JP2005055475A - Optical fiber terminal structure - Google Patents

Abstract

To provide an optical fiber terminal structure which is difficult to cause thermal damage to an optical fiber.
The optical fiber terminal structure includes a nose pipe 2 attached to an opening of a housing 1 in a semiconductor laser module, a tip part fitted into the nose pipe 2, and a metallized fiber 3 and a fiber resin coating part 6. And a protective tube 7 covering the outer peripheral surface of the seal bead 4 excluding the inserted portion, the main part of which is formed between the metallized fiber 3 and the seal bead 4. , And the nose pipe 2 and the seal bead 4 are solder-sealed. In this optical fiber terminal structure, the area to be sealed with solder is small, and the protective tube 7 is also fixed with an adhesive, so that the heat capacity during assembly can be reduced.
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber terminal structure for introducing and connecting an optical fiber into a housing of various optical communication modules used in the field of optical communication such as a semiconductor laser module, and in particular, it is difficult to cause thermal damage to the optical fiber. The present invention relates to an improvement of an optical fiber terminal structure.
[0002]
[Prior art]
[0003]
[Patent Document 1]
JP 07-198997 A (Claim 1, FIG. 1)
[Patent Document 2]
Japanese Patent Application Laid-Open No. 08-15572 (Claim 1, FIG. 2)
[0004]
In an optical communication module such as a semiconductor laser module or a semiconductor amplifier module used for optical communication, a casing having airtightness is used to prevent optical elements such as a semiconductor laser stored in the casing from deteriorating due to condensation. In order to extract light from the optical element to the outside, it is necessary to introduce an optical fiber into the casing without impairing the hermeticity of the casing.
[0005]
As this method, an optical fiber in which a metal film is applied to the outer surface of an optical fiber that is exposed by removing the resin coating is inserted into a metal cylinder (fiber fixing portion), and the optical fiber is provided with the metal film The element wire and the metal cylinder are fixed with solder to ensure the airtightness between the optical fiber and the metal cylinder, and the metal cylinder is fitted into an opening provided on the wall of the housing, and There is known a method of introducing an optical fiber into a casing of an optical communication module by fixing it with solder or welding while ensuring airtightness.
[0006]
And the optical fiber terminal structure described in patent document 1 and patent document 2 is known as a conventional method using this method.
[0007]
That is, in the optical fiber terminal structure described in Patent Document 1, an optical fiber in which a metal film is applied to the outer surface of an optical fiber strand is inserted into a pipe-shaped inner sleeve, and a resin-coated portion is bonded and fixed integrally. After inserting and inserting this inner sleeve into a separate intermediate sleeve and inserting the intermediate sleeve into which the inner sleeve is incorporated into the outer sleeve attached by welding or the like to the opening of the housing wall surface, The inner sleeve, the intermediate sleeve, and the outer sleeve are soldered to form an optical fiber terminal structure that is hermetically sealed.
[0008]
On the other hand, in the optical fiber terminal structure described in Patent Document 2, an optical fiber in which a metal film is applied to the outer surface of an optical fiber strand is inserted into a pipe member (metal cylinder) and soldered into the pipe member. After sealing the gap between the optical fiber strands and fixing the pipe member and the resin coating portion with an adhesive, the pipe member is attached and welded to the opening of the casing wall surface. An optical fiber terminal structure that is hermetically sealed is formed.
[0009]
[Problems to be solved by the invention]
By the way, in the former optical fiber terminal structure described in Patent Document 1, the structure is complicated, and it is necessary to solder between the inner sleeve, the intermediate sleeve, and the outer sleeve. When soldering using tin solder, it is necessary to apply a temperature of 220 ° C. or higher, which is the melting point of the lead tin solder, to the vicinity of the sealed portion for a long time even if an induction heating method that can be locally heated is applied. become.
[0010]
For this reason, the resin coating portion of the optical fiber is melted, and there is a problem that thermal damage is easily caused to the glass portion of the optical fiber.
