Using CWDM MUX/DEMUX has been widely accepted as the most cost-effective and time-save method to increase the existing fiber optic network without adding optical fibers. However, a CWDM network can only support up to 18 different wavelengths. Is there any possibility to increase the capacity of the existing CWDM network? Hybrid CWDM and DWDM network is being introduced to combine the DWDM wavelengths with the existing CWDM wavelengths.

As we know the CWDM wavelengths ranging from 1260nm-1625nm with space channel of 20nm actually cover all the range of DWDM wavelengths (ranging from 1470nm to 1625nm). However, DWDM wavelengths have much smaller channel spaces (0.4nm/0.8nm/1.6nm) and can provide larger bandwidth than that of the CWDM wavelengths. To combine DWDM with CWDM, the CWDM wavelengths that are near DWDM wavelengths can be used to transmit the DWDM wavelengths. However, not all these CWDM wavelengths are suggested. Generally, wavelengths of 1530nm and 1550nm are used to combine the CWDM and DWDM network together. Similarly, not all the DWDM wavelengths are suggested to be combined with CWDM network. The following picture shows DWDM wavelengths that are suggested to be combined with 1530nm and 1550nm.

To combine the DWDM wavelengths with CWDM wavelengths, both CWDM MUX/DEMUX and DWDM MUX/DEMUXs should be used. The following picture shows the connection methods for hybrid CWDM and DWDM. On both ends of the fiber link, a CWDM MUX/DEMUX and a DWDM MUX/DEMUX with corresponding wavelengths are deployed. Connect the line port of the DWDM MUX/DEMUX to the 1530nm/1550nm channel port of the CWDM MUX/DEMUX, the DWDM wavelengths can be added to the existing CWDM network.

In the CWDM and DWDM Hybrid network, the CWDM MUX/DEMUX and DWDM MUX/DEMUX play the most important roles. To offer better operation and cabling environment for these WDM MUX/DEMUX, FMU series products which are developed by FS.COM has been introduced. This series of products combines the MUX/DEMUX into half-U plug-in modules, and installed in 1U rack for better cable management and network operation as shown in the following picture.

For CWDM and DWDM hybrid network, a FMU CWDM MUX/DEMUX and a DWDM half-U plug-in module can be installed together in a FMU 1U rack chassis. Thus, the two modules can be linked together easily. Meanwhile, with clear port identification, the management and operation of the fiber optic network would be easier.

The CWDM network can be added with DWDM wavelengths by the using of CWDM MUX/DEMUX and DWDM MUX/DEMUX which support corresponding wavelengths. The DWDM wavelengths that are 6.5nm around 1530nm and 1550nm are suggested to be used for CWDM and DWDM hybrid network. For better network operation and cabling, FMU series WDM solutions are suggested, which can provide easier and more flexible connections between CWDM MUX/DEMUX and DWDM MUX/DEMUX. Kindly contact sales@fs.com for more details about DWDM over CWDM solution, if you are interested.

Source: How to Achieve DWDM Over CWDM