JP2616668B2 - Hermetically sealed structure of optical fiber introduction section - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber introduction portion used in optical fiber communication, and more particularly to a hermetically sealed structure thereof.

[0002]

2. Description of the Related Art An optical device generally contains an optical element such as an optical semiconductor element, a lens, or a prism. Usually, these optical devices are housed in a package or a holder. Among them, in particular, components such as optical semiconductor elements and LN (lithium niobate) optical waveguides have a problem that their characteristics are deteriorated by moisture. Therefore, these elements are configured so that the package and the holder can be maintained in an airtight structure so that the characteristics can be maintained.

Generally, when the package body and the lid are hermetically sealed, if a metal package is used or a ceramic package in which a sealing metal plate is brazed is used, the package and the lid are sealed. Seam welding such as resistance welding can be applied between them. By performing this seam welding, a sufficient airtightness of about 10 ⁻⁸ atm · cc / sec. That does not affect the characteristics of the elements in the optical device can be maintained. However, for the optical fiber introduction section that connects the optical fiber and the package,
Since the material of the optical fiber is glass, seam welding cannot be directly applied.

Therefore, in the past, it has been customary to hermetically seal this portion by fixing the optical fiber using a resin such as an adhesive. However, in the hermetic sealing using resin, unlike welding, gas is easily transmitted. Therefore, although it depends on the length to be fixed, it is generally 10 ^−5.
Atm ・ cc / sec.
For this reason, there is a problem that the reliability of the optical device is not sufficient. Therefore, it has been proposed to use solder instead of resin in order to increase the airtightness of the optical fiber introduction section.

FIG. 5 shows an example of a hermetically sealed structure of an optical fiber introduction portion in which an optical fiber is fixed using solder. In this hermetic sealing structure, a heat dissipation substrate 12 is fixed on an upper portion of a stem 11, and a semiconductor laser 13 is first mounted on this. Thereafter, the cap 11 is put on the stem 11, and the cap peripheral edge 15 and the stem 11 are seam-welded to hermetically seal them. A predetermined length of metal pipe (sleeve) 17 having a through hole through which the optical fiber 16 is passed is hermetically sealed with solder 18, and a polymer adhesive 20 is filled between the protective coating 19 and the metal pipe 17. I have to. When bonding the metal pipe 17 and the optical fiber 16, care must be taken so that the exposed portion of the optical fiber 16 is not exposed to the outside. To this end, the exposed portion of the optical fiber 16 is protected by hardening with the polymer adhesive 20 up to the protective coating 19. In this figure, an optical connector 21 is attached to the other end of the protective coating 19.

A metal pipe 17 in which an optical fiber 16 is hermetically sealed and fixed is passed through a cap opening 22 provided at the upper center of the cap 14. And the semiconductor laser 1
The tip of the optical fiber 16 is positioned at a position where it is optically connected to the optical fiber 3. Thereafter, the metal pipe 17 and the cap opening 22 are hermetically sealed with solder or an adhesive 24.

In the hermetic sealing structure of the optical fiber introduction section shown in FIG. 5, it is necessary to make the solder 18 adhere to both the metal pipe 17 and the optical fiber 16. Therefore, it is indispensable to use a metal-coated optical fiber whose surface is coated with metal. For this reason, it is necessary to deposit a metal on the optical fiber 14, which not only increases the deposition cost but also complicates the process.

Further, in this proposal, it is necessary to set the stripping dimension of the metal-coated optical fiber 21 to a relatively large value so that heat when melting the solder is not transmitted to the protective film 18 having low heat resistance. there were. For this reason, there has been a problem that downsizing of the optical device becomes difficult. Therefore, Japanese Patent Application Laid-Open No. 60-180183 proposes that the optical fiber, the package and the lid of the optical fiber introduction part are directly fixed with low melting point glass.

FIG. 6 shows an optical semiconductor device hermetic package according to this proposal as viewed obliquely from above, and FIG. 7 shows a cross section of this package. In this proposal, a package 33 containing a semiconductor laser 32 via a heat dissipation substrate 31 and a seal ring 3
5 and a metal-coated optical fiber 36 and an electric terminal 37.
And is fixed with the low melting point glass 38.

According to this proposal, as in the hermetic sealing structure using the above-described solder, it is possible to obtain a high air density comparable to that of seam welding. However, since the metal coated optical fiber 36 coated with a metal such as gold is used,
There is a problem that the cost of vapor deposition of metal on the optical fiber is high. In view of this, Japanese Patent Application No. 5-013955 proposes a technique for achieving high airtightness in an optical fiber introduction portion without depositing metal on the optical fiber.

