Delay optical path with long fiber toward absolute distance measurement by optical balanced cross-correlation

A set of delay optical path device with long fiber of various lengths are developed. They are applied in the absolute distance measurement system based on the principle of optical balanced cross-correlation. Limited with the repetition rate scanning range of femtosecond laser, dead zone exists in the absolute distance measurement range via a femtosecond optical frequency comb. With the fixed scanning range of repetition rate, the measurement system introduced different length of long fiber can realize different space scanning distance and the resolution of corresponding space scanning distance are given. Meanwhile, the optical path fluctuation of delay optical path with different length is measured by optical balanced cross-correlation absolute distance measurement technology. From the results, it is possible to realize arbitrary absolute distance measurement.