Passive optical components are physical elements in an optical communication system that guide, split, combine, filter, or connect optical signals without requiring external power or active signal processing. Their design allows them to reliably manipulate the light pulses that carry information, acting as the silent traffic controllers. This paper provides a comprehensive review of recent progress in the foundational passive devices that underpin this technological revolution. Unlike active devices, which need electrical energy to amplify or regenerate optical signals, passive devices simply guide, divide, combine, or modify the light signals traveling. In addition to fibers, light sources, and photodetectors, many other components are used in a complex optical communication network to split, route, process, or otherwise manipulate light signals. The devices can be categorized as either passive or active components. Passive optical components do. Optical passive components are the quiet workhorses in fiber systems. They don't add gain or require power, but they decide how efficiently, cleanly, and safely light moves through your network or laser chain.
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