thumb A '''delay line interferometer''' ('''DLI''') can be a Mach–Zehnder interferometer or Michelson interferometer based on two-beam interference, in which one beam is time-delayed to the other by a desired interval.
Delay line interferometers are also known as optical DPSK demodulators. They convert a phase-keyed signal into an amplitude-keyed signal. In this application, an incoming differential phase-shift keying (DPSK) optical signal is first split into two equal-intensity beams in two arms of a Mach Zehnder or Michelson interferometer, in which one beam is delayed by an optical path difference corresponding to ''1-bit'' time delay. After recombination, the two beams interfere with each other constructively or destructively. The resultant interference intensity is the intensity-keyed signal.
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Category:Fiber optics Category:Photonics