Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2001-09-26
2004-04-13
Nguyen, Khiem (Department: 2839)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06721472
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application No. 2001-2627 filed on Jan. 17, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical switch, and more particularly, to an optical switch which can control a proceeding direction of an optical signal by heating liquid with the use of a laser heating unit so that the liquid can move into or out of the path of the optical signal.
2. Description of the Related Art
An optical switch is used to transmit a particular optical signal among many optical signals for various channels to a channel in a desired direction in an optical communications system, in particular, in an optical communications system adopting a wavelength division multiplexing method. In this type of optical communications system, waveguides cross perpendicular to each other, and a cell capable of containing liquid is provided at the cross point of the waveguides to be angled with respect to the waveguides. To perform a switching operation, there are methods of generating air bubbles in the liquid in the cell and moving the liquid in the cell by using a change in surface tension according to a difference in temperature at a boundary surface of air.
Referring to
FIGS. 1 and 2
, in a conventional optical switch, waveguides
103
are arranged in the form of an N×M matrix on a substrate
100
. A cell
110
containing liquid
105
is diagonally installed at a cross point
103
a
of the waveguides
103
. A heater
115
that heats the liquid
105
is installed on the substrate
100
together with the waveguides
103
. Here, the cell
110
includes a head portion
110
a
where the liquid
105
is contained and a tail portion
110
b
disposed at the cross point
103
a.
The operation of the optical switch having the above structure is described with reference to FIG.
2
. First, when an optical signal is to be transmitted, the heater
115
heats the liquid
105
. Then, the surface tension of a boundary surface between the liquid
105
and air decreases so that the liquid
105
moves toward the tail portion
110
b
of the cell
110
. Since the optical switch is a micro device, a force mainly applied to the liquid
105
is not gravity but surface tension so that the surface tension greatly affects the movement of the liquid
105
. Also, since the surface tension has the feature of being inversely proportional to a temperature and an electric field, when heat is applied to the liquid
105
, the surface tension decreases and the liquid
105
moves in a direction in which the surface tension decreases.
When the liquid
105
moves toward the tail portion
110
b
of the cell
110
, an optical signal passes through the liquid
105
and proceeds forward. Here, the liquid
105
having a refractive index the same as or similar to that of the waveguides
103
is used so that when the optical signal meets the liquid
105
, the optical signal is hardly reflected and passes through the liquid
105
.
To reflect the optical signal, heating by the heater
115
is stopped to increase the surface tension between the liquid
105
and air so that the liquid
105
moves toward the head portion
110
a
of the cell
110
. When an optical signal is input after the liquid
105
completely moves toward the head portion
110
a
from the tail portion
110
b
, the optical signal is totally reflected by the cell
110
. Here, since the gas inside the cell
110
has a refractive index less than that of the waveguides
103
, an optical signal input at a predetermined angle or more can be total-reflected. For example, the liquid
105
of a cell (A) in row
3
, column
2
and a cell (B) in row
2
, column
3
, is heated to move the liquid toward the tail portion
110
b
so that an optical signal passes through the two cells. At the same time, the liquid
105
in the remaining cells is not heated, and therefore the liquid stays at the head portion
110
a
of the cell
110
so that the optical signal is total-reflected and can be alternatively transmitted along a desired path. Thus, the optical signal input is directed toward a cell in row
3
, column
1
, as shown in
FIG. 2
, is total-reflected at this cross point, and passes through the cell (A) in row
3
, column
2
and is then output to a desired channel after a predetermined number of transmissions and total reflections.
Accordingly, an optical signal can be transmitted to a channel in a desired direction by transmitting or total reflecting the optical signal. However, in the above optical switch, since the heater
115
that heats liquid is manufactured together with the cell
110
on the substrate
100
where the waveguides
103
are formed, if any of the heaters
115
do not work during the operation of the optical switch, the entire optical switch cannot be used due to that malfunctioning heater
115
, which results in inefficiency and increased costs in optical manufacturing. There is another method of heating the liquid by applying a voltage thereto instead of using the heater. This method also has the same problems. Further, since the optical switch is configured in the form of an N×M matrix, which is not a simple form, installing the waveguides, heaters, and cells together on the substrate requires a very accurate and complicated manufacturing process, thus reducing productivity.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an optical switch in which liquid is heated by using laser heating units that are installed in a separable manner from the substrate where waveguides are provided, so that, when any of the lasers within the laser heating units does not work, only the malfunctioning laser heating unit needs to be replaced rather than the whole optical switch.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing: optical switch substrates; waveguides through which an optical signal is transmitted, the waveguides being arranged in the form of a matrix between the substrates and having at least one cross point; cells, each containing liquid and arranged at each cross point of the waveguides; and a laser heating unit having lasers corresponding to the respective cells to selectively heating the liquid in each cell.
The above and other objects of the present invention may also be achieved by providing a microlens array between the cells and the lasers corresponding to each of the cells so that light emitted from each of the lasers is focused on each cell.
The above and other objects of the present invention may be achieved by providing that the laser heating unit is installed to be detachable from the substrates.
REFERENCES:
patent: 3085469 (1963-04-01), Carlson
patent: 3529156 (1970-09-01), Fergason et al.
patent: 4848879 (1989-07-01), Nishimura et al.
patent: 8-201856 (1996-08-01), None
LandOfFree
Optical switch does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical switch, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical switch will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3225464