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The objectives of this project are the development of optical sources able to generate and shape high speed optical signals suitable for soliton generation and regeneration. The sources include multicontact laser diodes and integrated electroabsorption sources optimised for low jitter and low chirp operation.The project has involved both experimental and theoretical work and has been carried out in close collaboration with BNR Europe Ltd.Progress:To date the project has concentrated on low chirp signal generation using electroabsorption modulators and multicontact laser diodes. In terms of the electroabsorption modulator, theoretical models have been developed which, using wafer electroabsorption data, allow the design of optimised negative chirp modulators. This model has led to the design and demonstration of the first negative chirp electroabsorption modulator, fabricated by BNR Europe Ltd, allowing the transmission of 10Gb/s signals over 100km of standard optical fibre [1]. The modelling has since been used to determine optimum bias conditions for low chirp picosecond optical pulse generation. Trade-offs between chirp and insertion loss have been identified. Since then integrated lasers and electroabsorption modulators with negative chirp have been studied [2]. A range of work has been concentrated on short pulse generation using multicontact lasers. Narrow-line, near bandwidth limited, picosecond pulses have been generated by gain switching and Q-switching multicontact dfb lasers [3]. In addition resolution limited multiwavelength pulses have been generated by sampled grating dbr lasers. Research has also concentrated on the development of low jitter pulse generation, with a novel feedback scheme having been identified to allow sub-picosecond optical jitter [4]. Finally research is being carried out to identify optimum layer configurations for short pulse generation, band calculations having recently been shown to account accurately for observations of linewidth enhancement factor and allow low chirp optimisation [5]. A theoretical model has been developed to identify optimum modulation requirements for soliton shaping and a recirculating loop system test-bed is presently being constructed. 1. J.A.J. Fells et al, Elect Lett, 1994, 30 p.1168.2. J.A.J. Fells et al, to be presented at OFC'95, 1994, San Diego.3. K.A. Williams et at, Invited Paper CTuL1, CLEO-Europe'94, 1994, Amsterdam.4. K.A. Williams, I.H. White, D. Burns and W. Sibbett, Elect Lett, 1994, 30, p.1687.5. H. Summers and I H White, Elect Lett, 1994, 30, p.1140.
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