Chinese English
Chinese English
The IT refers to a medium where information is transmitted via a link. If two locations want to communicate with each other, one link is sufficient. To connect more locations more links are required What if only one link e.g. between two cities is available, but more applications shall be connected? Using the WDM technology, fiber optic links can be utilized for data transmission more efficiently.
Choosing of the appropriate wavelength
By the use of appropriate transceivers (SFP, XFP etc.) with different power budget ranges from a few 100 m up to 160 km can be achieved. A major factor in the range is – next to the power budget of the transceiver – the used wavelength as a fiber has a specific attenuation behaviour for each wavelength. The higher the attenuation, the lower the overall distance. With a careful selection of the wavelength a higher range and better signal quality can be achieved.
Coarse Wavelength Division Multiplexing (CWDM) is a wavelength multiplexing technology for city and access networks. Transmission is realized using 18 channels with wavelengths between 1270 nm and 1610 nm. Due to the channel spacing of 20 nm cost-effective lasers can be used. The channel width itself is 13 nm. The remaining 7 nm is designed to secure the space to the next channel.
Pic.1 CWDM wavelength
Pic.2 CWDM
Pic.3 8ch CWDM
Pic.3 ABS BOX CWDM
The functionality of DWDM (Dense Wavelength Division Multiplexing) resembles to the one of CWDM. The DWDM channel spacing is 0.8/0.4 nm (100 GHz/50 GHz grid). This small channel spacing allows to transmit simultaneously more information. Currently a restriction on wavelengths between 1530 nm and 1625 nm exists which corresponds to the C and L band. DWDM wavelengths are more expensive compared to CWDM caused by the need of more sophisticated transceivers.
Pic.4 DWDM wavelength
Pic.5 DWDM
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