JP2003302536A - Optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element in which an optical fiber can be surely fixed to a fixing member and influences on optical characteristics can be suppressed even when the optical element is left to stand for a long period of time under high temperature and high humidity conditions after the optical fiber is housed in the housing member. <P>SOLUTION: The housing member 6 of the optical element is composed of two aluminum fixing members 3 each having a groove 4 and a glass base material 5 connecting the fixing members. The housing member 6 houses an optical fiber 1 from which the specified length of the coating 8 is removed. A grating 2 is formed in the center part in the longitudinal direction of the optical fiber 1. The boundary part between the coating 8 and the exposed optical fiber 1 is inserted into the groove 4 of the fixing member 3 and fixed in the groove 4 with an adhesive 7. The groove 4 formed in the fixing member 3 has an opening the width of which is smaller than the width of the inside of the groove in the cross section. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element which is manufactured by accommodating and fixing an optical fiber in an accommodating member and is installed in an intermediate part or a terminal part of an optical communication system.

[0002]

2. Description of the Related Art An optical fiber diffraction grating in which a diffraction grating in which a refractive index of a core portion of an optical fiber is periodically changed is formed, or an optical coupler in which two optical fibers are arranged in parallel and an intermediate portion thereof is fused An optical element using such an optical fiber is housed and fixed in a housing member to protect it from the external environment. In the above optical element, the light transmission mode changes when a substance with a high refractive index such as a coating or an adhesive agent is touched. It is common to fix with.

In such an optical element, the optical fiber and the housing member expand and contract due to the temperature change in the operating temperature range, which affects the optical characteristics of the optical fiber. Therefore, in order to control this, the material of the housing member, Various studies have been conducted on the structure and the fixing method of the optical fiber.

In Japanese Patent Laid-Open No. 2000-206347,
The optical fiber on which the diffraction grating is formed is fixed in a groove formed on a base material having a predetermined coefficient of thermal expansion and having the same cross-sectional area in the direction of the optical axis. There is disclosed an optical element adapted to appropriately apply a displacement generated in the axial direction to an optical fiber.

FIG. 7 is a perspective view showing a conventional optical element having an optical fiber diffraction grating. The housing member 36 has a groove for fixing both ends of the optical fiber 1 with an adhesive.
It is composed of one fixing member 33 and a semi-cylindrical glass base material 5 connecting the two fixing members 33. Diffraction grating 2
The optical fiber 1 having the above is inserted from the opening of the groove 34 of the fixing member, and both ends are fixed on the groove 34 by the adhesive 7.

When the optical element of FIG. 7 is subjected to a temperature change, the two fixing members 33 are formed in substantially the same shape, so that the warp deformation is suppressed and the storage member 3 is formed.
The displacement caused by the contraction of 6 due to the temperature change is appropriately applied to the optical fiber 1. Therefore, the optical fiber 1
The tension applied to the can be changed according to the temperature change, and parameters such as the wavelength of light can be controlled.
Further, the optical fiber 1 can be securely fixed to the housing member 36 without deteriorating the characteristics of the optical fiber 1 due to the temperature change.

[0007]

However, the fixing member 33 is used.
If there is insufficient adhesion between the optical fiber 1 and the optical fiber 1, leaving it under a high temperature and high humidity condition of 70 ° C. and 95% RH for a long period of time causes the central wavelength during optical transmission to become a long wavelength. The phenomenon of shifting to the side or short wavelength side was observed.

When left in a high temperature and high humidity condition of 70 ° C. and 95% RH for a long time, the adhesive force between the surface of the groove and the interface between the adhesive filled in the groove tends to decrease. Phenomenon in which when the adhesive strength at the interface between the groove surface and the adhesive decreases, the adhesive filled in the groove peels from the groove and slightly escapes upward from the groove opening together with the optical fiber in the groove. Happens. In particular, when the optical fiber is fixed by applying tension, the tension of the optical fiber exerts a stress in the direction in which the adhesive comes out of the groove, so that the adhesive is easily peeled from the groove. In this case, since the tension applied to the optical fiber changes in the direction of loosening, a change in the optical characteristics such as a shift of the central wavelength of light occurs.

