Spectrally stabilized broadband optical source
Methods and apparatus enable compensation of source light wavelength fluctuations due to instability of a broadband source within an optical sensing system. Tapping off two or more portions of the light output from the source at specific wavelength bands enables power based measurements of these portions. The measurements provide compensation ability by either use as feedback to control the source or for determination of the central wavelength so that adjustments can be applied to sensor response signals received at a receiver.
1. A sensor system, comprising:
a broadband light source for producing an optical spectrum defining interrogating light signals;
a sensor element coupled to the light source and configured to provide response signals from the interrogating light signals;
a receiver coupled to the sensor element and configured to detect and process the response signals;
a filter module in optical isolation from the response signals and having a filtering device that taps off first and second portions of the optical spectrum at, respectively, first and second wavelength bands, wherein control circuitry compares intensity between the first and second portions to determine wavelength fluctuations of the optical spectrum; and
signal processing equipment configured to determine a parameter based on the response signals that are detected, wherein the signal processing equipment accounts for effects on the response signals due to the wavelength fluctuations.
2. The sensor system of claim 1 , wherein the sensor element comprises a fiber-optic gyroscope.
3. The sensor system of claim 1 , wherein the light source is controlled based on a feedback from the filter module to compensate for the wavelength fluctuations.
4. The sensor system of claim 1 , wherein the control circuitry calculates a ratio of a first optical power of the first portion to a second optical power of the second portion in order to determine the wavelength fluctuations.
5. The sensor system of claim 1 , wherein the filtering device comprises first and second gratings that reflect respectively the first and second wavelength bands.
6. The sensor system of claim 1 , wherein the filtering device comprises first and second fiber Bragg gratings that reflect respectively the first and second wavelength bands.
7. The sensor system of claim 1 , wherein the control circuitry determines wavelength fluctuations of the optical spectrum without reliance on any optical parameter other than signal amplitudes to assess the intensity.
8. The sensor system of claim 1 , wherein the sensor element comprises a fiber Bragg grating.
9. A method of sensing a parameter, comprising:
producing a broadband optical spectrum defining interrogating light signals;
interrogating a sensor element with the interrogating light signals to provide response signals;
tapping off first and second portions of the optical spectrum without the response signals and at, respectively, first and second wavelength bands;
comparing intensity between the first and second portions to determine wavelength fluctuations of the optical spectrum;
compensating for the wavelength fluctuations, wherein compensating for the wavelength fluctuations includes accounting for effects on the response signals due to the wavelength fluctuations;
detecting and processing the response signals to determine the parameter; and
outputting determination of the parameter.
10. The method of claim 9 , wherein compensating for the wavelength fluctuations includes controlling production of the optical spectrum based on a feedback indicative of the wavelength fluctuations.
11. The method of claim 9 , wherein compensating for the wavelength fluctuations includes controlling a temperature of a source that produces the optical spectrum based on a feedback indicative of the wavelength fluctuations.
12. The method of claim 9 , wherein compensating for the wavelength fluctuations includes controlling a current supplied to a source that produces the optical spectrum based on a feedback indicative of the wavelength fluctuations.
13. The method of claim 9 , wherein first and second gratings reflect the first and second wavelength bands, respectively.
14. The method of claim 9 , wherein first and second fiber Bragg gratings reflect the first and second wavelength bands, respectively.
15. The method of claim 9 , wherein comparing intensity between the first and second portions to determine wavelength fluctuations of the optical spectrum occurs by measuring signal amplitudes to assess the intensity without reliance on any other optical parameter.
16. The method of claim 9 , wherein the response signals comprise reflections of the interrogating light signals from a single fiber Bragg grating.