JP2663992B2 - Hermetically sealed structure of optical fiber introduction section - Google Patents

Description

[Detailed description of the invention] Table of contents Overview Industrial application field Conventional technology Problems to be solved by the invention Means for solving the problem Action embodiment Effect of the invention Overview Optical fiber introduction part of device such as optical transceiver module The main object of the present invention is to provide the above-mentioned structure in which the deterioration with time of the hermetic sealing is small, and for example, an optical fiber in which a metal pipe into which an optical fiber is inserted and fixed is inserted and fixed in an introduction hole of a housing. In the introduction portion, a capillary press-fitting hole is formed in the metal pipe, a ceramic capillary shorter than the length corresponding to the depth of the press-fitting hole is press-fitted into the press-fitting hole, and an optical fiber is penetrated into the pores of the ceramic capillary. The opening of the press-fitting hole is filled with solder.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hermetic sealing structure of an optical fiber introduction portion of an apparatus such as an optical transceiver module.

As one form of a device such as an optical transmission / reception module having a portion in which an optical fiber and an optical component such as a waveguide type optical component are optically coupled, an optical fiber is inserted into the housing through an introduction hole formed in the module housing. There is a configuration in which the leading end is connected to a waveguide type optical component or the like. In this type of device, it is important to maintain the hermetic sealing of the optical fiber introduction portion in a good condition for a long period of time in order to improve the environmental characteristics of the device or to improve the optical and electrical characteristics of the device. It is.

FIG. 8 is a cross-sectional view showing an example of a conventional hermetic sealing structure of an optical fiber introduction section. The metal pipe 104 into which the optical fiber 102 is inserted and fixed is inserted and fixed in the introduction hole 108 of the housing 106. The insertion and fixing of the optical fiber 102 into the metal pipe 104 is performed by filling the metal pipe 104 with, for example, an adhesive in pores of a capillary 112 fixedly pressed into the metal pipe 104 and inserting the optical fiber 102 into the pores. Inlet 1 for metal pipe 104
Insertion and fixing to the 08 are performed by inserting the metal pipe 104 into the introduction hole 108 and welding the entire periphery of the end of these contact portions. 110 is a cover of the optical fiber 102, and 114 is a lid fixed to the upper surface of the housing 106 by, for example, welding.

Problems to be Solved by the Invention According to the conventional technique described above, although the deterioration with time of the hermetic sealing between the metal pipe and the housing is small, there is a problem that the deterioration with time of the hermetic sealing between the optical fiber and the metal pipe is large. Was. That is, since the metal pipe and the housing are hermetically sealed by welding, the deterioration with time is small. On the other hand, the optical fiber is fixed by an adhesive, so that the air is affected by the humidity outside the housing. Hermetic sealing sometimes deteriorated with time.

The present invention has been created in view of such circumstances,
It is an object of the present invention to provide a hermetically sealed structure of an optical fiber introduction portion which is less likely to deteriorate with time in hermetic sealing and is easy to manufacture. The purpose other than this purpose will be apparent from the following description.

Means for Solving the Problems The technical problem described above is solved by any of the following first to third configurations.

In a first configuration, a capillary press-fitting hole is formed in a metal pipe in an optical fiber introduction portion in which a metal pipe into which an optical fiber is inserted and fixed is inserted and fixed into an introduction hole of a housing, and the depth of the press-fitting hole is increased. A ceramic capillary shorter than the corresponding length is press-fitted into the press-fitting hole, an optical fiber penetrates through the pores of the ceramic capillary, and the opening of the press-fitting hole is filled with solder.

The second configuration is such that a capillary press-fitting hole is formed in the first metal pipe in the optical fiber and the introduction portion, in which the metal pipe into which the optical fiber is inserted and fixed is inserted and fixed in the introduction hole of the housing. A ceramic capillary longer than the length corresponding to the depth of the ceramic capillary is press-fitted into the press-fitting hole, the ceramic capillary protruding from the first metal pipe is inserted and fixed in a second metal pipe, and the optical fiber is inserted into the ceramic capillary. The second metal pipe is made to penetrate through the pores, and the opening of the second metal pipe is filled with solder.

The third configuration is such that, in the optical fiber introduction portion in which the metal pipe into which the optical fiber is inserted and fixed is inserted and fixed in the introduction hole of the housing, a fine hole and an opening having a diameter larger than that in the longitudinal direction of the metal pipe. At least a portion of the metal pipe near the opening is formed to have a small diameter, an optical fiber is penetrated through the pore, and the opening is filled with solder.

