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Download Information about ITU DWDM Channels [PDF]

How the DWDM Method Works

A DWDM system offers the possibility of collecting and amplifying optical signals while providing those signals without the need to convert them into electrical signals. The Dense Wavelength Division Multiplexing (DWDM) method increases the capacity of the transmitted optical signals by assigning the incoming signals to specific wavelengths within a frequency band and then multiplexing them over an optical glass fiber link. On the receiver side, a demultiplexer separates the combined optical signals and passes each channel to an optical receiver. Instead of using an optical fiber with only one transmitter and receiver pair, the DWDM technology allows several optical channels to be transmitted simultaneously via the fiber pair.

Available Frequency Bands and DWDM Channels

In the case of optical data communication there are different frequency bands which are suitable for the transmission of signals, providing a large number of different channels in the wavelength range from 1260nm to 1675nm. In this case, a distinction is made between Original (O-band 1260-1360nm), Extended (E-band 1360-1460nm), Short Wavelength (S-band 1460-1530nm), Conventional (C-band 1530-1565nm), Long Wavelength (L-Band 1565-1625nm) and Ultralong Wavelength (U-band 1625-1675nm).

Typical DWDM systems use 40 channels with a channel spacing of 100GHz from channel to channel or 80 channels with a channel spacing of 50GHz from channel to channel. The latter is used in all newer DWDM applications, since the dual number of channels is available. In both ways, primarily the bands of the C- or L-band are used, which are listed in the following table with a distance of 100GHz:

ChannelFrequency Wavelength ChannelFrequencyWavelength
(#)(GHz)(nm)(#) (GHz)(nm)
11901001577.0337 1937001547.72
21902001576.20 381938001546.92
31903001575.37 391939001546.12
41904001574.54 401940001545.32
51905001573.71 411941001544.53
61906001572.89 421942001543.73
71907001572.06 431943001542.94
81908001571.24 441944001542.14
91909001570.42 451945001541.35
101910001569.59 461946001540.56
111911001568.11 471947001539.77
121912001567.95 481948001538.98
131913001567.13 491949001538.19
141914001566.31 501950001537.40
151915001565.50 511951001536.61
161916001564.68 521952001535.82
171917001563.86 531953001535.04
181918001563.05 541954001534.25
191919001562.23 551955001533.47
201920001561.42 561956001532.68
211921001560.61 571957001531.90
221922001559.79 581958001531.12
231923001558.98 591959001530.33
241924001558.17 601960001529.55
251925001557.36 611961001528.77
261926001556.56 621962001527.99
271927001555.75 631963001527.22
281928001554.94 641964001526.44
291929001554.13 651965001525.66
301930001553.33 661966001524.89
311931001552.52 671967001524.11
321932001551.72 681968001523.34
331933001550.92 691969001522.56
341934001550.12 701970001521.79
351935001549.32 711971001521.02
361936001548.52 721972001520.25

Optical Data Transmissions with DWDM Transceivers

An important advantage of DWDM is that it is independent of protocol and bit rate. DWDM-based networks can transfer data in IP, ATM, SONET, SDH and Ethernet. Therefore, DWDM-based networks can transport different types of traffic at different speeds over an optical channel. The available channels allow multiple video, audio, and data signals (such as voice, e-mail and multimedia data and more) to be transmitted over an optical fiber while maintaining system performance.

For each of the channels an optical transceiver is needed on the transmission and on the receiver side. For single-mode data links of up to 3.072Gb/s DWDM SFP optics are used, for bandwidths of up to 11.3Gb/s DWDM XFP optics or for bandwidths up to 10.3125Gb/s DWDM SFP+ optics are available. In all variants, you can choose between modules with a fixed DWDM channel, which must be considered when planning the DWDM system. A more flexible solution is the tunable version, which is available as Tunable XFP or Tunable SFP+ variant. This offers the possibility to set the wavelength range in order to adapt the transceiver individually to your needs.

With these DWDM technology solutions, network administrators can respond to the growing need for more efficient and powerful data transfers and increase the bandwidth.