Research On Mode Division Multiplexing Communication Technology Based On Self-Homodyne Detection

With the continuous development of the mobile internet,data services represented by IP are showing an explosive growth trend.Especially in recent years,the rise and development of 5G mobile communications,big data,cloud computing,and the internet of things technology have made optical communications of short-distance represented by data centers and metropolitan area networks faceing enormous pressures on network traffic.Coherent communication technology,as an effective method,can realize the transmission of large capacity information,and the self-homodyne detection as another way of coherent communication can maintain the characteristics of high sensitivity,high efficiency,and simplify the system structure and reduce cost.Especially in recent years,the multiple parallel optical mode channels in the mode division multiplexing technology have provided the channel for the pilot in self-homodyne detection.Therefore,the combination of self-homodyne detection and mode division multiplexing can realize low-cost and large-capacity information transmission and provide new solutions for data center interconnection and metropolitan area networks.This paper mainly studies the self-homodyne detection technology and combines it with the mode division multiplexing technology.We thoroughly analyzed the various damages and corresponding solutions of the mode division multiplexing system based on self-homodyne detection(MDM-SHD).After that,a double-sideband pilot transmission method is proposed for the beating noise elimination,which is caused by inter-mode crosstalk.The methord can effectively improve the transmission performance of the system.The main work of this paper is as follows:First,the structure and characteristics of traditional self-homodyne detection are studied.Afterwards,the characteristics of self-homodyne detection in single mode fiber are verified through simulations,including phase noise suppression and the line-width tolerance for the light source.Then,a non-polarization sensitive self-homodyne detection system is simulated and studied.Secondly,the optical modes in few mode fibers are studied,and the orthogonality of the optical modes is deduced.The specific damages of few mode fibers are analyzed,including mode coupling,differential mode group delay,and mode-dependent loss.After that,the transmission characteristics of few mode fibers are analyzed and the transmission model is performed by studying the matrix transmission theory,Thirdly,the self-homodyne detection and mode division multiplexing technique are combined.The OSNR penalty in MDM-SHD system is deduced,and a MDM-SHD system based on 6-mode few mode fiber is established,which can achieve 50 km transmission for 56×5×3Gb/s PDM-QPSK signal.After that,the effects of mode crosstalk,differential mode group delay,and other factors on the system BER performance are analyzed through simulations,as well as the corresponding solutions.The MMA and CMA algorithm is compared in intra-mode crosstalk elimination.Then,the characteristics of the line-width tolerance of the light source and the influence of the bandwidth of the pilot filter on the system average BER are also analyzed.Finally,a double-sideband pilot scheme is proposed for the problem of the beating noise caused by inter-module crosstalk in MDM-SHD system.The characteristics of the beating noise suppression in this scheme are verified,and the transmission distance of the system can also be extended by establishing the double-sideband pilot MDM-SHD system of 56×2Gb/s PDM-QPSK signal based on 40 km 3-mode few mode fiber.