Evaluation of coherence length and related parameters in anisotropic Kolmogorov jet engine exhaust turbulence.

Abstract

Coherence length defined as the propagation distance over which a coherent wave maintains a specified degree of coherence is one of the main parameters in optical wireless communication (OWC). Knowledge about coherence length is important in the design of OWC systems operating in turbulent media. Such information is used in mitigating the turbulence degradation and enhancing the system performance in OWC links. Coherence length is also utilized in determining many entities in optical wave propagation in turbulence such as average intensity, transmittance, beam spreading, mutual coherence function, and scintillation index. In jet engine exhaust turbulence, coherence length becomes even more important since in such media, strong turbulence regimes are experienced over short link distances. Coherence length variations in anisotropic Kolmogorov jet engine exhaust turbulence are evaluated against the link, turbulence parameters, and anisotropic factors. Parameters related to the coherence length such as the atmospheric coherence time and the minimum number of required actuators on a deformable mirror for improving the performance of anisotropic jet engine exhaust are also presented. Results reported in this paper will help OWC engineers and researchers in promoting the use of OWC links operating especially in airports.