1：Experimental Design and Method Selection:

The experiment uses a dual-fiber structure to cascade Brillouin frequency shifter and amplification, employing stimulated Brillouin scattering (SBS) effects in two fibers to shift the filter center frequency higher and achieve wide tunability. The theoretical model includes Lorentzian gain profiles and equations for gain and filter response.

2：Sample Selection and Data Sources:

Optical fibers include a 6.2-km single mode fiber (SMF) with Brillouin frequency shift of 10.8 GHz and a 25-km non-zero dispersion shifted fiber (NZDSF) with Brillouin frequency shift of 10.6 GHz. Data is collected using a vector network analyzer (VNA).

3：2-km single mode fiber (SMF) with Brillouin frequency shift of 8 GHz and a 25-km non-zero dispersion shifted fiber (NZDSF) with Brillouin frequency shift of 6 GHz. Data is collected using a vector network analyzer (VNA). List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Tunable laser (Keysight 81950A), VNA (Keysight N5234A), phase modulator (Thorlabs LN65S), erbium-doped fiber amplifiers (EDFA, Amonics), optical circulators, polarization controllers (PC1, PC2, PC3), optical isolator (ISO), dispersion compensator (DC, TeraXion), photodetector (PD), intensity modulator (Sumitomo), optical bandpass filter (Finisar Waveshaper 4000s), and various fibers (SMF, NZDSF).

4：Experimental Procedures and Operational Workflow:

Light from the tunable laser is split into two branches. The upper branch modulates the signal with RF from VNA using a phase modulator. The lower branch amplifies the carrier, injects it into SMF for first-stage SBS, amplifies the Stokes light, and injects it into NZDSF for second-stage SBS. The phase-modulated signal passes through NZDSF, dispersion is compensated, and detected by PD. Frequency response is measured with VNA. Tunability is tested by inserting a CS-SSB frequency shifter.

5：Data Analysis Methods:

Frequency response is analyzed using the VNA to measure central frequency, bandwidth, and rejection ratio. Bandwidth and peak power are plotted against pump power variations.