Certified Fiber Optics Practice Exam

Which unit is used to express gain or loss in a fiber optic system?

1. Milliwatts

2. Decibel

3. Volts

4. Hertz

The correct answer is: Decibel

In fiber optic systems, gain or loss is commonly expressed in decibels (dB). This unit provides a logarithmic way to quantify the ratio of output power to input power. When assessing the performance of an optical signal as it travels through a fiber, measuring in decibels allows for an easier understanding of changes in signal strength. For instance, a gain of +3 dB indicates that the output signal is twice as strong as the input signal, while a loss of -3 dB indicates that it is half as strong. This logarithmic scale is particularly useful in optical communications where large variations in power can occur, thus making it more practical than linear measurements. Other units such as milliwatts, volts, and hertz serve different purposes. Milliwatts is a unit of power but does not directly convey the ratio necessary for understanding gain or loss within the context of optical signal transmission. Volts relate to electrical potential and are not applicable in this context. Hertz measures frequency rather than power or signal strength. Thus, decibels is the standard and most effective unit for expressing changes in gain or loss within fiber optic systems.