Research On Key Technologies Of Transmission Link In Mode-division-multiplexing System Based On Few-mode Fiber

As the transmission capacity of single-mode fiber is close to the theoretical Shannon limit,seeking for a new dimension multiplexing technology becomes a new focus for the researchers.The mode division multiplexing technology based on few-mode fiber may be a possible solution to solve the fiber communication capacity problem.By considering each mode of the transmission in a few mode fiber as an independent channel,the communication capacity will be doubled.This paper pursuits research in three key technical problems of few-mode fiber transmission links,with the view to the design problem of few mode fiber,few mode fiber transmission optical network for mode switching optical switch and the new method of dispersion monitoring mode in fiber links.First,this paper studies the issue of the few-mode fiber design,and finds out the two parameters to control the number of optical fiber transmission mode: core radius and refractive index difference of core and cladding.By controlling the values of these two parameters,a kind of few-mode fiber which can transmit four modes is designed.Based on the theoretical research,the method to restrain the nonlinearity of the few-mode fiber is found out.In addition,adopting the outer cladding subsidence design,this design can reduce the bending loss in few-mode fiber.The fiber we designed has a large model differential group delay,which can make the mode channel independent and reduce the complexity of signal processing at the receiver.Secondly,this paper studies the mode switch in the few-mode fiber network.The experiment shows that the existing optical switch suitable for automatic switched optical network(ASON)can also switch mode groups in few-mode fiber.On the basis of this conclusion,a kind of reconfigurable optical network platform is designed,and the fixed connection between multi-mode fiber,few-mode fiber and single-mode fiber is established.IP service and FTP,HTTP based on TCP/IP protocol in each optical node are demonstrated by this optical network platform.And through the network management center,the whole hybrid transmission optical network monitoring is achieved.Finally,this paper analyses four wave mixing in few-mode fiber.The existence of few-mode nonlinear Schrodinger equation is deduced in two mode,along with up to twelve types of wave/mode distributions and their corresponding phase matching conditions.Based on the principle of suppression of four wave mixing(FWM),a dispersion monitoring method suitable for few-mode fiber is proposed.The dispersion monitoring method can monitor the dispersion by FWM which can be easily excited in few-mode fiber.The few-mode fiber transmission system is built in the simulation software Optisystem 14.0 and the fiber dispersion is monitored.The dispersion monitoring method has the advantages of real time and no need to add any equipment in the system.This paper provides theoretical and technical support for the large scale application of mode division multiplexing system based on few-mode fiber.