High-precision and long-range distance measurement independent of temperature based on two optoelectronic oscillators

Abstract

A high-precision and temperature insensitive longrange distance measurement (DM) based on frequency detection is proposed and experimentally demonstrated. Two optoelectronic oscillators (OEOs) are grouped into a cross-referencing structure by Dense Wavelength Division Multiplexing (DWDM), which can greatly increase the measurement accuracy by reducing the influence of the environment such as temperature on the long fiber in the two OEOs. Because the long fiber is shared by the two OEOs, the frequency drifts caused by the long fiber are equal, then the surrounding disturbance for the measurement is overcome by mixing the oscillation frequency of the two OEOs. By measuring the intermediate frequency (IF) mixed by the two OEOs, the proposed DM acquires the frequency information converted by the distance information, which has taken advantage of the accumulative magnification in OEO and significantly improves the precision of the measured distance. In the experiment, the measurement error is ±20μm at an emulated distance of approximately 6km, and the measurement sensitivity is 17.867kHz/cm. The relative measurement precision in the proposed system is 10−9, which can be used to measure the displacement, refractive index change, temperature, etc.