Calibrating an optical FMCW backscattering measurement system

A method of calibrating an optical FMCW backscattering measurement system, the system comprising an excitation and evaluation part and a longitudinally extending sensor, the sensor having a first and a second end, the excitation and evaluation part being adapted for exciting a frequency modulated light signal with modulation frequency fm and for evaluating a sensor signal received from the first end of the sensor, the sensor being adapted for capturing a data signal based on the frequency modulated light signal from which physical parameters of spatially distributed measurement points of the sensor along its length between the first and second ends may be extracted, the method comprising the steps of

• A. converting said received sensor signal to a complex received electrical signal as a function of said modulation frequency fin, said complex received electrical signal being represented by a magnitude part and a phase angle part as a function of said modulation frequency fm;
• B. performing a transformation of said received electrical signal to provide a backscattering signal as a function of location between said first and second ends of said sensor and beyond said second end;
• C. indicating said backscattering signal as a function of location determining characteristics of a curve representative of said backscattering signal beyond said second end;
• D. correcting said magnitude part of said received electrical signal and said phase angle part of said received electrical signal in a predetermined dependence of said curve;
• E. repeating step B on the basis of the corrected received electrical signal.