Hello, everyone!
Today, I will explain WDM PON technology. This is the fourth article about PON technology. WDM PON is the future and revolution in PON technology.
WDM PON is an abbreviation from Wavelength Division Multiplexing PON. This is the new PON technology. This technology is still being developed and is not in use. This is the technology of the future.
WDM technology offers to increase the capacity of the fiber by utilizing more than one wavelength. We can send many optical signals at different wavelengths in one optical fiber.
There are three main types of WDM technology:
WWDM – Wide Wavelength Division Multiplexing. This is the simplest WDM technology. There are three wavelength ranges: 1310 nm, 1490 nm and 1550 nm. Channel spacing is min 50 nm.
CWDM – Coarse Wavelength Division Multiplexing. The range for this technology is from 1270 nm and 1610 nm, with a max of 18 wavelengths. This technology is based on the ITU-T G.694.2.
DWDM – Dense Wavelength Division Multiplexing. This technology is based on the ITU-T G.694.1. The range of wavelengths are in C and L bands. Channel spacing: 200 GHz, 100 GHz, 50 GHz, 25 GHz, or 12.5 GHz. DWDM is used for WDM PON. This technology uses the next standards for optical fibers: ITU-T G.652.D, ITU-T G.655 and ITU-T G.656.
All previous PON systems, which I explained in previous articles, were P2MP (point to multi point). The architecture of this technology (shown in the figure below) is made as P2MP, but it is used as P2P (point to point).
Figure 1. WDM PON - various scenarios
In this solution, an optical splitter is replaced for AWG (Arrayed-Waveguide-Grating), a wavelength demultiplexer. Every user has an independent wavelength. Therefore, this is a P2P solution and every user can use full bandwidth. This is a revolution in PON technology.
The main benefits are:
P2P offers full bandwidth for every user and network security, and
Different transmission rates and services can be easily implemented.
WDM PON can be applied to various scenarios: FTTH, FTTB, FTTC, FTTO, FTTA, etc. The architecture of this system is similar to previous PON solutions. The system consists of OLT (Optical Line Terminal), ODN (Optical Distribution Network) and ONU (Optical Network Unit). The OLT and ONU should be able to emit and receive the light of different wavelengths (figure 2). Wavelength selection can also be achieved by filtering at the user.
Figure 2. WDM PON – communication between OLT and ONUs
In the end, this is an expensive technology. The key elements are laser sources and WDM filters. During the implementation, the most expensive part of the system will be ONU devices.
Thank you!
