Study On Long-range High-precision Absolute Distance Measurement Based On Optoelectronic Oscillator

The development of measurement techniques is the premise and foundation of allscience and technology development, and the level of its technological developmentdetermines the level of human understanding as well as the transformation of theworld. Long range, high-precision absolute distance measurement technology canimprove the level of large equipment, scientific instruments, manufacturing, whichhave important implications for the promotion of technical progress and the level ofscientific research. So, the technology of long range absolute distance measurementhas been extensive researched in recent years.Traditional absolute distance measurement technology detects the information of thetime-of-flight information or phase change, whose measurement accuracy mainlydepends on the degree of precision of the test tools and instruments. This paperpresents a long range high-precision absolute distance measurement system based onoptoelectronic oscillator (OEO) which introduces the distance to be measured into theOEO loop by using the relation between the oscillation frequency and the loop length.The distance information could be obtained through the measurement of the frequencyinformation. Accumulative magnification theory is also used that the frequencyinformation is amplified by integral multiples, thus in the same condition ofobservation, the measurement could have higher accuracy. Besides, this concept is notlimited by the ambiguity range so it has larger measurement range.In order to achieve higher precision in the frequency measurement, the OEO systemshould have high-quality oscillation output. In this paper, the basic structure andworking principle of the OEO especially the noise performance were introduced. Theadopted optical domain polarization dual-loop structure suppresses the side-modenoise effectively. Output signal of OEO is of high quality with high spectral purityand low noise. The introduction of distance measurement into OEO system wastheoretically analyzed and the characteristics of long range and high precision wereclarified.The environmental factors such as temperature, vibration will greatly affect the OEO loop length, resulting in the fluctuation of oscillation frequency even the modejumping which greatly reduces the measurement stability and accuracy of the system.To solve this problem, we use two signals with different wavelengths to construct the“stabilization loop” and “measurement loop” respectively. The phase-locked looptheory was adopted in the stabilization loop to stabilize its oscillation frequency whichensures the stability of OEO basic loop length. So the exact value of the distanceinformation could be obtained by testing the oscillation frequency of the measurementloop.We also completed the test of the stability, accuracy and range ability of OEOmeasurement system. Results show that the measuring system has a very highstability that the stability of OEO basic loop length is approximately10-9whichensures the accuracy of the distance information. The maximum error1.4m isobtained at the simulated3-km distance over1.5m range. The maximum measureddistance range of our experiment is6km, which could be extended more withnon-ambiguity range. The errors do not exceed1.5m during different testing rangethat further validates the OEO ranging system’s capability of long range,high-precision absolute distance measurement.