Method and system for providing thermal control of superluminescent diodes

• US 6,859,471 B2
• Filed: 10/30/2002
• Issued: 02/22/2005
• Est. Priority Date: 10/30/2002
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Fibersense Technology Corp. (Northrop Grumman Corporation)
• Inventors: Healy, Alfred, Gregory, Peter
• Primary Examiner(s): Harvey, Minsun Oh
• Assistant Examiner(s): Jackson, Cornelius H
• Application Number:
  US10/283,672
• Publication Number:
  US 20040086008A1
• Time in Patent Office: 846 Days
• Field of Search: 372/32, 372/34, 372/46
• US Class Current: 372/34
• CPC Class Codes: H01L 33/0045 the devices being superluminescent diodes
• CPC Class Codes: H01L 33/645 the elements being electrically controlled, e.g. Peltier elements
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/18 using temperature feedback

Abstract

A method of stabilizing output characteristics of an SLD device with respect to ambient temperature is disclosed. The SLD device includes a cooling module for cooling an SLD chip, and a sensor for providing a set point signal corresponding to a set point temperature. The cooling module and the sensor, together with control electronics, form a feedback loop for maintaining the set point temperature within a predetermined range. The method comprises determining a variation of the output characteristics as a function of ambient temperature, and determining a variation of the set point signal as a function of ambient temperature, wherein the variation of the set point signal corresponds to the variation of the output characteristics. The method also includes modifying the feedback loop so as to offset the variation of the set point signal, and thereby stabilize the variation of the output characteristics as a function of ambient temperature.

Claims

1. A method of stabilizing an optical power output of an SLD device with respect to ambient temperature, the SLD device including (i) a thermoelectric cooling module (TEC) for cooling an SLD chip, and (ii) a temperature sensor for providing a set point signal corresponding to a set point temperature, wherein the TEC and the temperature sensor, together with a temperature control electronics, from a temperature control feedback loop for maintaining the set point temperature within a predetermined temperature range, comprising:

determining an incremental change of the optical power output as a function of ambient temperature, wherein the optical power output of the SLD device is proportional to ambient temperature;

determining a variation of the set point signal as a function of ambient temperature, wherein the variation of the set point signal corresponds to the variation of the optical power output; and

modifying the temperature control feedback loop so as to include the determined incremental change of the optical power output as a function of ambient temperature thereby stabilizing the variation of the optical power output as a function of ambient temperature.

2. A method according to claim 1, further including determining a variation of a thermistor set point resistance, wherein the temperature sensor includes a thermistor and the set point signal includes a set point resistance.

3. A method according to claim 1, further including sensing a case temperature of a case enclosing the SLD device, and using the case temperature as ambient temperature to modify the temperature control feedback loop so as to offset the variation of the set point signal, thereby stabilizing the variation of the optical power output and the wavelength output as a function of ambient temperature.

4. A method according to claim 1, further including determining ambient temperature by sensing a case temperature of a case enclosing the SLD device.

5. A method according to claim 1, further including modifying the temperature control feedback loop with a processor executing that algorithmically produces a compensated TEC control signal as a function of the set point signal and the ambient temperature.

6. The method of claim 1, wherein the step of modifying the temperature control feedback loop so as to offset the variation of the set point signal, and thereby stabilizing the variation of the optical power output as the function of ambient temperature comprises the step of:

stabilizing the optical power output to stabilize the wavelength output of the SLD device.

7. A method according to claim 1, further including disposing a thermistor substantially adjacent to the case enclosing the SLD device, and using a resistance associated with the thermistor in the temperature control feedback loop, so as to offset the variation of the set point signal.

8. A method according to claim 7, further including attaching the thermistor to the case enclosing the SLD device.

9. A method according to claim 7, further including electrically coupling the thermistor to a bridge circuit within the temperature control electronics so as to offset the variation of the set point signal.

10. A method according to claim 9, further including combining support circuitry with the thermistor in the bridge circuit such that the thermistor combined with the support circuitry exhibits a desired resistance profile.

11. A system for stabilizing an optical power output of an SLD device with respect to ambient temperature, the SLD device including (i) a thermoelectric cooling module (TEC) for cooling an SLD chip, and (ii) a set point temperature sensor for providing a set point signal corresponding to a set point temperature, wherein the TEC and the temperature sensor, together with a temperature control electronics, form a temperature control feedback loop for maintaining the set point temperature within a predetermined temperature range, comprising:

an ambient temperature sensor disposed substantially adjacent to a case enclosing the SLD device, for providing a sensing signal representative of ambient temperature;

offsetting circuitry, associated with the temperature control feedback loop, for receiving the sensing signal representative of ambient temperature, for offsetting a variation of the set point signal as a function of an incremental change in optical power output per ambient temperature change, and for providing a compensated TEC control signal to the TEC where the compensated TEC control signal includes the variation of the set point signal, thereby stabilizing the variation of the optical power output, wherein the optical power output of the SLD device is proportional to ambient temperature.

