Definition

wavelength

Contributor(s): Jessica Scarpati

A wavelength is a measure of distance between two identical peaks (high points) or troughs (low points) in a wave -- a repeating pattern of traveling energy like light or sound.

The distance between repetitions in the waves indicates the type of wavelength on the electromagnetic radiation spectrum, which includes radio waves in the audio range and waves in the visible light range. Wavelengths are measured in kilometers, meters, millimeters, micrometers and even smaller denominations, such as nanometers, picometers and femtometers, to measure ultraviolet radiation, X-rays and gamma rays. Conversely, radio waves have much longer wavelengths -- typically measured in meters.

Wavelength is inversely related to frequency, which refers to the number of wave cycles per second. The higher the frequency of a signal, the shorter the wavelength. A wavelength can be calculated by dividing the velocity of a wave by its frequency.

Wave division multiplexing

In fiber optic networks, techniques that include wavelength-division multiplexing (WDM) and dense wavelength-division multiplexing can add capacity to optical networks, also called photonic networks. This is achieved by enabling a single strand of optical fiber to transmit multiple signals -- beams of light -- that can travel through the fiber simultaneously by using different wavelengths.

The following graphic illustrates an example of a wavelength:

What is wavelength

The three most common wavelengths in fiber optics are 850 nanometers (nm), 1,300 nm and 1,550 nm.

In the 1990s, the ability to use fiber optic cable to carry data was significantly increased with the development of WDM. AT&T's Bell Labs originally developed the capability to split a beam of light into different wavelengths that could travel through the fiber at the same time. This created the ability to transmit multiple channels within a single optical fiber.

Wavelengths in wireless networks

Although frequencies are more commonly discussed in wireless networking, wavelengths are also an important factor in Wi-Fi networks. Wi-Fi operates at five frequencies, all in the gigahertz range: 2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz and 5.9 GHz. Higher frequencies have shorter wavelengths, and signals with shorter wavelengths have more trouble penetrating obstacles like walls and floors. As a result, wireless access points that operate at higher frequencies (with shorter wavelengths) often consume more power to transmit data at similar speeds and distances achieved by devices that operate at lower frequencies (with longer wavelengths).

This was last updated in December 2016

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How did the development of dense wavelength-division multiplexing improve the use of wavelengths in long-distance fiber communications?
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