New method for lightning location using optical ground wire

A new technology of lightning location is described, which is based on detecting the state of polarization (SOP) fluctuation of the laser light in the optic ground wire (OPGW). Compared with the conventional lightning location method, the new method is more accurate, more stable, and cheaper. Theories of Stokes parameters and Poincare sphere are introduced to analyze the SOP at the lightning strike point. It can be concluded that although the initial points of SOP on the Poincare sphere are random, the SOP fluctuation generated by lightning strike can still be accurately identified by detecting the velocity of polarization motion. A new algorithm to quantify the velocity is also introduced.     

Micro-Gal laser absolute gravimeter based on high precision heterodyne interferometer

A micro-Gal absolute gravimeter based on high-precision and high-stability heterodyne interferometer is presented.The distance measuring technology of the gravimeter is studied in detail.The experimental results of distance measuring for a free-falling motion show that the high-precision heterodyne interfer- ometer described in this paper can meet the demand of a micro-Gal absolute gravimeter with relative uncertainty of 6.4×10~(-9).Moreover,the heterodyne interferometer is more stable than the Mach-Zehnder interferometer(MZI)which is widely used in present absolute gravimeters.     

OPGW断股状态的光学监测技术研究

针对OPGW(光纤复合架空地线)易发生断股的现象,提出了采用布里渊光时域反射仪测量其内部光纤应变的断股检测方法。实验中将一段OPGW的两端固定在拉力机上并施加固定的拉力值,逐渐增加OPGW中断开的单丝数,记录布里渊光时域反射仪测量的光纤应变值。实验结果表明,该方法可实现对25%以上的断股区域截面积比的监测,为在线监测OPGW断股状态提供了一种新的思路。     

光传输链路高速自动增益控制研究

分析了光纤传输链路信号波动来源,得出引起信号波动的两种关键因素,针对该两种因素设计了一套高速自动增益控制系统(AGC)以及一套针对该系统的计算机软件效标方案,在光纤链路中通过引入该系统,使得光纤传输链路输出射频功率波动由以前的11 dB降低为0.5 dB以内。     

偏振光斯托克斯参量的高速实时测量技术

为了满足对高速变化的偏振态的测量,提出一种能够对偏振态实现高速测量的技术。阐述了利用1/4波片与起偏器测量偏振光的斯托克斯参量常规的原理和方法,根据高速测量的要求推导出了新的斯托克斯参量计算公式,并依据此公式设计了基于多通道偏振态高速测量的方案,设计了具体的方法并编写了控制与算法程序。测试表明,该系统的测量速度达到了每秒700次偏振态测量,测量速度主要由电子线路的性能决定,测得的结果稳定可靠实现了光纤传输偏振态的高速测量。     

Measuring of the maximum measurable velocity for dual-frequency laser interferometer

There is an increasing demand on the measurable velocity of laser interferometer in manufacturing tech- nologies.The maximum measurable velocity is limited by frequency difference of laser source,optical configuration,and electronics bandwidth.An experimental setup based on free falling movement has been demonstrated to measure the maximum measurable velocity for interferometers.Measurement results show that the maximum measurable velocity is less than its theoretical value.Moreover,the effect of kinds of factors upon the measurement results is analyzed,and the results can offer a reference for industrial ap- plications.     

加速度对激光双频干涉仪测量误差的影响

为了减少由于加速度所导致的激光双频干涉仪测量误差,引入二阶多普勒频移,建立了由被测物体加速度所引起的测量误差的理论模型。仿真结果表明,在0.4s时间内0.6g加速度所引起的累积误差可达2.5nm左右,这对于纳米精度的测量是不应忽视的;初速度不为零时加速运动会引起更大的误差,而减速运动所引起的误差则相对小。通过实验验证,所测的误差变化趋势与理论模拟比较吻合。