Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2001-04-09
2003-02-25
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
C359S199200
Reexamination Certificate
active
06526197
ABSTRACT:
BACKGROUND OF THE INVENTION
Optical switches formed on a substrate are known. Because of their reduced size, microelectromechanical (MEMS) technology is employed to provide the actuation to cause switching.
FIG. 1
is a top view of a switch
10
formed on a substrate
12
according to the prior art. The switch
10
includes a mirror
14
which can be moved in and out of an intersection region
15
by MEMS actuators (not shown).
FIG. 1
shows the mirror located in the intersection region
15
. The switch also includes a first alignment groove
16
, a second alignment groove
18
, a third alignment groove
20
and a fourth alignment groove
22
. Each alignment groove
16
-
22
has a central axis
24
. Each alignment groove is dimensioned to receive a piece of fiber or waveguide therein (not shown).
The first and the fourth alignment grooves
16
,
22
hold fiber or waveguides that form the inputting channels of the switch. The second and third alignment grooves
18
,
20
hold fiber or waveguides that form the receiving channels of the switch. Depending upon the position of mirror
15
, inputting channel
16
may be coupled to one of either receiving channels
18
,
20
. The same is true for inputting channel
22
.
The switch is a 2×2 switch. If a beam is input into a fiber or waveguide located in the first alignment groove
16
and the mirror
14
is retracted from the intersection region
15
, the beam passes straight through the intersection region
15
and is output from a fiber or waveguide positioned in the third alignment groove
20
. Now if the mirror
14
is positioned in the intersection region
15
, the beam is reflected by the mirror to a fiber or waveguide located in the second alignment groove
18
. The beam, however, is offset from the central axis
24
of the second alignment groove
18
as indicated by line
26
. The reason for this is that the mirror has a thickness associated therewith. The thickness of the mirror offsets the beam's path from the central axis
24
of the groove
18
receiving the beam after the beam is reflected by the mirror
14
.
Similarly, if a beam is input into a fiber or waveguide located in the fourth alignment groove
22
and the mirror
14
is retracted from the intersection region
15
, the beam passes straight through the intersection region
15
and is output by a fiber or waveguide positioned in the second alignment groove
18
. If the mirror is located in the intersection region
15
, the beam is reflected into a waveguide or fiber located in the third alignment groove
20
. Because of the thickness of the mirror, however, the beam is offset from the central axis
24
of the third alignment groove
20
.
This offset creates several disadvantages. First, the offset causes higher insertion loss than the case when the mirror
14
is retracted from the intersection region
15
and the beam travels straight through. This causes an output power differentiation between the straight through beam and. the reflected beam of as much as 1.3 dB. This differentiation is undesirable in optical networks. To overcome this variable, optical attenuators may need to be added to obtain uniform outputs, however, such a remedy results in higher costs and more complicated designs.
Thus, it is desirable to provide an optical switch that substantially reduces or eliminates offset in the reflected beam. In addition, it is desirable to provide an optical switch that substantially reduces or eliminates the offset without additional structure thereby simplifying the design of the switch. Also, it is desirable to provide an optical switch that has a simple design which is amenable to formation by batch processes.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an optical switch that includes a substrate having a first, second, third and fourth edge and a center region. Located on the substrate are a first, second, third and fourth alignment grooves. The first alignment groove extends from the first edge of the substrate to the center region of the substrate and has a first center axis that extends down the center of the first alignment groove. The second alignment groove extends from the second edge of the substrate to the center region of the substrate where the second edge of the substrate opposes the first edge of the substrate. The second alignment groove has a second center axis that extends down the center of the second alignment groove, and the second center axis is offset from the first center axis. The third alignment groove extends from the third edge of the substrate to the center region of the substrate and has a third center axis that extends down the center of the third alignment groove. The fourth alignment groove extends from the fourth edge of the substrate to the center region of the substrate and has a fourth center axis that extends down the center of the fourth alignment groove, and the fourth center axis is offset from the third center axis.
According to a second aspect of the invention, there is provided an alignment structure for an optical switch. The structure includes a first, second, third and fourth groove disposed in a substrate. The first groove extends from a first end to an intersection region, the second groove extends from a second end located remotely from the first end to the intersection region, the third groove extends from a third end located remotely from the first and second ends to the intersection region, and the fourth groove extends from a fourth end located remotely from the first, second, and third ends to the intersection region. The first and second groove meet in the intersection region and the second groove is offset from the first groove and the third and fourth groove meet in the intersection region and the fourth groove is offset from the third groove.
According to a third aspect of the invention, there is provided a method of making an optical switch. The method includes the steps of:
forming a first alignment groove on a substrate wherein the first alignment groove extends from the first edge of the substrate to the center region of the substrate, the first alignment groove having a first center axis that extends down the center of the first alignment groove;
forming a second alignment groove on the substrate wherein the second alignment groove extends from the second edge of the substrate to the center region of the substrate, wherein the second edge of the substrate opposes the first edge of the substrate, the second alignment groove having a second center axis that extends down the center of the second alignment groove wherein the second center axis is offset from the first center axis;
forming a third alignment groove on the substrate wherein the third alignment groove extends from the third edge of the substrate to the center region of the substrate; the third alignment groove having a third center axis that extends down the center of the third alignment groove; and
forming a fourth alignment groove on the substrate wherein the fourth alignment groove extends from the fourth edge of the substrate to the center region of the substrate, the fourth alignment groove having a fourth center axis that extends down the center of the fourth alignment groove wherein the fourth center axis is offset from the third center axis.
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patent: 5073040 (1991-12-01), Guinard
patent: 5245680 (1993-09-01), Sauter
patent: 5999303 (1999-12-01), Drake
patent: 6049650 (2000-04-01), Jerman et al.
patent: 6237370 (2001-05-01), Bloom
patent: 6343171 (2002-01-01), Yoshimura et al.
patent: 6360035 (2002-03-01), Hurst et al.
patent: 0 410 619 (1991-01-01), None
patent: WO 98/12589 (1998-03-01), None
patent: WO 98/43124 (1998-10-01), None
patent: WO 01/11411 (2001-02-01), None
ADC Telecommunications Inc.
Merchant & Gould P.C.
Ullah Akm E.
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