Fig. 2.

$f(z|t)$ as a function of z for $t=0.50,0.75,1.00,1.25,1.5,2.0,3.0,4.0\text{ns}$ (color code from brown to blue) for a two-layer medium ( $s_1=15\text{mm}$ , $s_2=75\text{mm}$ , $n_1=n_2=1.4$ , ${\mu }_{s1}^{\mathrm{\prime }}={\mu }_{s2}^{\mathrm{\prime }}=1.0\text{m}{\text{m}}^{-1}$ ). (a)-(e): variable ${\mu }_{a1}=0.005,0.010,0.015,0.020,0.025\text{m}{\text{m}}^{-1}$ , fixed ${\mu }_{a2}=0.015\text{m}{\text{m}}^{-1}$ ; (f)-(j): fixed ${\mu }_{a1}=0.015\text{m}{\text{m}}^{-1}$ , variable ${\mu }_{a2}=0.005,0.010,0.015,0.020,0.025\text{m}{\text{m}}^{-1}$ . In all cases $\rho =30\text{mm}$ , $n_{e1}=n_{e2}=1.0$ .