JPH04245207A - Method for fixing optical fiber to cage and optical device using it - 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 secular basis. CONSTITUTION:An optical fiber 3 is connected through ruby beads 3b to an optical waveguide path 2b of an optical waveguide path substrate 2a secured in a cage 12, curved as buckling, fixed to the exterior wall of the cage 12, and thereupon led out of the cage 12. The optical fiber 3 of this optical device is secured to the cage 12 by bonding it to the inner surface of the casing with a resilient adhesive 13 in positions at least at the two ends of the curved region and in the intermediate region.

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 fixing an optical fiber to a housing 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 generating an optical pulse signal by forcibly modulating the light intensity using an external modulation method has been put into practical use, but in this case, for example, the surface of lithium niobate (LiNbO3), which is an electro-optic crystal, is Titanium (Ti)
It is often used as an external modulator by connecting an optical fiber to the optical waveguide portion exposed on the end face of an optical modulator having an optical waveguide formed by diffusing the light.

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 fixing an optical fiber to a housing, and (2-1) is a diagram showing the configuration and method. (
2-2) is a plan view showing the completed state.

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 layer 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 layer 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 layer 3a.
When fixing with adhesive, the material is buckled and deformed in advance to have an extra length, as shown by the solid line F, and then 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]

Problems to be Solved by the Invention In the conventional method of fixing an optical fiber to a housing, there has been a problem in that the optical fiber itself may be peeled off at the connection part or the optical fiber itself may be damaged due to temperature fluctuations in the surrounding atmosphere.

[0019]

[Means for Solving the Problems] The above problem is to solve the above problem by attaching an optical fiber connected to an optical waveguide of an optical waveguide board located inside a housing via a ruby bead to an outer wall of the housing in a buckled state. A method for fixing an optical fiber to a casing of an optical device, which comprises guiding an optical fiber to an outside of the casing after fixing, the optical fiber in the casing connected to an optical waveguide being fixed at least at both ends of its curved region and This is achieved by a method of fixing the optical fiber to the housing by adhesively fixing the optical fiber to the inner surface of the housing using an elastic adhesive in the intermediate region.

[0020] Furthermore, the optical fiber connected to the optical waveguide of the optical waveguide board located inside the housing via ruby beads is fixed to the outer wall of the housing in a buckled state, and then the optical fiber is fixed to the outer wall of the housing. An optical device in which an optical fiber in a casing connected to an optical waveguide is adhesively fixed to the inner surface of the casing with an elastic adhesive at least at both ends of the curved region and in the middle region. This is achieved by optical devices that have

[0021]

[Function] By fixing the optical fiber near the two fixed parts and the intermediate part to the housing with an elastic adhesive, it is possible to avoid damage to the optical fiber and to prevent the connection part from changing due to temperature fluctuations. Loss fluctuations can be eliminated.

In the present invention, the buckled and curved optical fiber in the housing is fixed to the bottom surface of the housing near the ruby bead, near the housing wall fixing part, and approximately in the middle thereof, using a silicone-based elastic adhesive.

[0023] This means that the optical fiber, which has a degree of curvature that changes with temperature fluctuations, is fixed to the housing while being absorbed by the elastic adhesive, so that the internal stress of the optical fiber is made uniform. It means.

[0024] Therefore, connection loss between the optical waveguide and the optical fiber due to temperature fluctuations and damage to the optical fiber over time can be suppressed.

[0025]

[Example] Fig. 1 is a diagram illustrating a method of fixing an optical fiber to a housing according to the present invention and an optical device using the same, (1-1) is a diagram showing the configuration and method, (1-1) is a diagram showing the configuration and method, and (1-1) is a diagram showing the configuration and method. 2) is a side sectional view showing the completed state.

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 ruby bead 3b of an optical fiber 3 having a ruby bead 3b adhesively fixed at its tip to the optical fiber joining surface 2a-1 of the optical modulator 2 of FIG. 2 to which a block 2c is adhesively fixed. A housing 12 connects the end faces and further has a protective resin layer 3a area of the optical fiber 3 formed in the same manner as the V-groove 4a of the housing 4 in FIG.
It is fixed in the V-groove 12a and covered with a lid 5.

