  We show that a waveguide that is normally opaque due to interaction with a
drop-filter cavity can be made transparent when the drop filter is also coupled
to a dipole. A transparency condition is derived between the cavity lifetime
and vacuum Rabi frequency of the dipole. This condition is much weaker than
strong coupling, and amounts to simply achieving large Purcell factors. Thus,
we can observe transparency in the weak coupling regime. We describe how this
effect can be useful for designing quantum repeaters for long distance quantum
communication.
