1：Experimental Design and Method Selection:

The study employs two system experiments. The first uses electrical I/Q mixing for up/down-conversion and passive signal combining with an IM/DD-based optical link to transmit two independent sub-signals. The second generates a spectrally continuous PAM signal using two sub-signals with fixed phase and amplitude relations, transmitted over an IM/DD link. Both experiments involve advanced DSP for signal processing and impairment mitigation.

2：Sample Selection and Data Sources:

Not explicitly specified in the provided content; the experiments focus on signal generation and transmission without specific datasets.

3：List of Experimental Equipment and Materials:

Includes high-speed DACs (80 GS/s, 19 GHz bandwidth), I/Q mixers (Marki Microwave MLIQ-1845), Mach-Zehnder modulator (MZM) with 33 GHz bandwidth, distributed feedback laser at 1550.5 nm, SSMF of various lengths, wideband photodetector (50 GHz), EDFA, optical BPF, digital storage oscilloscope (80 GS/s, 30 GHz), resistive combiner, diplexer, RF mixer (Marki Microwave MML1-1850), frequency generator at 45 GHz, driver amplifier, clock divider, high-speed real-time sampling scope (Keysight DSAZ634A, 160 GS/s, 63 GHz bandwidth), and various amplifiers and filters.

4：5 nm, SSMF of various lengths, wideband photodetector (50 GHz), EDFA, optical BPF, digital storage oscilloscope (80 GS/s, 30 GHz), resistive combiner, diplexer, RF mixer (Marki Microwave MML1-1850), frequency generator at 45 GHz, driver amplifier, clock divider, high-speed real-time sampling scope (Keysight DSAZ634A, 160 GS/s, 63 GHz bandwidth), and various amplifiers and filters. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: For the first system, sub-signals are generated using DACs, up-converted with I/Q mixers and LO, combined using a diplexer or resistive combiner, modulated optically with MZM, transmitted over SSMF, detected with photodetector, amplified, split, down-converted, filtered, and recorded. DSP includes MIMO I/Q imbalance compensation and equalization. For the second system, sub-signals are generated, up-converted with RF mixer and LO, combined with diplexer, filtered, optically modulated, transmitted, and acquired with a sampling scope. Pre-equalization and post-equalization are applied.

5：Data Analysis Methods:

BER measurements, SNR analysis, bit loading for DMT and OFDM, eye diagram evaluation, and simulations for I/Q imbalance and mismatch effects using standard DSP techniques such as MMSE equalizers and frequency domain MIMO compensation.