Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1997-12-02
2001-11-20
Ngo, Hung N. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
Reexamination Certificate
active
06321009
ABSTRACT:
The invention pertains to a thermo-optical device comprising an optical waveguiding structure which comprises at least one input light path and at least two output light paths forming a first y-splitter, at least one output light path being provided with a primary heating element.
BACKGROUND OF THE INVENTION
Thermo-optical devices are known, e.g., from the description given by Diemeer et al. in
Journal of Lightwave Technology,
Vol. 7, No. 3 (1989), 449-453. Their working is generally based on the phenomenon of the optical waveguide material employed exhibiting a temperature dependent refractive index (polarisation independent thermo-optical effect). Such devices have been realised, int. al., in inorganic materials such as ion-exchanged glass and titanium-doped lithium niobate. An advantage of the use of all-polymeric waveguides for thermo-optical devices disclosed by Diemeer et al. consists in that a modest increase in temperature may result in a large index of refraction change. The device described by Diemeer is an all-polymeric planar switch. Switching is achieved by employing total internal reflection from a thermally induced index barrier. The device comprises a substrate (PMMA), a waveguiding structure (polyurethane varnish), and a buffer layer (PMMA), with the heating element being a silver stripe heater deposited by evaporation upon the buffer layer through a mechanical mask.
A thermo-optical switching device has also been disclosed by Möhlmann et al. in
SPIE Vol.
1560
Nonlinear Optical Properties of Organic Materials IV
(1991; ), 426-433. Use is made of a polymer in which a waveguide channel can be created through irradiation. The disclosed device is a polarisation/wavelength insensitive polymeric switch comprising an asymmetric Y-junction. The switching properties are based on heat-induced refractive index modulations causing variations in the mode evolution in such asymmetric Y-junctions. The device comprises a glass substrate and a polymeric multilayer comprising an NLO polymer. Another thermo-optical device disclosed is a thermo-optically biassed electro-optic Mach Zehnder interferometer.
In Electronic Letters, Vol. 24, No. 8 (1988), 457-458 an optical switch is disclosed in which optical fibers are coupled using a single-mode fused coupler having a silicone resin cladding material applied over the coupling region. Switching is achieved by a thermally induced refractive index change of the silicone cladding.
In U.S. Pat. No. 4,753,505 a thermo-optical switch is described comprising a layered waveguide in which the material having a temperature dependent refractive index is a polymer or glass.
In U.S. Pat. No. 4,737,002 a thermo-optical coupler is described which may be formed using either optical fibers or integrated optics.
In EP-A-0 642 052 and Granestrand et al., “Integrated Optics 4×4 Switch Matrix With Digital Optical Switches,” Electronics Letters, Jan. 4, 1990, Vol. 26, No. 1, pp. 4-5, a cascade or tree structure of 1×2 optical switches is disclosed.
In GB-A-225980 discloses a network comprising two 1×2 optical switches, wherein the input of one of the switches is optically connected to one of the output of the other switch.
While the disclosed polymeric thermo-optical devices sufficiently establish that thermo-optical effects can be employed to achieve, e.g., switching, in the known devices the extinction (defined as: 1010 log= (optical power on)/optical power off) leaves much to be desired and crosstalk is often a problem. These problems can be solved by providing a thermo-optical device with a waveguiding structure of a specific design.
SUMMARY OF THE INVENTION
To this end the invention consists in that in a polymeric thermo-optical device of the type identified in the opening paragraph the output light paths (
3
,
3
′) are provided with an additional branch (
6
) forming a second y-splitter (
7
), with at least one of the branches (
6
,
6
′) being provided with a secondary heating element (
8
,
8
′).
REFERENCES:
patent: 4737002 (1988-04-01), Boucouvalas
patent: 4753505 (1988-06-01), Mikami et al.
patent: 5832155 (1998-11-01), Rasch et al.
patent: 378 185 (1990-07-01), None
patent: 445 864 (1991-09-01), None
patent: 359 648 (1990-03-01), None
patent: 350112 (1990-01-01), None
patent: 350113 (1990-01-01), None
patent: 642 052 (1995-03-01), None
patent: 358 476 (1990-03-01), None
patent: 225980 (1924-12-01), None
Diemeer, et al., “Polymeric Optical Waveguide Switch Using the Thermooptic Effect”, vol. 7,Journal of Lightwave Technology,pp. 449-453 (Mar. 1989).
Singer, “Nonlinear Optical Properties of Organic Materials IV”, vol. 1560,SPIE—The International Society for Optical Engineering,pp. 426-433 (Jul. 1991).
Diemeer, et al., “Fused Coupler Switch Using a Thermo-Optic Cladding”, vol. 24, No. 8,Electronics Letters,pp. 457-458 (Apr. 1988.
Granestrand, et al. “Integrated Optics 4×4 Switch Matrix with Digital Optical Switches”, vol. 26, No. 1,Electronics Letters,pp. 4-5, (Jan. 1990).
O'Donnell, “Polarisation Independent 1×16 and 1×32 Lithium Niobate Optical Switch Matrices”, vol. 27, No. 25,Electronics Letters,pp. 2349-2350 (Dec. 1991).
Greene Kevin E.
JDS Uniphase Inc.
Lacasse Randy W.
Lacasse & Associates
Ngo Hung N.
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