A multicarrier light source based on a recirculating frequency shift loop (RFSL) driven by a parity-time (PT)-symmetric optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The impact of the side-mode suppression ratio (SMSR) of the radio frequency (RF) signal on the multicarrier is studied for the first time, to our knowledge. The RFSL driven by PT-symmetric OEO significantly optimizes the phase noise and flatness of the multicarrier, facilitating the system miniaturization. In the experiment, a 10.019 GHz RF signal with a SMSR of 42 dB is generated with -98.63d B c/H z measured phase noise at 10 kHz offset frequency (actual phase noise should be lower than -122.87d B c/H z). Up to 120 subcarriers with 2.32 dB flatness are obtained successfully, covering the overall bandwidth of approximately 1.2 THz.