Editing Intensity modulation (section)

== Intensity modulation with direct detection ==
Intensity Modulation / Direct Detection (IM/DD) is a scheme is simple and cost-effective in fiber optic communication, making it a suitable for various optical communication applications. It involves modulating the optical power of the carrier signal to represent the transmitted data. This modulation can be achieved using techniques, such as [[On–off keying|on-off keying]] (OOK). The intensity-modulated optical signal is generated by modulating the amplitude or the current of the light source, typically a laser diode with one or two cavity designs such as [[Fabry-Perot]] or [[Distributed-feedback laser|distributed feedback]] (DFB).<ref name=":0">{{Cite journal |last1=Cox |first1=C. |last2=Ackerman |first2=E. |last3=Helkey |first3=R. |last4=Betts |first4=G.E. |date=August 1997 |title=Techniques and Performance of Intensity-Modulation Direct-Detection Analog Optical Links |url=https://ieeexplore.ieee.org/document/618439 |journal=IEEE Transactions on Microwave Theory and Techniques |volume=45 |issue=8 |pages=1375–1383 |doi=10.1109/22.618439 |issn=0018-9480}}</ref>

At the receiver end, direct detection (DD) is used to recover the modulated signal. The modulated optical signal is detected by a [[photodetector]] (most commonly [[PIN photodiode|PIN]] or APD [[photodiode]]), which converts the optical power variations into corresponding electrical current or voltage variations. The output of the photodetector is then processed and decoded to retrieve the original information.<ref name=":0" />