Versatile optical frequency comb generation with Bessel spectrum using phase shifters and variable-voltage swing RF amplifiers
Commercially available optical communications systems achieve data rates of about 100 Gb/s by using one optical carrier. Future systems shall provide more than 1 Tb/s to satis-fy the growing demand of data rates in communications. Using more than one carrier may increase the data rates significantly. In this application, an integrated frequency comb generator with channel spacing of 50 GHz (ITU grid) based on a novel concept shall be designed and investigated. At first, an electrooptical phase modulator creates a frequency comb, from which two distant carriers are separated on one output each by a tuneable photonic wave-length selector. Only one monochromatic laser source is necessary for this approach. Out of each of the separated carriers a further frequency comb is generated, where both combs are superposed, which increases the number of carriers significantly. All used modulators are driven by radio frequency power amplifiers with tuneable gain. This flexibility of the system allows generating frequency combs with different number of carriers. By using highly efficient electrooptical polymers and photonic slot waveguides in the modulators, the necessary radio frequency power can be considerably reduced and a bandwidth of 50 GHz can be achieved. Especially with regard to monolithic integration, the efficiency becomes more important, since the temperature change due to power dissipation of the electric circuit may affect the photonic components. Hence, the emphasis is the investigation of efficient and flexible generation of several carriers in relation to the radio frequency power, which drives the modulators. In order to achieve the goals, the photonic group and the IC group of the Institute of Electrical and Optical Communications Engineering work closely with each other.