## 1 Introduction
The primary objective of THORMUX is the development of a 4-channel photonic-based multiplexer/demultiplexer (MUX/DEMUX) system capable of performing efficient RF multiplexing and demultiplexing operations in the Ka-, Q-, and V-bands. THORMUX operates using three PICs modules PIC_1: the carrier generation system, which is the module presented in this work; PIC_2: incorporates single side-band carrier re-injection (SSB-CRI) filters; and PIC_3: contains a 4-channel MUX/DEMUX filter. The operating principle of the overall system is as follows: an optical carrier at a wavelength of 1550 nm is generated by a laser integrated in the PIC_1 module. During demultiplexing, the optical carrier is split into five outputs via a 1-to-5 optical power splitter. One of the outputs is directed to an optical Mach-Zehnder modulator (MZM), which converts the incoming RF signal into an optical double side-band full carrier (DSB-FC) signal. This signal consists of the lower sideband (LSB), the carrier, and the upper sideband (USB). The RF input signal can operate within the Ka, Q, or V frequency bands. The optically modulated DSB-FC signal is then routed to the single sideband (SSB) filter within the module PIC_2, which suppresses the unwanted LSB and the carrier while allowing the USB to pass through without distortion. The resulting USB signal is subsequently demultiplexed into four distinct optical channels by the DEMUX filter within the PIC_3 module. Each demultiplexed USB channel is then combined with the re-injected carrier signals derived from the remaining four outputs of the 1 \(\times\) 5 splitter. This operation is performed via the respective SSB-CRI filters in PIC_2. Finally, the processed optical channel signals are sent to a photodiode (PD) array, where optical-to-electrical conversion is achieved through a beating process. During multiplexing, the process is similar but operates in reverse. Each channel uses a dedicated laser from PIC_1 and an individual modulator. This bidirectional operation is facilitated by the module PIC_3. The four multiplexed optical channels are aggregated into a single output, directed to a unique output photodiode. The project is motivated by the need to overcome the limitations of conventional RF systems. For example, analog RF systems typically operate at fixed frequencies, which inherently limits tuning flexibility. Furthermore, digital RF channelization systems, such as those offered by Teledyne Technologies, provide greater flexibility but are limited in terms of maximum operating frequency. In addition, the SWaP metrics of these systems are not optimal due to the high-power consumption (on the order of 30-100 W) associated with the field-programmable gate arrays (FPGAs) used in the signal digitization processes and the up- and down-converters. While the primary focus of the project is on the Ka-, Q- and V-bands, the photonic approach adopted enables operation beyond these frequency ranges while maintaining full flexibility. A critical aspect of this methodology is the establishment of a technology roadmap aimed at improving the performance and scalability of next-generation communications systems, with a particular focus on satellite-based applications. The paper is organized into the following sections. Section 2 provides a detailed description of the hybrid multi-laser module characterized in this study, along with an introduction to the hybrid lasers used for signal generation. Section 3 presents the experimental characterization of the lasers, focusing on the generation and frequency flexibility of the local oscillator signals produced by the module. Section 4 provides a detailed discussion of the results, analyzing the performance and highlighting the key findings related to the system's capabilities. Finally, Section 5 provides the conclusions drawn from this study.