Photonic generation of frequency-doubled sinc-shaped Nyquist pulse based on external modulation

A scheme for generating sinc-shaped optical Nyquist temporal pulse with a spectrum of 9 flat optical frequency combs (OFCs) by using cascaded Polarization modulator (PolM) and dual-electrode MZM (De-MZM) is proposed. By properly adjusting the polarization angle and modulation indices of two modulators, frequency-doubling OFCs are obtained. As a 5 GHz radio frequency driving signal is applied, a 10 GHz sinc-shaped Nyquist pulse with narrow zero-crossing-width is finally generated. The influence of key technique parameters on the performance of generated Nyquist pulse has been analyzed, and tolerable range are evaluated. The proposed approach provides the potential to generate a Sinc-shaped Nyquist pulse and promote its application in channel multiplexing.