber, which are important factors that affect the transmission efficiency of the optical signal in the optical communication system, but the characteristics are more stable, the mass productivity is high, and the cost is low. There is a demand for the development of a connection method that can be supplied to a computer.

[Conventional technology]

FIG. 4 is a diagram showing a conventional optical waveguide end shape and an optical fiber connection state, and FIG. 5 is a diagram showing another conventional optical waveguide end shape and an optical fiber connection state.

In FIG. 4 (A), reference numeral 1 denotes an optical waveguide substrate made of an electro-optic crystal such as lithium niobate (LiNbO ₃ ), on which a titanium (Ti) vapor-deposited film is patterned and thermally diffused. An optical waveguide 2 having a larger refractive index than the substrate is formed.

Next, a rectangular fixing piece 3 made of the same material as that of the substrate 1 and having substantially the same thickness is adhered on the surface of the optical waveguide substrate 1 on which the waveguide is formed with an epoxy-based adhesive 4. Fixed section 3 and optical waveguide substrate 1
Are both polished using mechanical means such as lapping to expose the bonding surface 2a of the optical waveguide 2.

FIG. 4B shows a state where the optical fiber is connected to the optical fiber in this case. That is, the bonding surface of the optical fiber 5 having a smooth surface equivalent to a polished surface as a connection end surface is applied to the bonding surface 2a of the optical waveguide 2, and the best condition is obtained while observing an optical signal on a device (not shown). In a state where the position is found, the joint surface is bonded and fixed with a fast-curing UV-curing adhesive 6.

FIG. 5A shows another embodiment in which the outer diameter (for example, 20 μm) of the optical fiber 5 which is thinned by etching is formed on the portion of the optical waveguide substrate 1 where the waveguide 2 is formed.
A groove having a width of about 20 μm corresponding to m), a depth of about 10 μm, which is almost half of the outer diameter, and a length of several mm is removed by etching by means of ordinary patterning or the like. In this case, the bonding surface 2a of the optical waveguide 2 is exposed in the above-described etching groove.

At this time, the connection with the optical fiber is made by applying the bonding surface of the optical fiber 5 to the bonding surface 2a of the optical waveguide 2 as shown in FIG. The joint surface between the fiber 5 and the optical waveguide 2 and the etching groove between the optical fiber 5 and the optical waveguide substrate 1 are bonded and fixed with a UV curing adhesive 6, respectively.

[Problems to be solved by the invention]

The method of bonding and fixing only the front end bonding surface of the optical fiber at the end of the optical waveguide as shown in FIG. 4 requires a step of polishing the end of the optical waveguide by mechanical means, and the bonding area is small because the bonding area is small. There is a problem that it is easy to peel off.

In the method of inserting and fixing an optical fiber in an etching groove at the end of an optical waveguide as shown in FIG. 5, it takes time to form an etching groove because an electro-optical crystal such as LiNbO ₃ is a material that is difficult to be etched. At the same time, the bonding surface of the optical waveguide 2 has some irregularities during etching, so that it does not adhere to the bonding surface of the optical fiber, and there is a problem that loss is easily accompanied by a connection surface when transmitting an optical signal.

[Means for solving the problem]

The above problem is that, in the method for connecting an optical fiber and an optical waveguide, a step of fixing a fixing piece on one end surface of the optical waveguide substrate on which the optical waveguide is formed, and a step of fixing the fixing piece and the optical waveguide substrate. By cutting and removing the portion, the step of exposing the end of the optical waveguide on its cut surface, the end of the optical waveguide exposed on the cut surface, and the end surface of the optical fiber, and both are Fixing the optical fiber at a position where the optical fiber is optically connected.

(Operation)

Since an ultra-high-precision grinding cutter (cutting saw) is used for cutting the optical waveguide, each cut surface has almost the same smoothness as that obtained by optical polishing.

That is, since the joint surface of the optical waveguide connected to the optical fiber forms a good surface where transmission loss does not occur when connected to the optical fiber, there is no need to re-polish.

Furthermore, the connection between the optical fiber and the optical waveguide can be fixed not only between the bonding surfaces of the optical fibers but also between the optical waveguide substrate and the optical fiber.

Accordingly, the connection between the optical waveguide and the optical fiber, which is resistant to external forces such as a pulling force and can be reduced in cost by shortening the processing time and which is rich in mass productivity, can be realized.

