Alternatively, InGaAs diodes appeared as a solution offering several distinct advantages, particularly in terms of lower power requirements. InGaAs mixers have already demonstrated local oscillator power requirements five to ten times lower than GaAs mixers, enabling efficient energy utilization leading to reduced power consumption without significantly compromising performance [26]. The successful operation of THz mixers is also dependent on the availability of reliable and efficient LO sources. Advances in fabrication technology and precision machining techniques have led to significant improvements in the output power of mm-wave and sub-mm-wave sources. Electronic sources based on multiplication chains currently hold a dominant position in the field due to the technology's longevity, reliability, and maturity. As an example, GaAs-diode-based sources have shown outstanding performances at frequencies beyond 1 THz [27]. However, their main disadvantage is the decrease in power handling and output power as the frequency increases. The development of InGaAs mixers opened up new possibilities in the available LO sources, allowing integration with optical down-conversion techniques [28; 29]. In this approach, two lasers at different frequencies are combined in a photodiode to generate a beat signal, which serves as the LO to pump the mixer [30]. This method provides a wide bandwidth and tunability over the LO range, enabling the use of a single source to cover several bands. In contrast, electrically generated LOs follow an up-conversion process. This means that the LO frequency is increased from DC to higher frequencies, typically by a multiplication factor denoted as '\(N\)'. As a consequence of this up-conversion, the phase noise of the LO signal suffers a notable increase in its power spectral density by a factor of \(20\cdot\log(N)\) dBc/Hz. However, when the LO is optically generated, it undergoes a down-conversion process from high to low frequencies. In the case of optical heterodyne mixing to generate THz signals, the UTC is responsible for converting the optical beat frequency into a lower-frequency electrical signal. In this scenario and applying phase locking to the lasers, optical pumping potentially offers a lower noise profile and higher purity of LO signals compared to electrical approaches [31]. In this paper, we provide a comparative analysis of GaAs and InGaAs mixers, focusing on both optical and electrical pumping techniques. GaAs diodes are known for their superior conversion efficiencies, while InGaAs diodes require lower input power, making them particularly compatible with optical pumping methods. Our objective is to explore these key differences and assess their impact on performance metrics such as the BER and EVM. By examining the advantages and limitations of both technologies, we assess their suitability for integration into future high-speed photonic-based THz wireless communication systems. This work is novel, as it presents a direct comparison of GaAs and InGaAs mixers under different LO pumping conditions, which is an analysis that has not been thoroughly explored in previous research. The article is structured as follows: Section 2 presents the THz wireless communication setup, providing a detailed description of both the transmitter and receiver sides. In the receiver, we discuss two different pumping techniques, electrical and optical, discussing their implementation in the system. Additionally, we introduce the mixers under study and describe the DSP technique used throughout the experiments. Section 3 then presents the experimental results, evaluating the performance of the mixers as receivers under both electrical and optical pumping. A comparative analysis is done in terms the BER and EVM. We then examine the effects of using a non-optimal phase noise cancellation DSP, highlighting its influence on system performance. Finally, the conversion loss improvement of InGaAs-based mixers is briefly discussed.