Using a computer and postulating highly idealized thundercloud conditions, we have modeled the interaction between a population of raindrops and a region of high electric field. Under favorable circumstances, the interaction produced a downward‐moving wave of potential gradient that intensified the preexisting field without apparent limit. The two major parameters that determined the intensification were the raindrop concentration and the amount of immobile negative charge produced by a stressed raindrop. Field intensification seems to depend critically on the peculiar characteristics of a water‐drop discharge at the altitude considered, namely the production of large numbers of highly charged negative droplets. Charged raindrops alone could not produce the required effect. It is suggested that the mechanism modeled here could be responsible for the initiation of cloud‐to‐ground lightning strokes. The mechanism should strongly favor a downward‐moving negative discharge.
Power penalties due to multipath interference have been measured for 1.7-Gbls lightwave systems that use single-or multifrequency lasers. Systems that use single-frequency (SF) lasers potentially exhibit worse degradation than those using multifrequency (MF) lasers. Bit-error-rate (BER) floors only occur under the worse-case conditions of poor receiver margin and large multiple reflections. The use of optical isolation, to reduce laser feedback, is ineffective in reducing multipath interference (MPI), and in many cases may worsen the penalty. We show that for a typical transmission system, these degradations are reduced if optical interconnection reflections are maintained below -20.5 dB, commercially available connector return loss. Our experimental study is in good agreement with theoretical predictions using an analytic expression of the MPI noise power spectral density, and computer simulations using multimode laser rate equations.
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