We present a approach aimed at generalizing Parity-Time symmetry to mesoscopic ensembles of coupled oscillators with gain and loss, with inspiration from graph-theoretic tools. We globally minimize the imaginary part of the eigenvalues for small gain/loss and describe how couplings adopt some topologies. We also discuss recent results on distributed-feedback laser diodes operating at 1550 nm and having both real and imaginary index modulation. We notably study their resistance to optical feedback.