Transparent optical WDM networks have been expected to be the most effective solution to achieve high throughput transmission, in which a GMPLS control plane is used to manage both IP layer and the optical transport layer. However, current GMPLS does not take the influence of physical impairments during data transmission process into account. This paper proposes a signaling-based approach to implement self-adaptive transmission control (SATC) in impairment-aware transparent WDM networks. The function of standard control plane of automatic switched optical network is enhanced to realize this aim. Two evaluation schemes are proposed for the implementation of this approach. Simulations are conducted for proof of benefits gained by introducing SATC.