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OTN / WDM Network / CWDM vs DWDM: What’s the Difference?

CWDM vs DWDM: What’s the Difference?

Posted on By FS.COM

When dealing with OTN (Optical Transport Network), there are two main types of Wavelength Division Multiplexing (WDM) systems: Coarse Wavelength Division Multiplexing (CWDM) and Dense Wavelength Division Multiplexing (DWDM). As two modern WDM technologies, they are both used for increasing the bandwidth of fiber by combining optical signals of different wavelengths on one strand of fiber. But CWDM vs DWDM, what are their differences?


To better understand the difference between CWDM and DWDM, we’d better get to know what’s WDM, CWDM and DWDM in the first place.

What’s WDM?

WDM is a technology for transporting large amounts of data between sites. It increases bandwidth by allowing different data streams to be sent simultaneously over a single optical fiber network. In this way, WDM maximizes the utilization of fiber and helps to optimize network investments.

What’s CWDM and DWDM?

As mentioned above, CWDM and DWDM are two technologies developed based on WDM, but with different wavelength patterns and applications. CWDM is a flexible technology that can be deployed on most types of fiber networks. It is typically deployed in point-to-point topology in enterprise networks and telecom access networks. While DWDM is viewed as an option for the metropolitan network. Now it is also used for interconnecting data centers and for financial services networks, and is often deployed in ring topology.

CWDM vs DWDM, What’s the Difference?

CWDM and DWDM are both effective methods to solve the increasing bandwidth capacity of information transmission at present. But they differ to each other in many aspects. Below parts will introduce some differences between CWDM and DWDM systems.

CWDM vs DWDM: Channel Spacing

The channel spacing is defined to be the nominal difference in frequency or wavelength between two adjacent optical channels. CWDM has a wider spacing than DWDM. It is able to transport up to 18 CWDM wavelengths with a channel spacing of 20nm in the spectrum grid from 1271nm to 1611nm. DWDM can carry 40, 80 or up to 160 wavelengths with a narrower spacing of 0.8/0.4nm (100 GHz/50 GHz grid). Its wavelengths are from 1525nm to 1565nm (C band) and 1570nm to 1610nm (L band).

cwdm vs dwdm wavelengths

CWDM vs DWDM: Transmission Distance

Since DWDM wavelengths are highly integrated in the fiber during light transmission, DWDM is able to reach a longer distance than CWDM. Unlike DWDM system, CWDM is unable to travel unlimited distance. The maximum reach of CWDM is about 160 km. While an amplified DWDM system can go much further.

CWDM vs DWDM: Modulation Laser

CWDM system uses the uncooled laser while DWDM system uses the cooling laser. Cooling laser adopts temperature tuning which ensures better performance, higher safety and longer lifespan of DWDM system. But it also consumes more power than the electronic tuning uncooled laser used by a CWDM system.

CWDM vs DWDM: Cost

Because the range of temperature distribution is nonuniform in a very wide wavelength, so the temperature tuning is very difficult to realize, thus using the cooling laser technique increases the cost of DWDM system. Furthermore, the DWDM devices are typically four or five times more expensive than that of a CWDM system. However, DWDM becoming increasingly popular, the price of DWDM transceiver is about 20-25% less than a CWDM transceiver. For example, the price of CWDM SFP+ transceiver from FS.COM is about $ 499, while the DWDM SFP+ is sold only at $ 369.

CWDM vs DWDM: Advantages And Disadvantages

As mentioned above, the primary difference between DWDM and CWDM is the channel spacing (CWDM has almost 100 times wider channel spacing). This makes CWDM is a simpler technology, resulting in advantages and disadvantages of the different systems with regard to cost, performance and so on.

CWDM Advantages and Disadvantages

CWDM Advantages CWDM Disadvantages
 Lower power consumption
 Smaller space requirements
 Can use SMF fiber or MMF cable
 Can use LED’s or Laser’s for power
 Larger individual payloads per channel
 Smaller and cheaper wave filters
 Cost savings on start up and expansion
 Less capacity than DWDM
 Less range
 Regeneration vs amplification
 O, A and M functions are not carrier class

DWDM Advantages and Disadvantages

DWDM Advantages DWDM Disadvantages
 Maximum capacity system available
 Maximum distance capability with EDFA’s
 Repeater “amp” sites can be reduced
 Pay as you grow expansion
 Mature O, A and M systems are developed
 Need more space
 Need more power
 Need high accuracy lasers and wave filters
 Expensive EDFA’s for amplifiers
 Start up costs are more than equivalent CWDM system

CWDM vs DWDM, Which do you prefer?

Since there is tremendous demand for more and more bandwidth, DWDM is much more favored in the market. And it has experienced great advancement in cost reduction. However, CWDM still has price advantage for connection rates below 10G and for short distances. With low data rates, it is currently most feasible technology. In this way, CWDM and DWDM each provides a unique “fit” in OTN network, and will complement rather than replace each other in the future.

Related Articles:

Everything You Need to Know Before Buying CWDM and DWDM SFP+ Transceivers

Complete Analysis on DWDM Technology

CWDM - Cost-Effective Alternative to Expand Network Capacity