All-Optical Signal Processing for 640 Gbit/s Applications

This thesis concerns all-optical signal processing technologies for 640 Gbit/s optical time-division multiplexing (OTDM) systems, including time-division add-drop multiplexing (TADM), polarisation-independent demultiplexing, and pre-scaled clock recovery. Two fibre-based switching methods for TADM are proposed and used to demonstrate error-free 640 Gbit/s TADM for the first time. The first method consists in performing the entire TADM operation simultaneously in a non-linear optical loop mirror (NOLM). The second method is based on a novel switch called the non-linear polarisation rotating loop (NPRL). The TADM performance for both switches is characterised by error-free operation with low penalties. A novel principle for polarisation-independent demultiplexing in a NOLM without structural modifications is proposed, and demonstrated in a 320 Gbit/s demultiplexing experiment, with prospect for 640 Gbit/s operation. Pre-scaled 40 GHz clock recovery from 640 Gbit/s OTDM data is demonstrated for the first time, by employing a semiconductor-based phase-comparator. Furthermore, the temperature-stabilisation of the NOLM by using a loose fibre coiling is investigated, and a good stability against room-temperature fluctuations is shown. Finally, a recently reported technique for nearly pedestalfree pulse compression is investigated, and implemented for 640 Gbit/s OTDM systems