The lightpaths within a wavelength switched optical network (WSON) are usually bi-directional, with a same route and a same wavelength which are allocated for both directions from the viewpoint of optical network operation. On the other hand, the introduction of generalized multi-protocol label switching (GMPLS) as a network control plane is expected to bring more intelligence and to provision the end-to-end lightpath in a cost-efficient manner. In this paper, we experimentally demonstrate and evaluate dynamic provisioning of bidirectional lightpaths in GMPLS controlled optical networks, considering the wavelength continuity constraint and the physical impairment constraint on both directions.Keywords: bi-directional label switched path (LSP), generalized multi-protocol label switching (GMPLS), impairment-aware routing and wavelength assignment (IA-RWA), wavelength continuity constraint (WCC), optical signal to noise ratio (OSNR)