whats difference between single drive and dual drive mach-zehnder?

[stack programerParticipant]

hi, in optic system i see two mach-zehnder:

sinlge drive
two drive

i want to can any one explain digest difference between of them?
thanks

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[stack programerParticipant]

Finally after searching i find good reference for defining it :
http://my.ece.queensu.ca/Current-Students/Undergraduate/Course-Homepages/ELEC-486/files/ELEC486_OptMod_Jan2013.pdf

• Dual-drive configuration; modulating voltages are applied to both arms of the
interferometer using GSG electrode patterns. Phase changes of ±π/2 in the arms
of the interferometer.

• Single-drive configuration; modulating voltage is applied to one arm of the
interferometer. Phase change of π in the arm of the interferometer.

some other useful link is shared too:

MZM and MZI

MZM and LiNbO3 MZM

it is good you know:
The MZ modulator are manufactured by using the different material, but presently most of the long distance high capacity optical communication systems utilize LiNbO for the same.
thanks