Operation According to the first configuration, since the ceramic capillary shorter than the length corresponding to the depth of the press-fitting hole is used, when this ceramic capillary is press-fitted into the press-fitting hole, the ceramic capillary in the press-fitting hole becomes smaller than the portion where the ceramic capillary is press-fitted. An opening is formed in the shallow part. Therefore, by filling the opening with the solder, the hermetic sealing between the optical fiber and the metal pipe with little deterioration over time becomes possible. The reason for using a ceramic capillary is that it is easy to form pores having a diameter of about 0.1 mm for inserting an optical fiber in a ceramic such as alumina. According to a preferred embodiment, a coating such as gold having good solder wettability is formed on the press-fitting hole of the metal pipe and the portion of the optical fiber located in the press-fitting hole.

Also in the case of the second configuration, since the space between the optical fiber and the second metal pipe is filled with the solder, a good hermetic seal between the optical fiber metal pipe is achieved. In this case, the hermetic sealing between the first metal pipe and the second metal pipe is favorably performed by welding, brazing, or the like as in the case of the related art.

Also in the case of the third configuration, since the opening of the metal pipe is filled with solder, good hermetic sealing is achieved.
In the case of the third configuration, at least a portion near the opening of the metal pipe is formed to have a small diameter. Therefore, when the opening is filled with solder, thermal diffusion of the metal pipe is suppressed due to a large thermal resistance of the metal pipe. Can be filled with solder. That is, in the case of the third configuration, the amount of heat required to fill the opening with the solder can be reduced, or the filling operation can be completed in a short time.

In the case of the first or second configuration, it is not necessary to form a pore having a diameter of about 0.1 mm for directly inserting an optical fiber into a metal material, so that these configurations can be easily realized.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of an optical fiber introduction section showing an embodiment of the first configuration. Reference numeral 2 denotes a metal pipe in which a coating insertion hole 4 and a capillary press-fitting hole 6 having a larger diameter than the insertion hole 4 are formed. The metal pipe 2 is formed of, for example, stainless steel. 8
Is a ceramic capillary made of ceramic such as alumina. The ceramic capillary 8 is press-fitted into the capillary press-fitting hole 6 so as to contact a step between the capillary press-fitting hole 6 and the coating insertion hole 4. The ceramic capillary 8 has pores of about 0.1 mm diameter for inserting an optical fiber. The optical fiber 12 from which the coating 10 has been removed at the distal end is made to penetrate through the pores of the ceramic capillary 8, and the coating 10 is fixed in the coating insertion hole 4 with an adhesive. Since the ceramic capillary 8 is shorter than the length corresponding to the depth of the press-fitting hole, when the ceramic capillary 8 is press-fitted deep into the press-fitting hole 6 as described above, the opening 13 is formed in the press-fitting hole 6. Become. Accordingly, by filling the opening 13 with the solder 14 using a high-frequency heater, a laser heater, or the like, the hermetic sealing between the optical fiber 12 and the metal pipe 2 can be achieved. Since the wettability of the molten solder to quartz, which is the material of the optical fiber 12, and stainless steel, which is the material of the metal pipe 2, is generally not good, in this embodiment, before the solder 14 is filled into the opening 13, the press-fit holes 6 are formed. On the surface of the optical fiber 12
Gold plating is applied to improve the wettability to the molten solder.

The metal pipe 2 into which the optical fiber is inserted and fixed is inserted into an insertion hole 18 formed in a side wall surface of a casing 16 made of, for example, metal.
, And hermetically sealed between the metal pipe 2 and the housing 16 by laser welding the entire circumference of the insertion portion as indicated by A. In this example, a waveguide type optical component is mounted and fixed in the housing 16. This optical component includes a waveguide substrate 20 made of LiNbO ₃ or the like, and a high-refractive-index optical waveguide 22 formed on the waveguide substrate 20 by diffusing Ti or the like. The end of the optical fiber 12 is optically coupled to the end of the waveguide 22 using an optical adhesive or the like. Reference numeral 24 denotes a lid provided on the upper surface of the housing 16, and the lid 24 is fixed to the housing 16 by, for example, welding.

Hermetic sealing of lid 24 and housing 16 and housing 16 and metal pipe 2
Can be performed by welding metal materials, so that good hermetic sealing characteristics can be stably maintained over a long period of time, as in the case of the related art. In addition, in this embodiment, since solder is used for hermetic sealing of the optical fiber 12 and the metal pipe 2, good hermetic sealing characteristics can be stably maintained for a long time in this portion. When this embodiment is compared with the case where the solder is directly filled without using the ceramic capillary 8, this embodiment is superior in that the molten solder does not come into contact with the adhesive used for fixing the coating 10.

