What does the term "fall time" refer to in a fiber optic system?

The term "fall time" in a fiber optic system specifically refers to the duration required for the output signal to decrease from 90% of its maximum value to 10% of that value. This parameter is crucial in understanding how quickly a fiber optic system can respond to changes in the input signal. A rapid fall time indicates that the system can swiftly handle changes and is essential for high-speed data transmission, as delays can lead to signal distortion and affect overall performance.

In fiber optics, the fall time is a key factor in determining the bandwidth and data rate, as data signals are typically represented as pulses that need to rise and fall rapidly to convey information effectively. If the fall time is too long, it can lead to overlapping signals in high-speed applications, resulting in diminished performance. Thus, B is the correct definition of fall time, as it precisely relates to the output signal's decline characteristics in response to the input signal changes.