The Design of Optical Fiber Transmission System Based on DCDM

Abstract

In this paper,we introduce a new technology named Duty Cycle Division Multiplexing(DCDM) which realizes multiplexing by assigning each user a different RZ duty cycle. Multiplexing and demultiplexing principle of DCDM are analyzed. And we design demultiplexer of DCDM system using Matlab. In order to verify the feasibility of DCDM, Here we have designed a optical fiber transmission system which is based on DCDM of three users by Joint simulation with Optisystem and Matlab.And simulation result shows the feasibility of the system. Index Terms DCDM, Multiplexing, demultiplexer, MATLAB. I . Introduction Multiplexing technology is a technology that allows multiple users to share one signal transmission channel to improve the transmission performance of optical fiber communication system .In existing systems.the most commonly used Multiplexing technique in practice are Wavelength Division Multiplexing (WDM),Time-Division Multiplexing(TDM), or code-division multiplexing (CDM). Even though WDM contributes grate efficiency, it is still quite far to get the electrical communication systems efficiency.In WDM systems, only one user can transmit data over a single carrier. In TDM systems,different users share a single optical carrier by signing each user at different time slot, resulting shorter pulse width.Thus, a high speed multiplexer and demultiplexer is required for TDM systems. And very high speed electronic component is required for multiplexer circuits, which results in a complicated and costly system. ] 1 [ Realizing these problems, An new multiplexing technique is proposed in this paper named duty cycle division multiplexing(DCDM), It based on Return-to-Zero (RZ) duty cycles and realized by different users assigned different RZ duty cycles .in this communication system where multiple data streams are transmitted simultaneously through a single fiber. This technique can be implemented in both wireless and wired communication systems, and it allows for better clock recovery. Here we have designed a optical fiber transmission system which based on DCDM of three users by Joint simulation of Optisystem and Matlab,And simulation result shows the feasibility of the DCDM system. II . Working Principle In DCDM,different users can share communication media and transmit data simultaneously using the same frequency band while each user signed with different duty cycle. Here we analyze the Multiplexing and demultiplexing principle of DCDM by a three users optical fiber transmission system. 0.25,0.5,0.75 are the RZ duty cycles assigned to the three users respectively,as the figure 1 (a), (b), (c)shows, Eight possible combinations of bits for 3 users are 10101010, 11001100, 00001111, and they are all period signals.These signals can be multiplexed by adding them up in the time axis as shown in Figure1(d) .The system can be extended to n users,1/n, 2/n, ..., (n-1)/n can be the RZ duty cycles made to n users in System of N user signals,the principle of Multiplexing and demultiplexing is just the same with the three users system..