Signal processing techniques for optical fiber networks

© 2007 Xingwen Yi.At present, optical fiber transmissions are dominated by intensity modulation and direct detection, which fundamentally limit the signal processing capabilities in optical fiber networks. On the other hand, manipulation of optical phase enables advanced signal processing techniques for various applications. This thesis includes three parts and makes contributions in three research areas in optical fiber networks, by applying optical and electronic signal processing techniques. In the first part of the thesis, optical signal processing is employed to realize a novel all-optical label swapping (AOLS) technique using synchronous phase modulation. This technique is shown to address the forwarding speed bottleneck in optical packet switched networks (OPSN). By exploiting the unique symmetry of phase-shift keying (PSK), for the first time, label erasure and insertion are performed in a single step by a phase modulator without wavelength conversion. We also propose and demonstrate a polarization insensitive phase modulator to address the polarization sensitivity of AOLS. Furthermore, we emulate multi-hop all-optical label swapping in a re-circulating loop to investigate the power penalties from the accumulated phase errors and the timing mismatch. Based on the experimental and analytical results, we show that this technique can save wavelength converters significantly if compared with conventional AOLS techniques requiring dedicate wavelength converters