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.

How to Expand Bandwidth in PON Network with CWDM Technology?

PON (passive optical network) is one of a common optical fiber network architectures. It is characterized by the “splitting” of the optical fiber one or more times, resulting in the sharing of optical fiber among multiple users. However, as networks grow in terms of subscriber counts, the scope and number of services offered, expanding the network bandwidth is inevitable. Coarse Wave Division Multiplexing (CWDM), known for its low cost and scalability to increase fiber capacity as needed, is a preferred method for PON network expansion. This article will focus on using CWDM technology to overcome bandwidth limitations in PON access networks.

CWDM Mux/Demux and OADM (Optical Add-Drop Multiplexer) in Access PON

Fibers in a PON are typically shared with several users. Hence the bandwidth of the fiber originating at the CO (center office) is shared among a group of users. The splitting of the network is accomplished by optical splitters. These splitters can split the fiber 2-32 times, which may introduce high losses in the network. Besides, as different places in a same network need different wavelengths, CWDM Mux is often deployed to multiplex these signals on a single fiber.

In PON (Passive Optical Network) network, whether in ring structures or point-to-point arrangements, different optical nodes need specific wavelengths. Therefore, at each node, a CWDM OADM is used to drop or add certain channels from the fiber as required,. Then the signals will be transmitted to the user through optical fibers. The following picture shows a simple PON network.


How to Expand Bandwidth of PON Network Using CWDM Technology?
Upgrading Access PONs Using Passive CWDM Mux/Demux

In PON networks, OLT has two float directions: upstream (getting an distributing different type of data and voice traffic from users) and downstream (getting data, voice and video traffic from metro network or from a long-haul network and send it to all ONT modules on the ODN).

The following figure represents a situation where existing subscribers intend to upgrade to higher value added bandwidth services. In order to satisfy customers’ needs for IPTV, VoIP, video on demand etc., the 622 Mb/s downstream capacity between the CO and the OLT, providing roughly 20 Mb/s to each subscriber, must increase.

PON network

Considering there may be new subscribers and services added, the targeted bandwidth requires at least a downstream CO/OLT link bandwidth of 2.5Gb/s. Therefore, four CWDM wavelengths are introduced to multiply the channels passing between the CO and OLT. This introduction of passive CWDM Mux/Demux can relieve the fiber exhaust effectively. The below figure shows the upgrading process.

PON upgrade

Advantages of This Upgrade

Compared with laying a new fiber cable, the upgrade with passive CWDM is easily accomplished within hours after some modest investment in network planning. And the sum of material, labor, equipment and training expense is far less, which explain why many enterprises, private business users of LAN and data storage networks use passive CWDM too.

Expanding EPON Bandwidth Using CWDM Mux/Demux

EPON stands for Ethernet passive optical network. It is an enabling technology that benefits consumers. Here is an EPON network, which was conceived to serve up to 64 subscribers. All users share a single bidirectional optical feed line. With the need for IPTV, HDTV and other higher bandwidth services growing, the downstream capacity 16Mb/s should be improved.


The picture below shows the same EPON deployment upgraded to 4Gb/s bandwidth capacity.

EPON network

This upgrade uses 4 channels passive CWDM Mux/Demux to extend the whole network capacity, allowing the downstream capacity increase four times without affecting the upstream traffic.

Advantage of This Expansion

Using CWDM Mux/Demux effectively increases the network bandwidth capacity and reduces the cost. At the same time, it requires minimal modification of the existing infrastructure, which also saves labors.


CWDM technology offers significant benefits of low investment, minimal operating cost and very simple and straightforward upgrade planning and implementation. In addition, passive CWDM also provides scalability and network flexibility for network growth and bandwidth demands in the future. FS.COM supplies different channels of CWDM components. Welcome to contact us via sales@fs.com.

Related article:Examples of CWDM Network Deployment Solution

Examples of CWDM Network Deployment Solution

Based on the same concept of using multiple wavelengths of light on a single fiber, CWDM and DWDM are two important technologies in fiber optical communications. As we all know, although the transmission distance of CWDM network is shorter than that of DWDM, it costs less and has the scalability to grow fiber capacity as needed. This article intends to give a simple introduction of components in CWDM networks and to explore some examples of CWDM network deployment cases.

Common Components Used in CWDM Networks
CWDM Mux/Demux

CWDM Mux/Demux, which is based on the film filter technology, is the basic component in CWDM networks. It can combine up to 4, 8 or 16 different wavelength signals from different fiber extenders to a single optical fiber, or it can separate the same wavelengths coming from a single CWDM source. That’s why CWDM can extend existing fiber capacity.

CWDM OADM (Optical Add-Drop Multiplexer)

A CWDM OADM is a device that can add (multiplex) and drop (demultiplex) channels on both directions in a CWDM network. It can add new access points anywhere in CWDM systems without impacting the remaining channels traversing the network. With this ability of OADM, the access points can be added to liner, bus, and ring networks, where the dual direction ring design provides redundant protected architecture.

CWDM Optical Transceiver

Optical transceiver is a necessary element in optical networks. And CWDM optical transceiver is a type of module supporting CWDM network application with CWDM wavelengths. When connected with CWDM Mux/Demux, CWDM transceiver can increase network capacity by allowing different data channels to use separate optical wavelengths (1270nm to 1610nm) on the same fiber. And the common CWDM transceiver type is SFP, SFP+, XFP, XENPAK, X2, etc.

