Depending on the wavelength of light, the transmission loss in optical fibers is also different. After continuous exploration and testing, scientists have found that the light in this region of 1260nm~1625nm has the least signal distortion and the lowest loss, which is most suitable for transmission in optical fibers.

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BandDescriptionWavelength range
O bandOriginal1260-1360 nm
E bandExtended1360-1460 nm
S bandShort wavelength1460-1530 nm
C bandConventional1530-1565 nm
L bandLong wavelength1565-1625 nm
U bandUltralong wavelength1625-1675 nm

O Band

O band: The O band is the original band, with a wavelength range of 1260nm-1360nm. The O-band was the first wavelength band historically used for optical communications with minimal signal distortion (due to dispersion).

E Band

E band: It belongs to the extended wavelength band, with a wavelength range of 1360nm-1460nm, which is the least common wavelength band among these bands. The E-band is mainly used for the extension of the O-band, but there are few applications, mainly because many existing optical cables show high attenuation in the E-band and the manufacturing process is very energy-intensive, so the use in optical communication is limited.

S Band

S band: It belongs to the short-wave band, the wavelength range is 1460nm-1530nm, its fiber loss is lower than that of the O-band, and the S band is used as a lot of PON (passive optical network) systems.

C Band

C band: The wavelength range is from 1530nm to 1565nm, which represents the conventional wavelength band. Optical fibers exhibit the lowest loss in the C-band and have a great advantage in long-distance transmission systems, and are usually used in many metro, long-haul, ultra-long-haul and subsea optical transmission systems combined with WDM and EDFA technology. With the advent of DWDM (Dense Wavelength Division Multiplexing), which enables multiple signals to share a single fiber, the use of the C-band has expanded.

L Band

L band: Long wavelength band, wavelength range 1565nm-1625nm, it is the second lowest-loss wavelength band, often used when the C-band is not enough to meet bandwidth requirements. With the widespread use of EDFA, DWDM systems have been scaled up to the L-band, and were initially often used to extend the capacity of terrestrial DWDM optical networks. Now, it has been introduced to submarine cable operators to expand the total capacity of submarine cables. Because the transmission attenuation loss of the C-band and L-band transmission windows is the smallest, the signal light in the DWDM system is usually selected in the C-band and L-band.

U Band

U band: In addition to the above five bands, there is also a U-band, U stands for “ultra-long-wavelength”, the wavelength range is 1625nm-1675nm, it is mainly used for network monitoring applications.

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