CWDM vs DWDM | Difference between CWDM and DWDM

By March 15, 2019NEWS
CWDM vs DWDM | Difference between CWDM and DWDM

CWDM-Coarse Wavelength Division Multiplexing


The figure-1 depicts CWDM based fiber system. As shown it is used to transmit 4 different applications using single optical finer instead of pair of fiber cables. Different applications are using different light wavelengths which helps in multiplexing and de-multiplexing applications at transmit and receive end.

DWDM-Dense Wavelength Division Multiplexing


The figure-2 depicts DWDM system consisting of transmitter and receiver parts. Typically DWDM consists of MUX, DEMUX, isolators, circulators, EDFA (Erbium Doped Fiber Amplifier) etc.
DWDM system basics

CWDM vs DWDM-spectrum

Figure-3 depicts spectrum of CWDM and DWDM technologies. As shown DWDM spectrum will have tighter wavelength spacing between the channels compare to CWDM counterpart. Following table compares the two.


Full formCoarse Wavelength Division Multiplexing,WDM system having less than 8 active wavelengths per optical fiberDense Wavelength Division Multiplexing, WDM system having more than 8 active wavelengths per optical fiber
characteristicDefined by wavelengthsDefined by frequencies
Distanceshort range communicationlong range communication
Frequenciesuses wide range frequenciesuses narrow range frequencies
Wavelength spacingmoreless, hence can pack 40+ channels compare to CWDM in the same frequency range
Amplificationlight signal is not amplified herelight signal amplification can be used here
DriftWavelength drift is possiblePrecision lasers are needed to keep channels on the target
Spectrum utilizationBreaks the spectrum into big chunksdices the spectrum into small pieces
No. of active wavelengths per fiberFewer than 8More than 8

WDM (Wavelength Division Multiplexing) is a commonly used technology in optical communications. It is often deployed to join multiple wavelengths onto a single fiber. In the WDM system, there are two main types: Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). Both CWDM and DWDM are available as active or passive systems. This article will focus on discussing the difference between passive CWDM vs DWDM.

passive cwdm vs dwdm

Figure 1: passive CWDM vs DWDM

What Is Passive CWDM?

CWDM is often employed in situations where only a few channels are needed and there is no need for distances longer than 70 km. The passive CWDM is an implementation of CWDM that uses no electrical power. It divides the wavelengths by passive optical components like bandpass filters and prisms. Most CWDM devices are passive. CWDM Mux Demux is the most commonly used device in passive CWDM system.

What Is Passive DWDM?

DWDW technology is used for long haul optical transmissions. It can be divided into two different versions: an active solution and a passive solution. The active solution is a good fit for applications involving more than 32 links over the same fiber. Passive DWDM solutions have fewer active elements, in other words, the solutions have higher reliability and less latency. In a passive DWDM network, the line functions only due to the use of optical transceiver. Passive DWDM systems allow to arrange a high speed system with high channel capacity, but the transmission distance and management are limited. The major applications of passive DWDM system are metro networks and high speed communication lines.

passive DWDM

Figure 2: passive DWDM

Passive CWDM vs DWDM: What’s the Difference?

Passive DWDM and CWDM are based on the same concept of using multiple wavelengths of light on a single fiber. Both of them require no power and are easy to employ. However, they still differ to each other in some aspects. The following will describe some differences between passive CWDM vs DWDM.

Wavelength Spacing

Passive CWDM transports up to 18 wavelengths (from 1470nm to 1610nm) with a channel spacing of 20nm. While passive DWDM can accommodate 40, 80 or up to 160 wavelengths with a narrower wavelength spacing of 0.8nm, 0.4nm or even 0.2nm. Its wavelengths are from 1525nm to 1565nm (C band) and 1570nm to 1610nm (L band).

Channel Number

Passive DWDM supports more channels than passive CWDM. The former can provide up to 80 channels while the latter just supports up to 18 channels.

Transmission Distance

The maximum reach of the passive CWDM is about 160 km. Although the passive DWDM system has no optical amplifiers to achieve a fairly long distance, it can reach longer than the passive CWDM.


Actually, the cost is associated with the deployment of the system. In general, the passive DWDM devices are more expensive than that of passive CWDM systems. But the passive CWDM is just cost-effective for the connection rates below 10G and for short distance.


After the comparison of passive CWDM vs DWDM, we can see that each one has its advantages and disadvantages. Which to deploy depends on the actual needs. Hope what we discussed in the article could help make an informed decision. If you want to know more details, welcome to visit FS.COM.


CWDM SFP vs DWDM SFP – Which One Suits You Better?

