Stabilization apparatus and method for an SFS

• US 5,313,480 A
• Filed: 08/04/1992
• Issued: 05/17/1994
• Est. Priority Date: 09/18/1990
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated
• Inventors: Fidric, Bernard G., Libman, David F.
• Primary Examiner(s): Scott, Jr., Leon
• Application Number:
  US07/926,007
• Time in Patent Office: 651 Days
• Field of Search: 372/32, 372/6, 372/69, 372/70, 372/31, 372/34, 385/15
• US Class Current: 372/32
• CPC Class Codes: H01S 3/06795 with superfluorescent emission, e.g. amplified spontaneous emission sources for fibre laser gyrometers fibre laser gyrometers per se G01C19/72
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/1312 by controlling the optical pumping
• CPC Class Codes: H01S 3/1317 by controlling the temperature

Abstract

A wavelength stabilization apparatus and method for a superfluorescent source comprising a SFS (superfluorescent source) comprising a fiber with a core doped with lazing material. The SFS source produces SFS light with an SFS wavelength when pumped with pump light from a pump light source having a pump light wavelength. An output controller responds to a sample of the SFS light and operates to maximize the power of the sample of SFS light by automatically adjusting the pump light wavelength. The output controller also has a pump power controller responsive to a sample of the pump light from the pump light source for stabilizing the output power of the sample of the pump light with respect to a predetermined reference output power level.

Claims

1. A wavelength stabilization apparatus for a superfluorescent fiber source comprising:

a SFS (superfluorescent source) means for producing SFS light having an SFS wavelength when pumped with pump light from a pump light source having a pump light wavelength;

an output controller means responsive to a sample of SFS light for maximizing the power of said sample of SFS light by automatically adjusting said pump light wavelength, said output controller means having;

a pump power controller means responsive to a broadband, non-wavelength dependent sample of the pump light from said pump light source for stabilizing the output power of the sample of said pump light with respect to a predetermined reference output power level.

2. The wavelength stabilization apparatus for the superfluorescent source of claim 1 wherein said SFS (superfluorescent source) means further comprises:

an SFS fiber source containing a single mode optical fiber having a core doped with at least one active laser material selected from the group of rare earth materials comprising neodymium or erbium.

3. The wavelength stabilization apparatus for the superfluorescent source of claim 1 wherein said output controller means further comprising:

a pump light source temperature control means responsive to a thermal drive signal for controlling the temperature of the pump light source, and

an output sense and control means for sensing the power of the sample of said SFS light and for dithering a thermal drive signal to slightly vary the temperature of the pump light source around an operating temperature, the variation in pump light source temperature resulting in a corresponding variation in pump light source wavelength, said SFS fiber source being responsive to said variation in pump light source wavelength to provide a corresponding variation in the power of the sample of the SFS light, the output sense and control means being responsive to the variation in the power of the sample of the SFS light for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to maximize the power of the sample SFS light.

4. The wavelength stabilization apparatus for the superfluorescent source of claim 3 wherein said pump light source temperature control means further comprises:

a thermoelectric cooler to which the pump light source is thermally coupled; and

a thermistor for measuring the temperature of the pump light source and for providing a pump temperature signal corresponding to the temperature of the pump light source;

said

output sense and control means being further characterized to be responsive to the pump temperature signal for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to maximize the power of the sample SFS light.

5. The wavelength stabilization apparatus for the superfluorescent source of claim 1 wherein said SFS (superfluorescent source) means further comprises an SFS fiber source, and said output controller means further comprising:

a temperature control means responsive to a an SFS temperature control signal for controlling the temperature of the SFS fiber source to correspond with a predetermined fixed value; and

a temperature control measuring means coupled to the SFS fiber source for providing said SFS temperature signal.

6. A wavelength stabilization apparatus for a superfluorescent source comprising:

a SFS (superfluorescent source) means for producing SFS light having an SFS wavelength when pumped with pump light from a pump light source having a pump light wavelength, a first portion of said pump light being absorbed in pumping the SFS means and a second portion of said pump light exiting said SFS means as a residual pump ray;

an output controller means responsive to the residual pump ray for maximizing the power of said sample of SFS light by automatically adjusting said pump light wavelength, said output controller means having;

a pump power controller means responsive to a broadband sample of the pump light from said pump light source for stabilizing the output power of the sample of said pump light with respect to a predetermined reference output power level.

