  There are two main approaches to generate the negative energy density (NED)
in the literature. The Casimir effect and the squeezed vacuum. The possibility
of the latter approach is qualitatively reviewed in this paper. It is proposed
that the soliton theory may give remarkable contributions to generate and
separate the NED out of the quantum vacuum. By applying the wavelength-division
multiplexing (WDM) method on the solitonized laser beams which give rise the
squeezed regions of the vacuum, it is shown the solitons' properties can be
useful to the chosen approach.
