What measurement unit is commonly used for wavelength in fiber optics?

The measurement unit commonly used for wavelength in fiber optics is nanometers (nm). This choice is correct because optical wavelengths, particularly those relevant to fiber optics, typically range from about 850 nanometers to 1550 nanometers. Wavelengths in this range correspond to the infrared spectrum, which is the part of the electromagnetic spectrum used for transmitting light through fiber optic cables.

Other options represent different types of measurements that are not suitable for expressing wavelength. Microns (um) are often used to describe fiber diameter and other dimensions rather than wavelength. Decibels (dB) are used to measure power loss or gain within the fiber optic system but do not describe wavelength. Gigahertz (GHz) pertains to frequency, which is related to wavelength but is not the correct unit for measuring wavelength itself. Understanding these distinctions is key in the context of fiber optic technology.