A novel non-return-to-zero (NRZ) to return-to-zero (RZ) format converter is proposed and demonstrated through an optical simulation software. This converter first adopt a polarizer modulator (PolM), to polarizer modulate the input NRZ signal, then a RF clock signal is used to restrain the side-lobes, thus to achieve NRZ/RZ conversion. The proposed converter features a convenient way to adjust the duty cycle of the output RZ signal, a same wavelength before and after converter, a very small time-jitter, high conversion efficiency, low cost and some other advantages, which could be expected to have an extensive use in high-speed optical communication networks.

-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.

-A method was proposed to implement data extraction using AND optical gate operation on semiconductor optical amplifier (SOA) based nonlinear optical loop mirror (NOLM). The optical data extraction in FSK/ASK orthogonal modulation system was achieved with the proposed AND gates, in order to prove its feasibility. Through the simulation, the data extraction in orthogonal modulation system with a 10Gbit/s NRZ pseudo-random payload signal and 2.5Gbit/s label signal was demonstrated.Index Terms -Optical label, optical logic gate, orthogonal modulation, semiconductor optical amplifier. I . IntroductionOptical swapping and optical computing are the core unit to achieve all optical signals processing in future all optical networks, they all based on optical logic gates, which are core devices to implement optical swapping system and the key factor of decision network performance. All optical logic gates(XOR、AND)are indispensable part for all optical signal processing,which can be used in all-optical clock recovery, alloptical demultiplexing, all-optical data extraction, etc. Therefore, it has great application potential in future all optical high speed communication network and new generation optical computing.At present, the research of all optical logic gates are focused on the using of nonlinear effect of optical fiber and semiconductor optical amplifier. The nonlinear effect of optical fiber is weak, so that the logic gates based on nonlinear effect of optical fiber will achieve idea effect only by high power input signal or long fiber. SOA become the main functional device to implement all kinds of optical logic gates, because it has many advantages such as small in size, easy to integrate, short response time and strong nonlinear effect. Taking the nonlinear effect advantage of SOA can realize many kinds of optical logic gates, but the design scheme to realize AND gate is relatively less, for example, using twolevel SOA's cross gain modulation effect implementing AND gate, using Mach-Zehnder interferometer based on SOA implementing AND gate, etc. optical data extraction is an important part in optical label swapping system, it is the key factor for all optical network. At present, there have been many design and experiment scheme about optical data extraction. These schemes have it own advantages, but they also have some disadvantages. Article [1] realized all optical data extraction by using start bit in data packet generating address. This method has the advantage of easy to realize and doesn't need complicated clock recovery module; but the realization of control pulse division module is closely related to the length of the packet address, it is needed to increase or decrease the same number of delay fiber when the length of address is increased or decreased. Article [2] realize data extraction from packet through the switch module which are consisted of Mach-Zehnder interferometer based on two-level SOA and Fabry-Perot filter, clock recovery module and address-data separation module; this scheme has ...