  A band-pass filtering scheme is proposed to mitigate spectral broadening and
channel coupling in the Nonlinear Schr\"odinger (NLS) fiber optic channel. The
scheme is modeled by modifying the NLS Equation to include an attenuation
profile with multiple brick-wall filters centered at different frequencies. It
is shown that this brick-walls profile conserves the total in-band energy of
the launch signal. Furthermore, energy fluctuations between the filtered
channels are characterized, and conditions on the channel spacings are derived
that ensure energy conservation in each channel. The maximum spectral
efficiency of such a system is derived, and a constructive rule for achieving
it using Sidon sequences is provided.