[0011]
On the other hand, in the latter optical fiber terminal structure described in Patent Document 2, thermal damage is avoided when solder is poured into the pipe member after the optical fiber is inserted into the pipe member (metal cylinder). Therefore, if the length of the pipe member is shortened, the portion for fixing the resin-coated portion in the optical fiber is insufficient. On the other hand, if the length of the pipe member is increased, the heating time is increased as in the former optical fiber terminal structure. Therefore, there is a problem that the optical fiber is likely to be thermally damaged.
[0012]
In addition, in order to avoid thermal damage to the optical fiber, when the optical fiber terminal structure is formed by weakening the soldering conditions, there is a problem that causes deterioration of mechanical strength, that is, when the optical fiber is fixed to the module. It has another problem that causes deterioration such as tensile test strength.
[0013]
The present invention has been made paying attention to such problems, and a problem to be solved by the invention is to provide an optical fiber terminal structure which is hard to cause thermal damage to the optical fiber.
[0014]
[Means for Solving the Problems]
Therefore, in the present invention, in order to minimize the heat capacity at the time of assembling the optical fiber terminal structure, a small cylindrical nose pipe is attached to the opening of the housing of the optical communication module, and the nose pipe By adopting a structure in which the tip of the optical fiber feedthrough with a small solder connection part is inserted and assembled, and a protective tube covering the outer peripheral surface of the optical fiber feedthrough excluding the inserted part is attached using an adhesive The above problems are solved.
[0015]
That is, the invention according to claim 1
An optical fiber having an optical fiber exposed portion in which an outer surface of the optical fiber is coated, a resin coating exposed from the resin coated portion and a metal film is applied to the outer surface, and a fiber fixing portion for fixing the optical fiber Assuming an optical fiber terminal structure in which the main part of the optical fiber feedthrough is attached to the opening of the housing of the optical communication module and the exposed portion of the optical fiber is introduced into the housing of the optical communication module age,
A cylindrical nose pipe that is attached to the opening of the housing of the optical communication module and into which the distal end side of the optical fiber feedthrough is fitted, and an optical fiber feedthrough that is fitted and fixed in the cylindrical nose pipe The main part of the optical fiber terminal structure is configured with a protective tube covering the outer peripheral surface of the optical fiber feedthrough excluding the inserted portion,
The first hollow portion in which the fiber fixing portion in the optical fiber feedthrough has an inner diameter larger than the outer diameter of the optical fiber exposed portion, and the exposed surface on the distal end side of the first hollow portion through which the optical fiber exposed portion is inserted A head portion that is hermetically sealed with the exposed portion of the optical fiber by solder filled in the concave portion and is fitted into the cylindrical nose pipe; A sleeve body comprising a second hollow portion communicating with the hollow portion and having an inner diameter larger than the outer diameter of the resin coating portion and accommodating an exposed portion of the optical fiber and a portion of the resin coating portion on the base end side thereof; Consists of
The cylindrical nose pipe has a length dimension equal to that of the head body in the fiber fixing portion or a larger value within 2 mm, and an inner diameter dimension larger than the outer diameter of the head body within 0.2 mm. Is set to a value within 2 mm, and the air gap between the cylindrical nose pipe and the head body in the optical fiber feedthrough fitted in the pipe is set. Hermetic sealing is performed using solder with a melting point of 180 ° C. or higher,
Furthermore, the protective tube covering the outer peripheral surface of the optical fiber feedthrough is fixed by an adhesive.
[0016]
The invention according to claim 2
On the premise of the optical fiber terminal structure according to the invention of claim 1,
The head body in the fiber fixing part is gold-plated on the outer surface, the outer diameter of the head body is set to 5 mm or less and the length dimension is set to 4 mm or less, and the first hollow part of the head body is An inner diameter is set to 160 μm or less, and the sleeve body in the fiber fixing portion has a thickness dimension set to 0.5 mm or less and a length dimension set to 10 mm or less, and a hole for increasing the thermal resistance to a part of the outer peripheral surface The department is established.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
FIG. 1 is a schematic cross-sectional view of an optical fiber terminal structure according to an embodiment of the present invention incorporated in a semiconductor laser module.