7. The wavelength stabilization apparatus for the superfluorescent source of claim 6 wherein said output controller means further comprising:

a pump light source temperature control means responsive to a thermal drive signal for controlling the temperature of the pump light source, and

an output residue sense and control means for sensing the power of the residual pump ray and for dithering the thermal drive signal to slightly vary the temperature of the pump light source around an operating temperature, the variation in pump light source temperature resulting in a corresponding variation in pump light source wavelength, said SFS means being responsive to said variation in pump light source wavelength to provide a corresponding variation in pump light source light absorption, the power of the residue ray varying as an inverse function to the power of the SFS light output, the output residue sense and control means being responsive to the variation in power of the residue pump ray for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to minimize the power of the residue pump ray.

8. The wavelength stabilization apparatus for the superfluorescent source of claim 7 wherein said pump light source temperature control means responsive to a thermal drive signal for controlling the temperature of the pump light source further comprises:

a thermoelectric cooler to which the pump light source is thermally coupled; and

,

a thermistor for measuring the temperature of the pump light source and for providing a pump temperature signal corresponding to the temperature of the pump light source;

said output sense and control means being further characterized to be responsive to the pump temperature signal for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to maximize the power of the sample SFS light.

9. The wavelength stabilization apparatus for the superfluorescent source of claim 6 wherein said SFS means further comprises:

a doped fiber having a first and second end, the first end being coupled to receive said pump light; and

a dichroic mirror having a reflective surface coupled to said doped fiber second end for passing light at the pump wavelength as a pump residual ray and for reflecting light at the SFS fiber source wavelength into the SFS fiber source; and

wherein said output controller means further comprises;

an output residue sense and control means for sensing the power of the pump residual ray exiting the dichroic mirror for dithering the thermal drive signal to slightly vary the temperature of the pump light source around an operating temperature, the variation in pump light source temperature resulting in a corresponding variation in pump light source wavelength, said SFS means being responsive to said variation in pump light source wavelength to provide a corresponding variation in pump light source light absorption, the power of the pump residue ray varying as an inverse function to the power of the SFS light output, the output residue sense and control means being responsive to the variation in power of the pump residual ray for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to minimize the power of the pump residual ray.

10. The wavelength stabilization apparatus for the superfluorescent source of claim 6 wherein said SFS means further comprises:

an SFS fiber source; and

wherein

said output controller means further comprises;

a temperature control means responsive to a an SFS temperature control signal for controlling the temperature of the SFS fiber source to correspond with a predetermined fixed value; and

,

a temperature control measuring means coupled to the SFS fiber source for providing said SFS temperature signal.

11. A wavelength stabilization method for stabilizing a superfluorescent source comprising the steps of:

broadband sampling the intensity of the output of a pump light source that provides a pump light ray and automatically adjusting the output power of the pump light source to maintain substantially constant output intensity of the pump light ray while concurrently;

pumping an SFS (superfluorescent source) with the pump light ray to produce SFS light having an SFS wavelength with pump light from the pump light source having a pump light wavelength;

sampling SFS light from the SFS and maximizing the power of the sample of SFS light by automatically adjusting the pump light wavelength.

12. A wavelength stabilization method for an SFS (superfluorescent source) source comprising the steps of:

broadband coupling a pump light ray with a pump light wavelength from the output of a pump light source to provide a pump monitor light ray and a pump drive ray each light ray having a pump light wavelength;

sampling the intensity of the pump monitor ray and automatically adjusting the output power of the pump light source to maintain substantially constant output intensity of the pump monitor ray while concurrently;

pumping the SFS source with light from the pump drive ray to produce SFS light from the SFS source having an SFS wavelength, a first portion of said pump drive ray light being absorbed in pumping the SFS source and a second portion of said pump drive ray light exiting the SFS source as a residual pump ray;

sampling the residual pump ray; and

maximizing the power of said SFS light by automatically adjusting the temperature of the pump light source to adjust said pump light wavelength to minimize the power of the residual pump ray.

