JPH04245208A - Method connecting optical wave guide path and optical fiber, and optical device using method thereof - Google Patents

Abstract

PURPOSE:To enhance the connection characteristic of a waveguide type optical device used in a photo-communication system or the like by avoiding loss variation of the connection part associate with temp. variation and also breakage of optical fiber on the secular basis. CONSTITUTION:In connecting an optical fiber with an optical waveguide path of an optical device at least equipped with an optical waveguide path base board for connection of optical fiber, a V-groove 12a for fixation of optical fiber 3 to be provided in the upper part of the peripheral wall of the casing 12 to hold and fix the optical fiber 3 connected with the optical waveguide path 2b and the optical waveguide path base board 2a is formed in a position deviated from the extension line of the optical waveguide path 2b while directed as facing the neighborhood of the connecting position of the optical waveguide path 2b and optical fiber 3 with each other. The optical fiber 3 whose one end is fixed to the exposed end face of the optical waveguide path 2b, is secured to the V-groove 12a in the region where a resin film 3a for protection of optical fiber 3 is formed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to waveguide type optical devices in optical communication systems, etc., and in particular improves connection characteristics by avoiding loss fluctuations in connection parts due to temperature fluctuations and damage to optical fibers over time. The present invention relates to a method for connecting an optical waveguide and an optical fiber, and an optical device using the same.

[0002] In recent years, in the field of optical circuit components such as waveguide type optical devices, there has been a strong demand for low loss connections between optical waveguides and optical fibers, as well as stability of loss changes due to temperature fluctuations. It's coming.

[0003] In order to cope with this, an optical system that can realize a direct connection between a waveguide type optical device and an optical fiber with low loss has been provided, but since the loss changes at the connection part due to temperature fluctuation is large, there is no solution is desired.

0004

[Prior art] For example, turning a semiconductor laser on and off
When transmitting an optical signal generated when a signal is transmitted over a long distance using an optical fiber, the bit rate of the optical signal tends to increase as the amount of information required increases. Long-distance transmission has become difficult due to the broadening of the wavelength range called wavelength chirping and the optical dispersion characteristics of optical fibers.

[0005] Therefore, a means of forcibly modulating the light intensity using an external modulation method to generate an optical pulse signal has been put into practical use, but in this case titanium ( An optical modulator having an optical waveguide formed by diffusing Ti) is often used as an external modulator by connecting an optical fiber to the optical waveguide portion exposed at the end face.

FIG. 2, which takes as an example the case where the optical device is an external modulator, is a diagram explaining a conventional method of connecting an optical waveguide and an optical fiber, and (2-1) is a diagram showing the configuration and method.
(2-2) is a plan view showing the completed state after connection.

In FIG. 2, the external modulator 1 is a plate-shaped optical modulator 2.
The optical fiber 3 is connected to the exposed surface of the optical waveguide on the end face of the optical fiber 3, and then fixed to the housing 4 and covered with a lid 5.
In the figure, connection parts related to the present invention are extracted and shown for ease of understanding.

The optical modulator 2 in this case is formed by diffusing patterned titanium (Ti) on the surface of the above-mentioned waveguide substrate 2a made of lithium niobate. The width of the connection part is 7μm,
A semicircular optical waveguide 2b with a depth of about 4 μm is exposed.

Further, the optical fiber 3 having a diameter of about 125 μm and having a central core covered with a cladding is protected around the optical fiber 3 with a protective resin film 3a such as vinyl resin. In this case, in order to reliably connect the optical modulator 2 and the optical fiber 3, it is desirable to make the bonding area between the two as large as possible.

[0010] First, a block 2c made of the same material as the waveguide substrate 2a is placed as shown by arrow A to sandwich the optical waveguide 2b, and after adhesively fixing the two, the block 2c is made of the same material as the waveguide substrate 2a. The substrate 2a is cut together with the block 2c, and the cut surface is, for example, optically polished to form an optical fiber bonding surface 2a-1 in which the optical waveguide 2b is exposed.

On the other hand, at the tip of the optical fiber 3, a ring-shaped ruby bead 3b having a through hole of approximately the same diameter as the optical fiber 3 and having an outer diameter of about 1 mm slightly protrudes from the tip of the optical fiber 3. It is fixed with thermosetting epoxy resin etc. in this state.

[0012] Therefore, an adhesive 3c such as an ultraviolet curable resin is applied to the end face 3b-1 of the ruby bead 3b on the tip side of the optical fiber.
After coating, the optical fiber 3 can be bonded to the substrate 2a with sufficient adhesive strength by positioning and pressing the optical fiber bonding surface 2a-1 consisting of the substrate 2a and block 2c to adhesively fix the two.

