We claim:
1. A variable optical attenuator for attenuating an optical signal, comprising:
an optical waveguide comprising a core and cladding; and,
an integrated coupling layer disposed adjacent to the optical waveguide, the coupling layer having a variable refractive index,
the attenuator being configured to stimulate at least the coupling layer via a contact such that the refractive index changes in response to a stimulus.
2. The attenuator of claim 1 wherein the optical waveguide comprises SiO2.
3. The attenuator of claims 1 or 2 further comprising at least one resistive heater disposed adjacent to the coupling layer.
4. The attenuator of claims 1 or 2 wherein the stimulus comprises a type selected from the group consisting of electric fields, heat, dynamic stress, piezo-optic stress, static-stress, photo-refraction, and refractive index changes using liquid crystals.
5. The attenuator of claims 1 or 2 wherein the coupling layer comprises a polymer.
6. The attenuator of claim 5 wherein the polymer is selected from the group consisting of polyacrylates, polymethacrylates, polysilicone, polyimide, epoxy, polyurethane, polyolefin, polycarbonate, polyamides, polyesters, and blends and copolymers of acrylates and methacrylates, acrylics and silicones, epoxies and urethanes, and amides and imides.
7. The attenuator of claims 1 or 2 wherein the core has a refractive index about 0.5-1% higher than a refractive index of the cladding.
8. The attenuator of claims 1 or 2 wherein the core has a thickness of about 5-8 m.
9. The attenuator of claim 8 wherein the core has a thickness of about 6 m.
10. The attenuator of claims 1 or 2 wherein the core has a characteristic thermal response such that the core decreases in refractive index upon a decrease in temperature.
11. The attenuator of claims 1 or 2 wherein the cladding further comprises an upper cladding disposed above the core and a lower cladding disposed below the core.
12. The attenuator of claims 1 or 2 wherein the coupling layer directly contacts the core.
13. The attenuator of claim 11 wherein the upper cladding has a thickness less than about 5 m.
14. The attenuator of claim 11 wherein the lower cladding has a thickness of about 15-30 m.
15. The attenuator of claims 1 or 2 wherein the coupling layer comprises at least one well disposed above the core.
16. The attenuator of claim 15 wherein the well has a width of about 6-10 m and a length of about 500-1000 m.
17. The attenuator of claims 1 or 2 wherein the coupling layer has a characteristic thermal response such that the coupling layer increases in refractive index upon a decrease in temperature.
18. A variable optical attenuator system for reducing polarization dependent loss, comprising:
at least two variable optical attenuators as described in claims 1 or 2, each of the attenuators being disposed on a substrate and located symmetrically about a groove defined in the substrate, the attenuators being in optical communication with one another; and,
a waveplate disposed along the groove such that a signal passing between the two attenuators passes through the waveplate.
19. A combination variable optical attenuator system, the combination comprising:
at least one variable optical attenuator as described in claims 1 or 2, the attenuator being disposed on a substrate; and,
an optical device disposed on the substrate and in optical communication with the attenuator, the optical device being selected from the group consisting of optical switches, passive waveguides, arrayed waveguide grating wavelength multiplexers and demultiplexers, waveguide optical amplifiers, and optical waveguide splitters.
20. An array of variable optical attenuators comprising:
a plurality of input waveguides disposed in parallel on a substrate;
a plurality of attenuators, each as described in claims 1 or 2 and optically connected to a corresponding input waveguide; and
a plurality of output waveguides optically connected to a corresponding attenuator.
21. A controllable optical shutter comprising:
a variable optical attenuator comprising
an optical waveguide comprising a core and cladding and,
an integrated coupling layer disposed adjacent to the optical waveguide, the coupling layer having a variable refractive index,
the attenuator being configured to stimulate at least the coupling layer via a contact such that the refractive index changes in response to a stimulus,
the attenuator being configured to have an attenuation state comprising a maximum attenuation state and a minimum attenuation state,
whereby an optical signal is prevented from being transmitted through the attenuator in the maximum attenuation state, and
whereby the optical signal is transmitted through the attenuator in the minimum attenuation state.
22. A high-isolation optical switch comprising:
an optical switch; and
at least one controllable optical shutter as described in claim 21 optically connected to the optical switch.
