Arbitrary and absolute length measurement based on femtosecond optical frequency comb

Abstract

High-accuracy distance measurement plays an important role in many applications, such as industry measurement, Aerospace and scientific research. The continual development oflaser ranging technique is always a frontier topic of geometric measurement, therefore this paper develops the application of femtosecond optical frequency comb for length measurement. Time-of-flight principle for distance measurement is widely used by pulse laser, however, achievable resolution reaches only a few millimeters at best due to the limited bandwidth of electronics. In this paper, the temporal coherence of multiple pulse train is analyzed, and an arbitrary and absolute length measurement system is set up based on modified Michelson interferometer by combining multiple pulse train interference and time-of-flight method. The timing difference is separately calculated by the first-order and second-order optical cross-correlation signals, therefore the absolute distance is calculated. An experiment is conducted by measuring a 60 cm length, and the measurement result is compared with a high precision laser displacement sensor. The result shows a good measuring linearity, and the measurement precision of ±0.5 μm is achieved.