Laser aided tilt adjustment of an optical lens

Details Laser aided tilt adjustment of an optical lens Laser aided tilt adjustment of an optical lens

1999-09-30

2001-09-11

Chang, Audrey (Department: 2872)

Optical waveguides

With optical coupler

Input/output coupler

C385S031000, C385S047000, C385S052000, C219S121650, C219S121660, C219S121790, C219S121820

Reexamination Certificate

active

06289153

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of fiber optics, and in particular, to a method and apparatus for altering a mirror orientation in a fiber optic device.
DESCRIPTION OF THE RELATED ART
Fiber optics have become increasingly popular in the field of telecommunications in recent years. This is in part because significantly more information can be transmitted using fiber optic lines than traditional telecommunications lines.
In the field of fiber optics there is often a need to have a reflective path that couples light from an input wave guide to an output wave guide. In most cases, the input and output wave guides are optical fibers. In such a case, the input fiber and output fiber are typically coupled together so that they are substantially parallel to one another. This is known in the art as a “dual termination” fiber optic wave guide.
An exemplary optical apparatus
5
and dual termination fiber optic wave guide
10
are shown in FIG.
1
. The dual termination wave guide
10
includes a pair of fibers
11
,
12
that are placed in a common ferrule (not shown) so that their center-to-center spacing is fixed. If, in construction, the ferrule is moved to align the fibers
11
,
12
, both fibers are moved as a unit. Alternatively, the dual termination wave guide
10
may simply be the end of a PLC (Planar Light guide Circuit) where two lithographically defined optical wave guides terminate; again alignment steps can only move both wave guides en masse.
In
FIG. 1
the wave guide
10
supplies light that diverges from the end of the fiber
11
of the guide as it approaches a lens
20
; this diverging beam is labeled “incident beam”. With proper spacing of the lens
20
from the dual termination wave guide
10
, the incident beam is collimated into a beam that has a constant cross-section along it length (ignoring diffraction effects). This collimated beam impinges upon a mirror
30
disposed on an opposite side of the lens
20
. The mirror
30
reflects the collimated beam back towards the lens
20
; this beam is labeled “reflected beam”. It should be noted that a portion of the collimated beam which impinges upon the mirror
30
may not be reflected, but is transmitted to the other side of the mirror
30
; this beam is labeled the “transmitted beam”. The reflected beam is again collimated as it is returned to the lens
20
. The lens
20
focuses the reflected beam to an end face of the fiber
12
of the dual termination wave guide
10
. Thus, for a perfectly aligned system, a perfect 100% reflectivity mirror component, and a perfect lens, it is possible to attain perfect optical coupling between the top
11
and bottom
12
fibers of the dual termination wave guide
10
.
The mirror
30
may, in practice, include a beam-splitting coating and/or a
13
) wavelength dependent coating applied to one or the other face of a transparent substrate. Good practice dictates that the other face (if light is intended to pass through it) be Anti Reflection (AR) coated and that the transparent substrate be slightly wedged to further reduce the possibility of Fabry-Perot interference effects.
The lens
20
shown in
FIG. 1
is shown only in a schematic representation. It may be asymmetric, such as plano-convex, it may be aspherical, or it may use gradient index techniques such as a GRIN (GRadient INdex) lens. The lens
20
may even include more than one element. Obviously, the main requirement is that it does an excellent job inter-converting the divergent beams associated with the free space propagation of light at the ends of the optical fibers
11
,
12
with the collimated beams.
FIG. 2
shows an alternate fiber optic apparatus
5
′ in which a mirror
30
′ is used for combining an “expanded beam” with a “beam to be combined”. Alternatively, in
FIG. 1
, the mirror component
30
was used to split the “incident” beam into a “reflected” beam and a collimated “transmitted” beam.
The positioning requirements are the same for the apparatus
5
,
5
′ shown in
FIGS. 1 and 2
respectively, in that the dual termination wave guides
10
,
10
′ are on the opposite side of the lens
20
,
20
′ from the mirror
30
,
30
′. The relative positioning is quite demanding because beams must be coupled between the ends of the two fibers
11
,
12
. “Passive positioning” occurs where the three optical components (i.e. dual termination wave guide, lens, and mirror) are all placed in their positions by mechanical registration. The optical components are then automatically held in the proper relationship. “Active positioning” is the alignment of parts while they are being monitored optically for performance. When the requisite performance is found, the parts are fixed relative to one another. This fixing is usually done by laser welding, soldering, or epoxy. Usually one uses “active positioning” instead of “passive positioning” because the optical positioning requirements are too exacting for the variations in the mechanical piece parts.
FIG. 3
shows an “active” alignment of the optical apparatus
5
of FIG.
1
. The active alignment may be accomplished by tilting the mirror
30
to compensate for small Hoffsets (i.e. “lateral offset” in
FIG. 3
) of the dual termination waveguide
10
. In
FIG. 3
, the fibers
11
,
12
have been moved upwards by a specified “lateral offset” amount. If the mirror
30
were to remain in the position shown in
FIG. 1
, the degree of optical coupling between the first
11
and second
12
fibers would be decreased due to the misalignment. In order to realign the apparatus
5
, the mirror
30
is tilted, because the fibers
11
,
12
are now fixed in position. The degree of optical coupling between the first
11
and second
12
fibers may be measured as the mirror
30
is tilted to attain the optimal tilt angle with respect to the “lateral offset” of the fibers. In the production of an apparatus such as
5
or
5
′, one could initiate “passive” positioning of the dual termination wave guide
10
relative to the lens
20
, followed by “active” tilt alignment of the mirror
30
. Yet another variation in production techniques might be to use “active” alignment of the dual termination waveguide
10
and mirror tilt simultaneously.
However, the following problem persists: after fixing the positions of the parts by laser welding, solder, or curing epoxy, because of thermal expansion and/or contraction, uneven shrinkage of adhesive or otherwise, good alignment of the waveguide, lens and mirror may not be achieved or maintained.
Thus, there is currently a need for an improved method and apparatus for compensating for variations in the position of a waveguide due to slight movements of the waveguide.
SUMMARY OF THE INVENTION
The present invention involves an apparatus including an optical wave guide including at least one optical fiber, a retaining structure, said retaining structure having at least one lens disposed therein, and a mirror. The optical wave guide is coupled to a first end of the retaining structure and the mirror is coupled to a second end of the retaining structure.
The present invention also involves a method for altering the orientation of the mirror of the fiber optic assembly, including the steps of: illuminating a portion of a mirror retainer structure which holds the mirror until said portion partially melts, and removing illumination from the portion of the mirror retainer structure.
The above and other advantages and features of the present invention will be better understood from the following detailed description of the preferred embodiments of the invention which is provided in connection with the accompanying drawings.


REFERENCES:
patent: 4208094 (1980-06-01), Tomlinson, III
patent: 4569569 (1986-02-01), Stewart
patent: 5381494 (1995-01-01), O'Donnell
patent: 5729377 (1998-03-01), Bergmann
patent: 6122420 (2000-09-01), Satoh

Affiliated with

Also associated with

Rating

Laser aided tilt adjustment of an optical lens does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Laser aided tilt adjustment of an optical lens, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laser aided tilt adjustment of an optical lens will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2497094