All optical systems for terabit network era
University College Cork
The continuous growth of the network capacity demand drives the development of the optical fiber networks. Since optical super-channels carrying multi- Terabit/s transmissions are the next evolution of the optical links, future transmitters and receivers systems will be required to handle vast volume of information while maintaining reasonable power consumption and cost. In addition, when point-to-point links are approaching the fundamental limit of standard fiber, the efficient use of the entire transmission window for optical networks will only be achieved through flexible superchannels compatible with flexible optical nodes. This thesis describes the research work carried out to investigate the future optical systems that will support the Terabit era networks. All-optical systems are presented, allowing for high spectral efficiency in future networks, from the comb sources to the optical nodes. The following manuscript firstly reports on the development of optical combs based on external modulators to provide transmitters with a large number of optical carriers. Then, the implementation of an experimental all-optical super-channel through the use of optical signals and wavelength manipulations is described. Finally, a novel all-optical node called Terabit Interferometric add, Drop, and Extract (TIDE) is presented. With a management of the super-channel components in the optical domain, the optical node offers transparency and flexibility while maintaining the high spectral efficiency of the super-channel carrying links. An optical frequency comb source was developed, generating a high quality 9-line comb with a spectral flatness < 0.3 dB and side-mode suppression ratio > 20 dB. A single Mach-Zehnder modulator was driven with a low power multi- harmonic electrical signal. Furthermore, a large 36 line comb was obtained by the addition of a two cascaded modulators comb source driven with a 90 GHz signal The implementation of an alloptical Orthogonal Frequency Division Multiplexing (OFDM) super-channel, using a high quality single sideband modulation scheme based on a dual-parallel Mach-Zehnder modulator, allowed for the development and test of the all-optical TIDE node. The interferometer-based structure was capable of managing (add, drop, and extract) channel from a super-channel strictly in the optical domain. In this manuscript, we prove that it is possible to extract channels even with overlapping spectrum super-channel aggregation for both single and dual quadrature modulation formats.
Photonics , ROADM , OFDM , Optical signal processing , Optical comb
Fabbri, S. 2016. All optical systems for terabit network era. PhD Thesis, University College Cork.