In this paper, we consider the fast simulation of traffic groomed optical networks, in which multiple sub-rate traffic streams may be carried on the same wavelength. For real-sized systems, call blocking probabilities may be rare events and require a large amount of CPU power to simulate. We present two importance sampling methods for fast simulation. For a light-load case, we prove that static IS using the Standard Clock (S-ISSC) method does indeed have bounded relative error (BRE) even in multi-class case. For a non-light-load case, we suggest, alternatively, adaptive ISSC (A-ISSC) which calculates the relative possibility of reaching each target in every step of simulation. Using A-ISSC, biasing methods which are proven to be optimal or have bounded error can be extended to multi-dimensional cases while still retaining a very favorable performance.