Free-space optical transmission measurements from 0.532 to 10 µm in real controlled fog

Free-space optical transmission at 0.532, 1.55, 4, and 10 µm through real controlled fog with simultaneously measured droplet size distributions representative of continental and maritime fogs is reported. Measured attenuation is compared with predictions from Mie theory and two visibility-based models, the latter of which fail to predict transmission performance beyond the near-infrared. Although the 4 µm wavelength shows no meaningful advantage over 1.55 µm, long-wave infrared transmission at 10 µm is shown to provide a gain in transmission exceeding 20 dB in continental fog conditions.