## 2 Electro-Optical Basic Concept of Architectural Standard Modulation
### Optical Conversion Gain Features
However, this power level undergoes a 3-dB reduction due to optical losses within the OBPF. At the SOA-MZI outlet, thermal and shot noises are generated during the conversion of the optical photon to the electrical one by the PD2. Subsequently, the electrical signal undergoes additional amplification using LNA2. Consequently, all computations for the EVM metric, as depicted in Figure 8, must account for the noise introduced during signal sampling, filtering, photodetection, and subsequent amplification. Figure 7: Electrical conversion gains at \(nf_{s}+f_{IF}\) for experimental and simulation investigations contingent on the SOA-MZI standard modulation modes. The input IF signal at \(f_{IF}=0.5\) GHz is up-converted at \(nf_{s}+f_{IF}\). Figure 8 illustrates that in both real-world and simulated measurements, the EVM of QPSK up-shifted signals varies with the mixing outgoing frequency at 5 Gbit/s. In simulations, it ranges from 5% at \(f_{s}+f_{IF}=20\) GHz to 24% at \(10f_{s}+f_{IF}=195.5\) GHz. In real-world measurements, due to unexpected noise, the EVMs are 2% higher than the simulated values over the limited range of mixing frequencies up to \(3f_{s}+f_{IF}=59\) GHz. However, with the exception of the highest mixing frequencies in simulations, all EVM values for the up-converted signals remain under the EVM criteria of 17.5%. Within the electrical domain, the mixed signal, as illustrated in the electrical spectrums in Figures 5 and 6, exhibits multiple replicas. This enables the measurement of EVM and ECG for each frequency of these replicas. A higher ECG corresponds to improved EVM performance in our system, which also has an excellent OCG of 44.5 dB. On the other hand, the relationship between ECG and EVM is still nuanced because there is no direct link, and while a higher ECG indicates improved efficiency in the conversion process, the overall system performance, as assessed by EVM, depends on various factors, including signal quality and accuracy in the mixing and conversion process. Therefore, in the context of our system, a higher ECG may indeed correspond to improved efficiency in the conversion of replicas obtained by mixing through SOA-MZI, but it does not directly imply better EVM performance unless other factors influencing EVM are also considered. As a result, the ECG depends only on power, while the EVM depends on many other factors. EVM in our communication system is influenced by a myriad of factors, each contributing to the accuracy and fidelity of the transmitted signal. Noise and distortion within the communication channel, nonlinearities in system components, and the presence of phase noise from signal sources are the primary contributors to increased EVM. Additionally, imperfections in modulation and demodulation processes, frequency and timing offsets, and variations in carrier frequency can introduce errors in both magnitude and phase. Signal impairments stemming from channel fading, dispersion, and multipath propagation, particularly in wireless or optical systems, further impact EVM. Consequently, a comprehensive assessment of EVM necessitates addressing these multifaceted influences through our meticulous system design, the incorporation of error correction techniques, and the optimization of components to minimize distortions and inaccuracies in the communication system. However, a lower output power leads to a lower ECG and, consequently, a higher EVM value. Figure 8: The EVM metric of QPSK shifted signals from \(f_{IF}=0.5\) GHz to \(nf_{s}+f_{IF}\) at the data transfer rate of 5 Gbit/s for the empirical and simulated investigations.