Understanding WDM MUX/DEMUX Ports and Its Application

Wavelength division multiplexing (WDM) is a commonly used technology in optical communications. It combines multiple wavelengths to transmit signals on a single fiber. To realize this process, CWDM and DWDM mux/demux are the essential part. As we all know, there are several different ports on the WDM mux and demux. This article will give a clear explanation to these ports and their applications in WDM network.

Overview of Different Ports on WDM MUX/DEMUX
Line Port

Line port, sometimes also called as common port, is the one of the must-have ports on CWDM and DWDM Mux/Demux. The outside fibers are connected to the Mux/Demux unit through this port, and they are often marked as Tx and Rx. All the WDM channels are multiplexed and demultiplexed over this port.

Channel Port

Like the line port, channel ports are another must-have ports. They transmit and receive signals on specific WDM wavelengths. CWDM Mux/Demux supports up to 18 channels from 1270nm to 1610nm with a channel space of 20nm. While DWDM Mux/Demux uses wavelengths from 1470nm to 1625nm usually with channel space of 0.8nm (100GHz) or 0.4nm (50GHz). Services or circuits can be added in any order to the Mux/Demux unit.

40ch dwdm mux demux

Monitor Port

Monitor port on CWDM and DWDM Mux/Demux offers a way to test the dB level of the signal without service interruption, which enable users the ability to monitor and troubleshoot networks. If the Mux/Demux is a sing-fiber unit, the monitor port also should be a simplex one, and vice verse.

Expansion Port

Expansion port on WDM Mux/Demux is used to add or expand more wavelengths or channels to the network. By using this port, network managers can increase the network capacity easily by connecting the expansion port with the line port of another Mux/Demux supporting different wavelengths. However, not every WDM Mux/Demux has an expansion port.

dwdm mux demux

1310nm and 1550nm Port

1310nm and 1550nm are one of WDM wavelengths. Many optical transceivers, especially the CWDM and DWDM SFP/SFP+ transceiver, support long runs transmission over these two wavelengths. By connecting with the same wavelength optical transceivers, these two ports can be used to add 1310nm or 1550nm wavelengths into existing WDM networks.

Application Cases of Different Ports on WDM MUX/DEMUX

Although there are several different ports on WDM Mux/Demux, not all of them are used at the same time. Here are some examples of these functioning ports in different connections.

Example One: Using 8 Channels CWDM Mux/Demux with Monitor Port

cwdm mux demux with monitor port

This example is a typical point-to-point network where two switches/routers are connected over CWDM wavelength 1511nm. The CWDM Mux/Demux used has a monitor port and 1310nm port, but the 1310nm does not put into use. In addition, an optical power meter is used to monitor the power on fibers connecting the site A and B.

Example Two: Achieve 500Gbps at Existing Fiber Network with 1310nm Port

dwdm mux with 1310nm port

In this example, two 40 channels DWDM Mux/Demux with monitor port and 1310nm port are used to achieve total 500Gbps services. How to achieve this? First, plug a 1310nm 40G or 100G fiber optical transceiver into the terminal equipment, then use the patch cable to connect it to the existing DWDM network via the 1310nm port on the DWDM Mux/Demux. Since the 1310nm port is combined into a 40 channels DWDM Mux, then this set-up allows the transport of up to 40x10Gbps plus 100Gbpx over one fiber pair, which is total 500Gbps. If use 1550nm port, then the transceiver should be available on the wavelength of 1550nm.

Example Three: Stack Two CWDM MUX/DEMUX Using Expansion Port

cwdm mux with expansion port

The connection in this example is similar to the last one. The difference is that this connection is achieved with expansion port not 1310nm port. On the left side in the cases, a 8 channels CWDM Mux/Demux and a 4 channels CWDM Mux/Demux are stacked via the expansion port on the latter Mux/Demux. And the two 4 channels CWDM Mux/Demux are combined with the line port. If there is a need, more Mux/Demux modules can be added to increase the wavelengths and expand network capacity.


Different ports on the CWDM and DWDM Mux/Demux have different functions. Knowing more their function is helpful in WDM network deployment. FS.COM supplies various types of CWDM and DWDM Mux/Demux for your preference. And customer services are also available. If you have any needs, welcome to visit our website www.fs.com.

Solutions to Achieve Long-haul Transmission With DWDM Systems

In order to increase the transmission distance of optical signals, many technologies, like the TDM (time division multiplexing) and WDM (wavelength division multiplexing), have been used. Except for that, several optical components like single mode fiber optic cables, optical amplifiers and dispersion compensating modules (DCMs) are also put into use to realize the goal. Today, this article intends to illustrate the solutions to achieve longer transmission distances with DWDM technology.

Solutions to Extend Transmission Distances

When it comes to long-haul optical transmissions, DWDM (dense wavelength division multiplexing) is a topic that cannot be ignored. DWDM technology enables different wavelengths to transmit over a single optical fiber. Different wavelengths are combined in a device—Mux/Demux which is short of multiplexer/demultiplexer. The DWDM Mux/Demux provides low insertion loss and low polarization-dependent loss for optical links. Here take a 8CH DWDM Mux/Demux for example to illustrate how to extend distance in long haul transmission.

Solution One

The first solution is suitable for applications that are less than 50km. The picture below shows a unidirectional application with 8CH DWDM Mux/Demux. As we can see, in this links, the DWDM Mux/Demux transmits 1550nm signal over one single mode fiber. The eight different signals from the transmitters are multiplexed into 1550nm signal by the 8CH DWDM Mux. Then they go through the single mode fiber and are separated into the original wavelengths by the DWDM Demux. The use of DWDM Mux/Demux and single mode fiber allows the system to transmit over 50km without optical amplifier or DCM.