Thereafter, the substrate 2a portion is placed at a predetermined position on the bottom surface of the casing 4 made of a material such as Super Invar, which has a small coefficient of thermal expansion near room temperature, as shown by arrow B, and the two are bonded and fixed, and the optical fiber is fixed. 3, the area covered with the protective resin film 3a is fitted into the V-groove 4a formed at a predetermined position on the peripheral wall of the housing 4 as shown by arrow C, and fixed with adhesive using thermosetting epoxy resin or the like; A lid 5 is fixed to the housing 4 as shown by arrow D, thereby configuring the required external modulator 1 shown in (2-2).

In this case, if there is a temperature fluctuation in the surrounding atmosphere,
The optical fiber 3 having a coefficient of thermal expansion larger than that of the housing 4 is connected to the fixed optical fiber joint surface 2a-1 and the housing 4.
It is subjected to thermal stress due to temperature fluctuations between it and the surrounding wall.

This means that if the optical fiber 3 is fixed to the housing 4 in a tensioned state as shown by the dashed line E, the optical fiber will be subjected to compressive stress due to temperature fluctuations in the surrounding atmosphere, causing it to bend or move the bonded point. This means that peeling becomes more likely to occur and at the same time, the connection loss at the connection portion fluctuates.

Therefore, the optical fiber 3 is placed in a V-groove 4a provided at a predetermined position on the peripheral wall of the housing 4 in an area covered with a protective resin film 3a.
When bonding and fixing to the holder, the holder is buckled and deformed in advance as shown by the solid line F, and then the holder is bent and fixed.

However, the buckling deformation of the optical fiber 3 in this case applies internal stress to the fiber 3, and if the buckling deformation is large, there is a high risk that the fiber 3 itself will be destroyed. In particular, since the two fixed parts at both ends, that is, the ruby bead 3b and the peripheral wall of the housing, become inflection points during buckling deformation, bending stress is constantly concentrated on these fixed parts, and when the radius of curvature becomes small. It has the disadvantage that it tends to break in some parts.

[0018]

The conventional method of connecting an optical waveguide and an optical fiber has the problem that the optical fiber itself may be broken or peeled off at the connecting portion due to temperature fluctuations in the surrounding atmosphere.

[0019]

[Means for Solving the Problems] The above object is to provide a method for connecting an optical waveguide and an optical fiber of an optical device, which is provided with at least an optical waveguide substrate for connecting an optical fiber. A V-groove for positioning the optical fiber, which is provided on the upper part of the peripheral wall of the casing that holds and fixes the optical fiber connected to the optical waveguide, is connected to the optical fiber of the optical waveguide at a position away from the extension line of the optical waveguide. A method for connecting an optical waveguide and an optical fiber, in which the optical fiber is formed in a direction facing near the connection position of the optical waveguide, and one end is fixed to the exposed end surface of the optical waveguide, and the optical fiber is fixed to the V-groove in the protective resin film forming area. achieved by.

[0020] Further, the optical device is provided with at least an optical waveguide substrate for connecting optical fibers, and a housing for holding and fixing the optical waveguide substrate and the optical fibers connected to the optical waveguides of the optical waveguide substrate. This is achieved by an optical device in which a V-groove for positioning the optical fiber provided on the upper surface of the peripheral wall is formed at a position away from the extension line of the optical waveguide and in a direction facing near the connection position of the optical waveguide with the optical fiber. .

[0021]

[Operation] By fixing the optical fiber so that no inflection points occur at the two fixing portions of the optical fiber, concentration of bending stress applied to the optical fiber can be eliminated.

Therefore, in the present invention, the fixing position of the optical fiber on the circumferential wall of the housing is shifted from the extension line of the optical waveguide, and a V is provided on the circumferential wall of the housing so that the fixing direction of the optical fiber at that position is directed approximately toward the vicinity of the optical waveguide connection part. forming a groove.

[0023] This means that the optical waveguide connecting portion, and thus the optical fiber between the ruby bead and the housing wall, is curved into approximately one circular arc shape, and at the same time, no inflection point occurs at the fixed portions at both ends.

Therefore, it is not necessary to buckle the optical fiber, and the generation of internal stress can be suppressed. In addition, it is possible to eliminate the inflection points at both ends, that is, the two fixed parts of the ruby bead and the peripheral wall of the housing, so that it is possible to It is possible to realize a method for connecting an optical waveguide and an optical fiber that can cope with temperature fluctuations, and an optical device using the same.

