JP2003004952A - Structure for fixing optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for fixing a optical fiber, a structure that can suppress failure of adhesive hardening and maintain an improved fixed state of the optical fiber for a long period. SOLUTION: Optical fiber fixing parts 2 are formed at positions spaced in the longitudinal direction of an optical fiber 1, and optical fiber inserting grooves 3 are formed on the upper side of the fixing parts 2. The optical fiber 1 is put in the inserting grooves 3 of the fixing parts 2 placed on both sides of the fiber grating-formed region 6 of the optical fiber 1, and is fixed with an adhesive. Lids 4 are provided above the optical fiber inserting grooves 3, and the optical fiber 1 is fixed with the adhesive 13 in the area surrounded by the lid 4 and the inserting groove 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber fixing structure having a fiber grating.

[0002]

2. Description of the Related Art A fiber grating is one in which a diffraction grating is formed by periodically changing the refractive index along the longitudinal direction of an optical fiber. The fiber grating can be formed, for example, by irradiating the optical fiber with interference fringes of ultraviolet light to cause a photo-induced refractive index change in the core of the optical fiber.

The interference fringes of the ultraviolet light are formed by irradiating the ultraviolet light through a mask (phase mask) having a grating formation pattern, and thus the grating is formed by using the phase mask. This method is called the phase mask method. Also,
A holographic method or the like in which interference fringes of ultraviolet light are formed without using a phase mask is also known.

The fiber grating has a function of reflecting light in a relatively narrow wavelength range centered on the Bragg reflection wavelength, and the Bragg reflection wavelength is determined from the period of the diffraction grating and the effective refractive index of the core. To be done. Such a fiber grating can be used as a single wavelength filter having excellent wavelength selectivity.

When the Bragg reflection wavelength of the fiber grating is λ, the effective refractive index is n, and the grating pitch is Λ, there is a relation of λ = 2nΛ. Since both the effective refractive index n and the grating pitch Λ have temperature dependence, for example, the Bragg reflection wavelength in a silica-based optical fiber is 0.0
It is known to have a temperature dependence of about 1 nm to 0.15 nm / ° C.

As described above, when the Bragg reflection wavelength changes depending on the temperature, the intended function cannot be achieved by the fiber grating. Therefore, in general, a temperature compensation package for compensating the temperature dependence of the fiber grating is formed. An optical fiber having a fiber grating is fixed to the temperature compensation package.

When fixing the above-mentioned optical fiber to the temperature compensation package, an appropriate tension is applied to the fiber grating to adjust it to a set wavelength, and as shown in FIG. The optical fiber 1 is arranged on the upper surface of the optical fiber 2 and the both sides of the fiber grating forming region 6 are fixed by an adhesive 13 such as an epoxy ultraviolet curing adhesive.

[0008]

However, when the optical fiber 1 is fixed to the flat fiber fixing portion 2 as described above, the thickness of the adhesive 13 is not constant, so that curing failure of the adhesive 13 occurs. There was a problem. Further, if the thickness of the adhesive 13 becomes thick, it becomes impossible to exert a sufficient adhesive force. Therefore, if the optical module formed by fixing the optical fiber 1 to the temperature compensation package is used for a long time, The tension applied when fixing the optical fiber 1 is released, and the Bragg reflection wavelength shifts.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is an optical fiber which is less likely to cause defective curing of an adhesive and which can maintain a good fixed state for a long period of time. To provide a fixed structure.

[0010]

In order to achieve the above object, the present invention has the following constitution as means for solving the problem. That is, the first invention is an optical fiber fixing structure for fixing an optical fiber on which a fiber grating is formed, and an optical fiber fixing portion is formed at a position with a space in the longitudinal direction of the optical fiber to form the optical fiber. The problem is solved by forming an optical fiber insertion groove on the surface side of the fiber fixing portion and inserting both sides sandwiching the fiber grating forming region of the optical fiber into the optical fiber insertion groove of the optical fiber fixing portion to be adhesively fixed. As a means.

Further, in the second invention, in addition to the structure of the first invention, a lid is provided on the upper side of the optical fiber insertion groove, and a region surrounded by the lid and the optical fiber insertion groove. The optical fiber is fixed by an adhesive as a means for solving the problem.

