Summary
Mach-Zender Modulators (MZM) are electro-optic devices used to encode information into a laser beam before transmission, using materials such as Lithium Niobate (LiNbO₃) that exhibit the Pockels effect, whereby the laser’s refractive index changes in response to the electric field produced by the MZM. The overall effect is to modulate or turn output from the laser on and off very quickly in order to encode data, while allowing the laser itself to remain active continuously active.
Thermo Optic (TO) phase modulators create a similar effect, but via a different and slower mechanism.
Process
- A beam of light is continuously created by a laser.
- The beam is split into two paths, via a beam splitter or Y-junction.
- Via an MZM, an electrical signal carrying data is applied to one or both paths. This changes the light’s refractive index, which changes its phase.
- The two beams are then recombined. Depending on the difference in phase between both beams:
If they are in phase → constructive interference → light passes.
If they are out of phase → destructive interference → light is blocked.
These two phases are the equivalent of a on or 1 state when light is passing, or a 0 state when light is blocked.
References
https://www.codeseeder.com/examples/mach-zehnder-modulator/
https://academy.lucedaphotonics.com/training/topical_training/mzm