JPH01145608A - Fixing structure for optical fiber - Google Patents

Abstract

PURPOSE:To improve the productivity and reliability by welding an metallic cylinder made of stainless steel to the part of a ring made of stainless steel fitted to a metallic package previously. CONSTITUTION:The tip fitting part of an metallic cylinder 3 is fixed to the metallic package 3 which contains an optical element 1. The metallic cylinder 3 made of stainless steel is spot-welded to the stainless steel ring 20 of the metallic package 2 at a weld zone 5. The stainless steel ring 20 is placed with metal and joined with the metallic package 2 with solder with a high fusion point in a joining surface 22. Consequently, the optical fiber is fixed with superior productivity and reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a structure for fixing an optical fiber in the structure of an optical component in which an optical element and an optical fiber are optically coupled together for use in optical fiber communications and the like.

[Conventional technology]

In recent years, optical 7-eye communication has attracted attention as a long-distance, large-capacity information transmission means, but it requires elements such as light-emitting and light-receiving elements and optical components such as optical 7-eye light. A typical example is a semiconductor laser module that is made by optically coupling and integrating optical fibers.

These optical components incorporate optical fibers as a means of inputting and outputting light, and coupling lenses for coupling light to the optical fibers, but extremely high precision is required for the assembly of these components. Ru.

For example, when assembling a module that combines a semiconductor laser and a single mode fiber (hereinafter referred to as SMF-LD module), it is necessary to adjust the position of the fiber tip to the optimal position and permanently fix it. The position of the fiber tip is only about Lo in the direction perpendicular to the optical axis.
Even a deviation of about am will reduce the coupling efficiency by 10%. Therefore, it is an important technical issue to devise a mechanically stable structure with little change over time so that the bond does not change even after assembly.

For this reason, high n1 as in the SMF-LD module
Laser welding technology using a YAG laser or the like is increasingly used in the assembly of optical parts that require fabrication. That is, the optical element, the coupling lens, and the optical fiber are each held in advance by parts made of gold (M), and these metal parts are assembled by joining each other by laser welding. In this method, metal parts with high melting points are joined by direct welding, so there is less mechanical deterioration over time than when assembling with adhesives or solder, and a stable optical bond is maintained for a long period of time. It is expected that highly reliable optical components that can be maintained for many years can be realized. In addition, non-contact, local, and instantaneous processing can be performed simply by irradiating laser light, so no skill is required, and the reproducibility of working conditions is good, so quality is expected to be stable.

As a conventional optical fiber fixing structure, there is one shown in FIG. This is a metal package 2 containing an optical element 1 and an optical fiber 4 surrounded by a metal tube 3.
When fixing by welding, the two are welded in a spot shape and the two are joined.

Normally, when protecting the outside of the optical fiber with a metal tube 3,
Since the end face of the optical fiber is polished together with the metal tube to make it a flat surface, the metal tube is usually made of a material such as stainless steel, which rusts and corrodes even without plating. In such cases, it is common to insert a ceramic or glass pipe between both the optical fiber and the metal tube, but since there is no direct relationship here, the explanation will be omitted. On the other hand, materials such as Kovar and Tekken nickel alloy are used as materials for metal packages containing optical devices such as semiconductor lasers, and Copal is often used because the terminals need to be hermetically sealed by glass sealing. These alloys are susceptible to rust without plating, so the surface is usually gold-plated.

In addition, as another conventional structure, as shown in FIG. The same thing can be said when fixing the metal package 2 as shown in FIG. While being joined, the outer peripheral surface 32 of the metal tube 3 and the slide ring 6
The inner circumferential surface 62 of is welded in a spot shape at the welding portion 52, and the two are joined. This structure is necessary when the position of the tip of the optical fiber 4 must be adjusted not only in the direction perpendicular to the optical axis but also in the optical axis direction. Stainless steel, which does not require plating, is suitable as the material for the slide ring 6, considering the absorption rate of laser light on the surface of the component.

Furthermore, as shown in FIG. 6, a coupling lens 8 whose periphery is held by a metal holder 7 may be fixed to the metal package 2 containing the optical element 1 by welding. This coupling lens 8 is used to condense the light beam emitted from the metal package 2 and couple it to the original fiber 4. In the figure, a metal holder 7 for protecting this coupling lens 8 is shown.
and the flat surface 21 at the tip thereof, and are welded in a spot shape at the welding portion 53, thereby joining the two. Furthermore, in the same manner as in FIG. 5, a slide ring 6 is fixed to the flat surface 71 at the opposite end of the metal holder 7, and a metal tube 3 is fixed to the slide ring 6 by welding. In this case as well, stainless steel is suitable as the material for the slide ring 6 and the metal holder 7.