8 channel mux demux in long haul transmission

Notes: this solution is the basic application of DWDM Mux/Demux in a relative long distance comparing to CWDM technology which suits short distance deployment.

Solution Two

Different from the first solution, if the link distance is longer than 50km, this solution can be taken into account. Optical signal loss will become greater as the links are getting longer, which means an optical amplifier module or dispersion compensator is needed. Therefore, to achieve a satisfying signal quality in long-distance transmission, an EDFA which can boost the weakened optical signals is added in this solution (as shown in the picture below).

edfa in long haul transimission

Solution Three

This DWDM configuration is similar to the former one, but with the EDFA, the link distance on the single mode fiber is up to 200km. However, sometimes an EDFA is not enough to achieve a quality signal, especially in some long haul systems like CATV system. Because these systems often have a high requirement for the quality of optical signal. Therefore, as we can see in the following picture, except for the DWDM Mux/Demux and EDFA, there is also a DCM.

edfa and dcm in long haul transmission

This solution is a point-to-multipoint long haul system deploying a DCM to extend the transmission distance. From the picture, the EDFA is placed midway between the transmitter and receiver in the transmission path. And in order to ensure the quality of the whole transmission, a DCM module is added in this link to deal with the accumulated chromatic dispersion without dropping and regenerating the wavelengths on the link.

Notes: all the three solutions are unidirectional transmission on single mode fiber cables. If a network requires bidirectional transmission to transfer eight signals, you can use a 16CH DWDM Mux/Demux over single fiber or a 8CH DWDM Mux/Demux over dual fiber.


WDM technology, especially the DWDM, is the critical step to go into the super-long distance transmission in optical communication. This post mainly introduces three basic solutions to realize long haul transmission with DWDM Mux/Demux. All the components including the DWDM Mux/Demux (both 8 channels and 16 channels), EDFA, DCM and optical modules are available in FS.COM. If you have any needs, please contact us via sales@fs.com.

How to Optimize Your Network Performance with LC Assemblies?

High-density and compact data center cabling has become the consequent trend as the rapid development of fiber optic communication. Under this trend, LC assemblies, like the LC connector, LC adapter and LC attenuator, are more and more popular in the applications of cable television (CATV), fiber-to-the-home (FTTH) and dense wave division multiplexing (DWDM) Markets. Today this post intends to explore how to optimize network performance with LC assemblies.

LC Adapter for Easy Installation

It’s familiar to us that fiber optic adapters are used to connect fiber optic components with the same or different interfaces. Due to their ability to interconnect two connectors, they are widely applied in optical management systems. And nowadays there are various LC adapters available in the market for both single mode and multimode applications. Take the quad LC adapter for example, Quad LC adapters, designed for high-density applications, provide 4-position LC adapter solution in a traditional duplex SC footprint. The mating sleeve can connect four duplex or eight simplex LC fiber optic cables, saving more space and bring more flexibility.

Quad Plastic LC Fiber Optic Adapters

LC Attenuator for Better Transmission Quality

As we all know, signal strength needs to be reduced in some case. For instance, if a transmitter delivers too much light power, at the receiver end the power must be reduced by using fiber optic attenuator. Or it may degrade the bit error ratio (BER). LC attenuator is a type of widely applied fiber optic attenuator. It is designed to provide horizontal spectral attenuation over the full spectrum vary from 1260nm to 1620nm in single mode transmission. Therefore the LC attenuators can expand the capacity of optical networks by using the E-band (1400-nm window) for optical transmission.

LC fiber optic attenuator

LC HD Plus+ Fiber Cable for High Density Application

Designed with flexible “push-pull tab” uniboot connector, bend insensitive fiber and ultra-low insertion loss, LC HD plus+ fiber cables are the best choice for high-speed, high-bandwidth 1GbE and 10GbE networks in data centers. People with working experiences in data centers may know it’s not an easy task to add or remove one connector in numerous network cables. But with the push-pull tab uniboot connector, this problem can be solved perfectly. Firstly, the LC uniboot connector encloses two fibers firmly in a single cable, saving cable management space greatly. Secondly, the push-pull design enables connectors to be extracted or inserted into the port freely, which simplify the connectivity problems of limited access to the connector.

LC HD Plus+ Fiber Cable

LC Mux/Demux for More Flexibility in WDM Network

CWDM and DWDM Mux/Demux play an important role in combining data rate of different wavelengths over the same fiber cable to increase network capacity. No matter CWDM or DWDM Mux/Demux, there are several types of ports on them to ensure the normal function: channel port and line port. Of course, some Mux/Demux also have an expansion port and monitor port. A LC Mux/Demux means the LC Mux/Demux has LC connector for interfacing. It’s known to us that LC design is popular in fiber optic links. Mux/Demux with LC interface is easy to install and add WDM capacity to an existing network.

The following picture shows how to use two CWDM Mux/Demux at the same time to increase the wavelengths and expand the network capacity. The 8 CH and 4CH CWDM Mux/Demux are connected using the expansion port (LC interface).



LC interface is the result of increased demands for smaller easier-to-use fiber connectivity. And a wide range of optical components with LC interface are widely used in optical networks. This article just introduces parts of them. Some other LC assembles such as optical transceivers, LC pigtails and LC adapter panels are available in Fiberstore. If you want to know more details, please visit FS.COM.