Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-04-13
2002-09-24
Ullah, Akim E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06456751
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of fiber optics, and more particularly to the field of optical signal switching, routing, and monitoring.
2. Description of Related Art
FIG. 1
is an illustration of an exemplary optical switching system
10
for practicing the invention. For example, optical switching system
10
may represent a 3-dimensional optical switching system. A 3-dimensional optical switching system allows for optical coupling between input fibers and output fibers in different planes using lens arrays and mirror arrays. The lens arrays and mirror arrays provide proper angle and position of light beams traveling from input fibers to output fibers. That is, a light beam must leave and enter a fiber in a direct, beam path.
Referring to
FIG. 1
, a generalized optical switching system
10
includes input fiber array
12
, first lens array
14
, first beam steering apparatus (e.g., Micro-Electro-Mechanical-System, or MEMS, mirror array)
16
, second beam steering apparatus (e.g., MEMS mirror array)
18
, second lens array
20
, and output fiber array
22
. System
10
might also include additional or different elements, such as apparatus
24
and
26
for controlling the mirror arrays
16
and
18
, respectively.
Input fiber array
12
provides a plurality of input optical fibers
28
for forming light beams
30
transmitted to (and through) first lens array
14
. First lens array
14
includes a plurality of optical lenses
32
, which are used to focus beams of light from each input optical fiber
28
to individual mirror devices
34
on mirror array
16
. Mirror devices
34
may be electronically, magnetically, or otherwise individually movable to control the beam path of each beam formed by the input optical fibers
28
.
Mirror device
34
may be a gimbaled mirror device having a rectangular, elliptical, circular, or other appropriate shape. The plurality of mirror devices
34
for mirror array
16
can pivot a reflective component thereof (not specifically shown in
FIG. 1
) to redirect or reflect light to varying mirror devices on second mirror array
18
. Second mirror array
18
also includes a plurality of mirror devices, similar to those described with regard to first mirror array
16
, which are used to redirect and reflect light beams to varying lenses
36
on second lens array
20
. second lens array
20
focuses beams of light from second mirror array
18
t o individual output fibers
38
of output fiber array
22
.
Optical switching system
10
allows light beams from any input fiber
28
of input fiber array
12
to be redirected t o any output fiber
38
of output fiber array
22
. The above arrangement, including mirror arrays
16
,
18
may also be used in scanning systems, printing systems, display systems, and other systems that require redirecting beams
20
of light.
It should be noted that for each input optical fiber
28
there is an associated mirror device (such as mirror de vice
34
) on mirror array
16
, and for each output optical fiber
38
there is an associated mirror device on mirror array
18
. In general, there will be a minimum of two input optical fibers and two output optical fibers, and correspondingly two mirrors on each of arrays
16
and
18
. There need not be an identical number of input and output optical fibers, although this is typically the case. Also, there will typically be more than two such input and output optical fibers.
In general, many types of beam steering arrangements will lend themselves to use with the present invention. For example, two mirror arrays
16
,
18
are shown in FIG.
1
. Good coupling of a beam into an output optical fiber typically requires controlling fiber position and angle in two dimensions, in addition to the two dimensions of mirror rotation. So, four degrees of freedom are required. However, in some instances, few or greater degrees of freedom may suffice. For example, a one-mirror array shown
FIG. 2
, where a single mirror array
42
controlled by apparatus
44
is used for directing the beams, or a three or more mirror array arrangement (not shown) may be appropriate. Also, while the above description has been in terms of reflective beam steering, other types of beam steering, such as refractive or diffractive beam steering may employ the present invention with equal advantage (although not otherwise discussed in detail herein).
Coupling a light beam from an input optical fiber to an output optical fiber requires that the mirrors of mirror arrays
16
,
18
be angularly controlled, and that the mirror angles be precise. Such precision, and a degree of control thereover, is needed to optimize output optical power. To obtain such precise positioning, one can either employ or not employ knowledge of actual mirror angle. One method to determine the mirror angles is to add structures to the mirrors that indicate the angle of mirror rotation. One example of this is torsion sensors attached to suspension elements associated with each mirror. See, for example, U.S. Pat. No. 6,044,705. This approach has several disadvantages, including a relatively large number of required interconnections, added processing and manufacturing steps, greater risk of yield losses, etc.
BRIEF SUMMARY OF THE INVENTION
The present invention recognizes the limitations of direct measurement of mirror position, and presents an alternative technique for allowing optimization of output optical power. Our approach is to use an optical signal incident on each mirror to determine the mirror's angle. According to one embodiment, the output optical power is measured, for example at each output optical fiber, and compared with either the input optical power or a reference value, and based on the results of the comparison, a mirror or mirrors are rotated, and output power measured again. This process is referred to herein as feedback stabilization control of mirror position. According to another embodiment, this may be an iterative process, to allow narrowing in on a desired mirror angle for loss optimized output optical power.
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patent:
Bowers John Edward
Helkey Roger Jonathon
Blakley Sokoloff Taylor & Zafman LLP
Calient Networks, Inc.
Ullah Akim E.
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