Abstract: Every time the C+L optical transmission system expands its services or fails services, the stability of the system will be affected. In order to ensure the stability of the system, the configuration of the entire line system needs to be adjusted. In this paper, an auto-filling scheme is proposed in a variety of scenarios, in which the C and L bands are filled with filling waves, so that the system works in full waves. In the experiment, filler light, 3 C-band and 3 L-band service lights are used to increase or decrease the filler wave and the service wave. Experiments show that the OSNR is basically stable when the wave increases and decreases. When a service wave is added or a service wave fails, the normal operation of other existing services is not affected. The optical power fluctuation of the filler wave system is small, which meets the requirements of long-distance transmission signal flatness, and the system performance is stable and reliable. The auto-populating feature reduces the strain on operations staff.