Wavelength division multiplexing (WDM) is a technology for increasing the transmission capacity of optical fiber communications by sending multiple data channels simultaneously through a single fiber, each on a different wavelength of light. This technique enables bidirectional communications over a. Here, we develop a novel design approach that co-optimizes inverse-designed wavelength division multiplexers and distributed Bragg gratings to achieve ultra-low crosstalk without compromising insertion loss. The article explains the fundamental principle and its.