Optical waveguides – With optical coupler
Reexamination Certificate
1998-10-06
2001-03-20
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With optical coupler
C385S050000, C385S052000, C385S088000, C385S090000, C385S093000
Reexamination Certificate
active
06205266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to photonics assemblies, and more specifically to a monolithically integrated alignment photonics assembly for actively coupling optical energy between optical devices.
2. Description of the Prior Art
Compact and simple photonics systems are essential in optical communication applications. Photonics systems require high light transmission efficiencies in order to obtain low error rates. The transmission efficiency is measured as insertion loss for photonics applications and becomes more important for photonics systems working at high data transmission rates. The high data transmission (high bandwidth) rates require the use of single mode and polarization maintaining fiber optics where optical alignment from fiber to fiber, transmitter to fiber, transmitter to modulator, transmitter to multiplexer and fiber to receiver becomes critical to minimizing insertion loss. Optical alignment requirements for single mode fibers are at micron and sub-micron levels as opposed to supermicron levels for lower bandwidth multimode fibers. Optical alignment methods are near the limit of improvement using conventional alignment techniques. For example, single mode fiber connectors using actively aligned ferrules, like that described in the publication “Packaging Technology for a 10-Gb/a Photoreceiver Module”, by Oikawa et al., Journal of Lightwave Technology Vol. 12 No. 2 pp.343-352, February 1994, are typically limited to 0.2 dB insertion loss. The Okiwawa publication discloses an optical coupling system, illustrated in
FIG. 1
, containing a slant-ended fiber
46
secured in a fiber ferrule
48
where the fiber ferrule
48
is welded to a side wall
50
of a flat package
52
and a microlens
54
is monolithically fabricated on a photodiode
56
where the photodiode
56
is flip-chip bonded to the flat package
52
. An optical signal
58
enters horizontally and is reflected vertically at the fiber's
46
slant-edge. The microlens
54
then focuses the optical signal
58
on the photodiode's
56
photosensitive area.
As described in the Oikwawa publication, maintaining alignment between the fiber and the photodiode chip is essential for optimal coupling of the optical signal. Misalignment can occur as a result of mechanical stress to the fiber ferrule or thermal fluctuations of the entire system. In an attempt to overcome these factors, complex assembly and fabrication techniques are used. The fiber attachment is a complex ferrule attachment which seeks to optimize the mechanical strength of the attachment and therefore minimize the effects of fiber displacement. Finally, in order to provide a high optical coupling efficiency wide misalignment tolerances must be built in to the photodiode chip during fabrication to compensate for both displacement by the fiber attachment and deformation by temperature fluctuation.
Disclosed in U.S. Pat. No. 5,346,583 is an active alignment system for laser to fiber coupling, as illustrated in FIG.
2
. The '583 patent attempts to minimize optical coupling losses by actively coupling optical energy between a source and a transmission medium. A laser
11
directs a beam
10
in the direction of a first mirror
13
and from the first mirror
13
the beam
10
is reflected to a second mirror
17
where the beam
10
is again reflected. The two mirrors are mounted on flexure elements and the flexure elements each have the capability to adjust the beam
10
in one dimension. The beam direction which is determined by the two mirrors
13
and
17
is focused by a lens
18
onto an input aperture for a waveguide contained within a modulator
20
. The modulator
20
splits the beam
10
into two output beams. The two output beams are coupled at a lens
22
and focused onto a pair of fiberoptic fibers
43
and
44
. Fibers
43
and
44
are each connected to electromechanical transducers
23
and
24
respectively, where the transducers have the ability to adjust the input ends of the fibers
43
and
44
in two dimensions. The active adjustment of both the mirrors (
13
and
17
) and the fibers (
43
and
44
) is accomplished by a controller
27
. The controller
27
receives as input an indication of the amount of light passing through the fibers
43
and
44
from receivers
38
and
39
and supplies corrective feedback to the mirrors (
13
and
17
) and the fibers (
43
and
44
).
As discussed, present optical coupling systems use a variety of coupling schemes to obtain efficient coupling within photonics applications. However, many of these schemes use static components which are typically made of different materials and have different thermal expansion coefficients. These differences can cause optical misalignment during temperature changes, which are common in space applications. Photonics systems which are disclosed in the art and attempt to overcome misalignment problems by using active alignment control feedback techniques, typically use discrete bulk optical components and the complexity of the assembly process is increased. The greater the complexity the more assembly costs are increased and reliability decreased.
Based on techniques known in the art for photonics coupling schemes, a monolithic alignment assembly for active alignment of an optical fiber core to an optical device is highly desirable.
SUMMARY OF THE INVENTION
It is an aspect of the present invention to provide an active alignment photonics assembly. Briefly, the photonics assembly includes a fiber optic means for carrying an optical signal and, a first optical element spaced from the fiber optic means and having an input means for accepting the optical signal. Optionally, the photonics assembly may provide a second optical element having an optical coupling means, the second optical element being disposed in an optical signal path between the fiber optic means and the first optical element. To maintain the alignment of the photonics assembly, a sensing element is provided having a means for determining the power of the optical signal at the first optical element and producing a status signal in response thereto. A controller is provided having a means for receiving the status signal and distributing a correction signal and an adjusting means for receiving the correction signal and adjusting the path of the optical signal in response to the correction signal. The adjusting means comprises at least one servo-mechanism controlled microactuator capable of adjusting the fiber optic means, the second optical element, or both simultaneously.
It is also an aspect of the present invention to provide an active alignment photonics assembly. Briefly, the photonics assembly includes a fiber optic means for carrying an optical signal, a first optical element spaced from the fiber optic means and having an input means for accepting the optical signal. Optionally, the photonics assembly may provide a third optical element having an optical coupling means, the third optical element being disposed in an optical signal path between the fiber optic means and the first optical element. To maintain the alignment of the photonics assembly, a second optical element is provided spaced from the fiber optical means and having an input means for accepting the divergent power of the optical signal. Further, a sensing element is provided having a means for determining the divergent power of the optical signal at the second optical element and producing a status signal in response thereto. A controller is provided having a means for receiving the status signal and distributing a correction signal and an adjusting means for receiving the correction signal and adjusting the path of the optical signal in response to the correction signal. The adjusting means comprises at least one servo-mechanism controlled microactuator capable of adjusting the fiber optic means, the third optical element, or both simultaneously.
REFERENCES:
patent: 3959729 (1976-05-01), Marchetti
patent: 4452506 (1984-06-01), Reeve et al.
patent: 44
Hirschberg Alan M.
Palen Edward J.
Pak Sung
Sanghavi Hemang
TRW Inc.
Yastsko Michael S.
LandOfFree
Active alignment photonics assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Active alignment photonics assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Active alignment photonics assembly will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2477468