Optical Frequency-Domain Reflectometry (OFDR)

The OFDR technology provides information on the local characteristic only when the backscatter signal detected during the entire measurement time is measured as a function of frequency in a complex fashion, and then subjected to Fourier transformation. The essential benefits of OFDR technology are the quasi continuous wave mode employed by the laser and the narrow-band detection of the optical back scatter signal, whereby a significantly higher signal to noise ratio is achieved than with conventional pulse technology (OTDR). This technical benefit allows the use of affordable semiconductor laser diodes and electronic assemblies for signal averaging. This is offset by the technically difficult measurement of the Raman scatter light and rather complex signal processing, due to the FFT calculation (FFT, Fast Fourier Trans-formation) with higher linearity requirements for the electronic components.