Absolute distance measurement based on spectral interferometry using femtosecond optical frequency comb

We demonstrated an absolute distance measurement method based on the frequency folding effect using the spectral interferometry of femtosecond optical frequency comb. And the investigation was carried out on the ranging accuracy influence of the phase noise in the traditional complicated phase unwrapping method via band-pass filter and Fourier Transform. To reduce the effects of the phase noise, we proposed the non-filtered and differential envelop phase demodulation method, and its robustness was illustrated with a standard deviation of 75 nm for the stability of single point measurements. Further, through the extension of the non-ambiguity range, we achieved a resolution of better than 30 gm in a long distance measurements range of 70 m, yielding a relative precision of 3.1 x 10(-7).