〔Example〕

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

FIG. 1 is a process chart showing a method of forming an optical waveguide end according to the present invention, FIG. 2 is a view showing a connection state between an optical waveguide end and an optical fiber according to the present invention, and FIG. FIG. 7 is a view showing another embodiment according to the present invention.

In FIG. 1 (A), reference numeral 1 denotes an optical waveguide substrate made of an electro-optic crystal such as LiNbO ₃ and having a thickness of about several hundreds to 1000 μm. On the surface thereof, patterning or the like is performed so as to form a waveguide. An optical waveguide 2 having a larger refractive index than that of the substrate 1 is formed by vapor-depositing Ti using the means described above and further thermally diffusing the Ti.

At one end on the optical waveguide substrate 1, a rectangular fixing piece 3 made of the same material as the substrate (1) and having substantially the same thickness is adhered and fixed with an epoxy adhesive 4.

FIG. 1 (B) shows a state in which a rotary cutting saw is working, and reference numeral 7 denotes a working blade of the cutting saw.

The processing depth from the surface of the fixing piece 3, that is, the dimension d shown in the figure, is set to be several μm larger than the dimension obtained by adding the radius of the optical fiber diameter to the thickness of the fixing piece 3.

Under these conditions, the processing blade 7 is moved in the width direction (Y direction in the figure) while rotating the processing blade 7 in the arrow direction (R direction in the figure) to form a processing groove over the entire width.

Further, the processing is continued by gradually expanding the groove while slightly shifting the processing blade 7 in the rotation axis direction (X direction in the drawing).

FIG. 1 (C) shows the shape of the end of the optical waveguide in the middle thereof, and the formed processing groove has a cut cross section of the optical waveguide 2 having the same smoothness as when the surface is polished. 2b is exposed.

Thereafter, the processing is continued up to the end of the optical waveguide substrate 1,
An end portion of the optical waveguide according to the present invention shown in FIG. 2 (D) is formed.

FIG. 2 is a diagram showing a connection state between an optical fiber end and an optical fiber according to the present invention.

That is, the joining surface of the optical fiber 5 having the connection end surface having the same smooth surface as the polished surface is applied to the cut section 2b (shown in FIG. 1 (D)) exposed on the processing surface of the optical waveguide 2, and is not shown. While observing the optical signal transmitted on the device side, the respective bonding surfaces and the processing surfaces of the optical fiber 5 and the optical waveguide substrate 1 are both fast-cured UV-curing adhesive 6 at the position where the best conditions are obtained.
It is fixed with adhesive.

 FIG. 3 is a view showing another embodiment according to the present invention.

That is, FIG. 3A showing the shape of the end of the optical waveguide as another embodiment is different from the state of FIG. 1C described above in that the processing direction is changed by 90 ° and the center of the optical axis of the optical waveguide 2 is changed. And a groove having a width w (about 130 μm when the optical fiber diameter is 125 μm) that allows the optical fiber to be easily inserted under the above processing conditions.

FIG. 3 (B) showing the connection state of the optical fiber 5 and the optical fiber 5 in this case is shown in FIG. As in the case of FIG. 2, a fast-curing UV-curing adhesive 6 is used for bonding and fixing.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide an end shape of an optical waveguide that can be firmly connected to an optical fiber, can be reduced in cost by shortening a processing time, and is rich in mass productivity.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a method of forming an optical waveguide end according to the present invention, FIG. 2 is a diagram showing a connection state between an optical waveguide end and an optical fiber according to the present invention, and FIG. 3 is the present invention. FIG. 4 is a view showing another embodiment, FIG. 4 is a view showing a conventional optical waveguide end shape and a state of optical fiber connection, and FIG. 5 is another conventional optical waveguide end shape and a state of optical fiber connection. FIG. In the figure, 1 is an optical waveguide substrate, 2 is an optical waveguide, 2b is a cut section, 3 is a fixing piece, 4 is an epoxy adhesive, 5 is an optical fiber, 6 is a UV curing adhesive, and 7 is a processing blade. Represents.

Claims (1)

(57) [Claims] 1. A method for connecting an optical fiber to an optical waveguide, comprising: fixing a fixing piece on one end surface of the optical waveguide substrate on which the optical waveguide is formed; By cutting and removing the portion, the step of exposing the end of the optical waveguide on its cut surface, the end of the optical waveguide exposed on the cut surface, and the end surface of the optical fiber, and both are Fixing the optical fiber at a position where the optical fiber is to be optically connected.