A delay line interferometer (DLI) can be a
Mach–Zehnder interferometer
The Mach–Zehnder interferometer is a device used to determine the relative phase shift variations between two collimated beams derived by splitting light from a single source. The interferometer has been used, among other things, to measure p ...
or
Michelson interferometer
The Michelson interferometer is a common configuration for optical interferometry and was invented by the 19/20th-century American physicist Albert Abraham Michelson. Using a beam splitter, a light source is split into two arms. Each of those ...
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.
External links
Delay line interferometer and Optical DPSK demodulatorAll-Fiber Delay line interferometer and Optical DPSK demodulator
Fiber optics
Photonics