A coherent optical fiber sensor for characterizing a turbulent medium

Laser beam propagation through a turbulent medium has long been a subject of fundamental interest, but experimental investigations have been largely limited to the measurement of intensity fluctuations over long path lengths. By turbulence, we mean the small but rapidly fluctuating temperature inhomogeneities ever present in the atmosphere. The phenomenon is not well understood, but may be characterized by several statistical parameters, and in particular by a parameter C_n ², which is a measure of the correlation of refractive index fluctuations at spatially separated points. In this investigation, we utilize an optical fiber Mach-Zehnder interferometric probe to characterize a turbulent region. By analyzing the phase correlation between two parallel laser beams that travel through a short turbulent region and whose separation can be varied, we are able to characterize the turbulence and possibly gain further insight into this poorly understood phenomenon