Absolute Distance Measurement Using an Optical Comb and an Optoelectronic Oscillator

We demonstrate a method for absolute distance measurement based on an optical frequency comb and an optoelectronic oscillator. The unknown distance is measured using optical sampling by cavity tuning. A 1000-m-long fiber is used as a reference path and actively stabilized by the optoelectronic oscillator without ambiguous range. The optical path length of the long fiber is converted to oscillation frequency of the optoelectronic oscillator and locked to an atomic clock. A 0.357-μm standard deviation of the long fiber reference path is verified by the experimental results, corresponding to a 10
^-10
level relative stability. The proof-of-principle absolute distance measurement is implemented and compared with a commercial interferometer. An agreement better than 4 μm is achieved in 22-mm tuning range with the 1000-m imbalanced interferometer setup.