Furthermore, a third invention is the above-mentioned first or second invention.
In addition to the configuration of the invention described above, the optical fiber insertion groove has a U-shaped configuration as means for solving the problem.

Further, in the fourth invention, in addition to the structure of the third invention, the distance between the inner surface of at least one of the optical fiber insertion grooves and the outer circumference of the optical fiber facing the inner surface is set to 0.
A structure of 1 mm or less is used as a means for solving the problem.

Further, a fifth aspect of the present invention is the above-mentioned first to fourth aspects.
In addition to the structure of any one of the inventions, a means for solving the problem is a structure in which the length of the optical fiber insertion groove in the fiber longitudinal direction is 2.2 mm or more.

In the present invention having the above-mentioned structure, an optical fiber insertion groove is formed on the surface side of the optical fiber fixing portion formed at a position spaced apart in the longitudinal direction of the fixing optical fiber, and an optical fiber of the optical fiber is formed. Since both sides sandwiching the grating forming region are respectively inserted and fixed in the optical fiber insertion groove of the optical fiber fixing portion, unlike the conventional case where the optical fiber is fixed to the flat fixing portion by adhesion, an appropriate amount of The optical fiber is fixed by the adhesive, and the thickness of the adhesive on the lower side and the side of the optical fiber becomes substantially uniform.

Therefore, according to the optical fiber fixing structure of the present invention, it is possible to realize the optical fiber fixing structure in which the curing failure of the adhesive hardly occurs and the good optical fiber fixing state can be maintained for a long period of time.

In the present invention, a lid is provided above the optical fiber insertion groove, and the optical fiber is fixed to the area surrounded by the lid and the optical fiber insertion groove with an adhesive. In the optical fiber fixing part, the optical fiber can be fixed with an adhesive having a substantially uniform thickness over the entire circumference of the optical fiber, the curing failure of the adhesive can be suppressed more reliably, and the optical fiber that is good for a long period of time can be suppressed. The fixed state can be maintained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same reference numerals will be given to the same names as those in the conventional example, and duplicate description thereof will be omitted or simplified. FIG. 1 shows an embodiment of an optical fiber fixing structure according to the present invention.

The optical fiber fixing structure of this embodiment is as follows:
This is an optical fiber fixing structure for fixing the optical fiber 1 on which a fiber grating is formed. As shown in the figure, a trapezoidal optical fiber fixing portion 2 protruding upward is formed at a position spaced apart in the longitudinal direction of the optical fiber 1, and an optical fiber fixing portion 2 is formed on the surface side of the optical fiber fixing portion 2. A fiber insertion groove 3 is formed. Both sides of the optical fiber 1 sandwiching the fiber grating forming region 6 are inserted into the optical fiber insertion groove 3 of the optical fiber fixing portion 2 and fixed by adhesion.

As described above, the feature of this embodiment is that the optical fiber inserting groove 3 is formed on the surface of the optical fiber fixing portion 2 and the grating forming region 6 of the optical fiber 1 is formed in the optical fiber inserting groove 3. This means that both sides of the sandwich are fixed by adhesion. In this embodiment, the thickness of the adhesive 13 is made substantially uniform by this configuration, and the optical fiber 1 is fixed by an appropriate amount of the adhesive 13.

In the present embodiment, the lid 4 is provided above the optical fiber insertion groove 3, and the optical fiber 1 is bonded to the area surrounded by the lid 4 and the optical fiber insertion groove 3. It is fixed by the agent 13. In this embodiment, the adhesive 13 is the same epoxy-based ultraviolet curing adhesive as in the conventional example.

As shown in FIG. 2, the optical fiber insertion groove 3 is U-shaped, and its groove width W is 0.325 mm or less. The outer diameter of the optical fiber 1 is 0.125 mm, and the distance between the inner surface of at least one of the optical fiber insertion grooves 3 (here, the entire inner wall of the groove) and the outer circumference of the optical fiber 1 facing the inner surface is 0.1 mm or less. There is. The length of the optical fiber insertion groove 3 in the fiber longitudinal direction is set to 2.2 mm or more.