CWDM Network Deployment Solution
Example One

Description: there are five buildings (Sheriff, Courthouse, Admin, Police & Fire, & Public Works) connected via multimode fiber cables (MMF) or single mode fiber cables (SMF). These buildings are linked via multimode SFPs in an existing D-link switches to create one network for internal use of the city offices. Below is a simple graph to show the situation.

CWDM Network 1

Requirements: the goal is to install a single mode fiber network in town to connect numerous buildings. Some of these buildings have access to the city LAN. The Public Works building need to connect with Youth & Recreation Center, Library, Immanuel Lutheran School and the Senior Center. And all these buildings should have unfiltered Internet. Besides, the Waster Water Treatment Plant should be connected passing through the Senior Center. All these services are achieved using CWDM technology.

Solution: according to the requirements, this is a CWDM networks with several buildings to connect with. Here is the solution diagram.

CWDM Network

In the diagram above, we can see there is an 8CH CWDM Mux/Demux connected with the switches. According to the requirements, Youth & Recreation Center, Library, Immanuel Lutheran School and Senior Citizen Center should be connected with the Public Works and need unfiltered services. Therefore, a 4CH CWDM OADM is placed after the CWDM Mux/Demux. Then the four wavelengths will be drop and into the four buildings. In addition, another CWDM OADM is deployed in Senior center to connect the Waster Water Treatment Plant, to meet the requirement. And each site also needs to use CWDM optical transceivers.

Example Two

Description: on site A, there are three Ethernet switches and a T3 router. And their working wavelengths 1470nm, 1490nm, 1510nm, 1530nm and 1610nm. Other three sites B, C, and D also have three Ethernet switches. And a T3 router is in site E. As the following figure shows.


Requirements: Considering the cost, all the wavelengths should be transmitted on a single fiber using CWDM technology.

Solution: according to the requirements, here is a simple diagram showing the solution.

CWDM Mux Demux

In order to save cost, a 4CH CWDM Mux/Demux is used to multiplex four wavelengths (from three switches and one router) into one single fiber. At the first site B, a 1CH CWDM OADM is installed to remove one wavelength which is associated with network B. And other three sites are the same—dropping one wavelength associated with corresponding switch or router.


This article mainly introduces two CWDM network deployment examples. All the components like the CWDM Mux/Demux, CWDM OADM and CWDM transceiver are available in FS.COM. If you are interested in them, please contact us via sales@fs.com.

Related article:Differences between CWDM and DWDM

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.

Optical Add-drop Multiplexer Overview

With an explosive growth in the amount of information transmission, the optical telecommunication networks develop rapidly. The progress of single wavelength point-to-point transmission lines to wavelength division multiplexed optical networks has introduced a demand for wavelength selective optical add-drop multiplexer (OADM) to separate or route different wavelength channels. This paper will have an overview of the OADM.

OADM Technology

The introduction of optical add drop multiplexers into optical networks allows traffic to be inserted, removed and, most importantly, bypassed. Moreover, OADM can support functions such as protection, drop/continue, loop-back and wavelength reuse of the optical channels. Drop and continue refer that the channel is removed at the node but allowed to pass through to the next OADM. Wavelength reuse means the dropped channel does not pass through to the next OADM, instead, a new channel of the same wavelength can be added. Below figure explains OADMs work in a CWDM system.

Passive and Dynamic OADM

OADM can be used in the dynamic as well as static mode. The add and drop wavelengths are fixed in the passive OADM, while in dynamic mode, the OADM can be set to any wavelength after installation. Passive OADM is mainly used in networks with WDM systems (CWDM and DWDM) or hubbed structures, where the OADM is connected to a central hub, e.g. in the metropolitan network. In order to utilize resources in a more efficient way, the OADM with dynamic wavelength assignment are preferred when traffic variations are comparable to network capacity. It can select any wavelength by provisioning on demand without changing its physical configuration.


OADM has many advantages. The most striking one is that its multiplexing happens to coincide with the minimum loss area of single mode fiber. This reduces the transmission loss of the light signal which can be transmitted relatively far distance. Additionally, it is transparent to digital signal format and data rate. Its gain saturation recovery time is long, and has a very small crosstalk between the respective channels. What’s more, multiple channels of information carried over the same fiber with each using an individual wavelength. Narrow channel spacing or wavelength selection give rise to denser channels in the same wavelength range. Last but not the least, repeater or amplification sites are reduced, which results in large savings of funding.


OADM supports standard network topologies such as point-to-point and ring. It can be used at different points along the optical link to insert/remove or route selected channels increasing the network flexibility. This feature is particularly important in metropolitan WDM lightwave services where offices or sites can be connected by different add-drop channels, for instance in an interoffice ring. In WDM systems, OADM is installed in a multi-wavelength fiber span, and allows a specific wavelength on the fiber to be demultiplexed (dropped) and remultiplexed (added) while enabling all other wavelengths to pass. Then it can provide flexibility and scalability to optical networks as it allows users to optimize the use of existing fiber by adding or dropping channels on a per-site basis, thereby maximizing fiber bandwidth.

In conclusion, optical add-drop multiplexer can contribute to improve and optimize the network performance. Fiberstore, a professional supplier in the optical industry, has lots of CWDM OADM and DWDM OADM. Besides these, the WDM fiber optic multiplexer, CWDM Mux/Demux and DWDM Mux are also available. Welcome to visit www.fs.com for more information.