JP2581256B2 - Method for fixing optical waveguide device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for fixing an optical waveguide device to a housing in an optical circuit component such as an optical communication system, and to improve the productivity by eliminating the characteristic change of the optical waveguide device during fixing. A method of fixing an optical waveguide device made of a ferroelectric crystal to a housing, wherein the optical waveguide device is connected and fixed to a predetermined position of the housing only at one small area on the back surface of the optical waveguide device. It is composed.

[Industrial applications]

The present invention relates to optical circuit components such as optical communication systems,
In particular, the present invention relates to a method for fixing an optical waveguide device that improves productivity by eliminating a change in characteristics of the optical waveguide device that occurs when the optical waveguide device is fixed to a housing.

With the development of optical communication technology, optical circuit components having various functions are required, and these optical circuit components are usually configured by fixing an optical waveguide device having various functions to a housing.

However, when the optical waveguide device is fixed to the housing, internal stress is generated in the optical waveguide device due to a difference in thermal expansion coefficient between the two and the like, and the characteristics as the optical waveguide device are changed. I have.

[Conventional technology]

Generally, an optical circuit component is configured by fixing an optical waveguide device having various functions at a predetermined position of a box-shaped housing and then connecting an optical fiber for transmitting an optical signal to an input / output optical waveguide end face of the device. Like that.

FIG. 3 is a view showing a configuration example of a conventional optical circuit component, where (1) is a perspective sectional view and (2) is an enlarged view showing an optical waveguide device portion.

In FIGS. 3 (1) and 3 (2) showing the completed state, a square-shaped projecting stage 1a is formed at a predetermined position on the inner bottom of a box-shaped housing 1 made of stainless steel or the like.
An optical modulator formed by diffusing titanium (Ti) patterned on the surface of an optical waveguide substrate (hereinafter simply referred to as a substrate) 2a made of a ferroelectric crystal such as lithium niobate (LiNbO ₃ ). An optical waveguide device 2 in which an optical waveguide 2b (not shown in the drawing) and an optical waveguide 2b connected to the optical modulator are formed is fixed via a conductive adhesive 3, for example.

In particular, the optical waveguide 2b of the optical waveguide device 2 connected to the optical modulator is exposed in a substantially semicircular shape on each end face of the substrate 2a on both sides of the optical modulator. A buffer layer is further formed on the entire surface of the optical waveguide device 2 on the side where the modulator and the optical waveguide are formed, but is not shown in the drawing for easy understanding.

Further, a through hole 1b is formed at a position corresponding to each of the optical waveguides on each wall surface of the housing 1 which is parallel to an end surface of the optical waveguide device 2 where the respective optical waveguides are exposed. An optical fiber 5 whose surface is covered with a vinyl tube 4 is inserted into and fixed to.

The end of each optical fiber 5 on the optical waveguide device 2 side is substantially coaxial with the semicircular end face where the core 5a of the optical fiber 5 is exposed as shown in FIG. It is joined so that it becomes.

 Reference numeral 6 in the figure is a cover of the housing 1.

An optical circuit component having such a configuration is generally prepared by applying a conductive adhesive 3 to the stage 1a surface of the housing 1 and then placing the optical waveguide device 2 on the stage 1a so that the optical waveguide forming surface is exposed. Adhesively fix both at a temperature of about ℃,
Further, a hole fiber 4 covered with a vinyl tube 4 is inserted and fixed from the outside into each of the two through holes 1b, and the end of the hole fiber 4 is placed on the semicircular exposed end surface of the optical waveguide 2b of the optical waveguide device 2. They are configured by matching and bonding.

However, in order to fix the optical waveguide device 2 to the housing 1, it is necessary to heat to about 120 ° C. as described above.
Since the stage 1a of the housing 1 and the back surface of the optical waveguide device 2 are bonded in a state of being in surface contact with each other via the conductive adhesive 3, a temperature change, a difference in the thermal expansion coefficient between the housing 1 and the optical waveguide device 2, and the like. As a result, a local internal stress is generated in the optical waveguide device 2, and as a result, a partial distortion is generated in the optical waveguide device 2.

