1：Experimental Design and Method Selection

The method employs stimulated Brillouin scattering (SBS) to amplify the +1st-order sideband and attenuate the -1st-order sideband of the phase-modulated signal from a PM under test, converting it into an optical single-sideband (OSSB) modulation signal. After square-law photodetection, the overall frequency responses are obtained.

2：Sample Selection and Data Sources

A commercial broadband electro-optic PM (EOSPACE Inc.) serves as the device under test.

3：List of Experimental Equipment and Materials

Tunable laser source (TLS, Agilent N7714A), broadband MZM (FUJITSU FTM7938EZ-A), modulator bias controller (MBC, YYlabs), erbium-doped fiber amplifier (EDFA, Amonics Inc.), 4.4-km single mode fiber (SMF), broadband photodetector (Finisar, XPDV2120RA), electrical vector network analyzer (VNA, R&S ZVA67), optical spectrum analyzer (OSA, Yokogawa AQ6370C).

4：Experimental Procedures and Operational Workflow

An optical carrier is split into two paths. In the upper path, a broadband MZM modulates the optical carrier by the RF signal to generate an ODSB signal used as the pump signal. In the lower path, a PM under test modulates a RF signal on the injected optical carrier. The SBS processes the signal, which is then detected by a PD.

5：Data Analysis Methods

The frequency responses of the PM are obtained by removing the responses of the SBS gain and the PD from the overall responses. The gain of the SBS is characterized in a calibration process using a broadband MZM biased at the quadrature transmission point (QTP).