Channel-switched cross-connect
First Claim
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1. A grating coupled add-drop device comprising:
- a resonator having a round trip optical path characterized by a round trip optical length defining a free spectral range and a plurality of longitudinal resonator mode frequencies;
an intracavity waveguide segment disposed along the optical path of said resonator, said intracavity waveguide having an effective refractive index that is substantially independent of a variation in temperature;
a thermo-optic waveguide segment disposed adjacent said intracavity waveguide, said thermo-optic waveguide having a temperature dependent refractive index;
a resistive heater electrode characterized by a temperature thermally coupled to said thermo-optic waveguide;
a grating disposed in overlapping relation with a light beam propagating in said thermo-optic waveguide and inducing a grating coupling between said intracavity and thermo-optic waveguides, wherein a grating frequency of the grating coupling is tuned by the variation in temperature and at least a first resonator mode frequency is substantially independent of the variation in temperature, and an external waveguide segment disposed adjacent the optical path of said resonator and optically coupled to said resonator in a broadband parallel coupler arrangement.
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Abstract
The different embodiments of the invention include tunable add-drop and cross connect devices. The add-drop and cross connect devices include materials with negative dependence of refractive index on temperature and temperature independent coincidence between resonator modes and a set of specified frequencies, e.g. for DWDM telecommunications channels. The free spectral range may be adjusted to equal a rational fraction of the specified frequency interval. The operating frequency may be selected without substantially tuning the cavity modes. This can be accomplished by means of a waveguide pair with differential thermal response.
202 Citations
27 Claims
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1. A grating coupled add-drop device comprising:
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a resonator having a round trip optical path characterized by a round trip optical length defining a free spectral range and a plurality of longitudinal resonator mode frequencies;
an intracavity waveguide segment disposed along the optical path of said resonator, said intracavity waveguide having an effective refractive index that is substantially independent of a variation in temperature;
a thermo-optic waveguide segment disposed adjacent said intracavity waveguide, said thermo-optic waveguide having a temperature dependent refractive index;
a resistive heater electrode characterized by a temperature thermally coupled to said thermo-optic waveguide;
a grating disposed in overlapping relation with a light beam propagating in said thermo-optic waveguide and inducing a grating coupling between said intracavity and thermo-optic waveguides, wherein a grating frequency of the grating coupling is tuned by the variation in temperature and at least a first resonator mode frequency is substantially independent of the variation in temperature, and an external waveguide segment disposed adjacent the optical path of said resonator and optically coupled to said resonator in a broadband parallel coupler arrangement. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
an input waveguide segment; and
an output waveguide segment; and
wherein said external waveguide further comprises,an add waveguide segment; and
a drop waveguide segment.
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12. The device of claim 11 wherein a substantial fraction of an optical input power in said input waveguide is coupled at the first resonator mode frequency into said drop waveguide and said device is a frequency selective drop device.
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13. The device of claim 11 wherein a substantial fraction of an optical input power in said add waveguide is coupled at the first resonator mode frequency into said output waveguide and said device is a frequency selective add device.
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14. The device of claim 11 wherein substantially all of an optical input power in said input waveguide at a second resonator mode frequency is coupled into said output waveguide.
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15. The device of claim 1 wherein said intracavity waveguide is characterized by a first effective refractive index adjacent said thermo-optic waveguide and said intracavity waveguide further comprises:
an adjusted waveguide segment characterized by an adjusted effective refractive index different from the first effective index.
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16. The device of claim 12 further comprising:
an optical detector coupled to receive said substantial fraction of an optical input power, and wherein said device is a frequency selective detector.
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17. A grating coupled optical cross connect comprising:
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a resonator having a round trip optical path characterized by a round trip optical length defining a free spectral range and a plurality of longitudinal resonator mode frequencies;
a first intracavity waveguide segment disposed along the optical path of the resonator, said first intracavity waveguide having a first effective refractive index that is substantially independent of a first variation in temperature;
a first thermo-optic waveguide segment disposed adjacent said first intracavity waveguide, said first thermo-optic waveguide having a first temperature dependent refractive index;
a first resistive heater electrode characterized by a first temperature disposed adjacent said first thermo-optic waveguide and thermally coupled for heating said first intracavity and thermo-optic waveguides;
a first grating disposed in overlapping relation with light propagating in said first intracavity and thermo-optic waveguides and inducing a first grating coupling between said first intracavity and thermo-optic waveguides, wherein a first grating frequency of the first grating coupling is tuned by the first variation in the first electrode temperature and at least a first resonator mode frequency is substantially independent of the first variation in the first electrode temperature;
a second intracavity waveguide segment disposed along the optical path of the resonator, said second intracavity waveguide having a second effective refractive index that is substantially independent of a second variation in temperature;
a second thermo-optic waveguide segment disposed adjacent said second intracavity waveguide, said second thermo-optic waveguide having a second temperature dependent refractive index;
a second resistive heater electrode characterized by a second temperature disposed adjacent said second thermo-optic waveguide and thermally coupled for heating said second intracavity and thermo-optic waveguides;
a second grating disposed in overlapping relation with light propagating in said second intracavity and thermo-optic waveguides and inducing a second grating coupling between said second intracavity and thermo-optic waveguides, wherein a second grating frequency of the second grating coupling is tuned by the second variation in the second electrode temperature and the first resonator mode frequency is substantially independent of the second variation in the second electrode temperature. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
a first input waveguide segment; and
a first output waveguide segment;
and wherein said second thermo-optic waveguide further comprises, a second input waveguide segment; and
a second output waveguide segment.
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22. The cross connect of claim 21 wherein said resonator is a ring resonator characterized by a resonator loss, wherein a first fraction of an optical field in said first input waveguide is coupled into the first resonator mode, a second fraction of the input field propagates into said first output waveguide and a third fraction of the first resonator mode field is coupled into said first output waveguide, and wherein one of the first grating coupling or the resonator loss is adjusted to impedance match said resonator at the first resonator mode frequency such that the second and third fractions interfere destructively and a first output optical power at the first resonator mode frequency in the first output waveguide is substantially nulled.
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23. The cross connect of claim 22 wherein substantially all of a first optical input power at the first resonator mode frequency in said first input waveguide is coupled into said resonator.
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24. The cross connect of claim 23 wherein a fourth substantial fraction of the first input power at the first resonator mode frequency is coupled into said second output waveguide.
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25. The cross connect of claim 24 wherein a fifth substantial fraction of a second optical input power at the first resonator mode frequency in said second input waveguide is coupled into said first output waveguide.
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26. The cross connect of claim 21 wherein substantially all of a first optical input power at a second resonator mode frequency in said first input waveguide is coupled into said first output waveguide.
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27. The cross connect of claim 17 wherein said first intracavity waveguide is characterized by a first effective refractive index adjacent said first thermo-optic waveguide and said first intracavity waveguide further comprises:
a first adjusted waveguide segment characterized by a first adjusted effective refractive index different from the first effective index.
Specification