A feedback system for the stability improvement of optical frequency comb generating system based on a single integrated PM-DMZM

Optical frequency combs (OFCs) have discrete optical spectra with equidistant spacing and equal intensities over a broad spectral range. In recent year, OFCs have been widely researched in many areas. However, the traditional methods of generating optical frequency comb are suffered from the long-term instability. In this article, a feedback system of the stability improvement of optical frequency comb (OFC) generating system based on a single integrated polarization multiplexing dual-drive Mach-Zehnder modulator (PM-DMZM) is proposed. The effect of the fluctuation of the halfwave voltage on the amplitude of the OFC spectra is analyzed. The proportion between the optical power of OFC and the optical carrier power of OFC is used as a feedback parameter to guarantee the simplicity and effectiveness. The stability of the proposed OFC system based on PM-DMZM is also analyzed by the numerical simulation. The results show that the flatness of 7-line OFC is improved for about 3 dB when only the bias voltage is regarded as the controlled parameter. In addition, the flatness of OFC can be improved for about 10 dB when the bias voltage and the amplitude of the modulated RF signal are all used as the controlled parameters simultaneously.