[0025]

[Example] Fig. 1 is a diagram illustrating a method of connecting an optical waveguide and an optical fiber according to the present invention, and an optical device using the same. )
FIG. 3 is a plan view showing the completed state after connection.

In the figure, the case where the optical device is an external modulator is taken as an example as in FIG. 2, and the same objects as in FIG. 2 are denoted by the same symbols. In FIG. 1, the external modulator 11 includes a block 2c in the plate-shaped optical modulator 2 as explained in FIG.
A rear housing 1 in which an optical fiber 3 having a ring-shaped ruby bead 3b adhesively fixed at the tip is connected to an optical fiber joint surface 2a-1 formed by cutting and polishing the rear end face fixed with adhesive.
2 and is further covered with a lid 5.

In particular, the housing 12 in this case has a V-groove 12a corresponding to the V-groove 4a of the housing 4 explained in FIG. It is formed with an angle α so as to face the direction of the exposed end surface of 2b.

Therefore, as explained in FIG. 2, the optical fiber 3 is fixed on the ruby bead 3b side to the optical fiber bonding surface 2a-1 of the waveguide substrate 2a, and the substrate 2a portion is attached to the housing 12.
At the same time, the optical fiber 3 is bent slightly and the area covered with the protective resin film 3a is fitted into the V-groove 12a of the housing 12, and then the optical fiber 3 is fixed with a thermosetting epoxy resin at a predetermined position on the bottom of the housing 12. When the housing 11 is fixed with adhesive and further covered with the lid 5, the required external modulator 11 shown in (1-2) is assembled.
can be configured.

In this method of connecting an optical waveguide and an optical fiber, no inflection point occurs at the two fixed parts of the optical fiber 3, and at the same time, light generated in the optical fiber 3 due to temperature fluctuations in the surrounding atmosphere is prevented. Since the internal stress between the fiber joint surface 2a-1 and the peripheral wall of the housing 12 is absorbed by the curved portion, an optical waveguide is created that does not peel off at the connection portion or destroy the optical fiber itself due to temperature fluctuations in the surrounding atmosphere. An optical fiber connection method and an optical device using the same can be realized.

It has been experimentally confirmed that if the V-groove 12a is formed at a position where the angle α is within 2 to 3 degrees, it can almost completely cope with temperature fluctuations in the surrounding atmosphere.

[0031]

Effects of the Invention As described above, the present invention provides a method for connecting an optical waveguide and an optical fiber, which improves the connection characteristics by avoiding loss fluctuations in the connection portion due to temperature fluctuations and damage to the optical fiber over time, and the method therefor. An optical device using the above can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a method of connecting an optical waveguide and an optical fiber according to the present invention and an optical device using the same.

FIG. 2 is a diagram illustrating a conventional method of connecting an optical waveguide and an optical fiber.

[Explanation of symbols]

2 Optical modulator
2a Waveguide substrate 2a-1 Optical fiber bonding surface
2b Optical waveguide 2c Block
3 Optical fiber 3a Protective resin film
3b Ruby beads 5 Lid 11 External modulator
12 housing 12a V groove

Claims (2)

[Claims] 1. A method for connecting an optical waveguide and an optical fiber in an optical device including at least an optical waveguide substrate for connecting an optical fiber, the method comprising: an optical waveguide substrate (2a) and an optical waveguide substrate (2a); A V-groove (12a) for positioning the optical fiber (3), which is provided on the upper part of the peripheral wall of the housing (12) that holds and fixes the optical fiber (3) connected to the waveguide (2b), is connected to the optical waveguide (2b). ) of the optical fiber (3b) of the optical waveguide (2b).
) The optical fiber (3) is formed in a direction facing the vicinity of the connection position with the optical waveguide (2b), and one end is fixed to the exposed end face of the optical waveguide (2b). (12a) A method for connecting an optical waveguide and an optical fiber, characterized by fixing the optical waveguide to the optical fiber. 2. An optical device comprising at least an optical waveguide substrate for connecting optical fibers, the optical device comprising an optical waveguide substrate (2a) and an optical waveguide (2b) of the optical waveguide substrate (2a).
) The optical fiber (3) connected to
The V groove (12a) for positioning the optical waveguide (
The optical waveguide (2b) at a position away from the extension line of 2b)
An optical device characterized in that it is formed in a direction facing near a connection position with an optical fiber (3).