  We consider parity-time ($\mathcal{PT}$) symmetric arrays formed by $N$
optical waveguides with gain and $N$ waveguides with loss. When the gain-loss
coefficient exceeds a critical value $\gamma_c$, the $\mathcal{PT}$-symmetry
becomes spontaneously broken. We calculate $\gamma_c(N)$ and prove that
$\gamma_c \to 0$ as $N \to \infty$. In the symmetric phase, the periodic array
is shown to support $2N$ solitons with different frequencies and polarisations.
