Fiber Optic Wavelength Band O E S C L U

Fiber optic communication is the use of light as an information carrier to transmit and communicate within the fiber core.

However, not all types of light are suitable for fiber optic communication, and the transmission loss in optical fibers varies depending on the wavelength of the light.

In order to minimize losses and ensure transmission efficiency, researchers have been committed to finding the most suitable light.

In the early 1970s, fiber optic communication began the process of practical implementation. At that time, the main research and development target was multimode optical fiber. The core diameter of multimode fiber is larger, allowing different modes of light to be transmitted on one fiber. The earliest light used was light with a wavelength of 850nm, also known as the 850nm band. Later, in the late 1970s and early 1980s, single-mode fiber began to be widely used.

After test, engineers found that light in the wavelength range of 1260nm to 1360nm has the least signal distortion and loss caused by dispersion. So, they adopted this wavelength range as an early optical communication band and named it O-band. O means Original.

In the following thirty to forty years, after a long period of exploration and practice, experts gradually summarized a “low loss wavelength region”, which is the 1260nm~1625nm region. Light within this wavelength range is most suitable for transmission in optical fibers.

This area is further divided into five bands, namely O band, E band, S band, C band, and L band.

With the continuous evolution and changes of technology, experts have also verified the law between fiber optic transmission loss and light wave wavelength, as shown in the following figure:

The most commonly used band is called the C-band (1530nm~1565nm). C means’ conventional.

The C-band have the lowest loss and is widely used in metropolitan area networks, long-distance, ultra long distance, and submarine cable systems. In WDM wavelength division multiplexing systems, the C-band is also frequently used. The L-band (1565nm~1625nm) next to the C-band is the second lowest loss band and one of the mainstream choices in the industry. When the C-band is insufficient to meet bandwidth requirements, the L-band is also used as a supplement. L means  long wavelength.

The S-band (1460nm~1530nm), also known as the “short wavelength” band, has higher fiber loss than the O-band. It is often used for downstream wavelengths in PON (Passive Optical Network) systems. 

PON is the system for home fiber broadband. Its upstream wavelength is 1310nm and downstream wavelength is 1490nm. Finally, let’s take a look at the E-band.

This E band is a bit special, it is the least common band among the five bands. E means extended. When you observe the wavelength loss relationship graph just now, you will find that there is a clear irregular bulge in the E-band.

That’s because in the 1370-1410nm wavelength range, hydroxide ions (OH -) absorb, resulting in a sharp increase in losses. This is also known as the water peak.

In the early days, due to process limitations, water (OH group) impurities often remained in the fiber glass, resulting in the highest attenuation in the E-band and inability to function properly. Later, dehydration technology was invented during the glass making process, and the attenuation of the most commonly used optical fiber in the E-band (ITU-T G.652. D) became lower than that in the O-band. However, due to the high attenuation exhibited by many existing fiber optic cables installed before 2000 in the E-band, there are still some limitations to the use of the E-band in optical communication.

In addition to the above bands, there is actually another band that will be used, which is the U-band (ultra long wavelength band, 1625-1675 nm) and 850nm band. The U-band is mainly used for network monitoring, 850nm band is mainly used for multimode fiber.

To summarize,we made a table as below:

FAQ

What is the operating wave for WDM device?

There are many operating bands for WDM devices, such as the 1550 wavelength, which distinguishes three bands: S-band (short wavelength band 1460-1528 nm), C-band (conventional band 1530-1565 nm), and L-band (long wavelength band 1565-1625 nm).

Where are the main applications of several bands?

Due to the different characteristics of each band, the applications are different, as shown in the table below.

What band is G.657 fiber mainly used in?

G657 fiber belongs to single-mode fiber and can be selected from O-band, E-band, S-band, C-band, and L-band. Different bands have different bending radii, so optical fibers are also divided into four categories, as shown in the table below.