The present invention provides an optical element in which the optical fiber is securely fixed even after being left under high temperature and high humidity for a long time after the optical fiber is fixed to the fixing member, and the influence on the optical characteristics is suppressed. The purpose is to do.

[0010]

The optical element of the present invention comprises at least one fixing member having a groove for fixing an optical fiber, and the width of the opening of the groove is narrower than the width of the inside thereof. Has become.

An optical element according to another aspect of the present invention is provided with at least one fixing member having a groove for fixing an optical fiber, and unevenness is provided on either or both of a sidewall surface and a bottom surface of the groove. It has a structure.

An optical element according to another aspect of the present invention includes at least one fixing member having a groove for fixing an optical fiber, and has a structure in which the width of the groove changes in the longitudinal direction. .

By adopting any of these configurations, even when tension is applied to the optical fiber fixed to the fixing member, the optical fiber and the fixing member are securely bonded and fixed, and the optical characteristics are stabilized. Can be made.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the optical element of the present invention. The storage member 6 is composed of two fixing members 3 each having a groove 4 and arranged at both ends of the storage member 6, and a glass base material 5 connecting between the two fixing members 3. After the coating 8 is removed from the optical fiber core by a certain length, the diffraction grating 2 is formed at the center of the exposed optical fiber 1 in the longitudinal direction, and then the optical fiber 1 is housed in the housing member 6 and exposed to the coating 8. The portion near the optical fiber 1 is inserted into the groove 4 of the fixing member 3 and fixed in the groove 4 with an adhesive 7.

The cross-sectional shape of the groove 4 is such that the width of the opening of the groove 4 is narrower than the width of the inside thereof. 70 ° C 95% RH
When left for a long time under high temperature and high humidity conditions such as
The adhesive force at the interface between the groove 4 and the adhesive 7 is impaired, and stress acts in the direction in which the adhesive 7 tries to come out of the groove 4, but the adhesive 7 peels off because the opening of the groove 4 is narrow. Or
The optical fiber does not drop out. As a result, the shift of the center wavelength is not observed even during optical transmission, and stable optical characteristics can be obtained for a long period of time.

FIG. 2 is a cross-sectional view showing an example of an embodiment of the groove 4. In FIG. 2A, the opening is narrow in the rectangular groove. In FIG. 2B, the width gradually decreases from the bottom surface of the groove toward the opening. In FIG. 2C, the U-shaped opening is narrow. FIG. 2D has a structure that is substantially circular and has an opening. In FIG. 2E, the V-shaped opening is narrow.

The fixing member 3 is preferably made of a material having a coefficient of thermal expansion larger than that of glass, particularly made of metal. Use of a metal has sufficient strength to protect the internal optical fiber 1 and a coefficient of thermal expansion suitable for appropriately applying axial expansion / contraction of the optical fiber 1 due to temperature change to the optical fiber 1. You can Further, by forming an oxide film on the surface of the groove 4 or increasing the surface roughness, the adhesive force with the adhesive 7 can be further enhanced. Aluminum, brass, etc. are preferable as the metal. Aluminum is particularly preferable because it is lightweight and easy to process. Also,
Hard plastic or ceramics may be used.

The fixing member 3 and the optical fiber 1 preferably have a structure capable of transmitting the expansion and contraction of the fixing member 3 to the optical fiber 1 via the adhesive 7. In the present embodiment, the optical fiber 1 at the portion where the coating of a certain length is removed is directly bonded and fixed. However, when the coating is sufficiently hard to transmit the expansion and contraction of the fixing member 3 to the optical fiber 1, the coating is performed. You may adhere and fix to the fixing member 3 without removing. Alternatively, the cover may be partially adhered and fixed to the fixing member 3.

FIG. 3 is a perspective view showing another embodiment of the optical element of the present invention. The structure is the same as that of FIG. 1 except for the two left and right aluminum fixing members 13 having the grooves 14.

