Correction of Peak Tracking Ripple in Solid State Spectrometers

Errors in peak wavelengths from fiber Bragg gratings (FBGs) when monitored using a pixel-based solid state spectrometer have been investigated. These errors show a pseudo-sinusoidal ripple superimposed upon the expected linear response. The error is analogous to a peak-locking effect common to subpixel resolution particle tracking by CCD camera in particle image velocimetry. The amplitude of the error is calibrated as a proportion of the scaled variation of the change in the peak power of the calculated peak as the spectral peak is scanned across the pixel array. An error correction algorithm has been developed and verified in order to provide an increase in the accuracy of sensing solutions when using pixel-based spectrometers. The methods presented here permit the correction of pixel induced ripple errors in real time using data commonly available from many interrogation spectrometers. Calibration prior to use can be achieved by scanning each FBG spectral peak across the width of a single pixel. The proposed method of error correction is applied to a fiber optic sensor array utilized for biomedical pressure and temperature measurement and demonstrates a clear ability to increase the accuracy of measured signals.