18. The sequence $\left\{ a _ { n } \right\}$ is an increasing geometric sequence with $a _ { 1 } + a _ { 4 } = 9 , a _ { 2 } a _ { 3 } = 8$.\\
(1) Find the general term formula of the sequence $\left\{ a _ { n } \right\}$;\\
(2) Let $S _ { n }$ be the sum of the first $n$ terms of the sequence $\left\{ a _ { n } \right\}$, and $b _ { n } = \frac { a _ { n + 1 } } { S _ { n } S _ { n + 1 } }$. Find the sum $T _ { n }$ of the first $n$ terms of the sequence $\left\{ b _ { n } \right\}$.