Experimental demonstrations of optical techniques to implement networking functions in dynamically reconfigurable wavelength-division-multiplexed fiber-optic communication networks.

摘要

The deployment of optical networks will enable high capacity links between users but will accentuate the problems associated with transporting and managing even more numerous and inassimilable signals. Advances in photonic techniques suggest interesting solutions for expanding network transport capacity and for increasing transparency and flexibility by adding to node capabilities. There are many reasons to implement network functions in the optical domain: (i) to avoid electronic processing bottlenecks, (ii) to achieve data-format and data-rate independence, (iii) to provide reliable and cost efficient control and management, and (iv) to compensate the degradation effects.; It is critical for future networks to provide additional functionality in the optical physical layer to ensure high-speed and high throughput performance. In this thesis, the following novel implementations of network functions in the optical domain are presented: (i) Reconfigurable optical header recognition and penalty-free routing of a 2.5-Gb/s packet stream with a 1.6-ns guard time, using cross-gain compression in an SOA for time-to-wavelength mapping and two fiber Bragg grating arrays for tunable correlation decoding. (ii) Variable-bit-rate header recognition of incoming data packets at 155 Mb/s, 622 Mb/s and 2.5 Gb/s with fiber Bragg grating optical correlators, and switching. (iii) Optical time-slot-interchange and wavelength conversion of the bits in a 2.5-Gb/s bit stream to achieve a reconfigurable time/wavelength switch, using difference-frequency-generation (DFG) for wavelength conversion and fiber Bragg gratings (FBG) as wavelength-dependent optical time buffers. (iv) High precision packet and bit synchronization of an optical switching node to an incoming packet stream, employing only four preamble bits and FBG continuous optical correlators to determine the start of a packet with 1/8th of a bit time precision. (v) Penalty-free all-optical wavelength shifting of two subcarrier channels in a periodically poled lithium niobate (PPLN) structure, using a memoryless χ(2) :χ(2) difference-frequency-generation process, which has a large linear dynamic range for crosstalk-free transparent operation. (vi) A wavelength-to-time mapping technique for control monitoring in a WDM network. (vii) RF power degradation compensation in SCM systems, using a nonlinearly-chirped fiber Bragg grating.