Arrayed waveguide grating (AWG) devices play a crucial role in wavelength division multiplexing (WDM) networks and links. AWGs are key building blocks in multi-wavelength receivers and transmitters, wavelength routers, add-drop multiplexers and optical crossconnects. AWG size becomes a critical issue when they are used in higher complexity photonic integrated circuits. The last years have shown a steady reduction of AWG device dimensions in silica-on-silicon, silicon-on-insulator and InP-based technologies. Extremely compact AWGs with good performance are feasible and allow for a significant reduction in cost, when integrated with other components in photonic integrated circuits.