Optical fiber fusion splicer

Details Optical fiber fusion splicer Optical fiber fusion splicer

2001-06-18

2002-10-22

Nguyen, Khiem (Department: 2839)

Optical waveguides

With splice

Fusion splicing

C385S134000

Reexamination Certificate

active

06467973

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber fusion splicer that axially aligns optical fibers by clamping with a V-shaped groove, and more particularly, to an optical fiber fusion splicer that enables reliable end alignment of the optical fibers without allowing their axial centers to shift from the proper position even if the outer diameters of the optical fibers and jackets change.
2. Description of the Related Art
FIG. 3
schematically illustrates an optical fiber fusion splicer of the prior art in which the end aligned portions of optical fiber cores are observed from the side by clamping the jackets of optical fiber cores in a V-shaped groove. In
FIG. 3
, jackets
32
of left and right optical fiber cores
30
are respectively clamped between the a V-shaped groove of a V-shaped groove base
34
and a clamp
36
. Axial alignment of the optical fiber cores
30
is performed using an observation means having bi-directional image observation optical axes A that combine a microscope
40
and a TV camera
42
by observing the end aligned portions
44
of the cores on a monitor
46
, processing observation information from the two directions with a processor
48
, transmitting the output signal to a movement mechanism (not shown) of the V-shaped groove bases
34
, moving the V-shaped groove bases
34
to axially align with the two-dimensional X and Y directions at a right angle to the axis of the optical fiber cores
30
, advancing in the direction of the cores (Z direction) and then generating an electrical discharge to fuse and splice the cores. In this optical fiber fusion splicer, when the optical fibers are placed in the V-shaped grooves of the V-shaped groove base
34
, the height of the V-shaped groove bases
34
is adjusted so that the axis in the direction of the cores of the optical fibers is located in the vicinity of the proper position between electrodes
50
of electrical discharge for optimum fusing of the optical fibers. Moreover, in the case of observing images from two directions, the optical fibers are placed so that the intersection of the image observation optical axes A in two directions is located at the above proper position between the electrodes
50
.
FIGS. 4A and 4B
show the relationship between the electrodes
50
and the image observation optical axes A when the jacket
32
is placed in the V-shaped groove
34
a
of the V-shaped groove base
34
.
FIG. 4A
indicates the case of a sheath diameter of 250 &mgr;m, while
FIG. 4B
indicates the case of a sheath diameter of 400 &mgr;m. In
FIG. 4A
, a center point O, which is the intersection of image observation optical axes A, is set at the proper electrical discharge position between two stationary electrodes
50
, and if the optical fiber core
30
having a sheath diameter of 250 &mgr;m is placed on the V-shaped groove base
34
exclusively for use with a sheath diameter of 250 &mgr;m and having the V-shaped groove
34
a
formed therein so that the center of the core
30
coincides with the proper electrical discharge position and the center point O of the image observation optical axes, the image of the end aligned portion
44
can be captured without shifting from the proper position between the electrodes
50
or from the image observation optical axes A in two directions.
When an optical fiber core
30
′ having a sheath diameter of 400 &mgr;m is placed in the V-shaped groove base
34
in this state, as indicated with the broken lines in
FIG. 4A
, the center position of the optical fiber core
30
′ moves upward by a height corresponding to the difference in sheath thickness of 75 &mgr;m from the center position
0
of the optical fiber core
30
having a sheath thickness of 250 &mgr;m. This height is equal to 75×{square root over (2)}=106 &mgr;m in the case the angle formed between the slanted surface of the V-shaped groove
34
a
in contact with the optical fiber core
30
of the V-shaped groove base
34
and the upper and lower directions of the V-shaped groove
34
a
is 45 degrees.
Therefore, although it is necessary to move the V-shaped groove base
34
downward by the amount of this height in order to return this center position to the proper electrical discharge position, in the case of the X and Y direction movement mechanism of the V-shaped groove base
34
of the fusion splicer of the prior art, such movement in the vertical direction was difficult for the reasons described below.
FIGS. 5A and 5B
are drawings of the left and right V-shaped groove bases
34
of a fusion splicer of the prior art as viewed from direction B in FIG.
3
. As shown in
FIGS. 5A and 5B
, a V-shaped groove movement mechanism is placed so as to be able to move in two directions of movement of X and Y that are respectively perpendicular to each of the two directions of the image observation optical axes A so that observation images are not shifted out of focus due to the movement of the V-shaped groove
34
a.
On the other hand, the two directions of the image observation optical axes A are set so as to be mutually perpendicular to facilitate coordinate conversion during image processing, and the two directions of the image observation optical axes A normally coincide with axial directions X and Y at a right angle which form a 45 degree angle with the vertical direction of the V-shaped groove
34
a
as shown in FIG.
3
. Moreover, the movement mechanism of the left and right V-shaped grooves
34
a
in which left and right optical fiber cores
30
are respectively placed is normally composed so as to only allow movement in one mutually different direction of movement of the above two directions of movement in order to simplify the drive mechanism.
Thus, since the left and right V-shaped grooves
34
a
are only able to move in one direction that forms a right angle to the left and right in a direction that forms a 45 degree angle with the vertical direction of the V-shaped grooves
34
a
, it was difficult to move the left and right optical fiber cores equally in the vertical direction. In addition, in a device equipped only with this type of centering mechanism, it was not possible to correct shifts in the proper electrical discharge position or observation optical axes of 10 &mgr;m or more.
In addition, even if the V-shaped groove movement mechanism is not that which only allows movement in one direction for each side of the left and right V-shaped grooves
34
a
, since the purpose of the movement mechanism is to adjust slight axial shifts of the left and right optical fibers, the distance range over which movement is possible is limited by the movement resolution (on the order of 0.1 &mgr;m or less). Since such a mechanism makes movement of several tens of &mgr;m or more difficult, movement of several tens of &mgr;m or more due to differences in sheath thickness in the vertical direction of the V-shaped groove surface was difficult.
Thus, during optical fiber core
30
′ having a sheath diameter of 400 &mgr;m, it was necessary to either replace the V-shaped groove bases
34
with V-shaped groove bases
34
′ in which deeper V-shaped grooves
34
a′
are formed, or move the electrode rods and image observation system in the vertical direction.
However, a material such as ceramics that allows high-precision machining was used for the V-shaped groove bases
34
,
34
′ based on its role of maintaining parallelism and so forth. Thus, the providing of multiple V-shaped groove bases to match variations in sheath diameter was expensive. Moreover, the work involved in replacing the V-shaped groove base
34
required a high level of accuracy, and required an extremely delicate procedure. In addition, although another method for aligning the center of an optical fiber core at the proper electrical discharge position between two electrodes
50
without replacing the V-shaped groove base
34
is known in the prior art in which the electrodes and image observation optical axes are simultaneously moved up and down until th

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