WAVELENGTH-LOCKING A RING-RESONATOR FILTER

• US 20150277053A1
• Filed: 03/11/2014
• Published: 10/01/2015
• Est. Priority Date: 03/11/2014
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Zheng, Xuezhe, Li, Guoliang, Luo, Ying L., Krishnamoorthy, Ashok V.
• Granted Patent: US 9,310,562 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 6/2852 using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)
• CPC Class Codes: G02B 6/29341 Loop resonators operating in a whispering gallery mode evanescently coupled to a light guide, e.g. sphere or disk or cylinder evanescent coupling for sensing fluorescence G01N21/648
• CPC Class Codes: G02F 1/3132 of directional coupler type
• CPC Class Codes: H04J 14/00 Optical multiplex systems

Abstract

In an optical device, a ring resonator, having a resonance wavelength, optically couples an optical signal that includes a wavelength from an input optical waveguide to an output optical waveguide. A monitoring mechanism in the optical device, which is optically coupled to the output optical waveguide, monitors an output optical signal on the output optical waveguide. For example, the monitoring mechanism may dither a temperature of the ring resonator at a frequency using a heater, and the output optical signal may be monitored by determining amplitude and phase information of the output optical signal at the frequency and twice the frequency. Moreover, control logic in the optical device adjusts the resonance wavelength based on the monitored output optical signal, where the adjustment is made without monitoring an input optical signal on the input optical waveguide.

Claims

1. An optical device, comprising:

an input optical waveguide configured to convey an input optical signal that includes multiple wavelengths;

a ring resonator, having a resonance wavelength, optically coupled to the input optical waveguide;

an output optical waveguide configured to convey an output optical signal that includes a wavelength in the multiple wavelengths;

a monitoring mechanism, optically coupled to the output optical waveguide, configured to monitor the output optical signal; and

control logic configured to adjust the resonance wavelength based on the monitored output optical signal, wherein the adjustment is made without monitoring the input optical signal.

2. The optical device of claim 1, wherein the control logic adjusts the resonance wavelength to lock the resonance wavelength and the wavelength of the output optical signal.

3. The optical device of claim 1, wherein the control logic adjusts the resonance wavelength by adjusting a temperature of the ring resonator.

4. The optical device of claim 3, wherein the optical device further comprises a heater thermally coupled to the ring resonator.

5. The optical device of claim 3, wherein the control logic is configured to dither the temperature of the ring resonator at a frequency.

6. The optical device of claim 5, wherein the monitoring of the output optical signal involves detecting amplitude and phase information at the frequency and twice the frequency.

7. The optical device of claim 6, wherein, when the resonance wavelength and the wavelength of the output optical signal are locked, the amplitude at the frequency is zero and the amplitude at twice the frequency is non-zero.

8. The optical device of claim 6, wherein, when the resonance wavelength exceeds the wavelength of the output optical signal, a sign of the phase is opposite to the sign of the phase when the resonance wavelength is less than the wavelength of the output optical signal.

9. The optical device of claim 5, wherein the monitoring of the output optical signal involves a Fourier transform.

10. A system, comprising an optical device, wherein the optical device includes:

an input optical waveguide configured to convey an input optical signal that includes multiple wavelengths;

a ring resonator, having a resonance wavelength, optically coupled to the input optical waveguide;

an output optical waveguide configured to convey an output optical signal that includes a wavelength in the multiple wavelengths;

a monitoring mechanism, optically coupled to the output optical waveguide, configured to monitor the output optical signal; and

control logic configured to adjust the resonance wavelength based on the monitored output optical signal, wherein the adjustment is made without monitoring the input optical signal.

11. The system of claim 10, wherein the control logic adjusts the resonance wavelength to lock the resonance wavelength and the wavelength of the output optical signal.

12. The system of claim 10, wherein the control logic adjusts the resonance wavelength by adjusting a temperature of the ring resonator.

13. The system of claim 12, wherein the optical device further comprises a heater thermally coupled to the ring resonator.

14. The system of claim 13, wherein the control logic is configured to dither the temperature of the ring resonator at a frequency.

15. The system of claim 14, wherein the monitoring of the output optical signal involves detecting amplitude and phase information at the frequency and twice the frequency.

16. The system of claim 15, wherein, when the resonance wavelength and the wavelength of the output optical signal are locked, the amplitude at the frequency is zero and the amplitude at twice the frequency is non-zero.

17. The system of claim 16, wherein, when the resonance wavelength exceeds the wavelength of the output optical signal, a sign of the phase is opposite to the sign of the phase when the resonance wavelength is less than the wavelength of the output optical signal.

18. The system of claim 14, wherein the monitoring of the output optical signal involves a Fourier transform.

19. A method for locking a resonance wavelength of a ring resonator to a wavelength of an optical signal, wherein the method comprises:

dithering a temperature of the ring resonator at a frequency using a heater;

monitoring an output optical signal from the ring resonator;

determining amplitude and phase information of the output optical signal at the frequency and twice the frequency; and

adjusting the resonance wavelength based on the determined amplitude and phase information, wherein the adjustment is made without monitoring an input optical signal to the ring resonator.

20. The method of claim 19, wherein, when the resonance wavelength and the wavelength of the output optical signal are locked, the amplitude at the frequency is zero and the amplitude at twice the frequency is non-zero.