Develoment of Two-Wavelength Laser Precise Distance-Measuring Instrument for Earthquake Prediction

在激光测距仪中，有干涉法、脉冲法、调制法等几种方法。对于大气传输距离为1~50公里的介质，最合适的调制方法是测量传输距离所经历的相位延迟。因此，必须研制一种稳定、高效的微波电光调制器来精确测量大气中的距离。利用KDP晶体构建了一个具有较高激光强度调制指数的可再入圆柱腔。本文分析并研制了用于激光测距仪的S波段电光调制器，其工作频率约为3 GHz。通过在鱼子馆内使用KDP晶体建立了一个可再入的圆柱形空腔。用有限元方法对箱体效率进行了理论分析。在微波输入峰值功率为1W时，该调制器的S激光强度调制率为8%。在实验室中进行了测距试验，结果表明，该调制器能够以IMM的仪器精度测量距离。

In a laser distance-measuring instrument, there are several methods such as interformetric method, pulse method, and modulation method. To mesure medium distanced of one to fifty kilometers through atmosphere, the modulation method is most appropriate, which measures phase delay undergoing in traversing the distance. Terefore, a stable and efficient microwave electro-optic modulator must be developed for the accurate and precise measuement of distance through atmosphere by using the modulation method.A re-entrant cylindrical cavity using a KDP crystal is constructed which has a high laser intersity modulation index. An electro-optic modulator which operates at a frewuency of around 3GHz in the S-gand microwave regin is analyzed and developed for use in a laser distance-measuring instrument. A reentrant cylindrical cavity id consturcted by using a KDP crystal inside the caviry. %The cabity efficiency is theoreticaly analyzed by finite element method. The modulator has s laser intensity modulation index of 8% which has been obtained with a microwave input peak power of 1 W. The modulator is tested in the laboratory for distance measurement with the result that the modulator is capable of measuring a distance with the instrumental accuracy of imm.