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Atmospheric laser propagation at near infrared.

机译：大气激光在近红外处的传播。

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摘要

The main aim of this project is to investigate the characteristics of the propagation of laser beams through the atmosphere at the wavelengths of 0.83 and 1.55[mu]m across a 4km path in central London, a densely urbanised terrain. The thesis reports practical measurements of the propagation characteristics in clear air and in also in rain and mist conditions. Meteorological measurements of rainfall rate and wind speed were also made to supplement the propagation measurements. Measurements were also made at 1.55[mu]m with the transmitter modulated at 155Mbits/s. The analysis of the results is divided into four sections. (1) The statistical and spectral analysis of amplitude scintillations and angle of arrival in dry weather, (2) in rain, (3) modelling of the rainfall induced attenuation of the received optical power and (4) the performance evaluation of the prototype of a 155Mbits/s digital free space optical communications system operating at 1.55[mu]m. Results for studies (1) and (2) indicate that the gamma is the best distribution for the received amplitude scintillations for varying turbulence conditions in clear air and also in rain conditions. The normal distribution is the best fit for angle of arrival data, regardless of the strength of turbulence and weather. Level crossing statistics of amplitude scintillations are presented for clear air conditions. Spectral analysis of the scintillations and angle of arrival showed results that confirm theoretical assumptions in dry but not in rain conditions. No evidence of saturation of scintillations was found. In study (3), cumulative distributions of attenuation and rainfall for a year of measurements are presented and the rainfall induced attenuation is evaluated. Statistical comparison of the performances of both wavelengths in rain are shown and indicate that the 0.83[mu]m system has a slightly better overall performance. For study (4), reliability and quality analysis results are presented. Availability figures show values as high as 94.5[percent]. Analysis of bit error rates using level crossing statistics showed an approximate overall 92[percent]-95[percent] probability of error-free operation for the system.
机译：该项目的主要目的是研究激光束通过波长为0.83和1.55μm的空气在密集的城市化伦敦市中心的4公里路径上穿过大气的传播特性。本文报道了在清澈的空气中以及在雨雾条件下的传播特性的实际测量结果。还对降雨率和风速进行了气象测量，以补充传播测量。在发射器以155Mbits / s调制的情况下，也以1.55μm进行测量。结果分析分为四个部分。 （1）干旱天气下振幅闪烁和到达角的统计和频谱分析，（2）在雨中，（3）降雨引起的接收光功率衰减的建模，以及（4）原型的性能评估运行在1.55μm的155Mbits / s数字自由空间光通信系统。研究（1）和（2）的结果表明，对于在晴空和雨天条件下，不同的湍流条件，伽马值是接收振幅闪烁的最佳分布。无论湍流和天气的强度如何，正态分布最适合到达角数据。给出了在晴空条件下振幅闪烁的平交统计。闪烁和到达角的光谱分析表明，结果证实了在干燥条件下而不是在雨天条件下的理论假设。没有发现闪烁饱和的证据。在研究（3）中，给出了一年测量的衰减和降雨的累积分布，并对降雨引起的衰减进行了评估。示出了在雨中两个波长的性能的统计比较，并且表明0.83μm系统具有稍微更好的整体性能。对于研究（4），给出了可靠性和质量分析结果。可用性数字显示该值高达94.5％。使用电平交叉统计数据对误码率进行的分析显示，系统无误操作的总体可能性约为92％-95％。

著录项

  • 作者

    de Miranda, Erasmus Couto B.;

  • 作者单位

    University of London, University College London (United Kingdom).;

  • 授予单位 University of London, University College London (United Kingdom).;
  • 学科 Electrical engineering.
  • 学位 Ph.D.
  • 年度 1996
  • 页码 292 p.
  • 总页数 292
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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