Dual Electro-Optic Comb Generator by Heterodyning Two Combs for Extending the Optical Bandwidth

A novel dual-electro-optic (DEO) comb generator is proposed by heterodyning the optical frequency combs (OFCs) to achieve a high bandwidth of 2.74 THz with an efficient and cost-effective structure. This can attract the research community's interest, particularly for the inherent support in optical communications due to its simplicity and high throughput. The OFC is generated by cascading a continuous wave (CW) laser and Mach Zehnder modulator (MZM) coupled to a second laser source that produces a broad spectrum of frequencies by the frequency heterodyning after passing it through a second MZM. This is the highest number of comb lines produced so far in cascaded configurations of the electro-optic modulators. The frequency difference between the two lasers is carefully selected, equal to 1.38 THz, which combinedly produces around 137 well-flattened OFC lines with 20 GHz frequency spacing and more than 40 dBm tone to noise ratio and an amplitude difference of 0 to 6 dB. The bandwidth of the generated flattened comb source is approximately 2.74 THz, which covers over half of the optical C-band.