JOURNALOFMODERNOPTICS, 1994, VOL . 41, NO . 8, 1 59 1 -1605 Analysisofopticalpulsedistortionthroughcloudsfor satellitetoearthadaptiveopticalcommunication S .ARNON,D .SADOTandN .S .KOPEIKA DepartmentofElectricalandComputerEngineering, Ben-GurionUniversityoftheNegev,Beer-Sheva,Israel (Received19November1993 ;revisionreceived11February1994) Abstract . Clouds,ifpartofanopticalcommunicationchannel,causetemporal wideningandattenuationofopticalpulsepower .Spaceopticalcommunication fromsatellitetoearth(groundorairplane)occasionallyinvolvescloudsaspart oftheopticalchannel .Here,baseduponMonteCarlosimulations,mathematical modelsaredevelopedforthetemporalcharacteristicsofopticalpulsepropagation throughclouds .Theseincludetemporalimpulseresponse,transferfunction, bandwidth,receivedenergyandbodeanalysis .Themethodpresentedherecan beusedasaninclusiveframeworkfordevelopingothermathematicalmodelsof othercharacteristicsofradiationpropagatingthroughclouds,asrequired . Severalconclusionsofthisworkareobtained .Oneisthatsimpleprediction modelscanbeappliedtoadaptivemethodsofopticalcommunication .Another isthatusingshorterwavelengthssuchas0 . 532µmyieldsleasttemporalwidening andmaximumreceivedpower,andisthuspreferableforopticalcommunication . Inaddition,thesimulationresultsstronglysupporttheuseofthedoublegamma functionmodeltobestdescribeopticalpulsespreadthroughclouds .Thiswork isthefirst,tothebestoftheauthors'knowledge,topresentacomprehensive analysisofspaceopticalcommunicationthroughclouds . 1 . Introduction Opticalcommunicationbetweensatellitesandtheearthhasgreatpotentialand manyadvantageswithregardtobandwidth,radiationpower,directionalityand immunitytojamming .Opticalcommunicationsystemsmightincludeadeepspace satellite,ageostationaryearthorbitsatellite,alowearthorbitsatellite,anairplane, andagroundstation .Inallthescenarios,partoftheopticalchannelpassesthrough theearth'satmosphere,whichoccasionallycontainsclouds .Oneimportant distortioneffectimposedbytheatmosphereisthesignaltemporalbroadening .This imposesalimitationonthemaximumtransmissionbandwidthrealizableinorder toreceiveahighqualitysignalwithnointer-symbolinterference(ISI) [1] . Using transmissionwithawidertemporalfrequencybandwidthwillcausesignificant degradationinreceivedsignalqualitybecauseofthenarrowinformationbandwidth permittedbyclouds .Usually,inopenopticalcommunication,theingredient imposingthemostseverebandwidthlimitationistheatmosphericchannel bandwidth,particularlywhencloudsarepresent .Thus,inordertoachieveimproved systemperformance,adaptivemethodsmaybeusedaccordingtoatmospheric conditions .Onewayisbyusingadaptivetransmissionbandwidth .Inother words,thetransmitterbit-ratemaybeadaptedaccordingtothecloud'soptical thicknesstothereceivedpulsewidthatthedetectorresultingfromthetemporal 0950-0340/94$1000©1994Taylor&FrancisLtd .