[0019]
That is, this optical fiber terminal structure includes a nose pipe 2 having a cylindrical shape attached to an opening of a housing 1 in a semiconductor laser module, and a tip portion fitted into the nose pipe 2 and an optical fiber is fixed. At the same time, a metal seal bead (fiber fixing portion) 4 plated with gold and a protective tube 7 covering the outer peripheral surface of the seal bead 4 excluding the inserted portion constitute the main part.
[0020]
The optical fiber fixed to the seal bead 4 is an optical fiber (metallized fiber) having a fiber resin coating 6 and a metal film formed on the outer surface excluding the fiber cut surface exposed from the fiber resin coating 6. 3), and a ferrule (not shown) made of metal is soldered to the tip of the optical fiber strand (metallized fiber) 3 and mounted in the housing 1 (not shown). The ferrule is fixed to the housing 1 so that the coupling between the light from the semiconductor laser element and the optical fiber (metallized fiber) 3 is maximized.
[0021]
First, since the thickness of the casing 1 is not enough to fit the gold-plated seal bead 4 into the opening of the casing 1 and solder it in the correct direction, the nose pipe 2 is open to the opening of the casing 1. It is inserted into the part and attached by welding or brazing. Further, a part of the optical fiber strand (metallized fiber) 3 and the fiber resin coating portion 6 are accommodated in the hollow portion of the metal seal bead 4 as shown in FIG. The fiber strand (metallized fiber) 3 is fixed in advance to the metal sealing bead 4 by gold tin solder 4a. Further, after the optical fiber (metallized fiber) 3 is soldered, the fiber resin coating portion 6 accommodated in the hollow portion is fixed with an adhesive (not shown), and the fixed optical fiber and metal sealing beads are fixed. The optical fiber is prevented from being damaged during the handling of the optical fiber feedthrough constituted by the (fiber fixing portion) 4, and the tip end portion of the optical fiber feedthrough is fitted into the nose pipe 2.
[0022]
Next, the structure of the metal sealing bead (fiber fixing portion) 4 is specifically shown in FIG. That is, the metal sealing bead (fiber fixing portion) 4 includes a head body 10 having a cylindrical shape and a sleeve body 11 connected to the head body 10, and the head body 10 includes an optical fiber strand ( A first hollow portion having an inner diameter of 160 μm or less is provided so that the (metallized fiber) 3 is inserted, and a substantially conical concave portion 12 is provided on the exposed surface on the distal end side of the first hollow portion.
[0023]
The sleeve body 11 communicates with the first hollow portion and has an inner diameter larger than the outer diameter of the fiber resin coating portion 6 and accommodates a part of the optical fiber (metalized fiber) 3 and the fiber resin coating portion 6. The second hollow portion is provided. Further, in order to increase the thermal resistance of the sleeve portion, the thickness of the sleeve body 11 is set to be thin so that heat is prevented from being transmitted to the fiber portion. For the same reason, it is desirable that the sleeve body 11 has a hole 13 for increasing the thermal resistance in a part of the outer peripheral surface thereof. In FIG. 2, the outer diameter of the head body 10 of the metal seal bead (fiber fixing portion) 4 is set larger than the outer diameter of the sleeve body 11. The outer diameter may be set to be the same and is arbitrary.
[0024]
Here, the sizes of the head body 10 and the sleeve body 11 constituting the metal seal beads (fiber fixing portion) 4 are arbitrary, and are appropriately set in consideration of the dimensions of the optical fiber to be incorporated. For example, the outer diameter dimension of the head body 10 may be set to 5 mm or less, the length dimension to 4 mm or less, the wall thickness dimension of the sleeve body 11 to 0.5 mm or less, and the length dimension to 10 mm or less. The inner diameter of the second hollow portion of the sleeve body 11 is preferably set to be larger than the outer diameter of the fiber resin coating portion 6, for example, 1.5 mm or less. When the inner diameter of the second hollow portion exceeds 1.5 mm, the heat capacity increases. For example, the substantially conical concave portion 12 of the head body 10 is filled with gold tin solder and the optical fiber (metallized fiber) 3 is filled. When fixing is performed, the fiber resin coating may be melted by heat or the fiber may be damaged. Accordingly, the thickness is preferably set to 1.5 mm or less.
