\documentclass{standalone}
\pagestyle{empty}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}

\draw [ultra thin,cyan,->] (-5,0)--(5,0);

\draw [ultra thin,cyan,->] (0,-3)--(0,3);

%\draw [thick] (-5,1.75)--(-4,1)--(-2,2.5)--(0,1)--(2,2.5)--(4,1)--(5,1.75);
\draw [thick] (-5,-1.75)--(-2.5,2.5)--(-1.5,-2.5)--(0,0)--(1.5,2.5)--(2.5,-2.5)--(5,1.75);


\node at (-4.4, -.2) {$2l$};
\node at (-2.4, -.2) {$-l$};
 \node at (0, -.2) {$0$};
\node at (1.8, -.2) {$l$};
\node at (3.6, -.2) {$2l$};

\end{tikzpicture}
\end{document}