Long-range, high-precision absolute distance measurement based on two optoelectronic oscillators.

We demonstrate a scheme for long-range, high-precision absolute distance measurement based on frequency detection using two optoelectronic oscillators to convert distance information to frequency information. The two-oscillator design offers the unique advantage of self-referencing. By taking advantage of the accumulative magnification theory, the error of the measured distance is decreased by approximately 10⁵ fold, which significantly improves the precision of the measured distance. In our experiments, the maximum error is ±1.5  μm at an emulated distance of approximately 3.35 km, including a drift error of approximately 1 μm in the air path due to the variation of environmental conditions. The highest relative measurement precision achieved in our current system is 4.5×10⁻¹⁰.