13. A wavelength stabilization apparatus for a superfluorescent fiber source comprising:

a pump light source that provides a pump light ray;

a pump power controller means for broadband sampling the intensity of the pump light ray and automatically adjusting the output power of the pump light source to maintain substantially constant output intensity of the pump light ray;

a wavelength dependent multiplexer coupled to receive the pump light ray and to provide a WDM pump main ray;

an SFS (superfluorescent source) means responsive to the WDM main ray for producing SFS light having an SFS wavelength when pumped with the WDM main ray having a pump light wavelength;

an output controller means responsive to a sample of SFS light for maximizing the power of said sample of SFS light by automatically adjusting said pump light wavelength, said output controller means having;

a pump light source temperature control means responsive to a thermal drive signal for controlling the temperature of the pump light source, and

an output sense and control means for sensing the power of the sample of said SFS light and for controlling the thermal drive signal to vary the temperature of the pump light source around an operating temperature,

the variation in pump light source temperature resulting in a corresponding variation in pump light source wavelength,

said SFS fiber source being responsive to the variation in pump light source wavelength to provide a corresponding variation in the power of the sample of the SFS light,

the output sense and control means being responsive to the variation in the power of the sample of the SFS light for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to maximize the power of the sample SFS light.

14. The wavelength stabilization apparatus for the superfluorescent source of claim 13 wherein said SFS (superfluorescent source) means further comprises an SFS fiber source, and said

output controller means further comprising:

a temperature control means responsive to a an SFS temperature control signal for controlling the temperature of the SFS fiber source to correspond with a predetermined fixed value; and

a temperature control measuring means coupled to the SFS fiber source for providing said SFS temperature signal.

15. The wavelength stabilization apparatus for the superfluorescent source of claim 13 wherein said pump light source temperature control means further comprises:

a thermoelectric cooler to which the pump light source is thermally coupled; and

,

a thermistor for measuring the temperature of the pump light source and for providing a pump temperature signal corresponding to the temperature of the pump light source;

said output sense and control means being further characterized to be responsive to the pump temperature signal for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to maximize the power of the sample SFS light.

16. A wavelength stabilization apparatus for a superfluorescent source comprising:

a pump light source that provides a pump light ray;

a pump power controller means for broadband sampling the intensity of the pump light ray and automatically adjusting the output power of the pump light source to maintain substantially constant output intensity of the pump light ray;

an SFS (superfluorescent source) means for producing SFS light having an SFS wavelength when pumped with pump light from the pump light ray, the pump light ray having a pump light wavelength, a first portion of said pump light being absorbed in pumping the SFS means and a second portion of said pump light exiting said SFS means as a residual pump ray;

an output controller means responsive to the residual pump ray for maximizing the power of said sample of SFS light by automatically adjusting said pump light wavelength, said output controller means having;

a pump light source temperature control means responsive to a thermal drive signal for controlling the temperature of the pump light source, and

an output residue sense and control means for sensing the power of the residual pump ray and for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to minimize the power of the residue pump ray.

17. The wavelength stabilization apparatus of claim 16 wherein:

the output residue sense and control means is further characterized to vary the thermal drive signal to provide a variation in pump light source temperature around an operating point, the variation in temperature resulting in a corresponding variation in pump light source wavelength, and wherein;

said SFS means responds to the variation in pump light source wavelength to provide a corresponding variation in pump light source light absorption,

the power of the residue ray varying as an inverse function to the power of the SFS light output;

whereby,

the output residue sense and control means responds to the variation in power of the residue pump ray by adjusting the thermal drive signal to adjust the operating temperature of the pump light source to minimize the power of the residue pump ray.

18. The wavelength stabilization apparatus of claim 16 wherein the SFS means further comprises:

an SFS fiber source; and

a dichroic mirror for passing light at the pump wavelength and for reflecting light at the SFS fiber source wavelength into the SFS fiber source; and

wherein said output controller means further comprises;

an output residue sense and control means for sensing the power of the residual pump ray exiting the dichroic mirror and for dithering the thermal drive signal to slightly vary the temperature of the pump light source around an operating temperature,

the variation in pump light source temperature resulting in a corresponding variation in pump light source wavelength, said SFS means being responsive to said variation in pump light source wavelength to provide a corresponding variation in pump light source light absorption,

the power of the residue ray varying as an inverse function to the power of the SFS light output,

the output residue sense and control means being responsive to the variation in power of the residue pump ray for adjusting the thermal drive signal to adjust the operating temperature of the pump light source to minimize the power of the residue pump ray.