On Some Problems Of Future Passive Optical Network

With the advent of the information society, in the face of the requirements of the business services and the explosive growth of broadband demand, the existing optical fiber communication networks face huge challenges. People are studying next-generation networks to meet the expansively growing need. COF-PON system with a convenient, low cost and other advantages and OFDM-PON system which have high spectrum efficiency, anti-multipath interference and other advantages are very attractive to the new generation of passive optical network systems. Although both networks have a lot of advantages, there is inadequacy. Such as in COF-PON system, there is the multi-user access interference effect at the receiving end; in OFDM-PON system, peak to average ratio is relatively large, which is an important factor affecting system performance.For each of the above two issues, in this paper, we put forward the corresponding solution, and the main contents include:(A)As for the above-mentioned problem in COF-PON system, we propose to use the logical operations to avoid the multi-user access interference at the receiving end. At the transmitting end, the signal becomes the binary bits into the sub-carrier modulation after a logic OR gate; At the receiving end, in order to obtain the desired signal, we will put the corresponding carrier channel signal in the procession of logical AND operation. In order to be able to correctly receive the transmitted signal, we designed an appropriate set of code words and added some non-door in the appropriate positions of the transmitting terminal. By simulation, the proposed new system is proved feasible and consistent with the requirement to eliminate the multi-user access interference at the reception side.(B) As for OFDM-PON system, we propose to increase the operation of reducing the maximum value and the positioning operation in transmitter. After a certain processing, the OFDM symbol after IFFT is a sequence of real numbers. Then find the maximum point in each symbol in a given number of symbols, and record the position and reduce its value to half; the position information is recorded in4order3-bit signals and combined into a new OFDM symbol which is placed in front of the other symbols to form a frame of OFDM signal. Doing the corresponding inverse operation at the receiving end, will be able to restore the signal. By the comparison between simulations, we can see that, the peak-to-average power ratio of the new system has been a certain decline and the EVM is narrowed, so the system performance effectively improved.