Definition

wavelength

Wavelength is the distance between identical points in the adjacent cycles of a waveform signal propagated in space or along a wire. In wireless systems, this length is usually specified in meters, centimeters, or millimeters. In the case of infrared, visible light, ultraviolet, and gamma radiation, the wavelength is more often specified in nanometers (units of 10-9meter) or Angstrom units(units of 10-10 meter).

Instruments such as optical spectrometers or optical spectrum analyzers can be used to detect wavelengths in the electromagnetic spectrum. Wavelength is inversely related to frequency, which refers to the number of wave cycles per second. The higher the frequency of the signal, the shorter the wavelength.

This video is aimed at a young audience, but it does a good job showing how frequency and amplitude affect wavelength.

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.

How wavelength is measured

Instruments such as optical spectrometers or optical spectrum analyzers can be used to detect wavelengths in the electromagnetic spectrum. Wavelengths are measured in kilometers, meters, millimeters, micrometers and even smaller denominations, including nanometers, picometers and femtometers. The latter is used to measure shorter wavelengths on the electromagnetic spectrum, such as ultraviolet radiation, X-rays and gamma rays. Conversely, radio waves have much longer wavelengths, reaching anywhere from one millimeter to 100 kilometers, depending on the frequency.

 If f is the frequency of the signal as measured in megahertz, and w is the wavelength as measured in meters, then

w = 300/f

and conversely

f = 300/w

The distance between repetitions in the waves indicates where the wavelength is on the electromagnetic radiation spectrum, which includes radio waves in the audio range and waves in the visible light range.

Wavelength formula

A wavelength can be calculated by dividing the velocity of a wave by its frequency. This is often expressed as the following equation:

wavelength formula

The Greek letter lambda (λ) represents wavelength, expressed in meters. The v is wave velocity, calculated as meters per second. And the f stands for frequency, which is measured in hertz.

Wave division multiplexing

In the 1990s, fiber optic cable's ability to carry data was significantly increased with the development of wavelength division multiplexing (WDM). This technique was introduced by AT&T's Bell Labs, which established a way to split a beam of light into different wavelengths that could travel through the fiber independently of one another.

WDM, along with dense wavelength division multiplexing and other methods, permits a single optical fiber to transmit multiple signals at the same time. As a result, capacity can be added to existing optical networks, also called photonic networks.

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.

This was last updated in July 2019

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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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nice article
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What's your most reliable tool for analyzing wavelengths and frequencies?
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