Research On Transmission Characeristics Of The High Bitrate QAM Signal Over The DFF System

The demand and quality of mobile and broadband services such as webcasting,virtual reality,4K video and high-definition on-demand TV are increasing rapidly,which placing higher demands on the communication performance of optical fiber transmission systems.The modulation and demodulation technology and transmission optical fiber are important factors for ensuring the signal transmission quality of the optical fiber transmission system,which have always been a research hotspot for scientific and technological workers at home and abroad.Considering the quadrature amplitude modulation(QAM)modulation has high spectrum efficiency and good anti-noise performance,and the dispersion flat fiber(DFF)has a small dispersion value and a flat dispersion distribution.This paper combines the advantages of QAM technology and the low dispersion and flatness characteristics of DFF,and studies the transmission characteristics of high-speed QAM signals in DFF system,which can avoid the delay caused by dispersion compensation processing of digital signal processing(DSP).This study provides new ideas and experimental guarantees for the long-span transmission of mobile communication Front-haul.The main innovative works are as follows.:1.We proposed an experimental transmission system of 56Gbps?4QAM signal based on the DFF.The propagation rate of the system is 56 Gbps and modulation format is4 QAM.Linear transmission characteristics over DFF link system are experimentally studied,compared with those of non-zero dispersion shifted fiber(NZDSF)link and standard single mode fiber(SSMF)optical link.The experimental results show that56Gbps?4QAM signal transmission characteristics over the DFF link are superior to those over NZDSF and SSMF link under linear transmission conditions.And it more obvious the advantages of the DFF link with the longer optical link.The error vector magnitude(EVM)and Q factor of 56Gbps?4QAM signal over 25 km DFF link are 1.40% and 1.5dB better than those over 25 km NZDSF link,respectively.At different input optical power,the EVM and Q factor of 56 Gbps ? 4QAM signal over 50 km DFF link are 2.60-3.70% and0.80-2.20 dB better than those over 50 km NZDSF link,respectively.2.We proposed a DFF transmission system with high rate PM-QAM signal.The modulation format of the system is PM-16 QAM,the bitrates are 160 Gbps and 256 Gbps.The transmission characteristics over DFF link system are experimentally studied,which are compared with those of NZDSF link and SSMF link.The experimental results show that the EVM of 160 Gbps and PM-16 QAM over 50 km DFF link is 0.50% better than those over 50 km NZDSF link,the BER is 2 orders of magnitude better than that of NZDSF.When bitrate is 256 Gbps and transmission distance are 50 km and 75 km,the PM-16 QAM signal can be well demodulated only after the DFF link.The smaller the input optical power range while maintaining good characteristics with the longer the transmission distance.Compared 160 Gbps with 256 Gbps at lower input optical power,the high bitrate and PM-16 QAM signal transmission characteristics over the DFF link are superior to those over NZDSF and SSMF links.And it more obvious the advantages of the DFF link with higher the transmission rate and the longer optical link.