  We study the mechanism for realizing non-Hermitian skin effect (NHSE) via
dissipative couplings, in which the left-right couplings have equal strengths
but the phases do not satisfy the complex conjugation. Previous realizations of
NHSE typically require unequal left-right couplings or on-site gain and loss.
In this work we find that when combined with the multichannel interference
provided by a periodic dissipative-coherent coupling structure, the dissipative
couplings can lead to unequal left-right couplings, inducing NHSE. Moreover, we
show that the non-Hermiticity induced by dissipative couplings can be fully
transformed into nonreciprocity-type non-Hermiticity without bringing extra
gain-loss-type non-Hermiticity. Thus, this mechanism enables unidirectional
energy transmission without introducing additional insertion loss. Our work
opens a new avenue for the study of non-Hermitian topological effects and the
design of directional optical networks.
