Optical frequency comb with tunable free spectral range based on two Mach-Zehnder modulators cascaded with linearly chirped fiber Bragg grating and phase modulator

An approach for generating optical frequency comb(OFC)with tunable free spectral range(FSR)is proposed.Two Mach-Zehnder modulators(MZMs)driven by phase-shifted sinusoidal signals are cascaded to generate OFC with plentiful comb lines and the FSR controlled by the drive frequency.Subsequently,a linearly chirped fiber Bragg grating(LCFBG)and a phase modulator(PM)are used to increase the comb FSR by a particular integer multiple.Therefore,by simultaneously controlling the drive frequency of MZMs,the dispersion amount of the LCFBG and the drive signal of the PM,an OFC with desired FSR can be achieved.