EXTENDED-RANGE FMCW REFLECTOMETRY USING AN OPTICAL LOOP WITH A FREQUENCY SHIFTER

We propose a novel method to extend the measurement range of FMCW refl ectometry. In this method, an optical loop with a frequency shifter (w orking frequency f(FS) Hz) is incorporated in the reference arm of the reflectometry, As a result, the interference signal corresponding to the reference beam that circulates N rounds in the loop appears around (N x f(FS)) Hz, which means that the signals from different measureme nt ranges can be detected in different frequency domains, Therefore, i t is possible to extend the measurement range, In the experiment, the measurement range is extended from 15 m to 48 m.