In particular, the strain in this case is caused by the refractive index of the optical modulator portion and the optical waveguide 2b portion due to the piezoelectric effect and the photoelastic effect because the substrate 2a is made of a ferroelectric crystal “lithium niobate (LiNbO ₃ ) in the figure”. Is partially changed, and as a result, a change in characteristics as the optical waveguide device 2 is induced.

For example, in the case where the optical modulator formed in the optical waveguide device 2 is a Mach-Zehnder type modulator formed by branching the optical waveguide, a change in a partial refractive index induces a shift of an operating point. is there.

On the other hand, instead of the above-described conductive adhesive, for example, gold (A
u) There is also a method of fixing the both by soldering after depositing a deposited film or the like, but even in this case, even if a low melting point solder is used, the solder connection temperature is about 115 ° C. Will have the same result as using.

Therefore, no matter how accurate and characteristically the optical waveguide device 2 is formed as a single unit, the characteristics as optical circuit components change, so that an improvement in productivity cannot be expected. There is.

[Problems to be solved by the invention]

In the conventional method of fixing an optical waveguide device, since the stage surface of the housing and the back surface of the optical waveguide device are fixed in contact with each other, partial distortion occurs in the optical waveguide device, and characteristics as the optical waveguide device are generated. Had the problem of changing.

[Means for solving the problem]

The above problem is a method of fixing the optical waveguide device to the housing, wherein the optical waveguide device is located at a predetermined position of the housing only in a small area as compared with one optical waveguide device on the back surface of the optical waveguide device. The problem is solved by a method for fixing an optical waveguide device to be connected and fixed.

(Operation)

When the fixed area between the stage surface of the housing and the back surface of the optical waveguide device is a small area such as a point, the internal stress generated in the optical waveguide device can be eliminated, and the characteristics of the optical waveguide device change. Can be suppressed.

According to the present invention, one projection or a minute fixing region is provided on the stage surface of the housing, so that the fixing region between the stage surface of the housing and the back surface of the optical waveguide device is reduced to one minute region.

Therefore, it is possible to eliminate a change in the characteristics of the optical waveguide device when the optical waveguide device is fixed to the housing.

〔Example〕

FIG. 1 is a view for explaining a method of fixing an optical waveguide device according to the present invention, and FIG. 2 is a view showing another embodiment.

FIG. 1 shows a completed state similar to FIG. 3, and a projection 11b is formed at a substantially central portion of a stage 11a provided at a predetermined position on the inner bottom of a box-shaped housing 11 made of stainless steel or the like. The optical waveguide device 2 described with reference to FIG. 3 is fixed on the protrusion 11b with the conductive adhesive 3.

Further, a through hole 11c is formed at a position corresponding to each of the optical waveguides on each wall surface of the housing 11 which is parallel to an end face of the optical waveguide device 2 where the respective optical waveguides are exposed. An optical fiber 5 whose surface is covered with a vinyl tube 4 as shown in FIG.

The end of each of the optical fibers 5 on the optical waveguide device 2 side is bonded such that the core of the optical fiber 5 is substantially coaxial with the exposed semicircular end surface of the optical waveguide 2b. As described in the figure.

 Reference numeral 12 in the figure is a cover of the housing 11.

In such a configuration, first, the conductive adhesive 3 is applied to the protrusions 11b of the housing 11, and then the optical waveguide device 2 is placed so that the optical waveguide forming surface is exposed, and a jig (not shown) is used. While holding the optical waveguide device 2
At a temperature of about 120 ° C., the two are bonded and fixed, and as described in FIG. 3, the end of the optical fiber 5 inserted and fixed from the outside into each of the two through holes 11b is connected to the optical waveguide device 2.
A desired optical circuit component can be formed by removing the above jig by bonding it to the semicircular exposed end face of the optical waveguide 2b.

