1 Department of Photonics Engineering, Technical University of Denmark2 Networks Technology and Service Platforms, Department of Photonics Engineering, Technical University of Denmark3 High-Speed Optical Communication, Department of Photonics Engineering, Technical University of Denmark
This thesis covers two research topics concerning optical solutions for networks e.g. avionic systems. One is to identify the applications for silicon photonic devices for cost-effective solutions in short-range optical networks. The other one is to realise advanced functionalities in order to increase the availability of highly reliable optical networks. A cost-effective transmitter based on a directly modulated laser (DML) using a silicon micro-ring resonator (MRR) to enhance its modulation speed is proposed, analysed and experimentally demonstrated. A modulation speed enhancement from 10 Gbit/s to 40 Gbit/s in a directly modulated distributed feed-back (DFB) laser diode is achieved by using the proposed scheme. Enhancement is also achieved in vertical-cavity surface-emitting lasers (VCSELs). The cascadability of silicon MRRs is experimentally assessed as well for their applications in optical interconnects and network-on-chips. A novel concept of all-optical protection switching scheme is proposed, where fault detection and protection trigger are all implemented in the optical domain. This scheme can provide ultra-fast establishment of the protection path resulting in a minimum loss of data. It is experimentally demonstrated by using a bistable modulated grating Y-branch (MG-Y) laser structure. The achieved protection switching time is less than 200 ps and the signal switched by the fast establishment of the protection path has good quality at both 10 Gbit/s and 40 Gbit/s. The optically controlled bistable operation of the MG-Y laser with wide wavelength tunable range is also experimentally demonstrated within this thesis. Another protection method using network coding is also introduced. All-optical network coding for phase modulated signals (e.g. differential phase shift keying (DPSK) signals) using two exclusive OR (XOR) gates realised by four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is experimentally demonstrated and very low (~ 1 dB) total operation penalty is achieved.