In this class the most relevant active and passive components for photonic networks will be introduced and their system-level behavior will be proposed and analyzed. These components are: optical sources, modulators, amplifiers, detectors, filtering, and passive components in general, reconfigurable optical add/drop multiplexers (ROADMs) and their exploitation in network nodes. As well as in the optical transmission class, a special attention will be spent to properly train students on polarization-related effects that are the main possible source of impairments for metrology signals.