Laboratory-simulation experiment for optical communication through low-visibility atmosphere using a diode laser

A laboratory-simulation experiment has been performed to determine the feasibility of exploiting the scattered (in addition to the unscattered) radiation to improve optical communication through low-visibility atmosphere. A multiple field-of-views (FOV) ( full angle) optical receiver was designed which utilizes a narrow-band interference filter ( Å) for background-light suppression. The laser transmitter was a CW GaAlAs laser diode ( m) capable of emitting ∼ 7 mW power output of 15° divergent beam. Both polydisperse (particle diameters, in the range of m) and monodisperse ( m and m) latex spheres in water were used for simulating haze, fog, etc. Results include signal-to-noise ratio (SNR) and scattered-to-unscattered signal ratio as a function of field-of-view of reception for various optical thickness of the medium. Also, SNR is plotted as a function of optical thickness for various FOV\´s. The unique feature of this simulation is that it can simulate worst case solar background where the sun enters the FOV of receiver. Finally a new technique of estimating forward-scattering efficiency and root-mean-square forward scatter angle has also been presented with examples.