Optical Communication In Space

What is WDM?

WDM stands for Wavelength Division Multiplexing. What it does is to divide the light into an optical fiber in a number of discrete wavelengths (colors). Each wavelength (color) is an independent channel operating at a data rate 2.5Gbit / s, 10 Gbit / s, 40 Gbit / s or even 100Gbit / s (still under development). So, if the light in the fiber is divided into 16 wavelengths (colors or channels), and each wavelength is running at 40 Gbit s data rate /, we obtain a total of 40Gbit / sx = 16 Rates 640Gbit / s. This is particularly true in the long-haul and ultra long-haul fiber optic communication links.

In addition, fibers carrying 64 or more channels (wavelengths) are already available on the market today. This means that we can run 2560 Gbit / s data rate on a single fiber. How about 48 fibers in a single fiber optic cable? This gives us an incredible 2560 Gbit / sx 48 = 122 880 Gbps link s /. Of course, this type of broadband connections and number of fibers are generally made to the Internet backbone.

Using samples above, you can see the shocking truth about WDM. It dramatically increases the ability of a fiber optic link while minimizing the cost of equipment and fiber optic cables.

What is DWDM?

DWDM Dense Wavelength Division Multiplexing means. Here, "dense", the wavelength channels are very narrow and close to each other. For 100 GHz Dense WDM, the interval between adjacent channels are 100 GHz (or 0.8 Nm). For example, adjacent channels could be 1530.33nm, 1531.12nm and 1531.90nm.

DWDM are widely used for the band 1550nm to exploit the capabilities of EDFA (Erbium doped fiber amplifiers). EDFAs are commonly used for the 1525nm ~ 1565nm (C band) and 1570nm ~ 1610nm (L band).

Why is DWM so important?

The use of DWDM has fueled an explosion in transmission capacity. The amount of information that can be sent over fiber cables that span the world has increased so much that there is now a surplus of available capacity.

In practice, much can be wrung out of DWD systems by extending the upper or lower limits of the available transmission window or by spacing the wavelengths more closely, typically at 50 GHz or 25 GHz. To do this, providers can double or triple the number of channels. Each optical channel can now be routinely used for the transmission of light Pules 10Gbit / s or even higher rates of data at a spacing of 100 GHz. With the support of WDM, a pair of fiber can provide a data capacity of several hundred gigabits per second.

WDM technology does not require any upgrade or replacement of the fiber infrastructure that was put in the ground. Therefore, we can improve network capacity level to another simply by reconfiguring or upgrading of equipment terminals and repeaters.

WDM technology to provide the transmission capacity first. It must be structured in a way so they could carry useful traffic and be dispatched to where it should go. This is where the next layer of network protocol has to play. SDH and SONET (they are equivalent. SONET is used in the United States while SDH is used in the rest of the world). We will discuss SDH and SONET in some other tutorials.