  A mechanism for creating a Newton's cradle (NC) in nonlinear light wavetrains
under the action of the third-order dispersion (TOD) is demonstrated. The
formation of the NC structure plays an important role in the process of fission
of higher-order N-solitons in optical fibers. After the splitting of the
initial N--soliton into a nonuniform chain of fundamental quasi-solitons, the
tallest one travels along the entire chain, through consecutive collisions with
other solitons, and then escapes, while the remaining chain of pulses stays as
a bound state, due to the radiation-mediated interaction between them.
Increasing the initial soliton's order, $N$, leads to the transmission through,
and release of additional solitons with enhanced power, along with the emission
of radiation, which may demonstrate a broadband supercontinuum spectrum. The NC
dynamical regime remains robust in the presence of extra perturbations, such as
the Raman and self-steepening effects, and dispersions terms above the third
order. It is demonstrated that essentially the same NC mechanism is induced by
the TOD in finite segments of periodic wavetrains (in particular, soliton
chains). A strong difference from the mechanical NC is that the TOD-driven
pulse passing through the soliton array collects energy and momentum from other
solitons. Thus, uniform and non-uniforms arrays of nonlinear wave pulses offer
an essential extension of the mechanical NC, in which the quasi-particles,
unlike mechanical beads, interact inelastically, exchanging energy and
generating radiation. Nevertheless, the characteristic phenomenology of NC
chains may be clearly identified in these nonlinear-wave settings too.