FIG. 8 shows a longitudinal section of the hermetically sealed optical fiber terminal before melting the low melting point glass according to this proposal, and FIG. 9 shows a longitudinal section of the hermetically sealed optical fiber terminal after melting the low melting point glass. Things. In this proposal, first, a part of the protective film 41 is peeled off to expose the optical fiber 42. Then, the low-melting glass 43 is inserted into the metal pipe 45 by passing the optical fiber 42 through the through-hole of the low-melting glass 43 formed in advance in the pipe-shaped tablet. At both ends of the low-melting glass 43, glass pipes 46 for protecting the exposed portions of the optical fibers 42 are respectively provided with metal pipes 45.
It is arranged with the end inserted.

In the state shown in FIG. 8, a pair of glass pipes
46, 46 are brought into contact with the low-melting glass 43 to form a metal pipe.
45 is heated to melt the internal low melting point glass 43.
You. If SUS304 is used for the metal pipe 45,
Optical fiber 42, low melting point glass 43, metal pipe 4
5 each has a thermal expansion coefficient of 5 × 10^-7, 60 × 1
0 ^-7, 180 × 10^-7It is. Thus, the coefficient of thermal expansion
Are optical fiber 42, low melting point glass 43, metal pipe 4
Assuming that the size becomes smaller in the order of 5, heating ends and
When cooling is performed, the pressure is sequentially increased from the outer metal pipe 45.
Compression is performed. That is, it is strong due to the difference in the coefficient of thermal expansion.
A compressive force is generated, and these optical fibers 42, low melting point glass
43, the metal pipe 45 is fixed in a completely adhered state
be able to. At this time, the glass pipe 46 is also
They are in close contact with the lath 43, and the air
Tightly sealed and fixed, sufficient for ensuring the reliability of optical devices
Air tightness can be obtained. In addition, the glass pipe 46
The presence also protects the exposed portion of the optical fiber 42.
Will be revealed.

However, according to the proposals shown in FIGS. 8 and 9, in order to melt the low-melting
It is necessary to apply 0 ° C. heat. Therefore, the protective coating 41
In the case of a normal optical fiber using a nylon resin, the heat generated by heating the metal pipe 45 is transmitted to the nylon resin, causing thermal contraction. As a result, there is a problem that microbending occurs in the optical fiber 42 and its optical characteristics are deteriorated.

Therefore, use of an optical fiber having a protective coating made of an ultraviolet curable resin has been studied. When such an optical fiber is used, when the low-melting glass 43 is melted, the heat generated by heating the metal pipe 45 is applied to the protective coating 4.
Even if transmitted to 1, the ultraviolet curable resin does not shrink like a nylon resin, and burns out as it is. Therefore, the optical fiber 42 having a heat resistance of 1000 ° C. or more can be hermetically sealed and fixed without any adverse optical effect.

[0015]

In general, optical fibers for communication are made of quartz glass, and therefore have high brittleness.
It is very easy to break when handled in bare condition. For this reason,
The exposed portion of the optical fiber must not be exposed to the outside. The conventional hermetic sealing structure described above has a structure in which a metal coat is applied to prevent the optical fiber from being exposed, or a glass pipe is used to protect the exposed portion of the optical fiber.

However, in a structure using an optical fiber coated with a metal, there is no problem in the strength itself of the optical fiber, but the cost is increased by the amount of the metal coated and it is difficult to reduce the price. there were. Also,
In the structure using the glass pipe, the airtightness between the metal pipe and the optical fiber is sufficiently maintained, but in order to maintain the airtightness inside the package, it is necessary to further hermetically seal between the metal pipe and the package. . Therefore, the number of steps is increased by the extra airtight sealing step. Further, in the structure using this metal pipe, it is necessary to make a through hole for passing the metal pipe through the package, and a step of passing a gold loss pipe to which the optical fiber is fixed through this through hole is required. . Therefore, there has been a problem that workability is reduced and automation is difficult. This problem has been a major bottleneck in achieving mass production and cost reduction.

It is an object of the present invention to provide a hermetically sealed structure of an optical fiber introduction portion which is suitable for automation and mass production and which can hermetically seal an optical fiber.

It is another object of the present invention to provide a hermetically sealed structure for an optical fiber introduction portion which protects an optical fiber without exposing the optical fiber.

