TFF (thin film filter) and AWG (arrayed waveguide grating) are two commonly used WDM technologies. Here we will take an overview and comparison of these two WDM technologies.Both of these WDM technologies are widely used in optical communication systems. It is generally believed that AWG has a higher cost-effectiveness in long-distance, high-channel-capacity DWDM applications, while TFF is more ideal for low-channel-capacity CWDM metropolitan applications. TFF usually consists of multiple layers of films of different thicknesses, and the thin film filter is the key and most expensive component is the WDM devices.