Method for attaching and adjusting the end section of a glass fiber

A method for the attachment and adjustment of a glass fiber end section in which a single monomode glass fiber end section--within a protective housing in the optical active direction of an opto-electronic component (3), such as a GaAs-laser (3) is precisely adjusted and attached toward the optically active area or spot (4) of the laser whereby in a first step, the end section (1) is attached to a support (2) within the protective housing by cementing or soldering and that the axis of the end section (1) is held in the active direction by the support (2) and is provisionally directed at the active spot (4), and subsequently, in a second step, the end section (1) is precisely aligned with the active area or spot (4) through deformation of the support. Prior to the second step or during the first step or prior to the first step, the support (2), which is formed of a solid base (2) of ductile metal such as copper, tin solder or indium solder in a strong, very stiff construction on a common metal block (5) is mechanically coupled with its footing (10) to the laser (3) at a spacing of less than 5 mm from the component (3), and--the base (2) is deformed, through squeezing, in the second step.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
This present invention relates to a single mode glass fiber attachment 
within a protective housing. 
2. Description of the Prior Art 
Methods of the prior art are already known in German patents DE-A1 No. 34 
31 775 and DE-A1 No. 34 05 838 where not the support body, however, but a 
ductile intermediate element is deformed, in order to achieve the final 
precise adjustment. Both of these prior art procedures, however, 
involve--moreover highly complicated forms of--attachment arrangements, 
which still show considerable sensitivity to temperature variations after 
final adjustment, through which recurring, more or less substantial, 
adjustment shifts occur from time to time, which can result in significant 
malfunctions during operation. 
Especially, if the component is not simply a photodiode but rather is a 
semiconductor laser, the precision required for the adjustment of the 
distance of the point, the taper, of the end section from the active area 
or spot of the component is generally much lower than the precision of the 
adjustment perpendicular thereto, thus, than the precision of the 
adjustment perpendicular to the axial direction of the end section. For 
example, the point of the end section of a single mode glass fiber must 
often be positioned to an accuracy of .+-.0.1 .mu.m perpendicular to the 
axial direction, when however, the attachment of the end section, e.g. the 
soldering or cementing, is usually much too greatly distorted again during 
hardening and the adjustment achieved prior to hardening, is thereby again 
disturbed. 
This is disclosed in the pending US patent application U.S. Ser. No. 
704,332, filed Feb. 22, 1985, now U.S. Pat. No. 4,707,067, and in U.S. 
Ser. No. 659,892, filed Oct. 11, 1984, now U.S. Pat. No. 4,707,066. 
Additional similar prior art is known, for example: GB-A No. 2,146,841; 
U.S. Pat. Nos. 4,456,334; 4,296,998; 4,217,559; 4,064,203; 3,826,998; JP-A 
No. 57-100 781 [Vol. No. 189 (E-133) (1067) Sept. 28, 1982] as well as 
CA-A 1,108,900. 
SUMMARY OF THE INVENTION 
The highly precise adjustment of the point of the end section perpendicular 
to the axial direction of the attached glass fibers with high precision, 
for example to an accuracy of 0.1 .mu.m substantially independent of 
temperature and the attainment of this adjustment at especially low cost 
is the primary object of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The example shown in the figures relates to a detail within a special 
module for a glass fiber communications system. Within the protective 
housing of this module--not itself shown--a glass fiber end section is 
attached on a metal block 5 representing a support 5, the glass fiber 
being attached by means of the method according to the invention, in the 
optically active direction of an opto-electronic component 3, such as a 
GaAs-laser 3, for example. The metal block temperature may be stabilized 
by means of a PTC resistor--not shown. The end section 1, is precisely 
adjusted on the optically active area or spot 4 of this component 3. A 
groove may be formed in the uper surface of the block 5, see FIG. 1, which 
can facilitate the precise positioning of the component 3 during quantity 
production. 
