Figure 3(b) provides an interesting demonstration that there is very little side leakage of light from the plastic optical fibre. Relative to the illumination at the end of the fibre, the dominance of end-reflected light quickly gives way to the dark fibre surface as the observer's attention is directed away from the end of the fibre, thus confirming the effective confinement of the light within the plastic.Eventually, an integrated array of series-connected photo-voltaic diodes, designed for this application, will provide optimum performance. The light output from the plastic optical fibre will be confined to a small area, and the photo-diode receiving areas should be close-packed in order to avoid wasting light output and hence maximise transmitted power efficiency. This is in contrast with solar cells, where there is little restriction on the illuminated area.The purpose of this preliminary report is to confirm the viability of this interference-free method of power delivery rather than optimise high power and efficiency. Therefore, a small-scale demonstration of successful interference-free powering of a CMOS digital-signal generator has been constructed. This consists of four photovoltaic diodes connected in series, providing a supply of up to 1.6 V (DC) and driving a 555-CMOS counter/timer chip and microcircuit.
COMPARISON BETWEEN WIRE AND POF POWER DELIVERYThe comparison between the purely electrical (wired) and the optical power delivery can be observed in Figure 4.The output from the IC in the absence of externally generated electromagnetic noise was a square wave of ϳ2.5:1 mark-to-space ratio. Figure 4(a) shows the output waveform from the 555 IC, recorded using a fast oscilloscope with the microcircuit powered conventionally by a wired connection and an energised Tesla coil placed near the twisted-wire supply line. The EMI generated by this source is ideally representative of the noise present in the aforementioned medical installations, with both high voltage and RF properties. Large-amplitude, high-frequency voltage spikes were present on the output signal at random time intervals. Additional signal corruption was provided by mistriggering of the oscilloscope due to the method of monitoring employed. Figure 4(b) shows the output signal from the same I.C. powered by the POF power delivery system under identical EMI conditions, and should be compared directly with the trace shown in Figure 4(a). The immediate purging of electrical noise that results from the EMI being deliberately introduced into the local environment is readily noted.
STATUS FOR POF INTERFERENCE-IMMUNE POWER DELIVERYFigure 4(c) shows the complete scenario for these innovations, illustrating the advantage of POF power delivery.At the present time, the optical fibre instrument industry is mainly devoted to small-diameter glass fibres. It is therefore necessary to develop new power meters, etc., in order to enable measurements to be made in this new field of 1-mm-diameter plastic optical fibre power delivery technology. When these new ...
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