The present embodiment is configured as described above, and according to the present embodiment, the optical fiber insertion groove 3 is formed on the surface side of the optical fiber fixing portion 2 for fixing the optical fiber 1. Since both sides of the fiber grating forming region 6 of the optical fiber 1 are respectively inserted and fixed in the optical fiber insertion groove 3 of the optical fiber fixing portion 2, the adhesive 13 becomes excessively thick as in the conventional case. The optical fiber 1 can be fixed by an appropriate amount of the adhesive agent 13 without using the adhesive agent.
The thickness of can be made substantially uniform.

In particular, in this embodiment, the lid portion 4 is provided on the upper side of the optical fiber insertion groove 3, and the optical fiber is adhesive 1 in the region surrounded by the lid portion 4 and the optical fiber insertion groove 3.
Since it is fixed by 3, the thickness of the adhesive 13 on the upper side of the optical fiber 1 can be made substantially uniform, and the optical fiber fixing portion 2
In, the optical fiber 1 can be fixed with the adhesive 13 having a substantially uniform thickness over the entire circumference of the optical fiber 1.

Therefore, in this embodiment, the adhesive 1
The curing failure of No. 3 can be reliably suppressed, and a good optical fiber fixed state can be maintained for a long period of time.

In the present embodiment, the distance between the inner surface of the optical fiber insertion groove 3 and the outer circumference of the optical fiber 1 facing the inner surface is set to 0.1 mm or less, and the length of the optical fiber insertion groove 3 in the longitudinal direction of the fiber is set. Since the length is 2.2 mm or more,
The curing failure of the adhesive 13 can be suppressed more reliably, and the optical fiber 1 can be maintained in a good fixed state with good adhesive strength.

The inventors of the present invention have conducted various studies, and the smaller the distance between the inner surface of the optical fiber insertion groove 3 and the outer periphery of the optical fiber 1 facing the inner surface and the thinner the adhesive 13, the better the adhesion. It has been confirmed that the characteristics can be obtained, and that if the thickness of the adhesive 13 is 0.1 mm or less, very good adhesion characteristics can be obtained. Similarly, it was confirmed that the longer the length of the optical fiber insertion groove 3 in the longitudinal direction of the fiber, the better the adhesive property, and that if the length is 2.2 mm or more, very good adhesive property can be obtained. ing.

FIG. 3 shows an application example of the optical fiber fixing structure of this embodiment. In this example, an optical fiber fixing part 2 is formed in a package 10 for temperature compensation of a fiber grating, and an optical fiber 1 is fixed to the optical fiber fixing part 2 to form an optical module. When the optical fiber fixing structure of the present embodiment is applied to the module, the Bragg reflection wavelength of the fiber grating can be adjusted to the set wavelength when the optical fiber 1 is fixed, and the state can be maintained for a long time.

The present invention is not limited to the above-mentioned embodiments, but can take various modes. For example, although the adhesive 13 is an epoxy-based ultraviolet curing adhesive in the above-described embodiment, the type of the adhesive 13 is not particularly limited and may be set appropriately. However, it is preferable to use an epoxy ultraviolet curing adhesive as the adhesive 13 because the adhesive strength is high and the curing time is short.

Further, in the above embodiment, the lid portion 4 is provided above the optical fiber insertion groove 3, but the lid portion 4 may be omitted. However, if the lid portion 4 is provided and the optical fiber 1 is fixed to the region surrounded by the lid portion 4 and the optical fiber insertion groove 3 with the adhesive 13, the fixing of the optical fiber 1 can be performed more reliably, which is preferable. .

Although the optical fiber insertion groove 3 is U-shaped in the above embodiment, the shape of the optical fiber insertion groove 3 is not particularly limited and may be set appropriately.

Further, in the above embodiment, the groove width of the optical fiber insertion groove 3 is 0.325 mm or less, and the distance between the entire inner wall of the optical fiber insertion groove 3 and the outer circumference of the optical fiber 1 is 0.1 mm or less. However, the distance between at least one inner surface of the optical fiber insertion groove 3 and the outer periphery of the optical fiber 1 facing the inner surface may be 0.1 mm or less.