In a first step, the end section 1 within the protective housing, was so 
soldered to a solid base 2 on the support 5, that the axis of the end 
section 1, held in the active direction by the base 2, is provisionally 
directed more or less at the active area or spot 4, during soldering. 
During this step the base 2 was a solid base 2, itself consisting of 
ductile material ie. of solder upon the metal block 5. The base 2, 
therefore, had a very compact, stiff, stumpy construction whereby it was 
mechanically very rigidly coupled with the laser 3, on the common metal 
block 5, through its footing 10, with a 2 mm gap, for example, from the 
laser 3. Thereafter, in a second step, the end section 1 was precisely 
adjusted to the active area or spot 4 by cold deformation i.e. by 
squeezing of the solidified solder drop 2. 
Through the invention therefore, the support 2, i.e. the solder drop 2 
itself, and not some intermediate ductile element was deformed in order to 
achieve the final precise adjustment. The arrangement illustrated produced 
in accordance with the invention, is therefor substantially insensitive in 
its response to temperature excursions after final adjustment, as a 
result, almost no temperature dependent adjustment shifts of the end 
section occur. 
Thereby, through the invention, the precision of adjustment of the point of 
the end section 1, perpendicular to the axial direction of the end section 
1 can be held to an accuracy of .+-.0.1 .mu.m by squeezing, whereby the 
fabrication of the base 2, as well as the squeezing requires especially 
little expense and is thus especially well suited to the quantity 
production of such modules. 
Moreover, in accordance with the invention, it is especially simple to 
adjust the axial direction at will, upward, downward or sideways i.e. to 
the left and to the right: It is possible to deform this ductile base 2, 
e.g. through squeezing at the deformation points 11 and/or 12 between the 
end section 1 and the footing 10, whereby the axial direction is forced 
either sideways relative to FIG. 2, and/or upward, or in the direction of 
the location 14. If the pedestal 2 is thereby squeezed on one side only 
i.e. at the deformation point 12 for example, the axial direction is 
forced primarily in a sidewise direction, or in the direction of the 
location 11 for example, or primarily in an upward direction, i.e. in the 
direction of the location 14, depending on the position of the deformation 
point. If instead the base 2 is squeezed from both sides simultaneously, 
i.e. at locations 11 and 12 by means of the cutting edges 7/8 of a pair of 
tongs, the axial direction is essentially forced upward ie. away from the 
base toward the location 14. 
The displacement, occurring between the first and second step, of the 
provisional adjustment produced by the first step, is smaller if the base 
completely surrounds the end section, as shown in the Figures. The base 
need then be less severely deformed during the second step. 
The axial direction may, at will, be forced downward i.e. in the direction 
of the footing 10, if the base 2 is deformed on its side 14, opposite the 
footing 10, i.e. squeezed on top with a die 9. 
A substantial, purely sidewise pressing of the axial direction toward the 
left or right is achieved when the base 2 is squeezed adjacent to the 
glass fiber 1 at an outer surface, such as with reference to location 13, 
of the base 2, that is more or less perpendicular to the footing 10. 
The final adjustment will be especially precise if the base 2 is squeezed 
in a number of successive iterative steps, i.e. as required iteratively in 
a chosen series, at location 11, 12, 13 and/or 14, for example, until the 
adjustment is finally optimum, as can be measured by the optical coupling 
achieved between the component 3 and the glass fiber 1. 
Finally, the formed base 2 can be covered with a hardenable protective 
coating 6, in order to protect the base 2, and thereby the adjustment 
against chemical environmental effects, and in order to stabilize it 
mechanically. 
The base 2 may be formed by solder, e.g. tin solder or indium solder, as 
well as a drop of copper to which the fiber end section is attached e.g. 
by cement or solder. In particular, indium solder has the advantage that 
such a base 2 formed by indium solder and shaped by squeezing, precisely 
will keep its shape for a very long period of time, and that such a base 2 
may be produced easier than a copper base 2, to which the fiber end 
section has to be attached.