  We have investigated the interaction between a strong soliton and a weak
probe with certain configurations that allow optical trapping in gas-filled
hollow-core photonic crystal fibers in the presence of the shock effect. We
have shown theoretically and numerically that the shock term can lead to an
unbroken parity-time $ \left(\mathcal{PT}\right) $ symmetry potential in these
kinds of fibers. Reciprocity breaking, a remarkable feature of the $
\mathcal{PT} $ symmetry, is also demonstrated numerically. Our results will
open different configurations and avenues for observing $ \mathcal{PT}
$-symmetry breaking in optical fibers, without the need to resort to cumbersome
dissipative structures.
