Method and apparatus for stabilizing a broadband source

• US 6,744,793 B2
• Filed: 12/14/2001
• Issued: 06/01/2004
• Est. Priority Date: 12/21/2000
• Status: Expired due to Term

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Smith, Stephen P., Stoner, Richard E., Kelleher, William P., Willig, Reinhardt Leon, Govignon, Jacques P.
• Primary Examiner(s): Ip, Paul
• Assistant Examiner(s): Flores-Ruiz, Delma R.
• Application Number:
  US10/017,351
• Publication Number:
  US 20020191243A1
• Time in Patent Office: 900 Days
• Field of Search: 372/29.02, 372/32, 359/110, 359/187
• US Class Current: 372/32
• CPC Class Codes: H01S 5/0687 Stabilising the frequency of the laser
• CPC Class Codes: H04B 10/502 LED transmitters
• CPC Class Codes: H04B 10/506 Multiwavelength transmitters
• CPC Class Codes: H04B 10/572 Wavelength control

Abstract

The invention relates to a method and system for wavelength stabilization of a broadband optical source. The method and system are based on utilizing an optical power divider to generate two optical signals for each of the broadband source and a reference wavelength source. The difference in the power ratio of the two optical signals derived from the broadband source and the power ratio of the two optical signals derived from the reference wavelength source is determined. Because the power ratios are similarly affected by component aging and changes in environmental factors such as temperature and incident radiation, the difference in the power ratios can be used to adjust the wavelength of the broadband source so that its center wavelength is stabilized to the center wavelength of the reference source.

Claims

1. A method for wavelength stabilization of a broadband optical signal having a center wavelength, comprising:

generating a first split broadband optical signal and a second split broadband optical signal in response to a wavelength transfer characteristic and said broadband optical signal;

generating a first split optical reference signal and a second split optical reference signal in response to said wavelength transfer characteristic and a reference optical signal having a reference wavelength;

determining a broadband power ratio of said first and second split optical signals;

determining a reference power ratio of said first and second split optical reference signals; and

determining a difference of said center wavelength and said reference wavelength in response to said broadband power ratio and said reference power ratio.

2. The method of claim 1 further comprising the step of adjusting said center wavelength of said broadband optical signal in response to said difference of said center wavelength and said reference wavelength.

3. A system for generating a wavelength stabilized optical signal comprising:

a broadband optical source configured to provide a broadband optical signal having a broadband center wavelength;

a wavelength reference module configured to provide a reference optical signal having a reference center wavelength; and

an optical power divider having a divider input port, a first divider output port and a second divider output port, said divider input port being in optical communication with said broadband optical source and said wavelength reference module, said optical power divider adapted to provide a first split broadband optical signal and a second split broadband optical signal at said first and second divider output ports, respectively, in response to said broadband optical signal, said optical power divider adapted to provide a first split reference optical signal and a second split reference optical signal at said first and second divider output ports, respectively, in response to said reference optical signal,

wherein a power ratio of said first and second split optical signals is responsive to said broadband center wavelength and wherein a power ratio of said first and second split reference optical signals is responsive to said reference center wavelength.

4. The system of claim 3 further comprising:

a first detector in optical communication with said first divider output port; and

a second detector in optical communication with said second divider output port.

5. The system of claim 4 further comprising a wavelength control module in communication with said first and second detectors, said wavelength control module determining said power ratio of said first and second split broadband optical signals and determining said power ratio of said first and second split reference optical signals, said wavelength control module generating a broadband source control signal in response to said power ratios.

6. The system of claim 3 further comprising an optical combiner in optical communication with said broadband optical source, said wavelength reference module and said optical power divider.

7. The system of claim 3 further comprising a broadband optical modulator in optical communication with said broadband optical source and said optical power divider.

8. The system of claim 3 further comprising a reference optical modulator in optical communication with said wavelength reference module and said optical power divider.

9. The system of claim 3 further comprising an optical modulator in optical communication with said broadband optical source, said wavelength reference module and said optical power divider, said optical modulator adapted to intensity modulate said broadband optical signal and said reference optical signal.

10. The system of claim 3 further comprising a polarizer in optical communication with said divider input port.

11. The system of claim 3 wherein said wavelength reference module comprises a gas cell.

12. The system of claim 11 wherein a gas in said gas cell is one of acetylene, hydrogen cyanide and ammonia.