Wavelength Division Multiplexing
Wavelength Division Multiplexing (WDM) is when multiple
photonic beams of different wavelength carry multiple channels of information
through the fiber. WDM is cost effective.
The following wavelength bands exist:
· * Original: 1260 – 1360 nm
· * Extended: 1360 – 1460 nm
· * Short wavelength: 1460 – 1530 nm
· * Conventional: 1530 – 1565 nm
· * Long wavelength: 1565 – 1625 nm
· * Ultra Long wavelength: 1625 – 1670 nm
Dense Wavelength Division Multiplexing (DWDM)
DWDM channels are represented in terms of optical frequency
instead of wavelength. The reference frequency is 193.1 THz. Typical frequency
spacing is 100 GHz. Channel spacing of 50 GHz and 25 GHz is also used.
DWDM technology was enabled by optical amplifiers.
Coarse Wavelength Division Multiplexing (CWDM)
20
nm channel spacing is used for wavelength between 1270 nm and 1610 nm.
The
wavelength grid consists of the following bands:
· * O-band 1260 nm – 1360 nm
-· * E-band 1360 nm – 1460 nm
· * S-band 1460 nm – 1530 nm
· * C-band 1530 nm – 1565 nm
· * L-band 1565 nm – 1625 nm
Optical Add/Drop Multiplexers (OADM) are used in CWDM
systems to add and drop wavelength to optical fibre channels.
Wavelength Routing
Wavelength routing is used by scalable and re-arrangeable
optical networks. Transmission wavelength can specify the destination node.
Wavelength tuneable transmitters allow allocation of channels to according to
traffic requirements.
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