Different Ports on WDM Mux/Demux

WDM (wavelength-division multiplexing) is a commonly used technology in optical communications, which is one of the most common way of using wavelengths to increase bandwidth by multiplexing various optical carrier signals onto a single optical fiber.

CWDM (coarse wavelength-division multiplexing) and DWDM(dense wavelength-division multiplexing) MUX/DEMUX(multiplexer/demultiplexer) are two important components in WDM systems, which are often deployed to join multiple wavelengths onto a single fiber. There are many kinds of ports for different applications on a WDM Mux/Demux. This article will focus on discussing the functions of these ports on WDM Mux/Demux.

Necessary Ports on WDM Mux/Demux

Channel ports and line ports are the ports necessary to support the basic functions of WDM Mux/Demux to join or split signals in a data network.

Channel Port

Channel port is a communication link between two switches supported by matching channel group interfaces on each switch. They transmit and receive signals on specific WDM wavelengths. A WDM Mux/Demux usually has several channel ports on different wavelengths. Since there are 18 wavelengths of CWDM ranging from 1270 nm to 1610 nm with a 20nm interval, the number of channel ports on CWDM Mux/Demux also ranges from 2 to 18. DWDM has a more dense wavelength spacing of 0.8 nm (100 GHz) or 0.4 nm (50 GHz) ranging from S-Band to L-Band around 1490 nm to 1610 nm. The number of DWDM Mux/Demux channel ports is about 4 to 96 for high-density networks.

Line Port

Like the channel port, line ports are another must-have ports on CWDM and DWDM Mux/Demux. Line port also called as common port, can be divided into dual-fiber and single-fiber types. Dual-fiber line port is used for bidirectional transmission, therefore the transmit and receive port in each duplex channel must support the same wavelength. Single-fiber operates with bi-directional wavelengths, often referred to as BIDI. Typically BIDI single-fiber uses 1310 nm and 1550 nm wavelengths over the same fiber strand in opposite directions. The wavelengths’ order of single-fiber WDM MUX/DEMUX should be reversed at both sides of the network. All the WDM channels are multiplexed and demultiplexed over this port.


Special Ports on WDM Mux/Demux

In addition to the necessary ports, some special ports can also be found on WDM Mux/Demux for particular needs.

1310nm Port and 1550nm Port

The 1310 nm and 1550 nm are actually WDM wavelengths. Since a lot of optical transceivers use these two wavelengths for long-haul network, adding these two ports when the device does not include these wavelengths is very important. With these specially designed 1310nm port and 1550nm port, the signal running through ordinary fiber optic transceivers can be combined together with other CWDM wavelengths. CWDM Mux/Demux can add either type of wavelength ports, but the wavelengths which are 0 to 40 nm higher or lower than 1310 nm or 1550 nm cannot be added to the device.  However,DWDM Mux Demux can only add a special 1310nm port.

Expansion Port

Expansion port is used to add or expand more wavelengths or CWDM channels to the network,can be added on both CWDM and DWDM Mux/Demux modules. This is a special port to increase the number of available channels carried in the network. That is to say, when a WDM Mux/Demux can not meet all the wavelength needs, it is necessary to use the expansion port to add different wavelengths by connecting to another WDM Mux/Demux’s line port.

Monitor Port

Monitor port is used for signal monitoring or testing. Many technicians will add a monitor port on CWDM or DWDM Mux Demux for better network monitoring and management. Network administrators will connect this port to the measurement or monitoring equipment to inspect whether the signal is running normally without interrupting the existing network.


From this post, we can know that a WDM Mux/Demux has multiple types of ports and different ports on the CWDM and DWDM Mux/Demux have different functions. Channel and line ports are integral ports for normal operation of the WDM Mux/Demux. Channel ports supporting different wavelengths and Line ports used to connect the WDM Mux Demux are the must-have ports for these devices. 1310nm port, 1510nm port, expansion port and monitor port are used for special requests of the WDM application. Hence, you should have a thorough consideration of your project before choosing the WDM Mux/Demux module.

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