Most optical fibre analogue transmission systems use intensity modulation of the optical source with direct detection of the modulated optical signal in a depletion photo-detector. In this chapter, coherent techniques are introduced, and their advantages and disadvantages relative to intensity modulation/direct detection (IMDD) systems are considered. Coherent techniques are defined broadly to include all transmission methods where the precise frequency of the optical signal is important.

Inspec keywords: intensity modulation; optical modulation; photodetectors; optical fibre communication; optical signal detection

Other keywords: optical signal frequency; optical source; optical fibre analogue transmission system; depletion photodetector; analogue signal transmission; IMDD system; modulated optical signal detection; intensity modulation-direct detection system

Subjects: Optical communication