Relativistic frequency shifts in a rotating waveguide

A photon source is located in a rotating waveguide. An absorber with a sharp absorbing frequency absorbs some of the emitted photons. This decreases the number of photons which are detected by a detector. The frequency (energy) spectrum measured in the absorber depends on the setup (the positions of the source and the detector), and this spectrum determines the amount of absorption. The shifts are calculated for different configurations. Among other things, it is seen that even if the source and the absorber are at rest (while the waveguide is rotating), there is a nonzero frequency shift.