Optical waveguides – With optical coupler – Switch
Reexamination Certificate
1999-07-07
2001-02-13
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S017000, C385S018000
Reexamination Certificate
active
06188815
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to optical switches and, in particular, to an optical switch based on total internal reflection that controls fluid pressure in the switch to improve switching characteristics.
2. Related Art
Some internally reflective optical switches change states by forming a bubble in a liquid that is located at the intersection of various waveguide segments. For example, U.S. Pat. No. 5,699,462 entitled “Total Internal Reflection Optical Switches Employing Thermal Activation,” which is incorporated by reference, describes an optical switch that uses bubbles to change states.
As shown by
FIG. 1
, the switch
15
described by the foregoing patent has segments
22
-
25
of core material surrounded by cladding material
27
. Segments
22
and
23
are separated from segments
24
and
25
by a trench
32
, which is filled with a liquid
34
(FIG.
2
). The index of refraction of the liquid
34
is close to or the same as the index of refraction of the segments
22
-
24
. Therefore, in a first state of switch
15
, an optical signal passing through segment
22
is not substantially reflected or refracted when it reaches the trench
32
. Instead, the optical signal from segment
22
passes through the liquid
34
and then into segment
24
.
The trench
32
also includes a heating device
35
(
FIG. 2
) located on a substrate
38
that may be used to switch the state of the switch
15
. The heating device
35
includes control circuitry for selectively increasing or decreasing the amount of heat generated by the heating device
35
. To switch the state of the switch
15
, the temperature of the heating device
35
is increased until the temperature of the heating device
35
exceeds the boiling point of the liquid
34
, thereby causing a bubble
41
to form in the liquid
34
, as shown by FIG.
3
. The bubble
41
has an index of refraction substantially different than the index of refraction for the liquid
34
and the segments
22
-
25
, and the bubble
41
extends from segment
22
to segment
24
. Therefore, an optical signal passing through segment
22
is reflected at the interface of the segment
22
and the bubble
41
. Consequently, an optical signal transmitted by segment
22
is reflected at the boundary between the segment
22
and the bubble
41
and travels along segment
23
instead of segment
24
.
To place the switch
15
back into its original state, the temperature of the heating device
35
is decreased until the bubble
41
collapses. In other words, the temperature of the heating device
35
is decreased to or below the boiling point of the liquid
34
. Once the bubble
41
collapses, the optical signals traveling along segment
22
are no longer reflected at the end of segment
22
, and the optical signals, therefore, pass into segment
24
instead of segment
23
.
However, a problem with the switch
15
occurs when a bubble
42
(
FIG. 4
) inadvertently forms in the trench
32
. Under certain conditions, an inadvertent bubble
42
forms in the trench
32
even though the heating device
35
is below the boiling point of the liquid
34
. In this condition, signals traveling along segment
22
are reflected toward segment
23
regardless of the temperature of the heating device
35
.
Thus, an unaddressed need exists in the industry for a device and method for controlling the formation of bubbles in optical switches such that the bubbles do not inadvertently form in the trench and disrupt the operation of the switch.
SUMMARY OF THE INVENTION
The present invention overcomes the inadequacies and deficiencies of the prior art as discussed above. Generally, the present invention provides a device and method for preventing switching errors caused by the inadvertent formation of bubbles in optical switches.
The present invention includes a substrate, a first waveguide segment, a second waveguide segment, a heating device, a liquid, and a pressure controlling mechanism. The substrate is coupled to the first waveguide segment and the second waveguide segment, and the substrate includes a chamber that separates the first waveguide segment from the second waveguide segment. The liquid is disposed in the chamber and is responsive to the heating device. The pressure controlling mechanism controls the pressure in the chamber such that inadvertent bubbles are prevented from forming between the first waveguide segment and the second waveguide segment.
In accordance with another feature of the present invention, the chamber is comprised of a first compartment and a second compartment. The two compartments are interconnected via a passageway extending from the first compartment to the second compartment. To control the pressure in the chamber, the pressure controlling mechanism controls the temperature of the liquid in the second compartment.
In accordance with another feature of the present invention, the pressure controlling mechanism is comprised of a piston and an actuator. To increase the pressure in the chamber, the actuator moves the piston in one direction, and to decrease the pressure in the chamber, the actuator moves the piston in the opposite direction.
In accordance with another feature of the present invention, the pressure controlling mechanism may inject and/or remove a substance into and/or out of the chamber to control the pressure in the chamber.
The present invention can also be viewed as providing a method for switching optical signals. The method includes the following steps: providing a first waveguide segment, a second waveguide segment, and a third waveguide segment; providing a substrate, the substrate including a chamber filled with a liquid, the chamber separating the first waveguide segment from the second waveguide segment; providing a heating device; transmitting an optical signal via the first optical waveguide segment; forming a bubble in the liquid by increasing the temperature of the heating device from a first temperature to a second temperature; and adjusting a pressure in the chamber such that optical signals transmitted via the first waveguide segment pass through the chamber and into the second waveguide segment when the temperature of the heating device is at the first temperature and such that optical signals transmitted via the first waveguide segment are reflected at a boundary of said bubble and are transmitted via the third waveguide segment when the temperature of the heating device is at the second temperature.
Other features and advantages of the present invention will become apparent to one skilled in the art upon examination of the following detailed description, when read in conjunction with the accompanying drawings. It is intended that all such features and advantages be included herein.
REFERENCES:
patent: 4121884 (1978-10-01), Greenwood
patent: 5699462 (1997-12-01), Fouquet et al.
patent: 5828799 (1998-10-01), Donald
patent: 5960131 (1999-09-01), Fouquet et al.
patent: 6055344 (2000-04-01), Fouquet et al.
Schiaffino Stefano
Schroeder Dale W.
Troll Mark
Agilent Technologie,s Inc.
Doan Jennifer
Hardcastle Ian
Lee John D.
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