The Generation Scheme Of Multi-Frequency Optical Millimeter-Wave And Application Research

In order to improve the utilization rate of the lightwave,multiple service transport technology with a single optical sourceis is very important and necessary.By using the same optical source to achieve optical generationof multiple wireless signals of microwave/millimeter wave band,radio-over-fiber(ROF)transmission technology of multiple frequency millimeter wave,all-optical demodulation technology become the key to the realize the multi-service transport of ROF system.Multiple-frequency optical millimeter wave technology reflects the flexibility of wireless access.The frequency of different millimeter wave can meet the requirements of different bandwidth users.Moreover,the optical millimeter wave with different frequencies is an effective solution to reduce interference between signals caused by the same frequency of neighboring base stations,and it plays an increasingly important role in the future.Therefore,the main work of this paper is as follows:1?The improved multiple frequency optical carrier millimeter wave generation method is studied and implemented,using microwave subcarrier multiplexing and modulation technology to generate multiple frequency optical millimeter wave signal.At the transmitter,the optical frequency conversion is realized by the multiplexing of the subcarrier signal and driven by external modulator,and the multiple-frequency optical millimeter wave generation method based on microwave subcarrier multiplexing and modulation technology is simulation verified to be feasible.Compared with the common scheme using several optical modulators,the improved scheme can reduce system cost.2?The transmission performance of multiple-frequency optical millimeter wave signal based on different modulation formats are analyzed.For 4QAM and 16 QAM signal,we analyze the influence of transmission distance.The simulation results show that,after 20 km optical fibertransmission,the optical dispersion is smaller,and eye and constellation diagrams of receiver are relatively clear.However,with the increase of transmission distance,the effect of fiber dispersion and nonlinear will aggravate,sidetracking degree of eye diagrams become smaller gradually.By analyzing the bit error rate(BER)performance of 4QAM and 16 QAM modulation signal after optical back to back(OBTB)and 50 km standard single-mode optical fiber(SSMF)transmission,the simulation results show that,as the optical power increases,meaning that increasing signal noise ratio(SNR),thus the BER decreases.The reason is that,in the process of transmission,the performance limitation of deviceand intersymbol interference(ISI)caused by the noise accumulation and the chromatic dispersion of optical fiber has restrictedsignal transmission distance.