This paper proposes an effective mechanism for establishing protected connections in GMPLS-based multi-domain WSONs employing the Hierarchical PCE architecture. The proposed scheme exploits communication among parent PCE and child PCEs for computing a pair of link-disjoint paths satisfying the wavelength continuity constraint that are allowed to traverse the same domain sequence or partially overlapped domain sequences. The proposed scheme is evaluated by means of simulations in terms of achieved blocking probability, connection setup time, and control plane overhead. Simulation results show that the proposed scheme overcomes the state of the art in terms of blocking probability and setup time with a slightly increased control plane overhead.