1：Experimental Design and Method Selection:

The experiment involved direct modulation of a DFB laser diode with low frequency electronics in a self-heterodyne scheme. The excitation current waveform was calculated using the measured current-frequency transfer function of the DFB-LD. Polarization multiplexing was used to synchronize the up- and down-chirped pulses.

2：Sample Selection and Data Sources:

The experiment used a 1550 nm DFB-LD driven by an arbitrary function generator (AFG1) with specially shaped voltage pulses.

3：List of Experimental Equipment and Materials:

Equipment included an arbitrary function generator (AFG1), a laser bias source (LBS), an erbium-doped fiber amplifier (EDFA), an optical band-pass filter (OBPF), an unbalanced Mach-Zehnder interferometer (MZ1), a polarization controller (PC1), a second unbalanced interferometer (MZ2), a polarization beam combiner (PBC), a semiconductor optical amplifier (SOA), a variable optical attenuator (VOA), a 5 GHz-bandwidth photo-detector, an electrical spectrum analyzer, and a 3.5 GHz-bandwidth oscilloscope.

4：5 GHz-bandwidth oscilloscope. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The DFB-LD was modulated with a calculated current waveform to generate optical frequency variations. The optical signal was split, delayed, and combined to create dual-chirp microwave pulses. The pulses were then analyzed in both frequency and time domains.

5：Data Analysis Methods:

The instantaneous frequency of the generated microwave pulses was measured and analyzed for linearity. Time-domain analysis was performed to observe the phase stability of the pulses.