What is WDM (Wavelength Division Multiplexing) for Fiber Optic Communication? Fiber optic tutorial

WDM is the abbreviation for Wavelength Division Multiplexing. What it does is divide the light into an optical fiber into a number of separate wavelengths (colors). Each wavelength (color) is an independent channel running at data rates at 2.5 Gbit / s, 10 Gbit / s, 40 Gbit / s or even 100 Gbit / s (still under development). So if the light in the fiber is divided into 16 wavelengths (colors or channels) and each wavelength runs at 40 Gbit / s data rate, we get a total of 40 Gbit / s x 16 = 640Gbit / s speed. This is especially true in the case of long distance transport and long distance fiber optic communication connections.

In addition, fibers with 64 and more channels (wavelengths) are already available on the market now. Which means we can run 2,560Gbit / s data rate on a single fiber. How about 48 fibers in a single fiber optic cable? It gives us a fantastic 2.560Gbit / s x 48 = 122.880Gbit / s link. Of course, this kind of links to high-speed and fiber counting is usually only used for the Internet back.

From the above tests you can see the shocking truth about WDM. It dramatically increases the capacity of a fiber optic connection while minimizing the cost of equipment and fiber optic cable.

What is DWDM?

DWDM stands for Dense Wavelength Division Multiplexing. Here, “close” means the wavelength channels very narrow and close to each other. For 100 GHz dense WDM, the interval between adjacent channels is only 100 GHz (or 0.8 nm). For example, the adjacent channels may be 1530.33 nm, 1531.12 nm and 15311.90 nm.

DWDM is widely used for the 1550nm band to take advantage of opportunities in EDFA (Erbium Doped Fiber Amplifiers). EDFAs are often used for 1525nm ~ 1565nm (C-band) and 1570nm ~ 1610nm (L-band).

Why is DWM so important?

The exploitation of DWDM has caused an explosion in transmission capacity. The amount of information that can be transmitted over the fiber cables spanning the world has increased so much that there is now a power of available capacity.

In practice, several can be turned off by DWD systems by extending the upper or lower limits of the available transmission window or by wavelength distances, typically at 50 GHz or even 25 GHz. By doing this, suppliers can double or triple the number of channels. Each optical channel can currently be routinely used to transmit light bulbs at 10Gbit / s or even higher data rates at 100 GHz distance. Using WDM, a couple of fibers can provide data capacity of several hundred gigabits per second. Second.

WDM technology does not require upgrading or replacing the fiber infrastructure installed. Therefore, we can upgrade links from one capacity level to the next by simply reconfiguring or upgrading terminal equipment and repeaters.

WDM technologies provide the raw transmission capacity. This has to be structured in some way so that it can carry useful traffic and be directed where it needs to. This is where the next layer of network protocol plays. SDH and SONET (They are equivalent. SONET is used in the US while SDH is used in the rest of the world). We will touch on SDH and SONET in some other tutorials.