23. A controllable variable optical attenuator for attenuating an optical signal, said attenuator having an optical waveguide made from similar core and cladding materials and a coupling layer in close proximity to the waveguide mode, and configured to provide a difference between the effective index of the waveguide mode and the refractive index of the coupling layer in proximity to the waveguide mode which can be modified such that, if the refractive index of the coupling layer is substantially lower than the effective index of the waveguide mode, minimal attenuation occurs to the light in the waveguide mode, and such that, if the refractive index of the coupling layer is substantially greater than the effective index of the waveguide mode, light is coupled into the coupling layer out of the waveguide mode to attenuate the optical signal, and such that for refractive index differences between these cases the amount of attenuation varies smoothly between this maximum and minimum value.
24. The attenuator of claim 23 wherein the optical waveguide comprises SiO2.
25. The attenuator of claims 23 or 24 in which the attenuator has a source of thermal input that modifies the difference between the refractive index the coupling layer and the effective index of the waveguide mode.
26. The attenuator of claims 23 or 24 in which the coupling layer comprises a polymer.
27. A variable optical attenuator for attenuating an optical signal, comprising:
an optical waveguide comprising a core and cladding; and,
an integrated coupling layer disposed adjacent to the optical waveguide, the coupling layer having a variable refractive index and a characteristic thermal response such that the coupling layer increases in refractive index upon a decrease in temperature,
the attenuator being configured to stimulate at least the coupling layer via a contact such that the refractive index changes in response to a stimulus.
28. The attenuator of claim 27 wherein the optical waveguide comprises SiO2.
29. The attenuator of claims 27 or 28 further comprising at least one resistive heater disposed adjacent to the coupling layer.
30. The attenuator of claims 27 or 28 wherein the stimulus comprises a type selected from the group consisting of electric fields, heat, dynamic stress, piezo-optic stress, static-stress, photo-refraction, and refractive index changes using liquid crystals.
31. The attenuator of claims 27 or 28 wherein the coupling layer comprises a polymer.
32. A variable optical attenuator for attenuating an optical signal, comprising:
an optical waveguide comprised of SiO2, the waveguide comprising a core and cladding, the core and cladding having a variable refractive index; and,
an integrated coupling layer comprised of a polymer, the coupling layer disposed adjacent to the optical waveguide, the coupling layer having a variable refractive index,
the attenuator being configured to stimulate at least the coupling layer via a contact such that the refractive index changes in response to a stimulus.
33. The attenuator of claim 32 further comprising at least one resistive heater disposed adjacent to the coupling layer.
34. The attenuator of claim 32 wherein the stimulus comprises a type selected from the group consisting of electric fields, heat, dynamic stress, piezo-optic stress, static-stress, photo-refraction, and refractive index changes using liquid crystals.
35. The attenuator of claim 32 wherein the polymer is selected from the group consisting of polyacrylates, polymethacrylates, polysilicone, polyimide, epoxy, polyurethane, polyolefin, polycarbonate, polyamides, polyesters, and blends and copolymers of acrylates and methacrylates, acrylics and silicones, epoxies and urethanes, and amides and imides.
36. The attenuator of claim 32 wherein the core is doped with a dopant selected from the group consisting of Germanium, Phosphorus, and combinations thereof.
37. The attenuator of claim 32 wherein the cladding is undoped.
38. A method of attenuating an optical signal in a variable optical attenuator, comprising:
a) providing an optical waveguide comprising a core and cladding; and,
b) stimulating an integrated coupling layer disposed adjacent to the optical waveguide such that a signal in the core is attenuated via the coupling layer.
39. The method of claim 38 wherein the signal is attenuated by passing into the coupling layer.
40. The method of claim 39 wherein the signal passes into the coupling layer through the cladding layer.
41. The method of claim 39 wherein the signal passes directly into the coupling layer.
42. The method of claim 38 wherein the step of stimulating comprises a type of stimulation selected from the group consisting of electric fields, heat, dynamic stress, piezo-optic stress, static-stress, photo-refraction, and refractive index changes using liquid crystals.
43. The method of claim 42 wherein the heat stimulation is applied to the coupling layer through at least one resistive heater disposed adjacent to the coupling layer.
44. The method of claim 38 wherein the coupling layer comprises a polymer.
45. The method of claim 38 wherein the polymer is selected from the group consisting of polyacrylates, polymethacrylates, polysilicone, polyimide, epoxy, polyurethane, polyolefin, polycarbonate, polyamides, polyesters, and blends and copolymers of acrylates and methacrylates, acrylics and silicones, epoxies and urethanes, and amides and imides.
