Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-11-17
2002-06-18
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S017000
Reexamination Certificate
active
06408113
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application Serial No. 89107669, filed Apr. 24, 2000.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a switch structure. More particularly, the present invention relates to an optical switch structure.
2. Description of Related Art
In opto-electronic communication, an optical switch that employs a micro-electromechanical system (MEMS) has become an important component for relaying optical signals. A conventional optical switch has a one-to-one crossbar configuration.
FIG. 1
is a schematic layout of the mirrors inside a conventional one-to-one crossbar optical switch.
As shown in
FIG. 1
, the optical switch
10
, such as 4-by-4 optical switch, consists of a set of
16
reflecting mirrors S
ij
arranged into a 4-by-4 matrix configuration where i and j are integers that range from 1 to 4 respectively. An incident beam enters the optical switch from the left in one of the four input optical paths I
1
, I
2
, I
3
and I
4
. After an internal reflection takes place somewhere inside the optical switch, the incident beam leaves the optical switch
10
from the bottom out of one of the four output optical paths O
1
, O
2
, O
3
and O
4
. All the reflecting mirrors S
ij
can be individually raised or lowered. If the reflecting mirror S
ll
is raised while all the other mirrors are lowered, the incident beam that enters the optical switch
10
through input optical path I
1
will leave via output optical path O
1
. Similarly, the incident light beam from the optical path I
1
can be redirected to output optical paths O
2
, O
3
and O
4
by raising the mirrors S
12
, S
13
and S
14
while lowering the other mirrors, respectively. To carry out optical switching, such as redirecting the incident beam from input optical path I
3
to output optical path O
4
, the reflecting mirror S
34
can be raised while all the other mirrors, including S
31
, S
32
, S
33
and S
44
, are all lowered.
The raising and lowering of reflecting mirrors S
ij
is normally triggered by a control logic circuit (not shown in FIG.
1
). By raising and lowering the reflecting mirrors in various combinations, the incident beam can be reflected by an internal mirror to any desired output optical path of the optical switch. Hence, switching multiple light sources to multiple destinations is possible. Each row and each column must have one reflecting mirror raised depending upon the incoming-to-outgoing light path. The raising and lowering of the reflecting mirrors within the optical switch is normally controlled by a hardware or software program. In general, the reflecting mirrors are moved and controlled by a micro-electromechanical system, existing in exsitent patents or papers.
The aforementioned crossbar arrangement of reflecting mirrors has one major drawback. As the switching optical paths increase, the number of reflecting mirrors inside the optical switch increases as the square of the number of input or output paths. However, putting too many reflecting mirrors inside an optical switch may lower production yield and reliability.
Aside from the one-to-one crossbar configuration, an optical switch that uses double-sided reflecting mirrors
24
,
32
,
34
,
36
and
38
and fixed mirrors
22
a
,
22
b
is proposed in U.S. Pat. No. 4,815,827, which is shown in FIG.
2
. Although multiple reflections are used to carry out the optical switching, the prior art structure still has to use many reflecting mirrors.
FIG. 2
is a schematic diagram showing an optical switch that utilizes multiple reflections. As shown in
FIG. 2
, the optical switch
20
includes two single-sided reflecting mirrors
22
a
and
22
b
. The reflecting mirrors
22
a
and
22
b
are parallel to each other with their reflecting surfaces facing each other. Symmetrically positioned between the two reflecting mirrors
22
a
and
22
b
is an axis Y. Along the axis Y are twelve double-sided equidistantly spaced reflecting mirrors
24
. In addition, double-sided reflecting mirrors
32
,
34
,
36
and
38
are positioned between the reflecting mirrors
22
a
and
22
b
according to desired light-reflecting and switching conditions. With this structure, a 4-by-4 configuration switching can be achieved between input optical paths I
1
, I
2
, I
3
and I
4
and output optical paths O
2
, O
3
and O
4
. However, the structure requires
16
double-sided mirrors altogether in addition to the two fixed mirrors
22
a
and
22
b
. Hence, other than equalizing the propagation distance in each of the optical routes, the number of reflecting mirrors is the same as the crossbar structure shown in
FIG. 1
, not reducing the number of the doubled-side reflecting mirrors.
In short, the one-by-one crossbar configuration inside the optical switch in
FIG. 1
uses the largest number of reflecting mirrors. When a micro-electromechanical system is incorporated into the optical switch, the area needed to form the optical switch is proportional to the number of reflecting mirrors. In other words, the area required to form the optical switch is large when the one-by-one crossbar configuration is used. Hence, system production yield, system reliability and production cost all will be affected. If the number of reflecting mirrors inside the optical switch can be reduced without compromising its function, the manufacturing area can be reduced considerably. In addition, when the number of reflecting mirrors is reduced, circuits for driving the reflecting mirror are correspondingly reduced, and possible errors, chance of failures and power consumption of the optical switch are all lowered. Consequently, reducing the number of reflecting mirrors inside an optical switch not only improves the fabrication of internal optics, but also reduces complexity of control circuit elements as well.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a multi-mirror reflection optical switch structure capable of reducing the number of reflecting mirrors used and hence the required area of the optical switch.
A second object of the invention is to provide a multi-mirror reflection optical switch structure capable of simplifying control circuitry inside the optical switch by reducing the number of reflecting mirrors.
A third object of the invention is to provide a multi-mirror reflection optical switch structure capable of reducing operational error, failure rate and power consumption because of reducing the number of reflecting mirrors.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a 4-by-4 optical switch structure. The optical switch includes a first and a second fixed reflecting mirror, a first double-sided reflecting mirror group that includes a first, a second and a third double-sided reflecting mirror and a second double-sided reflecting mirror group that includes a fourth, a fifth and a sixth double-sided reflecting mirror. The reflecting side of the first and the second fixed reflecting mirrors are facing each other. The two fixed mirrors are parallel to each other and symmetrically positioned about an axis of symmetry. The first, the second and the third double-sided reflecting mirrors are positioned at equal distances from each other along a symmetric axis between the first fixed reflecting mirror and the axis of symmetry. The fourth, the fifth and the sixth double-sided reflecting mirrors are positioned at equal distances from each other along a symmetric axis between the second fixed reflecting mirror and the axis of symmetry. The first and the fourth, the second and the fifth, the third and the sixth double-side reflecting mirrors are symmetrically positioned. Furthermore, the first, the second, the third, the fourth, the fifth and the sixth reflecting mirrors all are capable of being raised or lowered to carry out optical switching. By controlling the raising and lowering of the six movable double-sided reflectin
Lin Shih-Chiang
Wang Ja-Nan
Wu Jiun-Shyong
Doan Jennifer
Industrial Technology Research Institute
J.C. Patents
Ullah Akm E.
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