[0019]

According to the first aspect of the present invention, the hermetically sealed structure of the optical fiber introduction portion has a rectangular parallelepiped shape.
Side closer to one end than the center of the top surface
Place a recessed part with an edge around it.
Ri, this optical fiber optically connected to the semiconductor laser
And the package body accommodated in the recess
The shape of the package
From the other end of the body to an area of a first width and to this recess
For sealing that is tightly fixed to the remaining edge except for the area
A metal plate and a second width on the other end side of the sealing metal plate
Is sealed to the remaining top surface excluding the area
A lid for hermetically sealing the concave portion in which the body laser is disposed , wherein the
In the area of the first width, the outer diameter of the protective coating of the optical fiber
Grooves for fixing glass pipes with large through holes are arranged
When the glass pipe is fixed in this groove
In both cases, the optical fiber is placed in the second width region of the sealing metal plate.
There is a notch along the base, and this notch
From the low melting glass placed inside the groove
The recess is hermetically sealed.

That is, in the hermetic sealing structure of the optical fiber introduction portion according to the first aspect, the first portion on the upper surface of the package body is provided.
A groove is provided in the area of width 1 to fix the glass pipe.
The glass pipe is covered with an optical fiber with a protective coating.
It is inserted in the state where it was inserted. This optical fiber is
Biased toward the opposite end of the glass body to this glass pipe
Optically contacts the semiconductor laser housed in the drilled recess
Has been continued. First width on top of package body
Region other than the region where the semiconductor laser is housed.
The edge-shaped area on the top surface excluding the part is
The sealing metal plate whose area is hollowed out is tightly fixed.
This sealing metal plate has a second end on the glass pipe side.
The lid is sealed in a shape excluding the width region. Sealing gold
The second width region of the metal plate is cut along the optical fiber.
A notch is provided, and the notch
The recess is airtight due to the melting of the low-melting glass placed in the section
It is designed to be sealed.

[0021]

[0022]

[0023]

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows the first stage of assembling the optical fiber introducing section in one embodiment of the present invention.
The package 51 made of ceramic is provided with the semiconductor laser 5.
In the right half of the figure, there is provided a concave portion 54 for accommodating the heat radiation substrate 53 to which the fixing member 2 is fixed, and a left half portion is provided with a pipe groove 55 having a semicircular cross section. Package 5
1, a pipe groove 5 is formed with an opening corresponding to the concave portion.
On the 5th side, a sealing metal plate 57 having a slightly wider edge is brazed. A cylindrical glass pipe 58 is fixed to the pipe groove 55. In the above-described slightly wider edge portion of the sealing metal plate 57, the semiconductor laser 52 and the central axis of the glass pipe 58 fixed to the pipe groove 55 are aligned with the arrangement of the optical fiber 62. Along the connecting straight line, a slit-shaped notch 61 is provided.

The optical fiber 62 is stripped by a predetermined length from the protective coating 63, and is passed through the hole of the glass pipe 58 together with the tip of the protective coating 58. The exposed portion of the optical fiber 62 passes through the notch 61 and the tip is optically connected to the semiconductor laser 52. In such an optical fiber introduction part, a rectangular metal lid 65 having a length slightly shorter than the metal plate for sealing 57 is prepared. The lid 65 is put on the metal plate 57 for sealing so as to match the back side in the figure, and these are seam-welded by a method such as resistance welding.

FIG. 2 shows a state after seam welding as a second stage of assembling the optical fiber introducing section shown in FIG. The notch 61 passing through the optical fiber 62 is not sealed only by sealing the package 51 and the lid 65. Therefore, after sealing the package 51 and the lid 65,
A low melting point glass 67 made of powder or the like is put in the notch 61. Then, by melting this, simultaneous sealing is performed between the optical fiber 62, the cutout portion 61 of the package 51, and the metal lid 65. Thus, the hermetic sealing inside the package 51 is completed.

The order in which the notch 61 is hermetically sealed will be described. First, a glass pipe 58 is passed through the protective coating 63 of the optical fiber 62, and a low-melting glass 67 is disposed in the cutout 61 as a remaining sealing portion. The low-melting glass 67 is partially heated by means such as a CO ₂ (carbon dioxide) laser. Thereby, the low melting point glass 67 is melted, and the optical fiber introduction portion can be hermetically sealed. As described above, since partial heating is performed in this embodiment, the protective film 63 is not affected by the heating, so that hermetic sealing and protection of the exposed portion of the optical fiber 62 can be performed. Further, in this embodiment, by melting the low melting point glass 67, not only the hermetic sealing of the optical fiber introduction portion but also the pipe groove 55 of the glass pipe 58 can be achieved.
At the same time, it is fixed to the surface.

