In a way inspired by quantum mechanics of one-dimensional systems
exhibiting the combined parity-reversal plus time-reversal symmetry
of their Hamiltonians {\em as well as} of their wave functions
(called, conventionally, an unbroken PT-symmetry) the authors
re-interpret the corresponding (discrete version of) Schroedinger
equation as an (Anderson's) localization problem defined on an
optical one-dimensional lattice where the original PT-symmetric
potential is simply treated as the refraction index. The main result
is the demonstration of the fragility of the PT-symmetric phase in
this model when equipped with a PT-symmetric, i.e., peculiar
long-range-correlated disorder. This means that the allowed interval
of strengths $\gamma$ of the imaginary part of the random refraction
index quickly (viz., exponentially) vanishes with the growth of the
lattice size $N$. Once we return to the original inspiration of the
model (viz., to quantum mechanics), this result appears
disappointing since the fragility could be considered generic [cf.
M. Znojil, Fragile PT-symmetry in a solvable model
(math-ph/0403033), J. Math. Phys. 45 (2004) 4418 - 4430 where I
brought a few more concrete arguments]. Indeed, what has really been
found surprising in {\em some} quantum-mechanical models (cf., e.g.,
reviews [1] for more details) was an opposite discovery of emergence
of non-vanishing and unexpectedly robust {\em large} domains of
admissible, unbroken-PT-symmetry-compatible parameters like
$\gamma$.

MR2538823 Bendix, Oliver; Fleischmann, Ragnar; Kottos, Tsampikos;
Shapiro, Boris Exponentially fragile $\scr{PT}$ symmetry in lattices
with localized eigenmodes. Phys. Rev. Lett. 103 (2009), no. 3,
030402, 4 pp. 81Txx (82Bxx)