46. The method of claim 38 wherein the core has a refractive index about 0.5-1% higher than a refractive index of the cladding.
47. The method of claim 38 wherein the step of stimulating comprises stimulation of the core, which has a characteristic thermal response such that the core decreases in an effective index upon a decrease in temperature.
48. The method of claim 38 wherein the coupling layer has a characteristic thermal response such that the coupling layer increases in refractive index upon a decrease in temperature.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for operating a fuel cell power plant to provide end-use electricity, end-use heat and end-use reformate, comprising the steps of:
providing a fuel cell power plant that consumes reformate to provide electricity and heat, said fuel cell power plant having a nominal reformate flow rate and including a fuel processor system for generating reformate from a hydrocarbon fuel;
operating said fuel processor system so as to provide a reformate flow at a rate greater than said nominal reformate flow rate;
operating said fuel cell power plant using a first portion of said reformate flow to generate said electricity and said heat, said first portion being less than or equal to said nominal reformate flow rate; and
providing a second portion of said reformate flow as said end-use reformate, wherein said fuel cell power plant includes a fuel cell stack, and said second portion is separated from said first portion upstream of said fuel cell stack.
2. A method for operating a fuel cell power plant to provide end-use electricity, end-use heat and end-use reformate, comprising the steps of:
providing a fuel cell power plant that consumes reformate to provide electricity and heat, said fuel cell power plant having a nominal reformate flow rate and including a fuel processor system for generating reformate from a hydrocarbon fuel;
operating said fuel processor system so as to provide a reformate flow at a rate greater than said nominal reformate flow rate;
operating said fuel cell power plant using a first portion of said reformate flow to generate said electricity and said heat, said first portion being less than or equal to said nominal reformate flow rate; and
providing a second portion of said reformate flow as said end-use reformate, wherein said second portion is selectively provided as end use reformate and further comprising the steps of sensing when said second portion is being provided as end-use reformate and selectively operating said fuel processor system to provide a first reformate flow rate when said second portion is not being provided as end use reformate, and to provide a second reformate flow rate greater than said first reformate flow rate when said second portion is being provided as end use reformate.
3. The method of claim 2, wherein said fuel cell power plant includes a fuel cell and wherein said second portion is separated from fuel cell power plant exhaust gas downstream of said fuel cell.
4. The method of claim 1, further comprising the step of storing said second portion.
5. A method for operating a fuel cell power plant to provide end-use electricity, end-use heat and end-use reformate, comprising the steps of:
providing a fuel cell power plant that consumes reformate to provide electricity and heat, said fuel cell power plant having a nominal reformate flow rate and including a fuel processor system for generating reformate from a hydrocarbon fuel;
operating said fuel processor system so as to provide a reformate flow at a rate greater than said nominal reformate flow rate;
operating said fuel cell power plant using a first portion of said reformate flow to generate said electricity and said heat, said first portion being less than or equal to said nominal reformate flow rate; and
providing a second portion of said reformate flow as said end-use reformate, wherein said fuel processor system includes a shift converter and said fuel cell power plant includes a fuel cell stack, and further comprising the step of separating said second portion from said first portion downstream of said shift converter and upstream of said fuel cell stack.
6. The method of claim 2, wherein said second portion contains water vapor, and further comprising the step of separating said water vapor from said second portion to provide said end use reformate and a recovered water portion, and returning at least a portion of said recovered water portion to said fuel cell power plant.
7. A fuel cell power plant for providing end-use electricity, end-use heat and end-use reformate, comprising:
a fuel cell that consumes a reformate to provide electricity and heat;
a fuel processor system for generating said reformate from a hydrocarbon fuel, said fuel cell being communicated to receive said reformate from said fuel processor system; and
a bleed flow path downstream of said fuel processor system and upstream of the fuel cell for conveying a portion of said reformate to an end use application.
8. The fuel cell power plant of claim 7, further comprising a control member adapted to detect flow in said bleed flow path, said control member being adapted to increase output of said fuel processor system upon detecting flow in said bleed flow path.
9. The fuel cell power plant of claim 7, further comprising a water recovery device positioned along said bleed flow path and communicated with said fuel cell power plant for returning recovered water to said fuel cell power plant.