Wendelstein 7-X (W7-X) is planned to work at high plasma densities aiming at detached steady-state operation for improved plasma confinement. For plasma densities beyond 1.2×10^20 m-3, electron cyclotron emission (ECE) from the optically thick X2-mode (120-160 GHz) is in the cut-off. Hence, the electron temperature profiles cannot be accessed from ECE for overdense plasmas, but X3-mode is still available to be investigated. A Martin-Puplett interferometer was commissioned in operational phase OP1.2b of W7-X to scan the higher harmonics of ECE for a broad spectral range of 50-500 GHz. The experimental results indicate that X3-mode (180-220 GHz) is optically thick enough to be explored for its diagnostic capabilities as high-density access to electron temperature. The forward modeling of experimental results is done in the bayesian Minerva modeling framework. The results of forward calculations show that X3-mode measurements can be used to provide the electron temperature profiles for overdense plasmas.
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