SFP (Small Form-Factor Pluggable) is designed to meet Multi-Source Agreement (MSA) standards to ensure network equipment compatibility. Recently, wavelength-division multiplexing (WDM) technology is warmly welcomed by internet users all around the world. It is a technology that multiplexes a number of optical carrier signals at different wavelengths of laser light over a single optical fiber. By using WDM technology, SFP modules will have different wavelengths assigned to them. The following passage will focus on the brief descriptions of the two types of SFP modules: DWDM vs CWDM.

Overview of CWDM SFP

CWDM SFP is a kind of optical transceiver that utilizes CWDM technology. Similar with traditional SFP module, the CWDM SFP is a hot-swappable input/output device. It plugs into an SFP port or slot of a switch or router and links the port with the fiber-optic network. CWDM SFP transceiver modules make use of the SFP interface for connecting the equipment and use dual LC/PC fiber connector interface for connecting the optical network. Colorful CWDM SFP modules are displayed below.

It is well known that CWDM SFP modules come in 8 wavelengths covering from 1470 nm to 1610 nm. Color markings on the devices identify the wavelength to which the Gigabit Ethernet channel is mapped. The following picture lists the CWDM SFPs with their wavelengths and color codes.

DWDM SFP Overview

DWDM (Dense Wavelength-Division Multiplexing) SFP transceivers are used as part of a DWDM optical network to provide high-capacity bandwidth across an optical fiber network, which is a high performance, cost-effective module for serial optical data communication applications up to 4.25Gb/s. There are 32 fixed-wavelength DWDM SFPs that support the International Telecommunications Union (ITU) 100-GHz wavelength grid. An inner structure of DWDM SFP is shown below.



CWDM SFP transceiver is widely used in optical communications for both telecommunication and data communication. It is designed for operations in Metro Access Rings and Point-to-Point networks using Synchronous Optical Network (SONET), SDH (Synchronous Digital Hierarchy), Gigabit Ethernet and Fibre Channel networking equipment. The DWDM SFP can be also used in DWDM SONET/SDH (with or without FEC), but for longer transmission distance like 200km links and Ethernet/Fibre Channel protocol traffic for 80km links.

Which SFP Module Type Should You Choose: DWDM vs CWDM?

From a low-cost point of view, the CWDM SFP module is inexpensive than DWDM SFP. It provides a convenient and cost-effective solution for the adoption of Gigabit Ethernet and Fibre Channel. On the other hand, the key in selecting DWDM vs CWDM SFP modules lies in the differences between CWDM and DWDM. They refer to different methods of splitting up the light. For example, CWDM uses broader spacing between channels, allowing for inexpensive SFPs, and DWDM uses denser channel spacing, which allows for more wavelengths to be used on a single fiber. DWDM is typically used in large optical networks over the longer distance. Thus if you are looking for SFP modules over long distance and with better scalability, DWDM SFP module is the ideal choice.


I hope this brief introduction to DWDM vs CWDM SFP modules is helpful for you to make a choice in selecting them. Based on the Cisco CWDM SFPs, FS CWDM SFPs are multi-rate transceivers, supporting data rates from 100 Mbps up to 4 Gbps. Besides, they support transfer distance at 20-40km, 40-80km and 80-120km in different colors, diversely satisfy the requirements of clients. All the DWDM SFP modules meet the requirements of the IEEE802.3 Gigabit Ethernet standard. They are suitable for interconnections in Gigabit Ethernet and Fibre Channel environments.



How to Add CWDM MUX/DEMUX System to Your Network?

Coarse wavelength division multiplexing (CWDM) technology is developed to expand the capacity of a fiber optic network without requiring additional fiber. In a CWDM system, CWDM Mux/Demux (multiplexer/demultiplexer) is the most important component. Usually, a CWDM Mux/Demux is used to increase the current fiber cable capacity by transmitting multiple wavelengths, typically up to 18 separate signals over one fiber. This article may mainly describe what is Mux in networking and how to install your CWDM Mux/Demux system. Unless you are an experienced user, we recommend that you follow the detailed installation steps described in the rest of this article.

Introduction to CWDM MUX/DEMUX Module

CWDM Mux/Demux module is a passive device, very reliable and simple to use. These devices are available with a variety of wavelength combinations, usually from 1270nm to 1610nm (20nm spacing). Based on different applications, a CWDM Mux/Demux module can be designed into different channels. A typical 4 channel Mux/Demux module will be used to multiplex four different wavelengths onto one fiber (shown in the picture below). This allows you to simultaneously transmit four different data over the same fiber. If you are using a CWDM multiplexer at the beginning of your network, you will use a CWDM demultiplexer at the opposite end to separate or demultiplex the wavelengths to allow them to be directed to the correct receivers. Usually, a CWDM Mux/Demux is a module that can be used as a multiplexer or demultiplexer at either end of the fiber cable span. However, it must still be used in pairs.

what is MUX in networking

What IS MUX in Networking?

