Which type of optical detection uses a photodiode that produces an electrical signal based on light intensity?

The type of optical detection that uses a photodiode to produce an electrical signal based on light intensity is known as direct detection. This method utilizes the inherent properties of the photodiode, which converts light into an electrical signal that is directly proportional to the intensity of the incoming light.

In direct detection systems, the photodiode responds to fluctuations in light, enabling it to detect variations in intensity accurately. This process is fundamental in various applications, from telecommunications to environmental sensing, as it enables real-time monitoring and measurement of optical signals.

Indirect detection, on the other hand, involves measuring secondary signals or effects that result from an initial optical signal, which does not directly translate light intensity into an electrical signal. Analog detection refers to signals that can take on any value, and while it can be related to direct detection in terms of output form, it does not specifically describe the mechanism of using a photodiode. Digital detection involves converting the signal into a binary form, which is not the primary function of a photodiode in the context of measuring light intensity directly.

Hence, the process of a photodiode efficiently yielding an electrical output based on the incident light makes direct detection the correct choice.