The casing 12 in this case has a waveguide substrate 2a on the inner bottom surface of the casing 4 explained in FIG.
A block-shaped silicon fixture 12-1, 1 that is longer in the direction perpendicular to the optical fiber 3 and has a height that is lower than the thickness t of
2-2 and 12-3 are fixed.

In this case, each of the fixtures 12-1, 12-2,
When the length L of 12-3 is set appropriately, the optical fiber 3 positioned and adhesively fixed to the optical fiber joint surface 2a-1 of the optical modulator 2 is bent and its protective resin layer 3a is the V-groove 12a of the housing 12.
Even if the optical fiber 3 is curved in any direction when it is adhesively fixed to the fixing tool 12-1,
, 12-2, 12-3.

Therefore, by supplying a sufficient amount of elastic adhesive 13 such as silicone onto each of the silicone fixtures 12-1 to 12-3, the optical fiber 3 is attached to each silicone fixture 1.
It can be adhesively fixed to 2-1, 12-2, and 12-3.

(1-2) shows this state. Note that the figure shows a case where the optical fiber 3 is curved toward the bottom of the drawing for ease of understanding, but it can also be adhesively fixed in the same way even when it is curved toward the top of the drawing or in the direction of the thickness of the paper. .

In this method of fixing the optical fiber to the casing, the optical fiber 3 is elastically held by the casing 12 at three locations: the optical waveguide connection side, the casing fixing side, and the intermediate area, so that the internal stress of the optical fiber 3 is reduced. A method for fixing optical fibers to a housing that prevents them from peeling off at the connection part or damaging the optical fibers themselves due to temperature fluctuations in the surrounding atmosphere, and using the method Optical devices can be realized.

[0032]

[Effects of the Invention] As described above, according to the present invention, a method for fixing an optical fiber to a housing improves the connection characteristics by avoiding fluctuations in loss at the connection portion due to temperature fluctuations and damage to the optical fiber over time. and an optical device using the same.

Although the present invention has been described with reference to the case where the silicon fixture is attached to the housing afterwards, the same effect can be obtained even if the silicon fixture is formed integrally with the housing.

[Brief explanation of the drawing]

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

FIG. 2 is a diagram illustrating a conventional method of fixing an optical fiber to a housing.

[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 layer
3b Ruby beads 5 Lid 11 External modulator
12 housings 12-1, 12-2, 12-3
Silicon fixture 12a V groove 13 Adhesive

Claims (4)

[Claims] Claim 1: Ruby beads (3b) are attached to the optical waveguide (2b) of the optical waveguide substrate (2a) located in the casing (12).
After fixing the optical fiber (3) connected via the casing (12) to the outer wall of the casing (12) in a buckled state,
2) A method for fixing an optical fiber of an optical device to a casing, which is led out to the outside, in which the optical fiber (3) in the casing (12) connected to the optical waveguide (2b) is at least curved. Apply elastic adhesive (
13) A method for fixing an optical fiber to a housing, characterized by adhesively fixing it to the inner surface of the housing. 2. The method of fixing an optical fiber to a housing according to claim 1, wherein the elastic adhesive for bonding the optical fiber to the inner surface of the housing in a curved region thereof is a silicon adhesive. 3. A position where the optical fiber is bonded to the inner surface of the casing with the elastic adhesive is on a silicon fixture formed on the inner surface of the casing that corresponds to a predetermined position of a buckled curved region of the optical fiber. 2. The method for fixing an optical fiber to a housing according to claim 1. 4. Ruby beads (3b) are attached to the optical waveguide (2b) of the optical waveguide substrate (2a) located in the casing (12).
An optical device is an optical device in which an optical fiber (3) connected via an optical waveguide (2b
) is configured such that an optical fiber (3) in a casing (12) connected to the casing (12) is adhesively fixed to the inner surface of the casing with an elastic adhesive (13) at least at both ends of the curved region and in the middle region. An optical device characterized by: