Wavelength division multiplexing (WDM) is a technique of multiplexing multiple optical carrier signals through a single optical fiber channel by varying the wavelengths of laser lights. WDM allows communication in both the directions in the fiber cable. It can perform additional roles like providing redundancy, supporting advanced topologies, reducing hardware and cost, etc. This allows multiple channels of data to be transmitted simultaneously. High-Performance Wavelength Division Multiplexers Enabled by Co-Optimized Inverse Design Sydney Mason1, Geun Ho Ahn1,†, Jakob Grzesik1, Sungjun Eun, and Jelena Vuˇckovi´c1,†† 1E. Ginzton Laboratory, Stanford University, Stanford, CA 94305, USA †gahn@stanford.