Certified Fiber Optics Practice Exam 2026 – All-in-One Guide to Mastering Your Certification!

Attenuation in fiber optics refers to the loss of signal strength as light travels through the fiber. The common unit used to express this loss is decibels per kilometer (dB/km). This unit measures how much intensity decreases over a distance of one kilometer.

Using decibels allows for a logarithmic scale, which is particularly useful in telecommunications because it simplifies the comparison of large quantities of power loss. For instance, if a fiber optic cable has an attenuation of 0.2 dB/km, this means that for every kilometer the signal travels, it loses only a fraction of its power, making it a critical factor in determining the performance and efficiency of fiber optic systems.

The other units mentioned, such as watts per meter, volts per millimeter, and hertz, are not appropriate for expressing attenuation in fiber optics. Watts per meter relates to power density, volts per millimeter is used for electric field strength, and hertz is a unit of frequency. Therefore, the use of decibels per kilometer is specifically relevant and standardized in the context of fiber optic communication.