Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1999-06-10
2001-06-26
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S027000, C385S034000
Reexamination Certificate
active
06253005
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to fiber optics and, more particularly, to an apparatus and method for compensating for shift in alignment of optical components after assembly of the optical package.
2. Description of the Related Art
The current explosion in the use of fiber optic technology in telecommunications and data processing is well documented. With this phenomenal technological growth, a wide variety of optical devices have become available. Interconnecting these optical devices, however, has remained a daunting task as such devices require extremely precise mechanical alignment. This problem is most severe for reflective applications, since the error in alignment cannot be greater than a micron.
One available form of optical packaging requires the mounting of optical components in separate metal holders. For example, fiber terminations are mounted in one metal holder and a focusing device such, for example, as Graded Index (GRIN) or conventional lens is mounted in another metal holder; additional optical components are mounted in still further metal holders. The optical components in these different metal holders are optically aligned by sliding the metal holders relative to each other. When proper alignment is achieved, the holders are typically laser-welded together so as to fix the alignment positions of these optical components.
FIG. 1
shows a typical prior art optical package
10
for reflective applications. The package has a dual fiber termination
12
disposed at one end of the package at which the upper fiber
14
is configured as an input to the package and the lower fiber
16
is configured as an output. As shown, the optical signal emitted from the upper fiber
14
is collimated by a double convex lens
18
and directed onto a mirror
20
. The mirror
20
reflects the collimated beam back toward the convex lens
18
which then converges the collimated beam onto the lower fiber
16
.
The termination
12
, and collimating lens
18
and mirror
20
are disposed in separate metal holders
21
; the metal holders
21
are laser welded together once the optical components have been optically aligned. Due to mechanical forces arising from the welding process, these optical components, even if perfectly aligned prior to welding, will often experience “post-weld shift,” i.e. changes in the relative positions of the metal holders, and thus the components, after welding. Such “post-weld shift” may be in the order of 1 &mgr;M or more, depending on various parameters such as the coefficients of thermal expansion of the metal holders and the geometry and arrangement of the weld zones. Although post-weld shift may be acceptable for transmission applications, the shift could be extremely detrimental in reflective applications as it causes unacceptably high optical losses.
For example, a shift of 1 &mgr;M between the dual fiber termination
12
and the center of lens
18
in the vertical direction in
FIG. 1
will cause the reflected beam to converge at a point 1 &mgr;M below the original position of the lower fiber
16
. Since the lower fiber
16
has been vertically displaced 1 &mgr;M from its original position, the reflected beam will miss the intended target, i.e. the center of the lower fiber
16
, by as much as 2 &mgr;M. Such misalignment will seriously degrade the performance of the optical package and thus render it unfit for use.
Thus, there is a critical need for an optical package having the ability to compensate for post-weld shifts of optical components.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an apparatus and method for compensating for shift in the alignment of optical components in an optical package.
A particular advantage of the present invention is that post-assembly shifts in alignment between a fiber termination and a collimating lens can be adjusted by a compensation lens disposed between the collimating lens and a reflecting mirror.
In accordance with an embodiment of the invention, an optical package includes a dual fiber termination having a first optical fiber end portion and a second optical fiber end portion. A collimating lens, spaced from the dual fiber termination, is configured for collimating and transmitting an optical signal from the first optical fiber end portion and for converging another optical signal onto the second optical fiber end portion. A mirror spaced from the collimating lens and having a reflective layer is configured and oriented for reflecting at least a portion of the optical signal from the collimating lens toward the second optical fiber end portion along a propagation path. A compensation lens is disposed between the collimating lens and the reflective layer of the mirror for correcting optical misalignment between the dual fiber termination and the collimating lens. The compensation lens is selectively movable in a direction transverse to the optical axis of the collimating lens and is configured for deflecting the optical signal from the collimating lens so that selective transverse movement of the compensation lens adjusts the propagation path of the reflected optical signal to assure that the second optical fiber end portion receives the reflected optical signal without significant optical loss.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.
REFERENCES:
patent: 4364639 (1982-12-01), Sinclair et al.
patent: 5143435 (1992-09-01), Kikuchi
patent: 5703992 (1997-12-01), Bergmann
patent: 5790314 (1998-08-01), Duck et al.
patent: 5991058 (1999-11-01), Feuer et al.
Bergmann Ernest Eisenhardt
Derkits, Jr. Gustav Edward
Agere Systems Optoelectronics Guardian Corp.
Bovernick Rodney
Cohen, Pontani, Lieberman & Pavne
Kim Ellen E.
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