What is MUX in networking? A basic CWDM Mux/Demux system comprises a Local unit, the CWDM Mux/Demux module and a Remote unit. Usually, a Local or Remote unit refers to two different switches. In general, to install a CWDM Mux/Demux module, a chassis should be installed first to hold the module. Besides, to connect a CWDM Mux/Demux module to a switch, we should install CWDM SFP transceivers in the switch first. Then using the single mode patch cables to connect the transceivers to the CWDM Mux/Demux module. Therefore, when we want to build a CWDM Mux/Demux system, the components we need usually include rack-mount chassis, CWDM Mux/Demux module, CWDM SFP transceiver and single mode patch cables (shown in the table below).

Part NameProduct PhotoDescription
Rack-mount Chassis2-Slot ChassisCustomized Empty  Rack Chassis to hold 2/3/4/12 Pieces custom small size LGX Cassette
CWDM Mux/DemuxCWDM Mux & Demux2/4/5/8/9/16/18 Channels CWDM MUX DEMUX 1270nm to 1610nm with Monitor Port
CWDM SFP TransceiverCWDM SFP1.25Gbps CWDM SFP 1270nm to 1610nm 20/40/80/100/120km Transceiver
Singlemode Fiber Cablessinglemode patch cableLC to LC 9/125 Simplex/Duplex Single-mode Fiber Patch Cable

How to Add CWDM MUX/DEMUX System to Your Network?

After knowing what is MUX in networking? Next, we’ll learn how to install a CWDM Mux/Demux system, there are four basic steps:

  • Install the Rack-Mount Chassis

The CWDM rack-mount chassis can be mounted in a standard 19-inch cabinet or rack. When to attach the chassis to a standard 19-inch rack, ensure that you install the rack-mount chassis in the same rack or an adjacent rack to your system so that you can connect all the cables between your CWDM Mux/Demux modules and the CWDM SFP transceivers in your system.

Install the 2-Slot Chassis

  • Install the CWDM Mux/Demux Modules

To insert a module, you should align the module with the chassis shelf (shown in the figure below) first and then gently push the module into the shelf cavity. Finally, tighten the captive screws.

Install the CWDM MuxDemux

  • Connect the CWDM Mux/Demux to Switch

After inserting the CWDM SFP transceiver into the switch, then we should use the single mode patch cable to connect the transceiver to the CWDM Mux/Demux.

Connect the CWDM Mux Demux to Switch

Please mind that CWDM Mux/Demux pairs must carry transceivers with the same wavelength. Because each transceiver will work only at the appropriate port and the data will always flow between devices with the same wavelengths. CWDM SFP transceivers with different wavelength may have a different color code. Use the CWDM SFP transceiver color codes shown in the picture below to help you connect the CWDM Mux/Demux to your system.

CWDM SFP transceiver

  • Connect the CWDM MUX/DEMUX Pairs

Once you use a CWDM multiplexer on one end of your networks, you must use a demultiplexer on the other end of the networks. Therefore, the last step to complete CWDM Mux/Demux system is to connect the Mux/Demux pairs (or multiplexer and demultiplexer). For duplex Mux/Demux, a pair of single mode patch cables must be used. For simplex Mux/Demux, only one single mode patch cable is enough. After all done, your CWDM Mux/Demux system is then installed successfully.

Connect the CWDM MUX DEMUX Pairs


What is MUX in networking? In summary, Mux/Demux system is a cost-effective solution which is easy to install. CWDM Mux/Demux, CWDM multiplexer only, and CWDM demultiplexer only are a flexible, low-cost solution that enables the expansion of existing fiber capacity and let operators make full of use of available fiber bandwidth in local loop and enterprise architectures. Fiberstore CWDM Mux/Demux is a universal device capable of multiplex multiple CWDM (1270~1610nm) up to 18 channels (2, 4, 5, 8, 9, 16, 18 channels are available) or optical signals into a fiber pair or single fiber. Together with our CWDM transceivers or the wavelength converters, the bandwidth of the fiber can be utilized in a cost-effective way.




fiber-optical-networking :- fiber-optical-networking
rfwireless-world :- rfwireless-world