The paper proposes a scaleable SRG-based restoration method in shared mesh wavelength-routed networks. We introduce a backup-SRG concept to identify which SRG is backed up by individual links. We have developed an admission control method for the backup path using the backup-SRG concept to achieve 100% recovery performance. The proposed method is extended to support networks with a large number of SRGs by introducing a hierarchical SRG assignment technique. Through computer simulation on the NSF network model, we confirmed that the proposed method achieves 100% recovery performance assuming a single link failure at the expense of 28.6% extra wavelength resource compared to the non-backup method. The proposed method requires less than 56.3% wavelength resource than that of the protection scheme while keeping 100% recovery performance. The hierarchical SRG assignment technique reduces the number of backup-SRGs to be used in admission control at each node at the expense of very little throughput degradation.