A novel approach to broad-spectrum optical frequency comb based on cascaded Mach-Zehnder modulators

Abstract This paper presents a theoretical investigation of a spectrally broad and tunable optical frequency comb to overcome the growing strains and effectively utilize the optical fiber network. The proposed Optical Frequency Comb (OFC) has high-quality frequency lines, whose parameters are analyzed with the initial line spacing of 10 GHz, offering the capability to tune the frequency spacing. The OFC constitutes two Dual Drive Mach–Zehnder Modulators (DDMZMs) and a phase modulator controlled by periodic radio frequency signals RF1 and RF2 respectively. The employed DDMZMs are configured deliberately, to focus on obtaining the low-duty cycle periodic signal, which automatically leads to the expansion of the spectrum. DDMZM1 changes the shape of the Gaussian periodic signal to produce output at the transition time of the input signal. DDMZM1 is connected to DDMZM2 by an optical delay line which gives a delay of approximately 25 ps. DDMZM2 is an intensity modulator that provides a very low-duty cycle Gaussian periodic signal. The phase modulator expands the spectrum by modulating the phase of the incoming signal. Therefore, the reported OFC exhibits tunability and broad spectrum with 86 frequency lines within a maximum power deviation of 2 dB. The OFC can be credibly used as a multichannel source in high-speed and flexible optical communication and all-optical computing systems.