Monolithic wavelength converters for high-speed packet switched optical networks

The past decade has seen a revolution in the field of information technology. The demand for data communication grew explosively in the mid 90's and has been steadily increasing since. Recent studies have shown that traffic over the Internet has been steadily increasing at a rate between 70% to 150% per year since 1997 and this trend is expected to continue over the next decade as well.; With ever increasing demand for bandwidth, the future fiber optic backbone networks are expected to employ optical packet switching over wavelength division multiplexed (WDM) high data rate channels as an ultimate solution for network capacity, utilization and flexibility. An optical packet switch looks to overcome the electronic bottleneck by moving the switching and routing functionality into the optical domain. Various new technologies are required to make an optical packet switch practical and it is expected that moving these various functions into the optical domain will results in a lower cost, and more scalable design. The key to achieving this is by realizing the full potential of photonic integrated circuits.; This thesis focused specifically on the development of advanced wavelength converter technology for high-speed packet switched optical networks, which allows the transcription of data from one wavelength to another and allows routing of optical data packets through fast wavelength switching. As a result, three major functions required for a high data rate packet-switched network node were for the first time realized on a single monolithic device, allowing for simultaneous wavelength switching, all-optical wavelength conversion and electro-optical label encoding.; Functionally complex photonic integrated circuits, such as those fabricated in this work, require various different components to be integrated on a single chip, using a common platform and a fabrication process. The two main challenges in doing so are that, firstly, the designs and fabrication processes that optimize the performance of a particular component can compromise the performance of others. Secondly, the interaction between different components can lead to effects and issues that are not typically encountered in functionally simpler devices based on the components. While the platforms and components were designed with a packet forwarding chip as the intended application, the tradeoffs encountered and design methodologies used are also applicable towards the development of functionally complex photonic integrated circuits in general.; The devices that were successfully demonstrated are based on monolithic all-optical wavelength converters utilizing a differential Mach-Zehnder interferometer (MZI) with semiconductor optical amplifiers (SOA). Additionally, a fast tunable Sampled Grating - DBR laser was integrated on-chip with the wavelength converter. The devices were fabricated in the offset quantum well, quantum well intermixing and butt-joint growth platforms to understand the relative performance of each. Experimental results are presented demonstrating error-free wavelength conversion at up to 40 Gbps data rates with very low signal quality degradation.; By also incorporating label modulation functionality on-chip, along with a fast tunable 40Gbps wavelength converter, fully monolithic packet forwarding chips are realized. Packet forwarding, which involves simultaneous wavelength conversion of 40 Gbps payloads, remodulation of 10 Gbps packet header and routing through fast wavelength switching, is demonstrated using layer-2 measurements.