chapter 10, Signal-to-Noise Ratio Enhancement Techniques

Excerpt

In this chapter, techniques to improve spectral SNR of measurements using an FT spectrometer are discussed. In attempting to improve spectral SNR, first it is important to recognize the limiting source of noise and error. In this chapter, some of the dominant sources of error are identified by analyzing the characteristics of the output spectra through practical and simple experimental procedures.

To begin, some of the various sources of errors are revisited, focusing mainly on their qualitative characteristics. Some practical ways to identify the instrument's limiting source of noise are presented. These procedures are certainly not set in stone, but are intended to provide the reader with a useful starting point in characterizing his or her instrument. Some accepted methods (for both hardware and software) to improve spectral SNR are then presented.

10.1 Identification of Error Sources

10.1.1 Detector noise

As discussed in Sec. 8.2, the allowable spectral SNR due to detector noise (in the detector-noise-limited case) is proportional to the radiation power P incident on the detector element, and is inversely proportional to the detector's NEP value: