Passive network components are network components that usually do not require any electrical power input. Key passive components include couplers/splitters, wavelength-selective splitters (WDM, CWDM, and DWDM), circulators/isolators, and optical switches. They are available for both single-mode (SM) and multi-mode (MM) applications. These parts are crucial for building a powerful and error-free network. Using unsuitable passive components at key locations in a network could have a quick and noticeable detrimental effect on system performance.