The cross section of the groove 14 has a structure in which a convex portion is provided on the side wall surface thereof. Even if the structure is provided with unevenness on the side wall surface or the bottom surface, the interface between the groove 14 and the adhesive 7 is left even when left standing for a long time under a high temperature and high humidity condition of 70 ° C. and 95% RH under tension. It is possible to prevent the adhesive strength of the optical fiber from being impaired, the adhesive agent 7 coming out, and the optical fiber falling off. Therefore, the shift of the central wavelength is not observed even during optical transmission, and stable optical characteristics can be obtained for a long period of time.

FIG. 4 is a cross-sectional view showing an example of an embodiment of the groove 14. In FIG. 4A, a triangular convex portion is provided on one side of the side wall surface. In FIG. 4B, a rectangular protrusion is provided on one side of the side wall surface. 4 (c) and 4 (d)
Is provided with periodic unevenness on both sides of the side wall surface. Figure 4
In (e), a projection is provided on the bottom surface. Fixing member 13
1 can be made of the same material as that of the fixing member 3 shown in FIG.

FIG. 5 is a perspective view showing another embodiment of the optical element of the present invention. The configuration is the same as that of FIGS. 1 and 3, except for the two left and right aluminum fixing members 23 having the grooves 24.

The width of the groove 24 changes so as to become gradually narrower toward the central portion of the optical element in the longitudinal direction. Since the adhesive 7 has a structure that does not easily come out in the direction of the tension of the optical fiber 1, the tension of 70 ° C.
Even when the adhesive 7 is left for a long time under a high temperature and high humidity condition of 95% RH, the adhesive force at the interface between the groove 24 and the adhesive 7 is impaired and the adhesive 7 can be prevented from coming out. Therefore, the shift of the central wavelength is not observed even during optical transmission, and stable optical characteristics can be obtained for a long period of time.

FIG. 6 is a horizontal cross-sectional view showing an example of an embodiment of the groove 24. In FIG. 6A, the groove width is changed so as to be gradually narrowed. 6 (b) and 6 (c)
Has a groove width that periodically changes in the longitudinal direction.
The fixing member 23 can be made of the same material as the fixing member 3 of FIG. 1 and the fixing member 13 of FIG.

[0025]

EXAMPLE An example of the present invention will be described with reference to FIG.
The diffraction grating 2 was formed in the center of the optical fiber 1 from which the coating of the intermediate portion was removed for a certain length. The storage member 6 was produced by attaching the fixing member 3 made of aluminum having a length of 9 mm to both ends of the glass base material 5 having a semi-cylindrical shape and made of quartz glass having a length of 40 mm. The fixed member 3 has a width of 0.3 mm and a depth of 0.5 m.
m grooves 4 are formed. The cross section of the groove 4 has a rectangular shape and the opening is slightly narrower than the inside thereof.
It has the structure of (a). The surface of the fixing member 3 was anodized. The optical fiber 1 is inserted into the housing member 6 and the groove 4
The boundary portion between the coating 8 of the optical fiber and the exposed optical fiber 1 was inserted into the inside of the above, and the adhesive 7 made of epoxy resin was filled into the inside of the groove 4 while the tension of 30 g was applied and cured.

The housing member 6 is left in a constant temperature and humidity chamber at 70 ° C. and 95% RH, light is incident from an LED light source in the 1550 nm band, the reflection characteristics are measured using a spectrum analyzer, and the central wavelength thereof is measured. Was calculated. 200
Even after being left for 0 hours, the shift amount of the central wavelength was within 0.05 nm.

200 in a constant temperature and humidity chamber at 70 ° C. and 95% RH
When the state of the cross section of the groove 4 in the fixing member 3 of the housing member 6 after being left for 0 hours was observed by an X-ray CT method,
No void was observed between the groove 4 and the adhesive 7.

Also, when the same experiment is carried out with the optical element having the structure of FIG. 3 or 5, the shift amount of the central wavelength when left for 2000 hours is as small as 0.05 nm or less.

