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We investigate new connection-provisioning algorithms to efficiently provide signal-quality-guaranteed connections in an optical wavelength-division-multiplexing (WDM) mesh network operating with high-speed wavelength channels. In an optical network, a connection is set up to carry a data signal via an all-optical channel (lightpath) from its source to destination node. The optical signal transmitted along the lightpath may need to travel through a number of crossconnect switches (OXCs), optical amplifiers, and fiber segments. While the signal propagates toward its destination, the optical components would continuously degrade the signal quality by inducing impairments. When the signal degradation is so severe that the received bit-error rate (BER) becomes unacceptably high, the lightpath would not be able to provide good service quality to a connection request. Such a lightpath, which has poor signal quality due to transmission impairments in the physical layer, should not be used for connection provisioning in the network layer. With increasing channel bit rate to 10 Gb/s or higher, fiber linear and nonlinear impairments become prominent factors, which affect the signal quality. Thus, new techniques in both physical layer and network layer are necessary for mitigating impairments to accommodate high-speed traffic. Therefore, to ensure service quality of high-speed connections, we develop intelligent impairment-aware routing and wavelength assignment (RWA) algorithms, which automatically consider the effects of high-speed transmission impairment when setting up a lightpath. The main contribution of our paper is that we investigate a novel hierarchical RWA model for high-speed connection provisioning where the optical signal-to-noise ratio (OSNR) and polarization mode dispersion (PMD) effect are estimated in the physical layer, and regarded as metrics for lightpath computation in the network layer. The performance of the proposed connection-provisioning strategies is demonstrated to be promising through illustrative numerical examples.