Simulation of real-time large-scale absolute distance measurement with a pair of femtosecond frequency comb lasers

Absolute distance measurement is essential in large-scale equipment manufacturing and scientific projects. Nowadays, sophisticated equipment manufacture demands for high-precision ranging with a high speed. Several raging methods utilizing the wide spectral range and stable frequency intervals of femtosecond frequency comb laser can achieve a high precision, but most of such systems suffer from relative low speed. Fortunately, the ranging method based on a pair of femtosecond frequency comb lasers can potentially resolve such problem. Combining time-of-flight and interferometry method, the measurement can accomplish rapid raging in a measurement period of 0.2ms, and achieve higher precision by interferometry after averaging of many periods. We performed a simulation of this method in Matlab/Simulink. The precision can achieve similar to 10nm in ideal simulation environment. By error analysis we estimated the data processing system, and gave the appropriate parameters of detector and A/D sampling. It comes to a conclusion that detector with relative long response time of similar to 7nm or about can be adopted, and fast Fourier transformation (FFT) of 16384 points contributes to higher precision. With such parameters, it is possible to realize real-time raging performed on field-programmable gate array (FPGA) with high precision.