[0025]
Next, the inner diameter of the nose pipe 2 having a cylindrical shape is set to a larger value within 0.2 mm than the outer diameter of the head body 10 (that is, the outer diameter difference from the head body 10 is 0.2 mm). And the wall thickness must be set within 2 mm. If the outer diameter difference with the head body 10 exceeds 0.2 mm and a gap is formed or the thickness of the nose pipe 2 exceeds 2 mm, the head body 10 is heated even when heated from the outside of the nose pipe 2. This is because it becomes difficult to transmit, and as a result, it is necessary to supply a large amount of heat to melt the solder interposed between the nose pipe 2 and the head body 10, and this causes thermal damage to the fiber portion. Further, the length dimension of the nose pipe 2 needs to be set to the same value as the head body 10 or a larger value within 2 mm. If the length of the nose pipe 2 exceeds 2 mm from the head body 10, heat is transferred to the entire nose pipe 2 during soldering, and as a result, it is difficult to efficiently transfer heat to the head body 10. This is because a large amount of heat needs to be supplied.
[0026]
And the front-end | tip part of the optical fiber feedthrough comprised with an optical fiber and metal seal beads (fiber fixing | fixed part) 4 with respect to the nose pipe 2 attached to the opening part of the said housing | casing 1 by welding or brazing etc. (Head body 10) is inserted, a soldering iron is brought into contact with the outside of the nose pipe 2 to heat the portion where the lead-tin solder 5 is performed, and airtight sealing is performed between them.
[0027]
Thereafter, a protective tube 7 having an inner diameter larger than that of the sleeve body 11 of the metal seal bead (fiber fixing portion) 4 and having an outer diameter smaller than the inner diameter of the nose pipe 2 is inserted, and adhesives 8 and 9 are inserted. And the protective tube 7 is fixed, and the optical fiber terminal structure according to the embodiment is formed.
[0028]
In this embodiment, a cylindrical protective tube 7 is applied as shown in FIG. 1, but a structure in which a collar portion that contacts the opening edge of the nose pipe 2 is provided as shown in FIG. The protective tube 7 may be applied.
[0029]
By adopting an optical fiber terminal structure as shown in FIG. 1 or FIG. 3, lead tin solder can be executed in a short time. Actually, when the cross section was scraped and observed after soldering, a portion dissolved in the fiber resin coating 6 was not observed. From this, it was confirmed that the temperature in the vicinity of the fiber resin coating portion did not increase as the fiber resin coating portion 6 melted. Further, this structure sufficiently satisfied the airtightness, and was able to maintain a sufficient strength in the tensile test.
[0030]
【Example】
Examples of the present invention will be specifically described below.
[0031]
First, the optical fiber strand exposed from the fiber resin coating 6 is subjected to metallization on the outer surface excluding its tip (cut surface), for example, gold plating with Ni as a base, thereby using gold tin solder. Solder sealing can be performed. The seal bead (fiber fixing portion) 4 is made of stainless steel, and the surface thereof is plated with gold with Ni as a base.
[0032]
Next, an optical fiber strand (metallized fiber) 3 is inserted into a seal bead (fiber fixing portion) 4 composed of a head body 10 and a sleeve body 11, and the optical fiber strand (metallized fiber) 3 is After adjusting the position to an appropriate length, the gold-tin solder 4a was filled into the substantially conical recess 12 of the head body 10. At this time, a ferrule (not shown) plated with gold is fixed to the tip of the optical fiber (metallized fiber) 3 with gold tin solder.
