Dear Ayesha,
the equation used in the PM component can be found in the datasheet of the component (attached). Your electrical signal is the voltage controlling signal to the PM. it can be normalized between 0 and 1 if you enable the related field in the component properties window. The output signal is an optical signal and can be viewed using the Optical Time Domain Visualizer. This optical signal is going to be modulated by the MZM. I am not sure why you are using this configuration in the design. It looks incorrect to me.
Yes, you may use the Matlab component in OptiSystem to design your modulator. You need to make sure that the signal structure is correct in the Matlab code. Please refer to the documentation for guidance on using the Matlab component.
Regards,
Ahmad