Research On Optical Orthogonal Frequency Division Multiplexing System Using Triple-Band

Because of high spectral efficiency and anti-dispersion capability,optical orthogonal frequency division multiplexing(OFDM)can greatly improve the transmission performance of the optical communication systems.In particular,adaptively modulated optical OFDM(AMOOFDM)can manipulate signal modulation format on each subcarrier.For upgrading the existing multimode fiber(MMF)-based networks,AMOOFDM has become a promising solution.To enable a cost-effective MMF networks,subcarrier modulation(SCM)can be used to relax the requirements on the sampling rate of the digital-to-analog converter(DAC)and analog-to-digital converter(ADC).In this paper,AMOOFDM using triple-band SCM is proposed and investigated.With the adoption of 6 GS/s DAC and ADC and the system error rate threshold of 0.001,the adaptive modulation technology can still obtain a large signal transmission rate in the three sub-bands.Through MATLAB programming constructs based on the three zones of adaptive modulation-optical orthogonal frequency division multiplexing system,one of which is a baseband,on the other two is to signal frequency on the two bands,mutual transmission of optical fiber communication,at the same time based on adaptive modulation and subcarrier modulation technique,three sub band can according to their respective signal corresponding to the spectrum of multimode optical fiber channel condition,the best way of signal modulation.Then,because the resolution of ADCs is one of the main factors that limit its maximum performance,the simulation of limiter and quantization effect is carried out under the condition of 0.001 bit error rate threshold.Firstly,for different signal modulation formats in AWGN channel,the optimal limiting ratio and quantizing bit number are determined by changing the limiting ratio and quantizing bit number to achieve the minimum SNR required by the bit error rate.Then,in the three-band system based on the worst case multi-mode fiber channel transmission,the simulation verifies the influence of the quantization bit number on the maximum signal transmission rate at different transmission distances,and provides parameter support for the maximum signal transmission rate obtained in the three-band optical orthogonal frequency division multiplexing system.The multi-mode fiber channel used is based on the worst case fiber link,that is,the larger signal transmission rate can still be achieved under this channel,then better results will be achieved under the actual fiber link.The results show that with 6GS/s DAC and ADC,46.5 Gb/s signal line rate is achieved at 400m.Even when the transmission distance is increased to 1200m,it is still possible to achieve a transmission rate of 30.225 Gb/s.