  We consider an alternative scenario of inflation which can account for a
spatially open universe. It is similar to the old inflation in which the bubble
nucleation occurs in the sea of false vacuum, but differs from it in that the
second slow rollover inflation occurs inside a nucleated bubble. Hence our
observable universe is entirely contained in one nucleated bubble. The
significance of the scenario is that apart from a variance due to model
parameters it gives us a definite prediction on the spectrum of the primordial
density perturbations, hence is observationally testable. Here we investigate
the spectrum of CMB anisotropies on large angular scales. We find that the
contribution from peculiar modes which never appear in the usual harmonic
analysis is significant in the case $\Omega_0\lesssim0.1$.
