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:
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