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首页> 外文期刊>Applied optics >Improved speckle statistics in coherent differential absorption lidar with in-fiber wavelength multiplexing
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Improved speckle statistics in coherent differential absorption lidar with in-fiber wavelength multiplexing

机译：光纤内波长复用的相干差分吸收激光雷达的散斑统计得到改善

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摘要

Remote detection of gaseous pollutants and other atmospheric constituents can be achieved with differential absorption lidar (DIAL) methods. The technique relies on the transmission of two or more laser wavelengths and exploits absorption features in the target gas by measuring the ratio of their detected powers to determine gas concentration. A common mode of operation is when the transmitter and receiver are collocated, and the absorption is measured over a return trip by a randomly scattering topographic target. Hence, in coherent DIAL. speckle fluctuation leads to a large uncertainty in the detected powers unless the signal is averaged over multiple correlation times, i.e., over many independent speckles. We examine a continuous-wave coherent DIAL system in which the laser wavelengths are transmitted and received by the same single-mode optical fibers. This ensures that the two wavelengths share a common spatial mode, which, for certain transmitter and target parameters, enables highly correlated speckle fluctuations to be readily achieved in practice. For a DIAL system, this gives the potential for improved accuracy in a given observation time. A theoretical analysis quantifies this benefit as a function of the degree of correlation between the two time series (which depends on wavelength separation and target depth). The results are compared with both a numerical simulation and a laboratory-based experiment.
机译：可以使用差分吸收激光雷达（DIAL）方法实现对气体污染物和其他大气成分的远程检测。该技术依靠两个或多个激光波长的传输，并通过测量目标气体的检测功率之比来确定气体浓度，从而利用目标气体中的吸收特征。一种常见的操作模式是将发射器和接收器并置在一起，并通过随机散射的地形目标在回程中测量吸收率。因此，在连贯的DIAL中。除非信号在多个相关时间（即在许多独立的斑点上）得到平均，否则斑点波动会导致检测到的功率具有很大的不确定性。我们研究了连续波相干DIAL系统，在该系统中，激光波长是由相同的单模光纤发送和接收的。这确保了两个波长共享一个共同的空间模式，对于某些发射器和目标参数，该模式可以在实践中轻松实现高度相关的斑点波动。对于DIAL系统，这可以在给定的观察时间内提高准确性。理论分析将这种收益量化为两个时间序列之间的相关程度的函数（取决于波长间隔和目标深度）。将结果与数值模拟和实验室实验进行比较。

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