Investigations of sub-systems for dynamic wavelength-routed optical networks

This thesis describes an investigation of technologies and sub-systems required for physical layer implementation of a range of dynamic wavelength-routed optical networks with a specific focus on acknowledged optical-burst-switching (OBS) architectures where burst lengths are expected to be in the millisecond regime. The key sub-systems are identified and examined both individually and in terms of their interoperability. The feasibility of existing systems is investigated and new control systems are developed where appropriate. The initial focus is the tuneable transmitter required to provide wavelength agility at the network edge. The available laser technology is identified and the switching operation of fast widely tuneable lasers in the context of dynamic optical networks is investigated. Using novel probe channel BER measurements, it is shown that additional control systems are required to provide adequate wavelength stability and prevent crosstalk caused by spurious modes excited during the switching process. Based on these findings, a tuneable burst transmitter using SOA blanking and a wavelength locking control loop is developed and its performance described. Next, the reception of the transmitted bursts is explored and the operation and characterisation of the first 10Gb/s digital burst-mode receiver is described. The receiver uses an AC-coupled photodiode, asynchronous digital sampling at 20GS/s and digital signal processing for clock and data recovery. The investigation reveals that the burst-to-burst dynamic range is ultimately limited by quantization noise and methods to improve the dynamic range are investigated and implemented. In the core network, an experimental investigation of optically gain-clamped erbium-doped-fiber-amplifers shows that them optimum feedback cavity designs depends on a trade off between gain transient suppression and reduced signal gain. Cascaded operation is investigated using an experimental OBS link model comprising burst-mode transmitter, receiver, amplifier and router within a recirculating transmission loop. These experiments reveal the importance of network size in feedback cavity design and that, for small networks, the use of the adaptive threshold receiver may negate all gain clamping requirements and allow maximum signal gain.

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

UCL (University College London)

Year dc:date.issued

2008

Author dc:creator

• Puttnam, Benjamin James

• Department of Electronic and Electrical Engineering

Language dc:language

en, eng