Which type of optical detection involves a photodiode that converts the light waves to an electrical signal that varies in proportion to the intensity changes in the light wave?

The type of optical detection that involves a photodiode converting light waves to an electrical signal in proportion to the intensity changes is referred to as direct detection. In this process, the photodiode directly responds to the incoming light by generating a current that correlates with the intensity of that light. This means that as the light intensity increases or decreases, the output electrical signal reflects these changes directly, allowing for accurate measurements corresponding to the light levels.

Direct detection is commonly used in various applications, including fiber optic communication, where it's essential for translating light signals into electrical signals that can be further processed. The ability of the photodiode to create a continuous and linear response to the varying light intensity makes it a critical component in optical sensing technologies.