19:30 〜 19:45
▲ [14p-2D-19] Absolute distance measurement by two-color heterodyne pulse-to-pulse interferometry of optical frequency combs
キーワード：Two-color,heterodyne inteferometry,synthetic wavelength
Optical frequency comb has led to revolutionary progress in absolute distance measurement. In our previous study, we have reported a synthetic-wavelength interferometry of optical frequency combs to improve the accuracy of pulse-topulse alignment [1]. However, the system that requires second harmonic generation and two acousto-optic modulators is complicated for practical applications. In the present study, we developed a compact heterodyne pulse-to-pulse interferometer for absolute distance measurement. Figure 1 illustrates the system layout configured for our measurements. The approach utilizes an optical frequency comb of Er-doped mode-locked fiber laser as the light source. The system is based on an unbalanced Michaelson interferometer. We use two band-pass filters to select two close wavelengths (λa=1550 nm and λb=1560 nm) to generate a synthetic wavelength of 240 μm. Long fiber is used to expand the dynamic range of distance measurement. With this system we made a step-by-step distance measurement up to 0.5m to confirm the measurement dynamic range expansion and evaluate the ranging accuracy. By using synthetic wavelength as a bridge between the interference intensity peakfinding method and the heterodyne interferometric phase measurement, we can achieve distance measurement in nanometer level.