Thank you for your reply. I have done the noise filtering using FFT and works fine, I have used a cosine tapered window to multiply with FFT. Now I have to remove the background using a polynomial fit. I have found one NI discussion about this and got a vi which does this. I have copied the vi to my FFT Vi, it removes the background but in wavelength data only. My final data after FFT will be in wavenumbers, here its not able to do I have adjusted the numbers accordingly still did not work. Is there any method in Labview to remove background of a spectrum automatically by estimating the standard deviation. Because in the present vi i have to choose wavelength range where there is no peaks and fit with a >4th order polynomial, instead I want to do this automatically. I have attached the VI and data file.
Here are the steps steps attached VI,
1. It loads the wavelength vs intensity data
2. background correction using polynomial fit
3. feed the background corrected spectra to interpolation vi