\begin{table}%t4
%\centering
\par
\caption{\label{opteffth}Break-down of the optical efficiencies of each component of a detection assembly.} 
\begin{tabular}{ccc}
\hline\hline
\noalign{\smallskip}
Component/coupling & Av. Return Loss & Av. In-band transm.\\
\hline
Back-to-Back horn & $-$19~dB & 98.7\%\\
Filter stacks & & 75\%\\
Horn coupling (lens) & & 90\%\\
Detector Horn & $-$19~dB &98.7\%\\
Coupling horn-detector & & 95\%\\
Detector efficiency & & 90\%\\
Total efficiency & & 56\%\\
\hline
\end{tabular}
\tablefoot{Except for the filters stack transmission which has been measured independently, the other values are the theoretical maximum transmission. The total gives the overall maximum optical
efficiency for each channel assuming perfect components.}
\end{table}