###### Abstract
In this manuscript, we study and compare a pioneering mixing operation of two channels by using two principles called standard and differential modulation modes in co- and counter-direction configurations based a SOA-MZI sampling mixer. Besides, we present the frequency up-conversion of two IF channels that carry QPSK data at \(f_{1}=1\) GHz (channel 1) and \(f_{2}=2\) GHz (channel 2) to an optical radio frequency (RF) signal that exhibits the mixing frequencies \(nf_{s}\pm f_{m}\), where \(n\) is the harmonics order and \(m\) is the IF channel index, at the output of the SOA-MZI photonic mixer. It is worth noting that we used four architectures (cases) that are standard modulation in co-direction, standard modulation in counter-direction, differential modulation in co-direction, and differential modulation in counter-direction. Then, for the second part of simulations, we also managed to simultaneously up-convert ten IF signals ranging from 0.2 to 2 GHz in the four different cases. The proposed up-conversion architecture utilizing a SOA-MZI showed features such as broad bandwidth, capability of simultaneous conversion, and high conversion gain. In addition, simulation results of two or ten simultaneous up-converted signals by all-optical sampling are achieved through conversion gains and error vector magnitudes (EVMs) for the first time through the Virtual Photonics Inc. (VPI) [28] simulator in order to evaluate the efficiency and quality of this optical transmission system. The benefits of this work are, the highest, to our knowledge, frequency range used, up to 158 GHz, EVM simulations at the bit rate up to 100 Gbit/s, and positive conversion gains, which were achieved at the SOA-MZI output in the four cases. Furthermore, the differential modulation principle improved considerably the quality of the sampled signal at the SOA-MZI output by maintaining the same level of its replicas. In that case, we could simultaneously up-convert more channels at the SOA-MZI output and study their quality. This work can be used in many applications, such as ultra-wideband communications, millimeter-wave and microwave applications, wireless access applications [29], and satellite communications. The implementation of the principle of the differential modulation provides fundamental features such as higher optical amplification, wider bandwidth, and higher conversion efficiency compared to the standard modulation. On the other hand, the experimental work for simultaneous ten channels up-converted at the SOA-MZIoutput confirms the results obtained by simulations and showing that the co-direction configuration exhibited higher performance than the counter-direction one. The remainder of the paper is arranged as follows. In Section 2, we describe the principle of operation for the standard and differential modulation modes. In Section 3, the conditions of the conducted simulations are analyzed and simulation setups are given for all cases. Then, the simulation results for the simultaneous frequency mixing are achieved by showing four electrical spectrums for different cases and then the conversion gain is obtained in order to assess the optical transmission system. In Section 4, frequency mixing of complex-modulated QPSK data by using the four cases against the EVM are presented. Besides, the real measurements are obtained in Section 5 and compared with the simulation work. Finally, in Section 6, the conclusions reached through this work are given.