[Problem that the invention seeks to solve]

However, when optical components are assembled using these conventional techniques,
There are the following problems.

First, as shown in Figures 4 and 5, when two types of alloys are joined by laser welding, the plating and the underlying metal of the plating mix in addition to the two types of alloys at the weld, so the composition become different alloys. In this case, the composition tends to vary, which poses a problem in stabilizing the quality. In particular, when metals are joined by welding, cracks are likely to occur in the welded part, but this is greatly affected by the composition of the alloy produced and the impurities mixed in. Moreover, if cracks occur, the cracks will gradually progress over time, and there is a risk that the welded portion will eventually break, resulting in a reliability problem.

Furthermore, even if no cracks occur, since the coefficients of thermal expansion of the two types of alloys are different, there is a risk that stress will be generated in the welded part due to temperature changes, and the joint strength will deteriorate due to fatigue.

These problems are particularly dangerous when spot welding is performed such as laser welding.

In addition to such problems regarding reliability, there are also problems in terms of productivity. In particular, when extremely high precision is required for fixing the fibers as in the case of SMF-LD module, positional deviation may occur during welding and the coupling efficiency may decrease. In such a case, if the welded portion is disassembled, a protruding welding mark will remain on the flat surface 21, but if the protrusion is removed by polishing, the original flat surface can be restored. However, if this is done, the plating on the Senpo surface 21 will also be removed, which will cause rust, and if the reassembly is performed with the plating removed, the composition of the weld will be the same as when the plating is not removed. The composition will be different from that of K, and the quality will not be constant. Particular attention must be paid to the fact that if the part is plated with gold, the absorption rate of the laser beam on the surface of the part is low, so a high-output laser beam is required, and the above-mentioned If the plating is removed, there will obviously be a difference in the welding conditions. Considering these factors, productivity must be sacrificed in order to maintain constant quality.

Further, in FIG. 6, there are problems similar to those in FIGS. 4 and 5, but there are also the following problems.

That is, when supporting the lens 8 with the metal holder 7, a highly reliable method is to apply metallization to the side surface of the lens and fix the metallized portion to the metal holder with solder. However, although the coefficient of thermal expansion of the glass that is the material of the coupling lens depends on the type, it is generally around IC5 deg-”
There is a large difference between the S and power values, so if the lens is fixed in this way, the lens may crack (
(cracks) are likely to occur, which may cause deterioration of coupling efficiency.

When assembling an optical component in which a single optical element and a seven-eye optical device are combined by laser welding, there are several important problems.

An object of the present invention is to provide an optical fiber fixing structure that can be assembled by laser welding and has excellent productivity and reliability in the structure of an optical component in which an optical element and an optical fiber are optically coupled. be.

[Means for solving problems]

The structure of the present invention includes a metal package containing an optical element,
In an optical fiber fixing structure for fixing a tip attachment portion of a source fiber whose periphery is protected by a metal tube, the tip attachment portion of the optical fiber is made of stainless steel, and the metal package portion is joined to the tip attachment portion. is provided with a stainless steel ring, and the stainless steel ring and the stainless steel of the tip attachment portion are fixed by welding.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a vertical cross-sectional view showing an optical fiber fixing structure according to an embodiment of the present invention. In FIG. 4 is fixed by welding, the metal part 3 is made of stainless steel, and the metal package 2 is composed of a stainless steel ring 20 and other parts that are previously joined to each other. This metal cylinder 3 is fixed by spot welding at a welding portion 5 to a portion of the stainless steel ring 20 of the metal package 2. The stainless steel ring 20 is plated with gold and is previously bonded to the other parts of the metal package 2 at the bonding surface 21 using a high melting point solder.

The joining of this part is only a preliminary processing at the component stage, and is not performed after high-precision optical adjustment, so the joining work is extremely easy. Welding part 5
Prior to welding in , the plating in the horizontal direction 21 on the tip of the metal package 2 is removed by polishing in advance.
The material of the stainless steel ring 20 is manufactured by IT.

Due to this structure, all exposed parts of the metal material are stainless steel, so there is no risk of rust or corrosion, and the welded parts are welded with alloys of the same composition, so there is no risk of composition variation. , For the same reason, cracks are less likely to occur in the weld.

