A radio base station has a baseband unit (BB) and multiple RF heads (RH1, RH2), which are interconnected by means of a bi-directional two-fiber optical ring (R). Each RF head (RH1, RH2) has a delay counter (31) for determining a propagation delay (tL) on the ring (R) and a variable delay circuit (16, 26) for compensating a difference between the propagation delay on the ring and a predefined target delay (tRR). The delay counter counts (31) the delay between a test signal sent on the first fiber (F1) of the ring to the baseband unit and a received test signal looped back by the baseband unit on the second fiber (F2) of the ring.