A novel scheme for 0.1 THz optical Tera-Hz signal generation in ToF(THz over Fiber) system is proposed and analyzed. The ToF system used widely in broadband access networks has more stringent requirements on the cost, while the scheme proposed can reduce the system costs. The scheme using frequency quadruplication is based on two Mach-Zender modulators in a certain parameter setting, and we clarify the frequency-multiplication principle from the perspective of both mathematics and physics and the operation principle of Mach-Zender modulator. The condition of the side-band generation and the method for suppressing the band are investigated, and the parameters of suppression ratio are obtained. Furthermore, the tolerance range of the device parameters in a certain suppression ratio is studied, in order to provide reliable basis for the study of device.