Generation of Flat Optical Frequency Comb Using a Single Polarization Modulator and a Brillouin-Assisted Power Equalizer

We propose a novel approach for the generation of flat optical frequency comb (OFC) using a single polarization modulator (PolM) and a Brillouin-assisted power equalizer (BAPE). The reference radio-frequency (RF) signal applied to the PolM is provided by an optoelectronic oscillator (OEO). The spectra of the optical signals launched to the BAPE are optimized in advance for the generation of OFCs with different number of lines. The BAPE is introduced to flatten the uneven OFC lines by attenuating the optical lines having power beyond the threshold of the stimulated Brillouin scattering (SBS) and amplifying the ones having power below the SBS threshold with the amplifier inside the BAPE. In addition, the OFC generator is optical wavelength independent since there is no optical filter involved in our approach. We experimentally demonstrated that the proposed OFC generator can produce 5, 7, 9, and 11 lines within a spectral flatness of 0.5, 1.5, 2, and 4.1 dB, respectively.