Pure silica core, high birefringence, single polarization optical waveguide
AssigneeWeatherford/Lamb, Inc.
InventorsPaul E. Sanders, Edward M. Dowd, Andrew S. Kuczma, Trevor W. MacDougall, Brian J. Pike
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Abstract
Methods and apparatus provide for birefringent waveguides suitable for optical systems exhibiting polarization dependence such as interferometer sensors including Sagnac interferometric fiber optic gyroscopes (IFOG). The waveguides, for some embodiments, may offer single polarization performance over lengths of about a kilometer or more due to polarization dependent attenuation. According to some embodiments, the waveguides incorporate a pure silica core for resistance to radiation-induced attenuation (RIA).
Claims21
A polarization maintaining, single polarization propagating, optical waveguide, comprising:
- a core forming a light guiding path, wherein the core comprises pure silica;
- an inner cladding layer surrounding the core and having a refractive index lower than the core;
- a stress region disposed around the inner cladding layer and defining in cross section an elliptical outer shape, wherein the stress region induces strain birefringence of the waveguide, wherein the stress region has a higher refractive index than the inner cladding layer;
- an outer cladding layer surrounding the stress region;
- and
- a substrate layer disposed outside the outer cladding layer.
A method of forming a polarization maintaining, single polarization propagating, optical waveguide, comprising:
- creating a preform having a core comprising pure silica, an inner cladding layer surrounding the core, a stress region, an outer cladding layer surrounding the stress region, and a substrate layer disposed outside the outer cladding layer, wherein an outer surface of the preform has a non-circular cross section, wherein the stress region has a higher refractive index than the inner cladding layer;
- and
- drawing the preform to produce the waveguide, wherein the drawing rounds the outer surface and makes the stress region assume in cross section an elliptical outer shape and induce strain birefringence of the waveguide.
A sensing system, comprising:
- a light source;
- an interferometric sensor coupled to the light source, wherein the sensor includes a polarization maintaining, single polarization propagating, optical waveguide, comprising:
- a core forming a light guiding path, wherein the core comprises pure silica;
- an inner cladding layer surrounding the core and having a refractive index lower than the core;
- a stress region disposed around the inner cladding layer and defining in cross section an elliptical outer shape, wherein the stress region induces strain birefringence of the waveguide, wherein the stress region has a higher refractive index than the inner cladding layer;
- an outer cladding layer surrounding the stress region;
- and
- a substrate layer disposed outside the outer cladding layer;
- and
- a sensor response signal detector coupled to the sensor.
Dependencies are inferred from the claim text.