How to Distinguish O, E, S, C, L, U Band Wavelengths?

What is O-band?

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

What is E-band?

E-band (extended wavelength band: 1360-1460 nm) is the least common of these bands. E-band is mainly used as an extension of O-band, but there are few applications, mainly because many existing optical cables show high attenuation in E-band, and the manufacturing process is very energy-intensive, so its use in optical communication is limited.

What is S-band?

The fiber loss in the S-band (Short-wavelength Band) (short-wavelength band: 1460-1530 nm) is lower than that in the O-band, and the S-band is used as many PON (passive optical network) systems.

What is C band?

The C-band (Conventional Band) ranges from 1530 nm to 1565 nm, representing the conventional band. Optical fiber exhibits the lowest loss in the C-band and has a greater advantage in long-distance transmission systems. It is usually used in many metropolitan, long-distance, ultra-long-distance and submarine optical transmission systems combined with WDM and EDFA technology. C-band becomes more and more important as transmission distances become longer and fiber amplifiers are used instead of optical-to-electron-to-optical repeaters. The use of C-band expanded with the advent of DWDM (Dense Wavelength Division Multiplexing), which enables multiple signals to share a single fiber.

What is L-band?

L-band (Long-wavelength Band) (long-wavelength band: 1565-1625 nm) is the second lowest-loss wavelength band and is often used when the C-band is not enough to meet the bandwidth requirements. With the widespread availability of b-doped fiber amplifiers (EDFAs), DWDM systems have been extended up to the L-band, and were initially used to extend the capacity of terrestrial DWDM optical networks. Now, it has been introduced to submarine cable operators to do the same thing - expand the total capacity of submarine cables.

Due to the transmission attenuation loss of the two transmission windows of C-band and L-band is the smallest, the signal light in the DWDM system is usually selected in C-band and L-band. In addition to O-band to L-band, there are two other bands, the 850 nm band and U-band (ultra-long band: 1625-1675 nm). The 850 nm band is the dominant wavelength for multimode fiber optic communication systems incorporating VCSELs (Vertical Cavity Surface Emitting Lasers). The U-band is mainly used for network monitoring.

WDM technology can be divided into WDM, CWDM, and DWDM according to different wavelength modes. The wavelength range specified by ITU for CWDM (ITU-T G.694.2) is 1271 to 1611 nm, but considering the relatively large attenuation of the 1270-1470nm band in the application, the wavelength range of 1470~1610nm is usually used. DWDM channels are more densely spaced, using C-band (1530nm-1565nm) and L-band (1570nm-1610nm) transmission windows. Ordinary WDM generally adopts 1310 and 1550nm wavelengths.