\documentclass{article}
\usepackage{feynmp}
\begin{document}
\thispagestyle{empty}
    \unitlength = 2mm
 \begin{fmffile}{graviton}
        \begin{fmfgraph*}(40,25)
             \fmfright{i1,i2}
             \fmfleft{o1,o2}
             \fmflabel{$\alpha\beta$}{v1}
             \fmflabel{$\mu\nu$}{v2}
             \fmf{phantom}{i1,v1,i2}
             \fmf{phantom}{o1,v2,o2}
             \fmf{dbl_wiggly}{v1,v2}
         \end{fmfgraph*}
 \end{fmffile}
\end{document}