Another embodiment of the first configuration will be described with reference to FIG. In this embodiment, at least a portion 2a of the metal pipe 2 near the opening 13 of the press-fit hole is formed to have a small diameter so that the thickness of the metal pipe in this portion is reduced. In this case,
Since the thermal resistance at the tip of the metal pipe 2 increases, the heat diffusion when filling the opening 13 with the solder 14 is suppressed, and the working time can be shortened. In this example, by providing a step on the outer periphery of the metal pipe 2,
Although the portion near the opening 13 is formed to have a small diameter, a portion near the opening 13 may be formed to have a small diameter by providing a groove on the entire circumference near the tip of the metal pipe 2.

Still another embodiment of the first configuration will be described with reference to FIG. In this embodiment, the metal pipe 2, the housing 16 and the lid 24 are not fixed to each other by welding but by soldering or brazing or fusion using low melting glass. When joining members by these means, it is effective to increase the contact area between the members and the brazing material in order to increase the joining force. Therefore, in this embodiment, a counterbore 26 having a larger diameter than the insertion hole 18 is formed outside the insertion hole 18 of the housing, and a chamfered portion 28 is provided on the housing 16 side of the lid 24, thereby The joining force is increased.

An embodiment of the second configuration will be described with reference to FIG. In this example, a capillary press-fit hole 32 is formed in the first metal pipe 30, and a ceramic capillary 34 longer than the length corresponding to the depth of the press-fit hole 32 is pressed into the press-fit hole 32. The ceramic capillary 34 protruding from the first metal pipe 30 is inserted into and fixed to the second metal pipe 36. This insertion and fixing is performed by the first metal pipe 30 and the second metal pipe 36.
This is performed by brazing the entire circumference of the contact portion with the contact.
When the length of the second metal pipe 36 is made longer than the length of the portion of the ceramic capillary 34 protruding from the first metal pipe 30, the second metal pipe 36 has a length similar to that of the first configuration. An opening 38 is formed.
By filling with 40, the optical fiber 12 and the second metal pipe 36 are hermetically sealed. In addition, the hermetic sealing between the first and second metal pipes 30 and 36 is favorable because brazing is applied to the entire circumference.

The first metal pipe 30 is welded to the metal ring 42 all around,
In this state, the first metal pipe 30 is loosely fitted into the insertion hole 44 formed in the side wall of the housing 16. If the inner diameter of the insertion hole 44 is larger than the outer diameter of the first metal pipe 30, the metal ring 42 is brought into close contact with the side surface of the housing 16 and slid, whereby the optical coupling of the optical fiber 12 is performed. In performing the above, the optical axis adjustment is easy. After adjusting the optical axis, the metal ring 42 and the housing 16 are laser-welded all around. This achieves hermetic sealing of the inside of the housing 16 as in the case of the first configuration.

When penetrating the optical fiber 12 through the pores of the ceramic capillary 34, the tip of the optical fiber 12 may be broken, which makes it difficult to perform good optical coupling between the optical fiber 12 and the optical component. Therefore, in such a case, after penetrating the optical fiber 12 through the ceramic capillary 34, it is preferable to correct the distal end shape by heating the distal end portion 12a of the optical fiber 12 by electric discharge.

C0.5 is applied to the joint of the metal ring 42 by welding or the like.
By performing the above chamfering, welding and the like are facilitated and the joining strength is increased.

Another embodiment of the second configuration will be described with reference to FIG. In this example, in order to facilitate the soldering operation as described with reference to FIG.
By forming a, at least a portion near the opening 38 of the second metal pipe 36 has a small diameter. This suppresses heat diffusion during the filling of the solder, and facilitates the work of filling the solder. As in the case of FIG. 2, by providing a step on the outer periphery of the second metal pipe 36,
The diameter of the corresponding portion of the metal pipe 36 may be small.

An embodiment of the third configuration will be described with reference to FIG. In this example, a metal pipe for hermetically sealing the optical fiber and the metal pipe is integrally formed. In the configuration shown in FIG. 6 (a), a coating insertion hole 48, a fine hole 50 for inserting a fiber, and an opening 52 having a diameter larger than the fine hole 50 are continuously formed in the metal pipe 46 in this order. Step 46a on the outer circumference of metal pipe 46
Is formed, so that at least a portion near the opening 52 of the metal pipe 46 has a small diameter. As a result, the optical fiber and the metal pipe can be hermetically sealed in the same manner as in the previous embodiments, and since the step 46a is formed, the heat diffusion during solder filling is suppressed, and the solder filling operation can be performed. Facilitated. When the metal pipe is integrally formed as described above, the amount of heat diffusion at the time of filling the solder is extremely large. This is extremely effective in facilitating work. The structure shown in FIG. 6B is different from the structure shown in FIG. 6B in that a groove 46b is provided on the entire outer circumference of the metal pipe 46 instead of providing a step on the outer circumference of the metal pipe 46. Is formed into a small diameter.

