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 American physicist Albert Abraham Michelson in 1887. Using a beam splitter, a light source is split into two arms. Each of those light be ...
based on two-beam
interference
Interference is the act of interfering, invading, or poaching. Interference may also refer to:
Communications
* Interference (communication), anything which alters, modifies, or disrupts a message
* Adjacent-channel interference, caused by extra ...
, 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
In optics, optical path length (OPL, denoted ''Λ'' in equations), also known as optical length or optical distance, is the length that light needs to travel through a vacuum to create the same phase difference as it would have when traveling throu ...
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