Furthermore, in the above embodiment, the length of the optical fiber insertion groove 3 in the longitudinal direction of the fiber is set to 2.2 mm or more, but the length of the optical fiber insertion groove 3 is not particularly limited and is set appropriately. It is what is done. However, when the length of the optical fiber insertion groove 3 is 2.2 mm or more, the fixed state of the optical fiber 1 can be further improved.

[0034]

According to the present invention, an optical fiber insertion groove is formed on the surface side of an optical fiber fixing portion formed at a position spaced apart in the longitudinal direction of the optical fiber, and a fiber grating forming region of the optical fiber is formed. By inserting both sides to be sandwiched into the optical fiber insertion groove of the optical fiber fixing portion and fixing them by adhesion, the amount of the adhesive is adjusted to an appropriate amount, and the thickness of the adhesive on the lower side and the side of the optical fiber is made substantially uniform. Therefore, the curing failure of the adhesive can be suppressed, and a good optical fiber fixing state can be maintained for a long period of time.

Further, in the present invention, a lid is provided on the upper side of the optical fiber insertion groove, and the optical fiber is fixed to an area surrounded by the lid and the optical fiber insertion groove by an adhesive. In the above, since the thickness of the adhesive on the upper side of the optical fiber can be made substantially uniform, the optical fiber can be fixed with the adhesive having a substantially uniform thickness over the entire circumference of the optical fiber at the optical fiber fixing portion. The curing failure can be suppressed more reliably, and a good fixed state of the optical fiber can be maintained for a long period of time.

Further, in the present invention, when the optical fiber insertion groove is formed in a U shape, the optical fiber insertion groove can be easily formed and the thickness of the adhesive can be more surely made substantially uniform. Therefore, the curing failure of the adhesive can be reliably suppressed, and a good optical fiber fixed state can be maintained for a long period of time.

Furthermore, in the present invention, the distance between the inner surface of at least one of the optical fiber insertion grooves and the outer circumference of the optical fiber facing the inner surface is set to 0.1 mm or less, and the length of the optical fiber insertion groove in the longitudinal direction of the fiber is set. According to the configuration in which the length is 2.2 mm or more, the fixing strength of the optical fiber with the adhesive can be made good, and a more excellent fixed state of the optical fiber can be maintained.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of an optical fiber fixing structure according to the present invention.

FIG. 2 is an explanatory diagram showing a cross-sectional structure of the fixing structure.

FIG. 3 is a cross-sectional explanatory view showing an example of an optical module to which the above fixing structure is applied.

FIG. 4 is an explanatory diagram showing an example of a conventional optical fiber fixing structure.

[Explanation of symbols]

1 optical fiber 2 Optical fiber fixing part 3 Optical fiber insertion groove 4 Lid 6 Grating formation area 13 Adhesive

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiko Ota             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. F-term (reference) 2H038 BA25 CA52

Claims (5)

[Claims] 1. An optical fiber fixing structure for fixing an optical fiber having a fiber grating, wherein the optical fiber fixing portion is formed at positions spaced apart in the longitudinal direction of the optical fiber. An optical fiber insertion groove is formed on the surface side of the optical fiber, and both sides of the optical fiber sandwiching the fiber grating forming region are respectively inserted into the optical fiber insertion groove of the optical fiber fixing portion for adhesive fixation. Construction. 2. A lid is provided on the upper side of the optical fiber insertion groove, and the optical fiber is fixed to an area surrounded by the lid and the optical fiber insertion groove with an adhesive. Item 2. The optical fiber fixing structure according to Item 1. 3. The optical fiber fixing structure according to claim 1, wherein the optical fiber insertion groove is U-shaped. 4. The distance between the inner surface of at least one of the optical fiber insertion grooves and the outer circumference of the optical fiber facing the inner surface is 0.1.
The fixing structure for an optical fiber according to claim 3, wherein the fixing structure is less than or equal to mm. 5. The length of the optical fiber insertion groove in the longitudinal direction of the fiber is 2.2 mm or more.
The optical fiber fixing structure according to claim 4.