Research On Radio-Over-Fiber System Based On Multicore Fiber

With the the concept of the Internet of everything proposed in recent years,fields such as industrial Internet,Internet of things,self-driving and so on are constantly developing.The global mobile data traffic is increasing explosively year by year,and the data rate of common public radio interface(CPRI)has been soaring,which limits the development of centralized radio access network(C-RAN)in the next-generation mobile communication system.Aming at the problem that the high data rate of CPRI interface in mobile fronthual is too high,this paper studies the radio-over-fiber(RoF)system based on multi-core fiber(MCF).The specific contents and innovations are as follows:1.Signals in analog radio-over-fiber(A-RoF)system do not need to be sampled and quantized,which can alleviate the problem of high data rate of CPRI interface.In this paper,eight-core optical fiber is used to build an A-RoF system based on space division multiplexing(SDM)technology,SDM combined with wavelength division multiplexing(WDM)technology to transmit WLAN and LTE-TDD wireless signals.The WLAN signal transmitted in the system conforms to the IEEE802.11ac standard,with a carrier frequency of 2.4GHz and a bandwidth of 20MHz.The LTE-TDD signal transmitted in the system conforms to the 3GPP standard,with a carrier frequency of 2.6GHz and a bandwidth of 20MHz.In the bulit A-RoF experimental link,the EVM of the WLAN signal can reach less than 1.65%,which meets the EVM threshold requirements of the IEEE802.11ac standard,and the EVM of the LTE-TDD signal can reach below 2.2%,which meets the EVM threshold requirements of the 3 GPP standard.2.Digital radio-over-fiber(D-RoF)technology based on efficient quantization coding algorithm can effectively alleviate the problem of high data rate of CPRI interface by reducing the quantization bits(QBs).In this paper,the D-RoF system based on SDM technology is constructed by using seven-core fiber and eight-core fiber respectively to transmit OFDM wireless signal with a carrier frequency of 2.5GHz and a modulation format of 64QAM.The quantization scheme adopts PCM scheme and DPCM scheme with prediction order of 3 and training coefficient of 0.01.Compared with the PCM scheme,the DPCM scheme can obtain the signal-to-quantization noise ratio(SQNR)gain of 4～7dB at low quantization resolution.In the bulit D-RoF experimental link,when QBs are 3～5 bits,the EVM performance of the system using DPCM scheme is better than that of PCM scheme.When the bandwidth of OFDM signal is 20MHz and 100MHz respectively,the signal EVM of DPCM scheme under 3-bit quantization is 2.2%and 6.3%lower than that of PCM scheme.The above experiments verify the feasibility of the high-fidelity,low-cost,large-capacity RoF transmission scheme based on MCF transmission mechanism.