Mach Zender Interferometer is a device used to determine the relative phase shift variations between two collimated beams derived by splitting light from a single source. It consists of two beam splitter and two mirrors.

From viewpoint of wavelength, Mach Zender interferomter can be considered as a simpple optical filter:

Wavelegnth 1,3 5...transmit ouput beamsplitter.

Wavelength 2,4,6.. reflect the output beamsplitter.

One of benefits is its flat phase response, which does not distort input pulse signal.

The other application is intensity modulator by tuning optical length of one arm.