  We investigate the prospects and consequences of the spectral level
reconstruction of primordial $B$-mode power by solving the systems of linear
equations assuming that the lensing potential together with the lensed
polarization spectra are already in hand. We find that this reconstruction
technique may be very useful to have an estimate of the amplitude of primordial
gravity waves or more specifically the value of tensor to scalar ratio. We also
see that one can have cosmic variance limited reconstruction of the intrinsic
$B$-mode power up to few hundred multipoles ($\ell\sim500$) which is more than
sufficient to have an estimate of the tensor to scalar ratio. Since the small
scale cosmic microwave background (CMB henceforth) anisotropies are not sourced
by the primordial gravity waves generated during inflation. We also find that
the impact of instrumental noise may be bypassed within this reconstruction
algorithm. A simple demonstration for the nullification of the instrumental
noise anticipating COrE like futuristic space mission complemented with Planck
2013 cosmology has been presented.
