Peak-Finding Algorithms for FBGs

International Zone (English) OFSCN Knowledge Base (Public)
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How do common methods like Centroid or Gaussian Fitting improve measurement precision?

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Both Centroid and Gaussian Fitting are commonly used peak-finding algorithms for Fiber Bragg Grating (FBG) spectra, and they significantly improve measurement precision by more accurately determining the Bragg wavelength.

Centroid Method:
This method calculates the “center of mass” of the FBG reflection spectrum. It treats the spectrum as a distribution of light intensity over wavelength and finds the weighted average wavelength.

  • Improvement in Precision: The Centroid method offers better precision than simply identifying the highest point (peak intensity) because it considers the entire shape of the reflection peak. This makes it less susceptible to noise spikes that might appear at the very top of the peak. It’s computationally less intensive, making it suitable for high-speed applications.

Gaussian Fitting Method:
This method fits a mathematical Gaussian curve (or other suitable functions like Lorentzian or Voigt) to the measured FBG spectrum. The center of the fitted Gaussian curve is then taken as the Bragg wavelength.

  • Improvement in Precision: Gaussian fitting provides a more robust and precise determination of the Bragg wavelength, especially when dealing with noisy spectra, asymmetrical peaks, or even overlapping peaks (though deconvolution techniques are needed for heavily overlapping ones). By modeling the entire peak shape, it can effectively filter out noise and extract the underlying Bragg wavelength with sub-picometer accuracy. While more computationally intensive than the Centroid method, its superior accuracy makes it preferred for applications requiring high measurement resolution.

In essence, both methods aim to move beyond simple maximum intensity detection to utilize more spectral information, with Gaussian fitting generally offering higher accuracy at the cost of computational complexity.

Accurate peak finding is crucial for the performance of any FBG sensor, such as the OFSCN® Alloy Tube Packaged Fiber Bragg Grating strain sensor.

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