This document discusses fiber optic communication systems. It provides advantages like high bandwidth, electrical isolation, low power consumption. However, it also notes disadvantages such as fragility, difficulty of installation, and need for specialized equipment. It describes the basic components of an optical fiber including the core and cladding. It explains how total internal reflection guides light through the fiber. Common light sources like LEDs and laser diodes are also discussed. The document provides details on types of optical fibers and classifications. It summarizes the working of optical receivers and different types of photodetectors used.