This paper deals with IQ modulation using the nested Mach-Zehnder modulator, studying its different parameters and the effect of their value in the resulting signal. The main goal is to obtain the parameters for which a frequency shift is obtained, using different approaches. First, the Bessel functions are used to study the transfer function analytically. Then, numerical representations (both using the Bessel functions and Fourier cofficients) are plotted in order to further illustrate the results obtained, adding up with the spectra of some cases obtained using VPIphotonics, creating a full picture of the solution proposed. 2019/2020