We describe applications of the Texas Instruments digital micromirror device (DMD) as a high efficiency spatial light modulator for dynamic optical filtering and switching in dense wavelength division multiplexed optical networks operating around 1550 nm. Whereas the DMD has found wide acceptance as a spatial light modulator in video display applications, the present paper describes applications of the DMD for modulating DWDM signals. The DMD is shown to behave as a 2-dimensional switched blazed grating when modulating coherent light beams. (C) 2002 Elsevier Science Ltd. All rights reserved.