Cascading of Dual Drive Mach Zehnder Modulator and Electro Absorption Modulator for producing an optical comb

A new scheme for generating a flat optical frequency comb using three Laser sources based on cascading of Dual Drive Mach Zehnder Modulator (DD-MZM) and Electro Absorption Modulator (EAM) through an optical nonlinear fiber loop is explored in this paper. A single RF signal of 25 GHz having different amplitudes feed into the two arms of DD-MZM and then feed the signal into EAM to modulate the pulse train. By controlling the DC bias of both modulators as well as the RF signal frequency, the scheme is successful in generating evenly spaced 15 flat comb lines among 25 lines with a spectral power variation of about 2dB.The paper compares the performance of the proposed scheme against other methods where only one modulator was used. The scheme is also analysed for producing an optimum number of spectral lines based on number of sources, channel spacing and RF signal frequency. Finally, the performance of the system was successfully evaluated in a preliminary WDM setup of five channels/modes at 10Gb/s for a channel of 1 km length. Results in the form of BER and Q factor are presented in this paper.