Fig. 1. Experimental setup for (a) turbulence due to air bubbles and (b) turbulence due to temperature.

Fig. 2. Measured reflectivity spectra of black silicon and black cloth.

Fig. 3.  Photographs of four different air bubbles in the water channel under four different water circulation levels with corresponding bubble size histograms.

Fig. 4. Optical signal through bubbly water with (a) no bubbles with ${\sigma }_I^2=1.0764\times {10}^{-4}$; (b) small bubbles with ${\sigma }_I^2=0.1027$; (c) medium bubbles with ${\sigma }_I^2=0.1569$; (d) large bubbles with ${\sigma }_I^2=0.3591$; and (e) x-large bubbles with ${\sigma }_I^2=0.5195$.

Fig. 5. Histograms of the received optical signal through bubbly water with (a) no bubbles with ${\sigma }_I^2=1.0764\times {10}^{-4}$; (b) small bubbles with ${\sigma }_I^2=0.1027$; (c) medium bubbles with ${\sigma }_I^2=0.1569$; (d) large bubbles with ${\sigma }_I^2=0.3591$; and (e) x-large bubbles with ${\sigma }_I^2=0.5195$. (f) A plot of the scintillation index and normalized received power against the mean bubble area.

Fig. 6. (a) Received optical signal through the temperature difference corresponding to 0°C, 6°C, and 10°C; (b) a plot of the scintillation index and normalized received power against the mean bubble area.

Table 1. Different Temperature Values Used to Create the Temperature Gradient