Research On Optimizing Spectrum Efficiency Of O-OFDM System Based On LTE

Orthogonal Frequency Division Multiplexing(OFDM)is widely used in the field of optical communication.The advantages of orthogonal Frequency Division Multiplexing(OFDM)are convenient processing,high spectral efficiency and strong resistance to dispersion and polarization mode dispersion in optical fiber links.At present,it is generally accepted that optical orthogonal frequency division multiplexing(O-OFDM)is one of the most promising technologies in the new generation of high-speed optical communication systems.Two schemes to improve the spectral efficiency of O-OFDM systems are proposed in this paper.Firstly,because the square detection of PD will lead to intermodulation interference(IMD)noise,we adopt balanced receiver to eliminate noise,reduce the protection band between optical carrier and signal spectrum components,and improve the spectral efficiency of intensity modulation direct detection of OFDM system(IMDD-OOFDM).The results show that the spectral efficiency of the system is 62.1% higher than that of the traditional Offset SSB-OFDM system.If the modulation format higher than 4QAM is used,the spectral efficiency of the system may be further improved.At the same time,the sensitivity of this scheme to carrier signal power ratio(CSPR)is not high,so compared with the traditional Offset SSB-OFDM system,the optical signal-to-noise ratio(OSNR)is also improved.Secondly,a scheme to improve the DAC/ADC rate bottleneck of electronic devices is proposed.Fiber Bragg grating(FBG)is used to introduce cyclic prefix(CP)into all-optical OFDM(AO-OFDM)system.Experiments on all-optical sampling OFDM(AOS-OFDM)system show that the scheme not only reduces the dispersion effect of optical links,but also greatly improves the decision accuracy of the receiver.At the same time,the subcarrier phase pre-emphasis technology is used to optimize the system.Experiments show that the subcarrier phase pre-emphasis technology can effectively suppress the pulse phase interference between adjacent symbols,thereby reducing the non-linear effect of the receiver.The experimental results show that the proposed scheme can effectively improve the spectral efficiency of O-OFDM system.