The design of equipment to sterilise solid-liquid food mixtures continuously requires that the flow properties of such mixtures be understood. Little information is available on food flows, which can consist of high solids fractions of particles of a range of densities in non-Newtonian and viscous liquids. A metal detection system which can log two types of particle in the same experiment has been constructed and used in a loop flow rig to study flows of single particles and carrot-water mixtures. Results can be correlated using the particle Froude number; some preliminary analysis is presented to suggest that data can be correlated against IIFr p . The effect of solids fraction on particle flow velocity has been investigated; greatest variations in the particle velocity appear for stratified flows for solids fractions between 10-20%.

We demonstrate for the first time the low penalty cascaded performance of a 1.3µm QD SOA. Eleven passes are feasible for 10Gb/s data while maintaining a Q-factor exceeding 6 for filter-free operation.OCIS codes: (250.5980) semiconductor optical amplifiers; (140.4480) optical amplifiers IntroductionQuantum dot semiconductor optical amplifiers (QD-SOAs), with their broad gain spectrum, ultra-fast gain recovery rates and consequent potential for low distortion are emerging as high performance devices [1] for prospective applications such as in power boosters, in-line repeaters [2], and reconfigurable network switches [3]. In several of these applications, it is of key importance to be able to cascade multiple amplifiers, while ensuring that penalties accrued from signal distortion and noise are tolerably low after the cascade. Work to date has however focussed in the main on the stand-alone performance of single components. Studies to date on quantum well SOAs, operating in the 1.55µm wavelength band, have been performed for up to eight cascaded amplifiers, this resulting in a power penalty of up to 1.5dB [4]. Field studies have also been performed for 1.3µm bulk and quantum well amplifiers [5], although here the number of amplifiers has been restricted to two for a detailed penalty assessment. Little work has addressed the dependence of power penalty on the number of cascaded amplifiers and so there is little understanding of the limits in performance. Recirculating loops have been proposed for example in the assessment of amplifiers based regenerators and the understanding of fibre propagation [6]. This work therefore is believed to be the first reported detailed study into the performance of cascaded quantum dot amplifiers.

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