  We study the large scale power spectrum of gravitational wave perturbations
of the microwave background in the context of single-bubble open inflation
models. We compute the ratio of tensor to scalar contributions to the CMB
anisotropies as a function of $\Omega_0$, the spectral index $n_S$ and the
tunneling parameter $2\pi GS_1/H$. We find that gravitational wave anisotropies
can be very large at small values of this tunneling parameter. We also consider
the contribution of supercurvature and bubble wall modes and find constraints
on the parameters of open inflation models from the observed temperature
anisotropies of the CMB. We show that the induced gravity and open hybrid
scenarios are compatible with present observations for a reasonable range of
parameters.
