Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-04-05
2003-04-01
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S017000, C385S024000, C385S014000
Reexamination Certificate
active
06542656
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to optical communication systems, and more particularly to add-drop optical switches and methods of fabricating same.
BACKGROUND OF THE INVENTION
Optical communication systems are increasingly being used to communicate data, voice, multimedia and/or other communications. Optical communication systems may employ optical fibers and/or free space optical communication paths. It will be understood by those having skill in the art that optical communication systems may use optical radiation in the visible, ultraviolet, infrared and/or other portions of the electromagnetic radiation spectrum.
An important component in optical communications is the add-drop optical switch, also referred to as an add-drop multiplexer. As is well known to those having skill in the art, an add-drop multiplexer receives optical radiation from an IN optical path and transmits this optical radiation to an OUT optical path. However, the add-drop optical switch also has the capability of removing an optical signal from the IN optical path and placing the signal on a DROP optical path. The add-drop optical switch also has the capability to place an optical signal on an ADD optical path, so that the optical signal from the ADD optical path is placed on the OUT optical path. Accordingly, the add-drop optical switch can selectively couple the IN optical path to the OUT optical path, the IN optical path to the DROP optical path and the ADD optical path to the OUT optical path. Add-drop optical switches can employ an array of fixed and/or movable reflectors, such as mirrors, to perform the above-described selective coupling. Add-drop optical switches are described, for example, in U.S. Pat. Nos. 5,778,118; 5,960,133 and 5,974,207, and need not be described further herein.
It has been proposed to fabricate add-drop optical switches using microelectromechanical system (MEMS) technology. As is well known to those having skill in the art, MEMS devices are potentially low cost devices, due to the use of microelectronic fabrication techniques. New functionality also may be provided, because MEMS devices can be much smaller than conventional electromechanical devices.
Unfortunately, it may be difficult to fabricate add-drop optical switches using MEMS technology. In particular, it may be difficult to fabricate reflectors that are oriented orthogonal to one another using MEMS fabrication processes. This potential difficulty now will be described in connection with FIG.
1
.
Referring now to
FIG. 1
, a conventional MEMS add-drop optical switch
100
is shown. As shown in
FIG. 1
, a conventional MEMS add-drop optical switch
100
can include a substrate
110
, generally a monocrystalline silicon substrate. An IN optical path
120
on the substrate receives optical radiation. An OUT optical path
130
on the substrate transmits optical radiation. An ADD optical path
140
on the substrate receives optical radiation and a DROP optical path
150
on the substrate transmits optical radiation. The ADD, IN, OUT and DROP optical paths
140
,
120
,
130
and
150
all are oriented on the substrate
110
in parallel, on opposite sides of the substrate
110
. A first fixed mirror
180
and a second fixed mirror
190
are fixedly coupled to the substrate
110
. A first movable mirror
160
and a second movable mirror
170
are movably coupled to the substrate
110
for movement to and away from a radiation reflecting position as shown by the respective arrows
162
and
164
. The fixed mirrors
180
and
190
and the movable mirrors
160
and
170
are arranged on the substrate
110
, to selectively couple the IN optical path
120
to the OUT optical path
130
, to selectively couple the IN optical path to the DROP optical path
150
and to selectively couple the ADD optical path
140
to the OUT optical path
130
.
As shown in
FIG. 1
, the adjacent fixed mirrors
180
and
190
and movable mirrors
160
and
170
are oriented orthogonal (at a 90° angle) to one another. Unfortunately, it may be difficult to fabricate orthogonally oriented mirrors on a monocrystalline silicon substrate
110
. In particular, since monocrystalline silicon does not include orthogonal crystalline planes, it may be difficult to fabricate orthogonal mirrors using conventional wet etching methods. Reactive Ion Etching (RIE) can be used to make the configuration shown in FIG.
1
. Unfortunately, reactive ion etching may produce surface imperfections that can degrade the quality of the mirrors, so that the add-drop optical switch
100
may have degraded performance compared to that obtained by wet etching along the crystalline planes.
SUMMARY OF THE INVENTION
The present invention can provide add-drop optical switches that include fixed reflectors, such as fixed mirrors, and movable reflectors, such as movable mirrors, wherein none of the fixed reflectors and none of the movable reflectors are oriented orthogonal to one another on a substrate when the movable reflectors are in a radiation reflecting position. In preferred embodiments, each of the fixed and movable reflectors is oriented parallel to or at a 70° angle to, the remaining fixed and movable reflectors when the movable reflectors are in the radiation reflecting position. Most preferably, the fixed reflectors and the movable reflectors all are oriented on the substrate in parallel when the movable reflectors are in the radiation reflecting position. By providing these orientations of fixed and movable reflectors, add-drop optical switches may be fabricated on silicon substrates using wet etching along crystallographic planes. High performance add-drop optical switches thereby may be provided.
First embodiments of add-drop optical switches according to the present invention include a substrate, an ADD optical path on the substrate that receives radiation, an IN optical path on the substrate that receives optical radiation, an OUT optical path on the substrate that transmits optical radiation and a DROP optical path on the substrate that transmits optical radiation. As was described above, the optical radiation can include visible, ultraviolet, infrared and/or other forms of electromagnetic radiation. A plurality of fixed reflectors are fixedly coupled to the substrate. A plurality of movable reflectors are movably coupled to the substrate for movement to and away from a radiation reflecting position. The fixed reflectors and the movable reflectors are arranged on the substrate to selectively couple the IN optical path to the OUT optical path, to selectively couple the IN optical path to the DROP optical path, and to selectively couple the ADD optical to the OUT optical path. None of the fixed reflectors that are used to provide the above-described functionality are oriented orthogonal to one another on the substrate. Moreover, none of the movable reflectors that are used to provide the above-described functionality are oriented orthogonal to one another on the substrate when the movable reflectors are in the radiation reflecting position.
In preferred embodiments of the present invention, the substrate comprises monocrystalline silicon, and each of the fixed and movable reflectors is oriented parallel to or at a 70° angle to the remaining fixed and movable reflectors when the movable reflectors are in the radiation reflecting position. In other preferred embodiments, all of the fixed and movable reflectors are oriented in parallel when the movable reflectors are in the radiation reflecting position. In preferred embodiments, the ADD, IN, OUT and DROP optical paths all are oriented on the substrate in parallel. In other preferred embodiments, the ADD, IN, OUT and DROP optical paths all are oriented on the substrate at a 45° angle or at a 65° angle relative to the fixed reflectors and the movable reflectors in the radiation reflecting position.
Other embodiments of the present invention orient the fixed reflectors and the movable reflectors on the substrate in parallel when the movable reflectors are in the radiation reflecting position and when the movab
Bovernick Rodney
JDS Uniphase Corporation
Myers Bigel & Sibley & Sajovec
Stahl Mike
LandOfFree
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