Generation of an ultraflat and power efficient optical frequency comb by cascading of electroabsorption and single-drive Mach-Zehnder modulator

We have investigated the theoretical and principal analysis of cascaded electroabsorption modulators (EAMs) and Mach-Zehnder modulator (MZM). We have proposed a technique to generate an ultraflat and power efficient optical frequency comb (OFC) by the serial cascading of two EAMs and one single-drive MZM. Continuous wave (CW) light source is modulated and spectrum broadened by two EAMs and MZM, respectively. Here, EAMs in cascaded mode produce ultrashort pulses followed by MZM, which is introduced to perform intensity modulation and tuned the power variation of even and odd order sidebands at the same level for obtaining a flat optical spectrum at the output. The first EAM acts as a subcarrier generator and the latter one acts as a subcarrier enhancer, which is followed by the MZM acting as subcarrier flatter. By this proposed technique, we have generated 63 subcarriers with 10-GHz spacing and within 2-dB power fluctuation. The generated OFC has a bandwidth of 630 GHz. This technique generates OFC with an appreciable power level and flattened optical spectrum, which is very much essential in dense wavelength division multiplexing and elastic optical networks.