Comparison of optical propagation properties in different wavelength regimes are difficult to measure, especially in continuous varying environment. Detector and measurement equipment are typically optimized for specific spectral band and utilize matching amplifiers with have different response and process time making it hard or impossible to match time sensitive data. In this paper we propose the use of a wavelength conversion imaging system which has a broad spectral response and large detector size for synchronous multi-wavelength measurement. We showcase the strength of this approach in comparing the effect of turbulence media on a 1.55 μm and a 4 μm lasers at ambient (20 °C), 45 °C and 75 °C air temperature. Recording the movement and size of the lasers spot and comparing it frame to frame allows for extraction of the effect of turbulence on the individual lasers. Furthermore using cross correlation technique the conditions under which a good comparison can be identified. The result shows peak at 0s time shift for 45 °C and 75 °C which confirms the correlated measurement while the beam wander shows no correlation for ambient temperature as it is random.
A combination of scattering and scintillation effects is considered to compare the resilience of mid-IR and near-IR free space communication links. Beam-wander rw(t) under different scintillation conditions for mid-IR and near- IR beams are recorded simultaneously in real-time by a unique broad-band camera. The correlation coefficients show that both beams undergo the same pathway and experience the same scattering and scintillation effect which allows to identify and distill wavelength dependent effects. Using the frequency dependence in the observed beam wander allows for classification of our simulated atmospheric turbulence. Under these lab conditions, perceived refractive index structure parameter C_n^2 is extracted for each wavelength and a long-term radius is estimated for a long-distance link. In addition, the transmissivity and broadening of beams are calculated using discrete ordinate method to account for the scattering by fog. Considering both scattering and scintillation effects, the experimental and analytical results show that mid-IR (4.328 μm) beam has higher resilience in low visibility conditions compared to a near-IR (1.550 μm) beam.
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