[0033]
Next, the tip of a seal bead 4 (ie, an optical fiber feedthrough) in which an optical fiber (metallized fiber) 3 is soldered to a nose pipe 2 attached to the opening of the housing 1 by brazing. After inserting (head body 10) and adjusting the position so that lead-tin solder can be made, the nose pipe 2 is heated using a soldering iron, and the temperature is locally increased to about 230 ° C. to perform soldering. I did.
[0034]
After the soldering, the protective tube 7 made of stainless steel having a larger inner diameter than the sleeve body 11 of the metal seal bead (fiber fixing portion) 4 and a smaller outer diameter than the inner diameter of the nose pipe 2 is provided. The protective tube 7 was fixed by inserting and filling the adhesives 8 and 9, and the optical fiber terminal structure according to the example was completed.
[0035]
【The invention's effect】
According to the optical fiber terminal structure according to the invention of claim 1 or 2,
Since the heat capacity during assembly of the optical fiber terminal structure can be reduced, sufficient hermetic sealing is possible without causing thermal damage to the optical fiber, and the optical fiber is mechanically protected by the action of the protective tube. Also has an effect that makes possible.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an optical fiber terminal structure according to an embodiment of the present invention.
FIG. 2 is a configuration explanatory view of a seal bead (fiber fixing portion) according to an embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of an optical fiber terminal structure according to another embodiment of the present invention.
[Explanation of symbols]
1 Housing 2 Nose Pipe 3 Optical Fiber (Metallized Fiber)
4 Seal beads (fiber fixing part)
6 Fiber resin coating 7 Protective tube

Claims (2)

An optical fiber having an optical fiber exposed portion in which an outer surface of the optical fiber is coated, a resin coating exposed from the resin coated portion and a metal film is applied to the outer surface, and a fiber fixing portion for fixing the optical fiber In the optical fiber terminal structure in which the optical fiber feedthrough constituting the main part is attached to the opening of the housing in the optical communication module and the exposed portion of the optical fiber is introduced into the housing of the optical communication module,
A cylindrical nose pipe that is attached to the opening of the housing of the optical communication module and into which the distal end side of the optical fiber feedthrough is fitted, and an optical fiber feedthrough that is fitted and fixed in the cylindrical nose pipe The main part of the optical fiber terminal structure is composed of a protective tube that covers the outer peripheral surface of the optical fiber feedthrough excluding the inserted part,
The first hollow portion in which the fiber fixing portion in the optical fiber feedthrough has an inner diameter larger than the outer diameter of the optical fiber exposed portion, and the exposed surface on the distal end side of the first hollow portion through which the optical fiber exposed portion is inserted A head portion that is hermetically sealed with the exposed portion of the optical fiber by solder filled in the concave portion and is fitted into the cylindrical nose pipe; A sleeve body comprising a second hollow portion communicating with the hollow portion and having an inner diameter larger than the outer diameter of the resin coating portion and accommodating an exposed portion of the optical fiber and a portion of the resin coating portion on the base end side thereof; Consists of
The cylindrical nose pipe has a length dimension equal to that of the head body in the fiber fixing portion or a larger value within 2 mm, and an inner diameter dimension larger than the outer diameter of the head body within 0.2 mm. Is set to a value within 2 mm, and the air gap between the cylindrical nose pipe and the head body in the optical fiber feedthrough fitted into the pipe is set. Hermetic sealing is performed using solder with a melting point of 180 ° C. or higher,
Furthermore, the protective tube which covers the outer peripheral surface with respect to the said optical fiber feedthrough is being fixed with the adhesive agent, The optical fiber terminal structure characterized by the above-mentioned. The head body in the fiber fixing part is gold-plated on the outer surface, the outer diameter of the head body is set to 5 mm or less and the length dimension is set to 4 mm or less, and the first hollow part of the head body is An inner diameter is set to 160 μm or less, and the sleeve body in the fiber fixing portion has a thickness dimension set to 0.5 mm or less and a length dimension set to 10 mm or less, and a hole for increasing the thermal resistance to a part of the outer peripheral surface The optical fiber terminal structure according to claim 1, wherein a portion is established.

Images