MZ, Mach Zehnder, Mach Zehnder modulator. The modulator divides the input light into two equal signals and enters the two optical branches of the modulator respectively. The materials used in the two optical branches are electro-optical materials, and their refractive index varies with the external applied electric signal. Because the change of the refractive index of the optical branch will lead to the change of the signal phase, when the output ends of the two branch signal modulators are combined together again, the synthesized optical signal will be an interference signal with varying intensity, which is equivalent to converting the change of electric signal into the variation of optical signal and realizing the modulation of light intensity.