Wavelengths

Each car represents a wavelength that carries a signal through the fiber. To achieve this, a wavelength multiplexer, which is a passive component, is used. On the transmitting end, it multiplexes multiple wavelengths onto a single fiber, and on the receiving end, a demultiplexer separates the different wavelengths. This significantly increases the capacity of the existing fiber line.

Different wavelengths are achieved by using specialized transceivers in the network electronics that are designed for specific wavelengths. The most common types today are SFP and SFP+, but there are also other variants. The choice depends on the equipment they will be connected to. Read more about our pluggable modules here.

xWDM

WDM – Wavelength Division Multiplexing

In WDM, the two wavelengths 1310 nm and 1550 nm are transmitted over a single fiber, either in the same direction or in opposite directions. The latter is used when running one fiber to a subscriber, point-to-point in FTH (downstream and upstream).
 

CWDM - Coarse Wavelength Division Multiplexing

CWDM allows for up to 18 channels over two fibers with a channel separation/bandwidth of 20 nm. The wavelength range used is 1271 - 1611 nm. It is common to start with 8 channels and upgrade as needed.

It is also possible to double the number of channels in a CWDM system by using 2WL SFPs. In practice, each channel is split into two, with a high and a low channel.

Example of CWDM in an FTTH network:

DWDM - Dense Wavelength Division Multiplexing

Passive DWDM can be used to further expand CWDM. Expand with 16 and/or 8 DWDM channels by using two CWDM channels.

Systems with 80 channels are possible. In a pure DWDM system, the wavelength range used is 1528.77 – 1560.61 nm. There is a spacing of 0.8 nm between channels for 40 channels, and 0.4 nm for 80 channels. The standard defines even more channels over a wider range, but the mentioned range is the most commonly used.

There are systems available today that can use both CWDM and DWDM simultaneously on the same fiber. This provides the flexibility to start with CWDM equipment and later upgrade to DWDM when needed.

Se xWDM products.