Photonic RF signal processors

The purpose of this thesis is to explore the emerging possibilities of processing radiofrequency (RF) or microwave signals in optical domain, which will be a key technology to implement next-generation mobile communication systems and future optical networks. Research activities include design and modelling of novel photonic architectures for processing and filtering of RF, microwave and millimeter wave signals of the above mentioned applications. Investigations especially focus on two basic functions and critical requirements in advanced RF systems, namely: • Interference mitigation and high Q tunable filters. • Arbitrary filter transfer function generation. The thesis begins with a review on several state-of-the-art architectures of in-fiber RF signal processing and related key optical technologies. The unique capabilities offered by in-fiber RF signal processors for processing ultra wide-band, high-frequency signals directly in optical domain make them attractive options for applications in optical networks and wide-band microwave signal processing. However, the principal drawbacks which have been demonstrated so far in the in-fiber RF signal processors arc their inflexible or expensive schemes to set tap weights and time delay. Laser coherence effects also limit sampling frequency and introduce additional phase-induced intensity noise

Opto-VLSI based WDM multifunction device

The tremendous expansion of telecommunication services in the past decade, in part due to the growth of the Internet, has made the development of high-bandwidth optical net-works a focus of research interest. The implementation of Dense-Wavelength Division Multiplexing (DWDM) optical fiber transmission systems has the potential to meet this demand. However, crucial components of DWDM networks – add/drop multiplexers, filters, gain equalizers as well as interconnects between optical channels – are currently not implemented as dynamically reconfigurable devices. Electronic cross-connects, the traditional solution to the reconfigurable optical networks, are increasingly not feasible due to the rapidly increasing bandwidth of the optical channels. Thus, optically transparent, dynamically reconfigurable DWDM components are important for alleviating the bottleneck in telecommunication systems of the future. In this study, we develop a promising class of Opto-VLSI based devices, including a dynamic multi-function WDM processor, combining the functions of optical filter, channel equalizer and add-drop multiplexer, as well as a reconfigurable optical power splitter. We review the technological options for all optical WDM components and compare their advantages and disadvantages. We develop a model for designing Opto-VLSI based WDM devices, and demonstrate experimentally the Opto-VLSI multi-function WDM device. Finally, we discuss the feasibility of Opto-VLSI WDM components in meeting the stringent requirements of the optical communications industry