Do you know these about CWDM Multiplexer and DWDM Multiplexer?

Do you know these about CWDM Multiplexer and DWDM Multiplexer?

Wavelength division multiplexing (WDM) is a technology or technique modulating numerous data streams, i.e. optical carrier signals of varying wavelengths (colors) of laser light, onto a single optical fiber. The goal of WDM is to have a signal not to interfere with each other. It is usually used to make data transmission more efficiently. It has also been proven more cost effective in many applications, such as WDM network applications, broadband network application and fiber to the home (FTTH) applications and so on. According to channel spacing between neighbored wavelengths, there are two main types of WDM, including Coarse WDM (CWDM) and Dense WDM (DWDM). Though both of them belong to WDM technology, they are quite different. Then, what are the differences between them? This paper will give you the answer.

Definition of CWDM

CWDM is a method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables, such that the number of channels is fewer than in DWDM but more than in standard WDM. “Course” means the channel spacing is 20nm with a working channel passband of +/-6.5nm from the wavelengths center. From 1270nm to 1610nm, there are 18 individual wavelengths separated by 20nm spacing.

Definition of DWDM

DWDM is a technology that puts data from different sources together on an optical fiber, with each signal carried at the same time on its own separate light wavelength. “Dense” refers to the very narrow channel spacing measured in Gigahertz (GHz) as opposed to nanometer (nm). DWDM typically uses channel spacing of 100GHz with a working channel passband of +/-12.5GHz from the wavelengths center. It uses 200GHz spacing essentially skipping every other channel in the DWDM grid. And it has also gone one step further using an Optical Interleaver to get down to 50GHz spacing doubling the channels’ capacity from 100GHz spacing.

CWDM vs DWDM

According to the content above, you will find some small differences between them. 16CH CWDM Module is defined by wavelengths and has wide range channel spacing. DWDM is defined by frequencies and has narrow channel spacing. What’s more, what other differences do they have?

Capacity of Data

In fiber optic network system, DWDM system could fit more than 40 different data streams in the same amount of fiber used for two data streams in a CWDM system. In some cases, CWDM system can perform many of the same tasks compared to DWDM. Despite the lower transmission of data through a CWDM system, these are still viable options for fiber optic data transmission.

Cost of Cable

CWDM system carries less data, but the cabling used to run them is less expensive and less complex. A DWDM system has much denser cabling and can carry a significantly larger amount of data, but it can be cost prohibitive, especially where there is necessary to have a large amount of cabling in an application.

Long-haul or Short-haul Transmission

DWDM system is used for a longer haul transmission through keeping the wavelengths tightly packed. It can transmit more data over a significantly larger run of cable with less interference. However, CWDM system cannot travel long distances because the wavelengths are not amplified, and therefore CWDM is limited in its functionality over longer distances. If we neeed to transmit the data over a very long range, DWDM system solution may be the best choice in terms of functionality of the data transmission as well as the lessened interference over the longer distances that the wavelengths must travel. As far as cost is concerned, when required to provide signal amplification about 100 miles (160km), CWDM system is the best solution for short runs.

According to the content above, maybe you have already understood some differences between CWDM and DWDM by the comparision of them from definition, capacity, cable cost and transmission distance etc. And here is also a figure of comparisons between CWDM and DWDM which may help you to consolidate your understanding of this paper.

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