基于交替起振光电振荡器的大量程高精度绝对距离测量技术

Long-range, high-precision absolute distance measurement technology based on alternately oscillating optoelectronic oscillator

提出了一种基于交替起振的光电振荡器的大量程、高精度绝对距离测量方法.此方法构建了两个光电振荡环路,分别为测量环和参考环.通过切换光开关实现测量/参考光电振荡器的交替起振;通过切换微波开关实现光电振荡器高阶/低阶振荡模式的转换;通过频率计依次记录测量/参考光电振荡器的高阶/低阶振荡频率,然后计算测量/参考光电振荡器的腔长进一步得到绝对距离.本方案的优点是:由于采用了测量/参考两个光电振荡器腔长相减的方法消除系统自身的漂移,不需要控制腔长,结构简单.实验中,利用公里量级的光纤来模拟大量程的待测距离,利用高步进精度的光延时线来模拟距离变化.在等效6 km的空间往返待测距离上,测量误差为3.5μm,相对测量精度达到5.8×10^10.

Absolute distance measurement plays an important role in many areas,such as aerospace and scientific research.Traditional measurement methods generally cannot meet requirements for long-range and highprecision at the same time.In this paper,an absolute distance measurement method based on alternately oscillating optoelectronic oscillator is proposed.This method places the distance to be measured in the loop of optoelectronic oscillator and takes advantage of accumulative magnification effect to achieve high accuracy.The measurement and the reference optoelectronic oscillators are established and selected by an optical switch,and a microwave switch is used to choose the high-order or low-order oscillating frequency.The high-order frequency and low-order oscillating frequency of the measurement and reference optoelectronic oscillators are measured in turn by frequency counter to calculate the loop lengths of two optoelectronic oscillators.The low-order frequencies are used to measure the fundamental frequency roughly and the high-order frequencies are used to calculate loop length precisely.Although the mode hopping occurs in the measurement process,it does not affect the loop length calculation by substituting the corresponding oscillating mode number.Note that the loop length measurement moments of two optoelectronic oscillators are different due to the switching order of optical switch and microwave switch.In order to calculate the absolute distance,which is the length difference between two optoelectronic oscillators at the same moment,the measured loop lengths should be averaged.In this way,systematic error accumulation caused by slow drift of environment can be eliminated,and this method does not need to control the length of reference optoelectronic oscillator.Meanwhile,the measurement system is simple.In the experiment,1 km,5 km and 8 km fibers are placed in a common part of the measurement and reference optoelectronic oscillators to simulate different long-range distances in space.A high-resolution optical delay line is placed in the measurement optoelectronic oscillator to verify the performance of the measurement system.The experimental results show that the measurement error is 3.5μm with a 3.5μm maximum standard deviation of each measurement distance at an emulated round trip distance of 6 km.The relative measurement accuracy reaches 5.8×10^-10.This method provides a feasible idea for solving the technical problems of longrange and high-precision absolute distance measurement.