Simulation Research On Non-ideal Damage Of OFDM Signal In Optical Fiber

Optical fiber communication has become the core means of modern communication backbone network and access network with low loss,low cost,high bandwidth,anti-interference and good privacy.With the deepening of informatization,the bandwidth required for streaming media transmission has increased.Internet users' requirements for transmission bandwidth have been increasing year by year.As the fiber backbone of communication backbone networks,there is an urgent need to increase their own transmission capacity.Communication technologies at 100 Gbps or even Tbps level are already It is implemented by laboratories through various means and is gradually entering the commercial stage.Orthogonal Frequency Division Multiplexing(OFDM)is a signal transmission method with high spectral efficiency and has been widely used in wireless communications.It is one of the core technologies used in modern 4G and 5G communications.The latest theoretical and experimental research shows that all-optical OFDM technology is an effective means to increase the optical fiber transmission capacity to Tbps level,and is an important hotspot in current fiber technology research.In this paper,a more in-depth theoretical simulation study of the transmission characteristics of optical OFDM signals in optical fibers is performed.Based on the detailed derivation of the optical signal transmission.equation in optical fiber,numerical analysis of fiber nonlinear transmission equations' and the corresponding numerical simulation program are performed.The loss,dispersion,self-phase modulation,cross-phase modulation and four-wave mixing are analyzed in detail.Optical fiber non-ideality affects the transmission characteristics of optical OFDM signals such as waveforms and spectrums in optical fibers.In order to get as many simulation results as possible,this paper only simulates the situation with four OFDM subcarrier channels,and the power of each subcarrier channel takes a higher value.The main reason for this arrangement is not only to reduce the running time of the simulation program in order to obtain more simulation results,but also take into account the following factors:(1)Linear effects such as dispersion and loss are independent of the number of subcarrier channels;(2)The limitation of the phase matching condition is that the nonlinear interaction among the subcarriers mainly occurs between the adjacent channels;(3)The nonlinear effect caused by the increase of the total signal power in the optical fiber caused by the increase of the number of subcarrier channels can be solved.This is partially solved by increasing the power of each subcarrier signal.The main work accomplished by the thesis is as follows:1.Based on the Helmholtz equation,nonlinear propagation equations of optical signals in optical fibers,including loss,dispersion,high-order dispersion and nonlinear effects,are deduced.Using Matlab integrated programming environment,a numerical program for solving nonlinear transmission equations of optical signals in optical fibers was developed,and the correctness and reliability of numerical simulation programs were fully verified.The results show that the simulation program compiled can give the numerical simulation results that are completely consistent with the theoretical and experimental research on optical signal transmission in existing optical fibers.2.Under the circumstance of ignoring the optical nonlinear effect in the fiber,the numerical simulation program compiled has been used to analyze in detail the effects of fiber dispersion,optical fiber transmission distance and high-order dispersion on the transmission characteristics of OFDM subcarrier signals in the optical fiber.The simulation results show that for all-optical OFDM,the influencing factors of dispersion are also related to the relative values of the dispersion length and the transmission distance,and all-optical OFDM can suppress the dispersion by adding a cyclic tap,and the main peak and the sidelobe both broaden and attenuate,and therefore Dispersion is easier to control with OFDM signals.3.The effects of self-phase modulation,cross-phase modulation,and four-wave mixing on all-optical OFDM transmission are analyzed.We can see that the individual self-phase modulation is partially suppressed by the dispersion effect,and the cross-phase modulation results in the signal spectrum.With the rapid widening,the effect of four-wave mixing leads to significant asymmetric energy transfer.The influencing factors of nonlinear effects can also be analyzed from the relative relationship between the nonlinear length and the transmission length and the dispersion length.By controlling the initial signal power and reasonably transmitting the distance,the nonlinear effect can be effectively suppressed and the communication system can be improved.The reliability.The work accomplished in this paper is part of the entire theoretical and experimental research work of the task force.The ultimate task of the project is to establish a set of all-optical OFDM systems capable of multiplexing and demultiplexing,signal transmission and detection of multi-pass pseudo-random subcarrier signal sequences containing hundreds of subcarrier channels and various modulation formats.Real simulation of numerical simulation program.