FIG. 2 is a longitudinal sectional view of a second embodiment of the optical fiber fixing structure of the present invention. In FIG. 0, the optical fiber 4 is fixed to the stainless steel ring 20 of the package 2 via the slide ring 6. However, although it is different from FIG. 1, it is obvious that the same effect as in FIG. 1 can be obtained.

FIG. 3 is a longitudinal sectional view of a third embodiment of the invention. In this figure, a coupling lens 8 whose periphery is held by a metal holder 7 is fixed to an optical element 1t and a built-in metal package 2 by welding. The metal holder 7 consists of a first stainless steel ring 20 and other parts that are joined together, and the metal holder 7 includes a second stainless steel ring foot that has been joined to each other in advance at a joining surface 75, a part 76 that holds the coupling lens 8, and a part 76 that holds the coupling lens 8. The second stainless steel ring 77 of the metal holder 7 is fixed to the first stainless steel ring 200 of the metal package 2 by spot welding at a welding portion 53. Prior to welding at this welding portion 53,
The plating on the flat surface 21 at the tip of the metal package 2 has been removed by polishing in advance, and the stainless steel ring 20
material is exposed.

It is obvious that the same effects as in the first embodiment can be obtained in this case as well, but there is also the effect that cracks occurring in the coupling lens 8 can be prevented. This is because the portion 76 holding the coupling lens 8 is not directly involved in laser welding, so the material can be freely selected so that the coefficient of thermal expansion closely matches that of the lens.

[Effects of the Invention] As explained above, the optical fiber fixing structure of the present invention has a structure in which an optical fiber whose periphery is protected by a metal tube is fixed to a metal package containing an element by welding. The tube is made of stainless steel, the metal package consists of a stainless steel ring and other parts that are joined together in advance, and the metal tube is welded and fixed to the stainless steel ring part of the metal package. Excellent performance and reliability.

In other words, ■Since all exposed metal parts are stainless steel, there is no risk of rust or corrosion.

■Since the welded parts are made of alloys of the same composition, there is no risk of compositional variations.

■For the same reason, cracks are less likely to occur in welded areas.

■Since parts with the same coefficient of thermal expansion are welded together, no stress is generated in the weld.

■Since there is no gold plating on the welded parts, the output of the laser beam can be small.

■Even if the welded part is disassembled, it can be easily repaired by polishing.

Effects such as this can be obtained.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 illustrate the first embodiment of the present invention. FIGS. 4 and 5 are longitudinal sectional views of the second and third embodiments. FIG. 6 is a longitudinal sectional view showing three examples of conventional fixing and groove construction of optical fibers and coupling lenses. 1... Optical element, 2... Metal package, 21... Flat surface at the tip of metal package 2,
20-...- Stainless steel ring, 22...
...Joint surface, 3...Metal cylinder, 31...
Outer peripheral surface of metal cylinder, 4... Optical fiber, 5.51
．． 52...Welded part, 6...Slide ring, 61...Flat follower surface at the tip of slide ring 6, 62...Inner circumference of slide ring 6 Face, 7.
...Metal holder, 71...Metal holder 7
flat surface at the tip of metal holder 7, 72...other flat surface at the tip of metal holder 7, 75...joint surface, 76...
... Portion that holds the coupling lens 8, 77...
Stainless steel ring, 8... Combining lens. Agent Patent Attorney Shinsei Uchihara 1 Father Kaya 2 Kaya 3 Figure φ Kaiei, 50 Teitsuzu

Claims (1)

[Scope of Claims] 1) In an optical fiber fixing structure in which a distal end attachment portion of an optical fiber whose periphery is protected by a metal tube is fixed to a metal package containing an optical element, the distal end attachment portion of the optical fiber is made of stainless steel. The metal package is made of steel, and a stainless steel ring is provided on the metal package portion joined to the tip attachment portion, and the stainless steel ring and the stainless steel of the tip attachment portion are fixed by welding. Optical fiber fixing structure. 2) The optical fiber fixing structure according to claim 1, wherein the optical fiber tip fixing part is a metal tube itself that protects the optical fiber. 3) The optical fiber fixing structure according to claim 1, wherein the optical fiber tip attachment part is a slide ring fixed to the tip of a metal tube of the optical fiber. 4) The optical fiber fixing structure according to claim 1, wherein the optical fiber tip attachment portion is a metal holder that holds a coupling lens provided at the tip of the optical fiber.