Optical theorem for active media

We generalize the optical theorem to active scatterers. This includes both the ordinary optical theorem related to the average, real power as well as the recently proposed reactive optical theorem. We demonstrate that the previous results on optical-theorem-based target and change detection have a broader applicability than previously anticipated. The optical theorem detection methods apply not only to passive scatterers, which has been the focus so far, but also to active scatterers composed of a scatterer component and a radiating (antenna) component.