Which of the following is the ratio of electrical output power from the detector to the optical input power, expressed by amperes or volts per watt of optical input power?

The correct answer is the term "Responsivity," which is defined as the measure of how effectively a photodetector converts optical power (light) into electrical output power. It is usually expressed in units of amperes per watt (A/W) or volts per watt (V/W) of optical input power. This characteristic is crucial for understanding the performance of fiber optic systems, as it indicates the sensitivity of the detector to incoming light.

Responsible adherence to the concept of responsivity allows designers and engineers to assess how well a photodetector will perform in various lighting conditions and optical signal strengths. A high responsivity indicates that even low levels of optical power can produce significant electrical output, which is essential for efficient fiber optic communication systems.

In contrast, the other terms reflect different concepts: efficiency pertains to the overall effectiveness in converting input power to output power and does not specifically focus on the ratio relative to light input; gain typically refers to an amplifier's ability to increase the signal strength rather than the ratio of optical to electrical power; and bandwidth defines the range of frequencies over which the system operates effectively, not the conversion efficiency of optical signals. Thus, responsivity is the most accurate term for describing the ratio of electrical output power to optical input power