The Novel Optical Communication System Based On OAM-SK

With the rapid development of communication technology,people are demanding more and more information transmission.Achieving higher data transmission capacity is one of the main directions of optical communications.Recently,a typical way to increase the transmission capacity of optical communication system is to multiplex multiple independent data channels.The multiple independent data channels can be located on the different wavelength,polarization,or space,which is corresponding to wavelength division multiplexing(WDM),polarization multiplexing(PDM)and space division multiplexing(SDM).For light waves,a special space combination-orbital angular momentum(OAM)has been attracted lots of attention by many researchers,especially application in optical communication.The mainly content of this dissertation:(1)A highly efficient digital communication system based on OAM-SK is designed.Based on the orthogonality between the vortex beams,we built an efficient digital communication system and successfully transmitted a picture.At the sending end,the multiplexing phase hologram that generates the multiplex vortex beam is realized by the iterative algorithm,and the gray value of the image is converted into binary digital signal and mapped to different topological charges of the vortex beam.This process stores the image information in the vortex beam and arrives at the receiver via free-space transmission.At the receiving end,a new efficient de-multiplexed hologram is designed after the orthogonal basis of the iterative algorithm is changed,so that the multiplex vortex beam can be separated and detected,and then converted into the digital signal.(2)The effect of different multiplexing/de-multiplexing methods on the performance of OAM-SK system.For the OAM-SK system,the efficient way of multiplexing and de-multiplexing is the key to affecting the performance of the communication system.We compare the different multiplexing methods as the encoder and the different diffractive optical elements as the decoder,and quantitatively analyze the accuracy of the transmission by transmitting the gray value of a picture.Then,we choose a better system combination to achieve efficient digital communication.At the same time,we still consider the different pinhole size and judgment threshold on the performance of the system to choose the best designing scheme.