Particularly in this case, the optical waveguide device 2 and the housing 11
Stage 11a is fixed at the projection 11b, so that even if there is a temperature change or a difference in the coefficient of thermal expansion between the housing 11 and the optical waveguide device 2, local internal stress is applied to the optical waveguide device 2. This does not occur, and as a result, the characteristics of the optical waveguide device 2 are not changed.

Even when the optical modulator formed in the optical waveguide device 2 is the Mach-Zehnder modulator or the like described in FIG. 3, the operating point does not shift because there is no partial change in the refractive index. The optical waveguide device 2 can be fixed to the housing 11 in a characteristically stable state.

Further, even when a gold (Au) vapor-deposited film or the like is formed on each of the projection 11b and the fixing surface of the optical waveguide device 2 instead of the above-described conductive adhesive, and then both are fixed by soldering, the above-mentioned conductive bonding is also used. The same effect as when the agent 3 is used can be obtained.

FIG. 2 showing another embodiment is a stage 1a in FIG.
Are formed with concentric grooves except for the central portion and the outer peripheral portion, and other configurations are the same as those in FIG. 3 and FIG.

In FIG. 2, a housing 13 is a box-shaped housing made of stainless steel or the like.
A concentric square groove 13d is formed in a region excluding a substantially central portion 13b and an outer peripheral portion 13c of a stage 13a provided at a predetermined position on an inner bottom portion of the stage 11 so as to protrude.

In such a configuration, first, the central portion 1 of the stage 13a of the housing 13 is
After applying the conductive adhesive 3 to the portion 3b, the optical waveguide device 2 is heated at about 120 ° C. with the optical waveguide device 2 mounted thereon as in FIG.

Therefore, as described with reference to FIG. 1, the optical fiber 5 is inserted and fixed from the outside into each of the two through holes 13e provided in the housing 13, and the end of the optical fiber 5 is positioned at the above-mentioned predetermined position of the optical waveguide device 2. The required optical circuit components can be formed by bonding the components in accordance with the above.

In this case, since the optical waveguide device 2 and the stage 13a of the housing 13 are fixed only at the central portion 13b,
Even if there is a temperature change or a difference in the coefficient of thermal expansion between the housing 13 and the optical waveguide device 2, local internal stress does not occur in the optical waveguide device 2, and the optical waveguide is similar to the case of FIG. The characteristics of the device 2 are not changed.

Further, the central portion 13b of the stage 13a and the optical waveguide device 2
Even if a gold (Au) vapor-deposited film or the like is formed on each of the fixing surfaces and then both are fixed by soldering, the same effect can be obtained.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a method for fixing an optical waveguide device in which productivity is improved by eliminating a change in characteristics of the optical waveguide device that occurs when the optical waveguide device is fixed to a housing.

Although the In description of the present invention are performed when using lithium Naiobeito (LiNbO ₃₎ substrate, the substrate is an optical waveguide substrate made of another ferroelectric crystal such as lithium tantalate (LiTaO ₃₎ Even in this case, the same effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of fixing an optical waveguide device according to the present invention, FIG. 2 is a diagram showing another embodiment, and FIG. 3 is a diagram showing a configuration example of a conventional optical circuit component. . In the figure, 2 is an optical waveguide device, 2a is an optical waveguide substrate, 3 is a conductive adhesive, 4 is a vinyl tube, 5 is an optical fiber, 11 and 13 are housings, 11a and 13a are stages, 11b is a protrusion, 11c and 13e. Represents a through hole, 12 represents a cover, 13b represents a central portion, 13c represents a rectangular groove, and 13d represents an outer peripheral portion.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinobu Kubota 1015 Kamikodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (56) References JP-A-63-205617 (JP, A)

Claims (1)

(57) [Claims] 1. A method for fixing an optical waveguide device to a housing, wherein the optical waveguide device is located at a predetermined position of the housing only in a small area as compared with one optical waveguide device on the back surface of the optical waveguide device. A method for fixing an optical waveguide device, comprising fixing and connecting.