This paper proposes a new optical path restoration method for wavelength division multiplexing (WDM) networks. In the method, the protection path is established by connecting several sub-lightpaths from the source node to the destination node of the original working lightpath, as opposed to conventional path restoration where a single protection lightpath between the source-destination pair performs restoration. The set of one or more consecutive lightpaths to connect a source-destination pair is called semi-lightpath. The semi-lightpath based restoration provides enhanced flexibility in protection path provisioning and relieves the cost of spare capacity reservation and wavelength conversion at intermediate optical cross-connect nodes. In terms of spare capacity utilization, our method shows substantial reduction of spare capacity overhead compared with dedicated path restoration in all optical networks without wavelength conversion, and shows similar capacity efficiency compared with shared path restoration in opaque networks with full wavelength conversion capability.