The Study Of Multi Carrier Source And Stokes Vector Direct Detection In Optical Communication

With the increasing amount of communication services,the advanced communication transmission system,with respect to the higher speed and bigger capacity,is needed by the common.In order to improve the transmission rate,the optical multiplexing technology can be applied.Uaually,it takes multi-carrier light source as the modulated light source by the actual optical system.However,each laser is susceptible to environment which can cause frequency instability.And the cost of optical communication system will be highly increased due to the use of a large number of lasers.These limitations affect the commercial application of the system.At the receiving end of the optical communication system,the coherent reception technology will make the system get a larger signal noise ratio,more types of signals and good frequency selectivity.This kind of technology has become the focus of research in recent years.But the received optical signal needs to be mixed with a local signal generated by local oscillator at the receiver in the coherent reception mode.When the communication system is connected to different locations,the use of a large quantity of local oscillators will result in the increase of the system cost.It also restricts the commercial application of the optical communication system.In order to reduce the cost of communication system,the paper has carried on the theoretical analysis and experimental research with respect to the content of the two aspects in the optical communication system.First,it takes the depth-modulation electro-optic modulators to achieve a multi-carrier light source;the second is to use Stokes received directly technologies to finish the received signal demodulation.The obtained results and innovation points are as follows:1.The thesis studies on the methods of generating multi carrier source.The simulation of cascaded phase modulator,hybrid cascaded phase modulator and Del-Maher modulator and cyclic shift frequency converter are realized.The author analyzes the characteristics of different ways to generate multi carrier light source and its application in optical communication system.Among them,the cascade phase modulator,hybrid cascaded phase modulator and Maher Del modulator can be used in the optical transmission system of T bit/s.The loop shifter can be oriented to the 10Tbit/s optical transmission system.2.The Stokes directly receive technology is studied,and a new Stokes direct receiving scheme based on 3*3 coupler is proposed.The error rate and signal to noise ratio of the system are compared,and theoretical study shows that the properties of stokes direct method based on the 3*3 coupler is basically the same as the stokes direct method based on the 90 degree mixer.However,the former is simpler in structure and lower in overall cost.3.The thesis focuses on multi-carrier light source based on cascaded phase modulator and stokes directly receiving technology.Theoretical studies and simulations are carried on the whole communication system.Finally,the data about the power and bit error rate are obtained under different transmission distance through the experiment,and the performance of the system is analyzed.4.The system performances of different type modulations are displayed in detail based on the analysis for the experimental result.The experiment realized a variety of modulated codes,including OOK,BPSK,QPSK.And the impacts of different types of code on the system are analyzed.