xWDM Technology
Wavelength Division Multiplexing (WDM) technology multiplies fiber capacity by multiplexing optical light signals of different wavelengths onto a single optical fiber. The technology is well standardized in the ITU G.695 and G.694 recommendations and widely used in datacom and telecom networks.
Passive Filters
Mux/Demux: A Mux/Demux unit terminates all wavelengths on the WDM system and is at the heart of point-to-point connections, The optical combining and splitting of wavelengths is a passive technology and a Mux/Demux unit requires neither electrical power nor software resulting in greatly increased reliability.
OADM: An Optical Add/Drop Multiplexer (OADM) unit terminates a limited subset of wavelengths in WDM systems. OADMs typically add/drop 1, 2 or 4 wavelengths and the remaining wavelengths are bypassed (expressed) through the fiber. It is possible to reuse the terminated wavelengths on the remaining span.
Due to the physical nature of light, the signals on WDM wavelengths are completely independent from each other and data streams with different line-rates and protocols can be transported on a single fiber or fiber pair. Traditional telecom signals (PDH, SDH/SONET), IP data (Ethernet, Gigabit Ethernet or 10G Ethernet) and storage data (8G/4G/2G/1G Fibre Channel) can therefore be transported over a single infrastructure without complex protocol conversion technologies To build a passive WDM system, two types of components are required:
- Optical Multiplexer Units (OMU's) which combine and split light signals of WDM wavelengths
- WDM transceivers, which generate light signals of specific WDM wavelengths
CWDM and DWDM
WDM comes in two flavours; CWDM and DWDM Coarse WDM is a robust technology able to create 18 independent channels and was first to adapt a transceiver footprint. The CWDM channel spacing is 20 nm and a specific color coding is used which enables simple industry standard setup procedures. CWDM is typically used for un-amplified transmission up to 200 km.
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