Broadband adaptive disturbance rejection is demonstrated on the artificial white-light source of the Deployable Optical Telescope (DOT) developed by the Air Force Research Laboratory (AFRL). Large deployable optical systems are envisioned as the future of space telescopes. These systems will require active control for disturbance rejection. In this paper, we consider a multi-input, multi-output discretetime adaptive disturbance rejection algorithm. The algorithm requires knowledge of some Markov parameters of the system from the control signal inputs to the performance variables. No information about the disturbance spectrum is required. We demonstrate broadband disturbance rejection numerically on an identified model of DOT's white-light source and experimentally on the system itself.