Optical waveguides – With optical coupler – Switch
Reexamination Certificate
1999-05-03
2001-06-12
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06246809
ABSTRACT:
BACKGROUND OF THE INVENTION
This application is based upon the European application S.N. 99400014.9, filed Jan. 5, 1999, which we claim as the priority date of this application.
1. Field of the Invention
This invention relates generally to thermo-optical switches, and more particularly to asymmetric thermo-optical switches that use waveguides arms fabricated from materials having different thermo-optical characteristics.
2. Technical Background
The growth in demand for bandwidth has pushed network operators to increase optical network capacity by transmitting many high bandwidth channels through a single fiber. The signal management of these channels would be greatly simplified by using optically transparent switches.
One approach that has been considered involves planar integrated switches. Planar integrated switches are particularly interesting for several reasons. They have a high potential for integration: a plurality of functional elements can be implemented in one planar device. In addition, they are compact and can be relatively inexpensive to produce. Several techniques may be used to achieve optical commutation in a planar device, but one proposal that has been the subject of intense consideration involves thermo-optical switching. This method is particularly advantageous, because it is one of the easiest approaches to implement. Thermo-optical switches operate by selectively changing the refractive index of a waveguide material.
It has been proposed to use polymer materials to implement thermo-optic switches. Polymer materials are well suited for this application. They are relatively easy to handle and can be easily processed to produce waveguides. The refractive indexes of polymer materials exhibit a wide variation in value with respect to temperature. When a polymer waveguide is heated, the large index variations can alter the phase of the signal propagating in the waveguide, or alter the guiding properties of a waveguide itself. Moreover, the change in the refractive index with respect to temperature (dn/dT) is a reproducible and reversible effect. Such switches of this type are already commercially available.
In other approaches, numerous designs have been used to make planar switches. These include Mach-Zehnder interferometers, directional couplers, Y-splitters, and X-splitters. However, one of the main drawbacks of these devices concerns the positioning and geometry of the heater element.
If the heater is not positioned accurately, or the geometry of the heater is not within proper design tolerances, thermal isolation between the arms of the switch will be inadequate, and unacceptable optical cross talk between output ports will result.
Thus, a need exists for a thermo-optic planar waveguide switch that eliminates both the need for designing heating elements that have strict tolerance requirements, and the expensive and time-consuming process of accurately positioning the heating elements on the planar waveguide switch devices.
SUMMARY OF THE INVENTION
Existing problems with conventional thermo-optic couplers are solved by the present invention. The present invention for an asymmetric thermo-optical switch includes a first waveguide and a second waveguide fabricated from materials having different dn/dT coefficients resulting in superior selectivity and low optical cross talk between outputs. Using different dn/dT coefficients enhances the strength of the thermo-optic effect and eliminates the need for designing heating elements that have strict tolerance requirements. Furthermore, this feature also eliminates the expensive and time-consuming process of accurately positioning heating elements on the device. Thus, geometry and positioning of the heater does not have to be implemented with any particular precision.
In one aspect of the invention, an optical device for switching a light signal is disclosed. The optical device includes a substrate having a first side and a second side. A first waveguide is disposed on the first side. The first waveguide has a core characterized by a first refractive index, a middle portion, and a first dn/dT coefficient. A second waveguide is disposed on the first side adjacent to the first waveguide. The second waveguide has a second core characterized by a second refractive index and a second dn/dT coefficient (different from the first dn/dT coefficient). An index-adjusting switch element is disposed on the first side. The index-adjusting switch element controls the proportion of the light signal coupled between the first waveguide and the second waveguide by adjusting the first and second refractive indexes.
In another aspect of the invention, a method for switching a light signal through an optical device is disclosed. The optical device includes a substrate having a first side and a second side. A first waveguide is disposed on the first side. The first waveguide has a middle portion and a first core characterized by a first refractive index and a first dn/dT coefficient. The method for directing a light signal includes the steps of providing a second waveguide on the first side, wherein said second waveguide has a second core characterized by a second refractive index and a second dn/dT coefficient (different from said first dn/dT coefficient). The method includes the step of switching a proportion of the light signal between the first waveguide and the second waveguide by adjusting either of the first refractive index or the second refractive index.
In another aspect of the present invention, a method of making an optical device for switching a light signal is disclosed. The method includes the steps of forming a substrate, wherein the substrate includes a first side and a second side. Forming a first waveguide structure on the first side, wherein the first waveguide structure has a middle region and a first core characterized by a first refractive index and a first dn/dT coefficient. Forming a second waveguide structure on the first side, wherein the second waveguide structure has a core characterized by a second refractive index and a second dn/dT coefficient. Disposing an index-adjusting switch element on the switching region.
The apparatus of the present invention results in a number of advantages over the related art. By using materials with different dn/dT coefficients, the strength of the thermo-optic effect is significantly increased and selectivity is far superior than the related art discussed above. These features eliminate the need for designing heating elements that have strict tolerance requirements to achieve low optical cross-talk. For the same reasons, the present invention also eliminates the expensive and time-consuming process of accurately positioning the heating elements on planar waveguide switch devices.
Additional features and advantages of the invention will be set forth in the detailed description that follows, and in part will be readily apparent to those skilled in the art from the description, or recognized by practicing the invention as described in the written description and claims hereof, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework to understanding the nature and character of the invention as it is claimed:
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.
REFERENCES:
patent: 4753505 (1988-06-01), Makami et al.
patent: 4886331 (1989-12-01), Peterson
patent: 5117470 (1992-05-01), Inoue et al.
patent: 5173956 (1992-12-01), Hayes
patent: 5319482 (1994-06-01), Tsuchiya et al.
patent: 5526156 (1996-06-01), Bostica et a.
patent: 5841912 (1998-11-01), Mueller-Fiedler et al.
patent: 5881199 (1999-03-01), Li
patent: 5892863 (1999-04-01), Ishid
Jouanno Jean-Marc Mg
Moroni Marc
Malley Daniel P.
Ullah Akm E.
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