Editing Wavelength-division multiplexing (section)

{{Short description|Fiber-optic communications technology}}
{{Redirect|DWDM|the Philippine radio station|DWDM-FM}}
{{More footnotes needed|date=December 2018}}
{{Use American English|date=December 2023}}

{{Multiplex techniques}}

In [[fiber-optic communication]]s, '''wavelength-division multiplexing''' ('''WDM''') is a technology which [[multiplexes]] a number of [[optical carrier]] signals onto a single [[optical fiber]] by using different [[wavelength]]s (i.e., colors) of [[laser]] [[light]].<ref name=":0">{{Cite journal|last1=Cai|first1=Hong|last2=Parks|first2=Joseph. W|year=2015|title=Optofluidic wavelength division multiplexing for single-virus detection|jstor=26465542|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=112|issue=42 |pages=12933–12937|doi=10.1073/pnas.1511921112 |pmid=26438840 |pmc=4620877 |bibcode=2015PNAS..11212933O |doi-access=free }}</ref> This technique enables [[Duplex (telecommunications)|bidirectional]] communications over a single strand of fiber (also called '''wavelength-division duplexing''') as well as multiplication of capacity.<ref name=":0" />

The term WDM is commonly applied to an optical carrier, which is typically described by its wavelength, whereas [[frequency-division multiplexing]] typically applies to a radio carrier, more often described by [[frequency]].<ref>{{Cite journal|last1=Yuan|first1=Ye|last2=Wang|first2=Chao|year=2019|title=Multipath Transmission of Marine Electromagnetic Data Based on Distributed Sensors|jstor=26853785|journal=Journal of Coastal Research|volume=97|pages=99–102|doi=10.2112/SI97-013.1 |s2cid=208620293 }}</ref> This is purely conventional because wavelength and frequency communicate the same information. Specifically, frequency (in Hertz, which is cycles per second) multiplied by wavelength (the physical length of one cycle) equals velocity of the carrier wave. In a vacuum, this is the [[speed of light]] (usually denoted by the lowercase letter, c). In glass fiber, velocity is substantially slower - usually about 0.7 times c. The data rate in practical systems is a fraction of the carrier frequency.