In this paper, we demonstrate a novel all-fiber wavelength-tunable acoustooptic switch utilizing intermodal coupling in a two-mode fiber (TMF). Its all-fiber configuration consisting of a fiber acoustooptic tunable filter and a mode-selective coupler results in the low loss (< 2 dB) operation. The operating bandwidth > 50 nm, the switching time of 40 musec, and the crosstalk of 20 dB were achieved. By controlling the design parameters of the two-mode fiber, the 3-dB bandwidth of the switched signal was varied from 2.5 nm to > 35 nm. A novel all-fiber dynamic optical add-drop multiplexer is also demonstrated using two acoustooptic switches in series.