Research And Application Of Optical Access System Based On EPON+EOC

With the elevation of communication technique, the transmission bandwidth of core net is increased rapidly for the development of SDH. But the capacity of access network limited by transmission medium is still inadequate, that can not meet the demand of user in the service of television, data, speech, etc. Therefore, none but overcome the bottleneck of access network bandwidth, the whole net could exert the effect of wide band efficiently to promote the development of broad band service.So far, fiber is the best transmission medium. Compared with other access techniques, fiber has the advantage of wider bandwidth, which can provide as high as 75000 Gb/s transmission speed. Fiber access network has the following features:good transmission quality, long transmission distance, antijamming capability, high network reliability, saving pipeline resource, etc. Accordingly fiber access technique is the optimum access network scheme.Passive Optical Networking (PON) technique has great potential in optical access network and PON technique went through narrowband PON to APON, from EPON to GPON. Currently, EPON that integrates the merits of PON technique and Ethernet has the following advantages:low cost, wide band, expansible, compatible, easy to manage, etc. EPON attracts more concern for above reasons. EPON is a fiber access technique which adopts point to multipoint network frame, passive optical fiber transmission, down stream adopting broadcast, upstream adopting TDMA to realize duplex transmission fiber.Ethernet Over Coax (EOC) technique combines IP signal and CATV signal into a complex signal which is sended to the user on a coaxial-cable sending. It would not influence the transmission of CATV signal and has duplex broad band integrated service access. The network access scheme based EOC is flexible. The basic principle of EOC is plotting out different frequency spectrum to transmit up and down signal separately beyond the CATV signal frequency spectrum. By comparison, the difference between diverse EOC schemes are data transmission band and modulation mode. Accordingly, there are two modulation methods, non-source base band transmission and source modulation transmission. Based on the features of EPON and EOC, EPON+EOC access scheme is proposed to provide integrated service such as CATV, IP data to the user. IP light signal is carried to community light terminal by EPON network while CATV light signal is sent from transmitter to community light terminal by fiber. These two signals are delivered from light terminal to the user by EOC. Thus the whole transmission service is accomplished. The wavelength of up and down light is 1310nm and 1490nm. The wavelength of CATV is 1550nm. The experiment platform was constructed based on EPON+EOC access scheme and the relative test was processed on the platform.At present, CATV network adopts fiber and coaxial-cable mixed transmission network. It has abundant bandwidth resource and mainly uses single way broadcasting mode. In order to take full advantage of bandwidth to realize the interact access, duplex alternation should be processed. The EPON+EOC scheme is more appropriate than others in practical application because the framework of present HFC network is similar to EPON network. The advertent problems in the process of project design were described and an engineering example was shown in the paper. Finally, the conclusion and prospect about EPON+EOC technique were discussed.