Method and apparatus for detecting peaks in an optical signal using a cross-correlation filter

1. A method for detecting peaks in an optical signal comprising:

sampling the optical signal to obtain sampled data containing information about the optical signal;

applying a cross-correlation filter on the sampled data to obtain cross-correlated data containing information about one or more peaks in the optical signal;

detecting the one or more peaks in the optical signal based on the cross-correlation data;

wherein the detecting includes filtering the cross-correlated data so that all potential peaks have a height in cross-correlation space greater than 1% of a maximum peak height.

2. A method for detecting peaks in an optical signal comprising:

sampling the optical signal to obtain sampled data containing information about the optical signal;

applying a cross-correlation filter on the sampled data to obtain cross-correlated data containing information about one or more peaks in the optical signal;

detecting the one or more peaks in the optical signal based on the cross-correlation data, the detecting including applying a zero-crossing test to detect potential peaks;

wherein the zero-crossing test includes comparing two sequential points of the cross-correlated data and determining a zero-crossing point if a second data point is less than or equal to zero and a first data point is greater than zero.

3. A method according to claim 2 , wherein the cross-correlation filter has an average value that is less than zero.

4. A method according to claim 2 , wherein the detecting includes clamping the cross-correlated data so that all cross-correlated data having a value less than zero is clamped to equal zero.

5. A method according to claim 2 , wherein the detecting includes taking a derivative of the cross-correlated data to derive a positive-to-negative zero-crossing to detect the one or more peaks.

6. A method according to claim 2 , wherein the method further comprises smoothing the sample data using a Savitzky-Golay smoothing filter to reduce random noise present in the sampled data.

7. A method according to claim 2 , wherein applying the cross-correlation filter includes removing quasi-dc components from the sampled data.

8. A method for detecting peaks in an optical signal comprising:

sampling the optical signal to obtain sampled data containing information about the optical signal;

applying a cross-correlation filter on the sampled data to obtain cross-correlated data containing information about one or more peaks in the optical signal; and

detecting the one or more peaks in the optical signal based on the cross-correlation data, the detecting including applying one or more peak rejection criteria tests, including either a width-depth test based on the cross-correlation data, a compute root test based on the cross-correlation data, an absolute power test based on the sampled data, one relative power test based on the cross-correlation data, another relative power test based on the sampled data , or a combination thereof;

wherein the width-depth test includes comparing two points in the cross-correlated data X bits before and after a zero-crossing location.

9. A method according to claim 8 , wherein the width-depth test also includes detecting a peak if the value on either side is less than a predefined percentage of a peak value.

10. A method according to claim 8 , wherein the compute root test includes fitting a quadratic to X points around a zero-crossing point in the cross-correlated data and detecting a peak if a turning point is located within X bit(s) of the zero-crossing point.

11. A method according to claim 8 , wherein the absolute power test includes requiring that all peaks have a power greater than an absolute minimum allowable power of a peak.

12. A method according to claim 8 , wherein the one relative power test includes requiring that all peaks be within a predefined percentage of a maximum peak level.

13. A method according to claim 8 , wherein the another relative power test includes removing all peaks that are lower than a predefined percentage below the highest peak in the sampled data.

14. A method for detecting peaks in an optical signal comprising:

sampling the optical signal to obtain sampled data containing information about the optical signal;

applying a cross-correlation filter on the sampled data to obtain cross-correlated data containing information about one or more peaks in the optical signal; and

detecting the one or more peaks in the optical signal based on the cross-correlation data,

wherein the sampled data includes raw channel data, including two data sets containing information about start and stop pulses whose locations are used to calibrate a wavelength measurement, and a third data set containing information about the optical signal having one or more wavelengths to be measured.

15. A method according to claim 14 , wherein the raw data sets contain high and low power values from both high gain amplifiers and low gain amplifiers.

16. A method according to claim 15 , wherein each of the high and low power values are a short signed 16-bit integer.

17. A method according to claim 15 , wherein the method includes combining the high power values and the low power values into a long data set.

18. A method according to claim 17 , wherein the long data set is a long unsigned 32-bit value.

19. A method according to claim 17 , wherein the combining also includes removing nominal dark output and amplifier offset dc components in the raw data sets.

20. A method according to claim 17 , wherein the method includes finding a maximum value in the long data set and scaling the long data set into short values.