Active photonic chips generate and manipulate light using electrical energy, while passive components guide and modify existing light signals without requiring external power. We survey the state of the art in fundamental building blocks, including strip, rib, and silicon nitride waveguides, with a focus on achieving ultra-low. Passive Optical Chips are integrated optical devices used in communication systems that operate without external power, leveraging optical principles for signal transmission. Passive optical components play a fundamental role within this infrastructure. These engineered devices manage and direct light signals through a. Passive optical chips are transforming how data travels across networks.