What distinguishes active optical devices from passive optical devices?

Active optical devices are defined by their need for an external power source to function. This power enables them to perform various tasks, such as amplification, modulation, or signal processing. The requirement for power is a critical aspect that differentiates them from passive optical devices, which operate without drawing energy from external sources and rely solely on the incoming light signals to function.

In the context of optical systems, active devices include components like lasers, light-emitting diodes (LEDs), and optical amplifiers, all of which require electricity to produce or manipulate light. This energy enables active devices to control and enhance optical signals, thereby contributing to functions such as signal transmission and amplification.

While other aspects may describe characteristics of optical devices—such as fragility or dependence on incoming signals—they do not fundamentally define the distinction between active and passive devices as clearly as the reliance on an external power source does. This core concept is essential for understanding the operational principles and applications of different types of optical technologies.