Research On The Application Of New Modulation Code Signals In Broadband Access Systems

Recently,the emerging access business based on the Internet drives people on the increasing demand for communication access bandwidth,and optical fiber access and has become the most promising access technology in broadband access network due to its large transmission capacity,low cost,no electromagnetic radiation.Different modulation formats have different dispersion and nonlinearity effect in the process of transmission,and different modulation formats directly affect the bandwidth efficiency.Hence,the suitable modulation format selection in optical access systems is not only one key factor to improve the quality of sending and receiving signals,but also an effective way to increase channel transmission capacity.In this paper,the most widely used passive optical network(PON)system is introduced relatively,then the historical inevitability of using PONtechnology is explained,and the typical composition of PON system is described.The two PON mainstream application mode are elaborated respectively:Ethernet Passive Optical Network(EPON)and Gigabit Passive Optical Network(GPON).And the modulation and demodulation principles of various critical modulation formats are described in detail in optical access system.The application of new modulation type is mainly studied in the article,and different duty cycle return to zero-4ary pulse amplitude modulation(RZ-4PAM)optical signal access systems and the chirped return to zero-4ary pulse amplitude modulation(CRZ-4PAM)optical access system are proposed and set up.By the comparative analysis of the eye diagrams and bit error rate(BER)of different duty cycle RZ-4PAM and CRZ-4PAM signal before and after transmission,the research results show that 66%RZ-4 PAM siginal can transfer a greater distance and have a higher bandwidth efficiency.Finally,the correlation filter and polarization multiplexing technique respectively are adopted to improve the existing optical network unit(ONU)configuration in a full duplex optical access system,both can effectively save operating costs in some degree.Moreover,the research results show that,the reception quality of optical access signals in the colorless ONU scheme with polarization multiplexing technology is better than the method using filter,especially the BER value of the uplink is lower.