Dense Wave Division Multiplexing (DWDM) is the technology, where one optical fiber is used for transmission of several signals with various wavelengths. Jump to DWDM systems - A DWDM terminal multiplexer. The terminal multiplexer contains a wavelength-converting transponder for each data signal,  ‎WDM systems · ‎Coarse WDM · ‎Dense WDM. There are two main types of WDM technologies used today: Dense Wavelength Division Multiplexing (DWDM) and Coarse Wavelength Division Multiplexing.


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EDFAs consisted of optical fiber doped with Erbium atoms which, when pumped with a laser of a different wavelength, created a gain medium which would amplify light in a band near the nm wavelength. EDFAs allowed amplification of the optical signals in fibers which could counter the effects dense wave division multiplexing optical loss, but could not correct for the effects of dispersion and other impairments.

As a matter of dense wave division multiplexing, EDFAs generate amplified spontaneous emission ASE noise and could cause fiber nonlinearity distortions over a long transmission distance.


So EDFAs did not eliminate the need for regeneration completely, but allowed the signals to go many 80 km hops before regeneration was needed. Since EDFAs were cheaper than full regeneration, systems were quickly designed dense wave division multiplexing used nm lasers instead of the then prevailing nm.

Because they are carried on distinct wavelengths, the streams -- also called channels -- do dense wave division multiplexing interfere with each other.

Consequently, data integrity is maintained, as well as any security-related partitioning -- separate tenants in the same data center, for example. This device contains a one wavelength converting transponder for each wavelength carried.

Dense Wave Division Multiplexing, DWDM

The MUX multiplexer takes a dense wave division multiplexing of nm optical signals and places them on a single optical fiber. WDM, DWDM and CWDM are based on the same concept of using multiple wavelengths of light on a single fiber, but differ in the spacing of the wavelengths, number of channels, and the ability to amplify the multiplexed signals in the optical space.

EDFA provide an efficient wideband amplification for the C-bandRaman amplification adds a mechanism for amplification in the L-band. For CWDM, wideband optical amplification is not available, limiting the optical spans to several tens of kilometres.

In general, these things dense wave division multiplexing the fact that the choice of channel spacings and frequency stability was such that erbium doped fiber amplifiers EDFAs could not be utilized.

Newer fibers which conform to the G.


The relaxed optical frequency stabilization requirements allow the associated costs of CWDM to approach those of non-WDM optical components. CWDM is also being used in cable television networks, where different wavelengths are used for the downstream and upstream signals.

DWDM (Dense Wavelength Division Multiplexing)

Thus, a legacy switch system can be dense wave division multiplexing "converted" to allow wavelength multiplexed transport over a fiber simply by judicious choice of transceiver wavelengths, combined with an inexpensive passive optical multiplexing device.

It separates the wavelengths using passive optical components such as bandpass filters and prisms. Many manufacturers are promoting passive CWDM to deploy fiber to the home.

EDFAs can amplify any optical signal in their operating range, regardless of the modulated bit rate. In terms of multi-wavelength signals, so long as the EDFA has enough pump energy available to it, it can amplify as many optical signals as can be multiplexed into its amplification band though dense wave division multiplexing densities are limited by choice of modulation format.

EDFAs therefore allow a single-channel optical link to be upgraded in bit rate by replacing only equipment at the ends of the link, while retaining the existing EDFA or series of EDFAs through a long haul route.

The most essential advantage of DWDM technology is connected with the possibility of substantial increase of carrying capacity without changing of electronic equipment and optical cable new channels with new wavelengths and without interfering to the already existing ones.

The point is that increase of carrying capacity is possible not for several percentage points, but by dense wave division multiplexing and hundreds times.

The channels may have different protocols and transmission speeds, and there is no necessity to synchronize them with dense wave division multiplexing other.


TDM technology may be applied in respect of each WDM channel; this makes it possible to allocate the bandwidth among consumers in the more flexible manner.