As a comparative example, the same evaluation was performed using the optical element shown in FIG. The diffraction grating 2 was formed in the center of the optical fiber 1 from which the coating of the intermediate portion was removed for a certain length. The storage member 36 was manufactured by attaching the fixing member 33 made of aluminum having a length of 9 mm to both ends of the glass base material 5 made of quartz glass having a length of 40 mm and having a semi-cylindrical shape. A groove 34 having a width of 0.3 mm and a depth of 0.5 mm is formed in the fixed portion 33. The shape of the cross section of the groove 34 is rectangular, and the width of the opening is the same as the width of the bottom. The optical fiber 1 is inserted into this housing member, the boundary between the optical fiber coating 8 and the exposed optical fiber 1 is inserted into the groove 34, and the groove 7 is filled with the adhesive 7 made of epoxy resin. Cured.

The storage member 36 is left in a constant temperature and constant humidity chamber at 70 ° C. and 95% RH, light is incident from an LED light source in the 1550 nm band, the reflection characteristics are measured using a spectrum analyzer, and the central wavelength thereof is measured. Was calculated. 10
A shift of the central wavelength was observed after 00 hours, and the shift amount gradually increased to 0.1 to 0.2 nm with the passage of time.

200 in a constant temperature and humidity chamber at 70 ° C. and 95% RH
When the cross section of the groove 4 in the fixing member 3 of the housing member 6 after being left for 0 hours was observed by an X-ray CT method, the groove 4
A 50 μm gap was observed between the bottom of the adhesive and the adhesive 7.

[0032]

The optical element of the present invention includes at least one fixing member having a groove for fixing an optical fiber, and the width of the opening of the groove is narrower than the width of the inside thereof. An optical element according to another aspect of the present invention includes at least one fixing member having a groove for fixing an optical fiber, and a structure having unevenness on either or both of a sidewall surface and a bottom surface of the groove. Has become. The optical element of the present invention in still another aspect includes at least one fixing member having a groove for fixing an optical fiber, and has a structure in which the width of the groove changes in the longitudinal direction. Three
The optical element of any one of the two aspects has a structure in which the adhesive does not easily fall off from the fixing member, and the optical fiber can be reliably retained even when left in high temperature and high humidity for a long time after the optical fiber is stored in the housing member. It is fixed, and the influence on the optical characteristics can be suppressed.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical element of the present invention.

FIG. 2 is a cross-sectional view showing an example of an embodiment of a fixing member that constitutes the optical element of the present invention.

FIG. 3 is a perspective view showing an embodiment of the optical element of the present invention.

FIG. 4 is a cross-sectional view showing an example of an embodiment of a fixing member that constitutes the optical element of the present invention.

FIG. 5 is a perspective view showing an embodiment of the optical element of the present invention.

FIG. 6 is a horizontal sectional view showing an example of an embodiment of a fixing member constituting the optical element of the present invention.

FIG. 7 is a perspective view showing a conventional optical element.

[Explanation of symbols]

1 optical fiber 2 diffraction grating 3 fixing members 4 grooves 5 glass substrates 6 storage members 7 adhesive 8 coating 13, 23, 33 fixing member 14, 24, 34 groove 36 Storage member

Claims (7)

[Claims] 1. An optical element having an optical fiber and a fixing member for fixing a part thereof, wherein the fixing member has a groove for inserting and fixing the optical fiber, and a width of an opening portion of the groove. Is an optical element characterized by being narrower than its internal width. 2. An optical element having an optical fiber and a fixing member for fixing a part of the optical fiber, wherein the fixing member has a groove for fixing the optical fiber, and any one of a side wall surface and a bottom surface of the groove is provided. An optical element having irregularities on either or both sides. 3. An optical element having an optical fiber and a fixing member for fixing a part thereof, wherein the fixing member has a groove for fixing the optical fiber, and the width of the groove changes in the longitudinal direction. An optical element characterized in that 4. The optical element according to claim 1, wherein the optical fiber is fixed to the two fixing members in a state where tension is applied. 5. The optical element according to claim 1, wherein at least a part of the fixing member is made of metal. 6. The optical element according to claim 4, wherein a diffraction grating is formed on a part of the optical fiber in the longitudinal direction. 7. The shift amount of the central wavelength of light within a wavelength range of 1550 nm before and after the optical element is left in an environment of 70 ° C. and 95% RH for 2000 hours, and is within ± 0.05 nm. 6. The optical element according to 6.