WDM technology enables the transmission of multiple wavelength signals over a single optical fiber, which exponentially increases the transmission capacity of the fiber. There are two main technologies used for implementing WDM optics technology in optical modules: Thin-Film Filters (TFF), based on free-space optics, and Arrayed Waveguide Grating (AWG), based on Planar Light Circuit (PLC) technology. The MUX/DEMUX component is one of the most crucial parts of high-speed optical modules, and the Z-block is the core device within this component. Key Components in TFF Technology will be introduced in this article, including Z-block, fiber collimator, optical isolator etc.