Modification

FIGS. 3 and 4 show a state of assembling the optical fiber introducing section according to a modification of the present invention. FIGS. 3 and 4 correspond to FIGS. 1 and 2, respectively. I have. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In this modification, a ferrule 71 made of a material such as ceramic is used instead of the glass pipe 58 used in the above embodiment. The ferrule 71 has a through hole at the center thereof, which is slightly larger than the outer diameter of the optical fiber 62.
2 is passed. The ferrule 71 holds the package 51 with one end of the ferrule 71 abutting against the end of the sealing metal plate 57.
Glass pipe 5 of the embodiment so that
It is slightly longer than 8. This allows direct connection with another optical connector.

In the hermetically sealed structure of the optical fiber introduction section of this modification, it is not necessary to heat only the low melting point glass 67 when melting the glass. That is, the whole package assembled as shown in FIG.
It is also possible to melt 7. In this case, there is an advantage that it is more suitable for automation than the previous embodiment.

In the above-described embodiments and modifications, the sealing metal plate 5 is attached to the package 51 made of ceramic.
7 was fixed, and the lid 65 was seam-welded to this. When the package is made of a sealable metal, a cutout for directly fitting the optical fiber into the package may be provided without using the sealing metal plate 57.

[0033]

As described above, according to the first aspect of the present invention , the sealing metal is provided stepwise on the upper surface of the package body.
The plate and the lid are arranged, and the package body is
Insert the optical fiber into the groove of the exposed first width area.
Fixing the optical fiber because the threaded glass pipe was fixed
Can be performed stably. In addition, the sealing metal plate is
Along the optical fiber in the second width region exposed from the
The notched part is provided, so from this notched part
By putting low melting glass in the groove and melting it,
The hermetic sealing of the portion can be easily and reliably performed. Only
The optical fiber is inserted into the glass pipe while the
Insert the metal plate through the notch and secure it
Since there is no need to pass an optical fiber through the through-hole of the package as in the conventional case, it is suitable for automation and has the effect of contributing to mass production and cost reduction.

[0034]

[0035]

[0036]

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first stage of assembling an optical fiber introducing section according to an embodiment of the present invention.

FIG. 2 shows a second example of assembling the optical fiber introduction section in the present embodiment.
It is the perspective view showing the stage.

FIG. 3 is a perspective view illustrating a first stage of assembling an optical fiber introduction section according to a modification of the present invention.

FIG. 4 is a perspective view showing a second stage of assembling the optical fiber introduction section in this modified example.

FIG. 5 is a cross-sectional view illustrating an example of a conventional hermetic sealing structure of an optical fiber introduction portion to which an optical fiber is fixed using solder.

FIG. 6 is a perspective view of an optical semiconductor element hermetic package according to another conventional proposal as viewed obliquely from above.

FIG. 7 is a sectional view of the optical semiconductor element airtight package shown in FIG. 6;

FIG. 8 is a longitudinal sectional view showing a hermetically sealed optical fiber terminal before melting a low-melting glass according to yet another conventional proposal.

9 is a longitudinal sectional view showing a state after melting the low melting point glass of the hermetically sealed optical fiber terminal shown in FIG. 8;

[Explanation of symbols]

 REFERENCE SIGNS LIST 51 package (package main body) 52 semiconductor laser 53 heat dissipation substrate 54 concave portion 55 pipe groove 57 sealing metal plate 58 glass pipe 61 cutout (groove) 62 optical fiber 63 protective coating 65 lid 67 low melting point glass 71 ferrule

Claims (1)

(57) [Claims] 1. A rectangular parallelepiped shape having a top surface
With an edge around the side closer to one end than the center
A package body in which a semiconductor laser optically connected to an optical fiber is accommodated in the concave portion, and a region facing the concave portion is hollowed out.
From the other end of the package body.
Excluding the area having the width of
A metal plate for sealing tightly fixed to the edge portion, and the sealing metal
The second width region on the other end side of the metal plate is excluded.
The semiconductor laser is sealed to the rest of the top surface
And a lid for hermetically sealing the recessed part , wherein the optical fiber is provided in the first width region of the package body.
Gas with a through hole larger than the outer diameter of the fiber protective coating
A groove for fixing the lath pipe is arranged, and this groove is
The glass pipe is fixed and the sealing metal
Along the optical fiber along the second width region of the metal plate
Notch is provided, and from this notch
By the melting of the low-melting glass placed inside the groove
The hermetically sealed structure of the optical fiber introduction portion, wherein the recess is hermetically sealed.