Waveguide couplers are devices used to connect two or more waveguides, which are structures that guide electromagnetic waves. They allow for the efficient transfer of energy between different waveguide systems, making them essential in applications like telecommunications and radar. By using various designs, such as E-plane or H-plane couplers, they can minimize signal loss and maintain the integrity of the transmitted signals. These couplers can be made from different materials, including metals and dielectrics, depending on the frequency and application requirements. They are commonly found in optical and microwave systems, where precise control of wave propagation is crucial for performance.