Fast Wavelength Calibration Algorithm for Optical Spectrum Analyzers

Authors: Thomas Fuhrmann

Abstract:

In this paper an algorithm for fast wavelength calibration of Optical Spectrum Analyzers (OSAs) using low power reference gas spectra is proposed. In existing OSAs a reference spectrum with low noise for precise detection of the reference extreme values is needed. To generate this spectrum costly hardware with high optical power is necessary. With this new wavelength calibration algorithm it is possible to use a noisy reference spectrum and therefore hardware costs can be cut. With this algorithm the reference spectrum is filtered and the key information is extracted by segmenting and finding the local minima and maxima. Afterwards slope and offset of a linear correction function for best matching the measured and theoretical spectra are found by correlating the measured with the stored minima. With this algorithm a reliable wavelength referencing of an OSA can be implemented on a microcontroller with a calculation time of less than one second.

Keywords: correlation, gas reference, optical spectrum analyzer, wavelength calibration

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1077084

References:

[1] ITU-T "Spectral Grids for WDM applications: DWDM frequency grid". ITU-T, G694.1, 06/2002.
[2] C. Palmer "Diffraction Grating Handbook", Newport Cooperation, 2005.
[3] K. Benzel, A. Conzelmann, T. Fuhrmann, E. Löcklin "Device for simultaneous analysis of multiple optical channels". European Patent EP 1106979, 1999.
[4] S. L. Gilbert, W. C. Swann "Acetylene 12C2H2 Absorption Reference for 1510 nm to 1540 nm Wavelength Calibration - SRM 2517a". NIST Special Publication 260-133, 2001.
[5] A. Savitzky, M. J. E. Golay "Smoothing and Differentiation of Data by Simplified Least Square Procedure". Analytical Chemistry, Vol. 36, No. 8, pp. 1627-1639, 1964