Incidentally, for example, when an optical device having an optical fiber introduction section shown in FIG. 1 is used, the linear thermal expansion coefficient of the optical fiber 12 and the linear thermal expansion coefficient of the housing 16 are generally different. The possible temperature range may be limited. An embodiment having good temperature characteristics suitable for alleviating such a limitation will be described with reference to FIG. In this example, the case
When the optical fiber 12 introduced into the optical fiber 12 is optically coupled to the hole waveguide 22, the portion of the optical fiber 12 exposed in the housing 16 is made longer than the shortest distance, and this portion is bent. Optical coupling is performed. In general, the linear thermal expansion coefficient of the housing 16 made of metal is larger than the linear thermal expansion coefficient of the optical fiber 12 made of quartz or the like, so that even if an apparatus manufactured at room temperature is used at high temperature, There is no risk of damage to the optical coupling section and the like. Further, even if the device manufactured at room temperature is used at a low temperature, only slight increase in the amount of bending of the exposed portion of the optical fiber has no effect on the characteristics. By performing optical coupling by bending the optical fiber in this manner, it is possible to realize a device having excellent temperature characteristics.

In the embodiment described above, the end face of the optical fiber introduced into the housing is directly connected to an optical component such as a waveguide to perform optical coupling, but the optical fiber is cut at the end face of the metal pipe, The optical fiber may be polished together with the solder and the metal pipe, and the polished end face of the optical fiber and the optical component may be optically coupled using a lens or the like. In this case, the generation of reflected light can be suppressed by depositing an antireflection film on the polished end face of the optical fiber.

Effects of the Invention As described above, according to the present invention, there is an effect that a hermetic sealing structure of an optical fiber introduction portion is provided, in which deterioration with time of hermetic sealing is small and which is easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical fiber introduction section showing an embodiment of the first configuration, FIG. 2 is a cross-sectional view of a metal pipe or the like showing another embodiment of the first configuration, and FIG. FIG. 4 is a cross-sectional view of an optical fiber introduction section showing another embodiment, FIG. 4 is a cross-sectional view of an optical fiber introduction section showing an embodiment of the second configuration, and FIG. 5 is a metal pipe showing another embodiment of the second configuration. FIG. 6 is a cross-sectional view of a metal pipe showing an embodiment of the third configuration, FIG. 7 is a cross-sectional view of an optical fiber introduction section showing an embodiment suitable for improving temperature characteristics, and FIG. It is explanatory drawing of a prior art. 2 ... metal pipe, 6 ... capillary press-fitting hole, 8 ... ceramic capillary, 12 ... optical fiber, 30 ... first metal pipe, 36 ... second metal pipe.

Claims (5)

(57) [Claims] In an optical fiber introduction part in which a metal pipe into which an optical fiber is inserted and fixed is inserted and fixed in an introduction hole of a housing, a capillary press-fit hole is formed in the metal pipe, and a depth of the capillary press-fit hole is defined. An optical fiber, wherein a ceramic capillary shorter than the length corresponding to the above is press-fitted into the capillary press-fitting hole, an optical fiber penetrates through the pores of the ceramic capillary, and the opening of the capillary press-fitting hole is filled with solder. Hermetic sealing structure of the introduction section. 2. The hermetic sealing structure of an optical fiber introduction part according to claim 1, wherein at least a portion near the opening of the metal pipe is formed to have a small diameter. 3. A capillary press-fitting hole is formed in a first metal pipe in an optical fiber introduction portion in which a metal pipe into which an optical fiber is inserted and fixed is inserted and fixed in a guide hole of a housing. A ceramic capillary longer than a length corresponding to the depth of the ceramic capillary is inserted into the capillary press-fitting hole, the ceramic capillary protruding from the first metal pipe is inserted and fixed in a second metal pipe, and the optical fiber is connected to the ceramic capillary. Characterized in that the opening of the second metal pipe is filled with solder, and the optical fiber introduction part is hermetically sealed. 4. The hermetically sealed structure for an optical fiber introduction part according to claim 3, wherein at least a portion near the opening of the second metal pipe is formed with a small diameter. 5. The optical fiber introduction part according to claim 1, wherein the optical fiber introduced into the housing is bent to optically couple the optical fiber. Airtight sealing structure.