Research on octupling frequency triangular-shaped waveform generator with flexible repetition rate tunability

In this manuscript, a novel scheme for generating a frequency-octupled triangular waveform based on an external modulator and fiber grating is proposed. The octuple frequency modulation is realized by dual-parallel Mach-Zehnder modulator (DP-MZM), and two main optical sidebands (±4th) are generated in the optical domain. Then, an intensity modulator (IM) is used to conduct the optical double sideband (ODSB) modulation, after which an optical signal with four sidebands (±4th and ±12th) is obtained. The four spectral lines are separated inside and outside by an optical circulator and fiber grating. After polarization controlling, the power ratio of ±4 and ±12 sidebands can be tuned to 9.5dB, and the expression of optical intensity is approximately equal to the Fourier expansion of the ideal triangular waveform. By applying a 5GHz driving frequency, a triangular waveform with a repetition rate of 40GHz is acquired, which achieves up conversion of octuple frequency.