How can I reduce the extra phase space between the equal sign and the equations? (It seems this question was previously answered in different softwares, i.e., Matlab, Python,..) many thanks in advance
\documentclass[9pt]{osa-supplemental-document}
\setboolean{shortarticle}{false}
\title{vvvv}
\author{} %leave this blank
%% DO NOT ADD AUTHOR INFORMATION HERE; IT WILL BE ADDED DURING PRODUCTION
\begin{abstract}
\end{abstract}
\setboolean{displaycopyright}{false} %copyright statement should not display in the supplementary document
\begin{document}
\maketitle
\section{,,,,}\label{ss}
I
\begin{eqnarray}
S_0&=&2+2\\
S_0&=&ssss
\end{eqnarray}
\end{document}