12. A system according to claim 11, wherein the offsetting circuitry includes a processor executing code that algorithmically produces a compensated TEC control signal as a function of the set point signal and the ambient temperature.

13. A system according the claim 11, wherein the offsetting circuitry includes an ASIC device for receiving the set point signal and the sensing signal representative of ambient temperature and producing a compensated TEC control signal therefrom.

14. The system of claim 11, wherein the offsetting circuitry offsets the variation of the set point signal as the function of ambient temperature and provides the compensated TEC control signal to the TEC to stabilize the optical power output to stabilize a wavelength output of the SLD device, wherein the SLD device is part of a gyroscope.

15. The system of claim 14, wherein upon stabilization of the optical power output and the wavelength output of the SLD device, the offsetting circuitry reduces a scaling error that occurs during rotation of the gyroscope.

16. The system of claim 14, wherein the gyroscope comprises a fiber optic gyroscope.

17. A system according to claim 11, wherein the set point temperature sensor includes a thermistor, and the set point signal includes a set point resistance.

18. A system according to claim 17, wherein the offsetting circuitry includes conductors for electrically coupling the thermistor to a bridge circuit within the temperature control electronics.

19. A system according to claim 18, wherein the offsetting circuitry is further combined with support circuitry such that the thermistor combined with the offsetting circuitry and the support circuitry exhibits a desired resistance profile.

20. A system according to claim 11, wherein the ambient temperature sensor includes a thermistor for sensing a case temperature of the case enclosing the SLD device.

21. A system according to claim 20, wherein the thermistor physically contacts the case enclosing the SLD device.

22. A system according to claim 21, wherein the thermistor is attached to the case enclosing the SLD device.

23. A system for stabilizing an optical power output and a wavelength output of an SLD device with respect to ambient temperature, the SLD device including (i) a thermoelectric cooling module (TEC) for cooling an SLD chip, and (ii) a set point temperature sensor for providing a set point signal corresponding to set point temperature, wherein the TEC and the temperature sensor, together with a temperature control electronics, form a temperature control feedback loop for maintaining the set point temperature within a predetermined temperature range, comprising:

means for sensing ambient temperature disposed substantially adjacent to a case enclosing the SLD device, for providing a sensing signal representative of ambient temperature;

means for receiving the sensing signal representative of ambient temperature, for offsetting a variation of the set point signal as a function of a determined incremental change of optical power output per degree of ambient temperature change, and for modifying the temperature control feedback loop so as to include the offsetting variation of the set point signal, thereby stabilizing the variation of the optical power output, wherein the optical power output of the SLD device is proportional to ambient temperature.

24. A method of stabilizing an optical power output of an SLD device with respect to ambient temperature, the SLD device including (i) a thermoelectric cooling module (TEC) for cooling an SLD chip, and (ii) a temperature sensor for providing a set point signal corresponding to a set point temperature, wherein the TEC and the temperature sensor, together with a temperature control electronics, form a temperature control feedback loop for maintaining the set point temperature within a predetermined temperature range, comprising:

determining an incremental change of the optical power output of the SLD device with respect to ambient temperature, wherein the optical power output of the SLD device is proportional to ambient temperature;

determining a variation of a thermistor set point resistance, wherein the temperature sensor includes a thermistor and the set point signal includes a set point resistance; and

sensing a case temperature of a case enclosing the SLD device via a thermistor disposed substantially adjacent to the case, and using the case temperature as ambient temperature to modify the temperature control feedback loop so as to offset the variation of the set point resistance by an amount corresponding to the determined incremental change, thereby stabilizing the variation of the optical power output as a function of ambient temperature.

25. A system for stabilizing an optical power output and a wavelength output of an SLD device with respect to ambient temperature, the SLD device including (i) a thermoelectric cooling module (TEC) for cooling an SLD chip, and (ii) a set point temperature sensor for providing a set point signal corresponding to a set point temperature, wherein the TEC and the temperature sensor, together with a temperature control electronics, form a temperature control feedback loop for maintaining the set point temperature within a predetermined temperature range, comprising:

a thermistor attached to a case enclosing the SLD device, for providing a sensing resistance representative of ambient temperature;

offsetting circuitry associated with the temperature control feedback loop, for receiving the sensing signal representative of ambient temperature, for offsetting a variation of the set point signal as a function of an incremental change in optical power output per ambient temperature change, for providing a compensated TEC control signal to the TEC where the compensated TEC control signal includes the variation of the set point signal, thereby stabilizing the variation of the optical power output, wherein the optical power output of the SLD device is proportional to ambient temperature;

wherein the offsetting circuitry includes conductors for electrically coupling the thermistor to a bridge circuit within the temperature control electronics, and includes support circuitry such that the thermistor combined with the offsetting circuitry and the support circuitry exhibits a resistance profile that includes a change in resistance corresponding to the incremental change in optical power output per ambient temperature change.