Simulative Study Of Optical Pulse Propagation Properties In Atmosphere-Seawater Hybrid Channel

To realize the communication between satellites and underwater vehicles by useof blue-green laser has been a major topic needed to be solved in the world. It iscommunication technology with advantages of large capacity, good directivity,anti-interference, high seawater penetration capacity, etc. When the blue-green laserpropagates in the atmosphere-seawater hybrid channel, it must propagates through theatmosphere first, then the air sea interface, and finally the seawater. As the hybridchannel is very complicated and changeable, the optical signal would be influencedby many physical effects. So an appropriate model of the channel would be veryimportant for the analysis of the optical transmission property.In this thesis, the influence of atmosphere, air sea interface and seawater channelon the optical pulse propagation is summarized firstly. Then a atmosphere-seawaterhybrid channel model, including the modified non-uniform atmospheric channelmodel and the non-uniform seawater channel model, is established. Finally, using theMonte Carlo method to simulate the propagation characteristics of a large number ofphotons through the non-uniform atmospheric channel, non-uniform seawater channel,and non-uniform hybrid channel, we record the photons’ arrival coordinates, thedirection cosine, and travel time and, after processing the recorded data statistically,we get the spatial distribution, impulse response, and probability distribution ofphotons’ arrival angle.From the simulation we can find that: after propagating50km in the non-uniformatmospheric channel, the optical pulse’s width is broadened about1s, arrival anglemainly distributes from0oto0.1o, and about70percent of the optical power canarrive at the receiving surface; when the optical pulse propagates in the non-uniformseawater channel, with the increases of the background and peak value of chlorophyllconcentration, the relative refractive index of scattering particles and small scatteringparticles’ relative quantity, the width of optical pulse is broadened in time domainmore evidently while the forward scattering becoming weaker with more disperse space distribution and arrival angle distribution; when the optical pulse propagates inthe hybrid channel, the saturate receiving radius is0.55m after propagating50kmthrough the atmosphere and then100m through water.