Numerical investigation of fiber transmission of a chaotic encrypted message using dispersion compensation schemes

A detailed numerical investigation of the transmission properties of all-optical chaotic communication systems is presented for two data-encoding techniques and for various dispersion compensation maps. A semiconductor laser subjected to optical feedback generates the chaotic carrier, and the data is encoded on it by chaotic modulation (CM) or chaotic-shift-keying (CSK) methods. The complete transmission module consists of different types of fiber, inline amplifiers, and Gaussian optical filters. Different dispersion maps based on either Nonzero dispersion-shifted fibers (NZ-DSFs) or combinations of single-mode fibers (SMF) along with dispersion-compensating fibers (DCF) were considered. The system's performance is numerically tested by calculating the Q factor of the eye diagram of the received data for 1 and 2.4 Gb/s. The influence of the optical power launched into fiber and the transmission distance to the quality of the decoded message has been investigated. The CSK scheme appears to have better performance relative to the CM scheme, while dispersion maps utilizing NZ-DSFs are superior to that employing DCF. In all encoding methods and transmission maps, a decrease in the Q factor is observed when the repetition bit rate of the encoding message and the transmission distance increases.     

光纤中的色散和非线性效应对混沌同步的影响

基于描述光反馈半导体激光器的动力学以及信号在光纤信道中传输的理论,研究了光纤中色散和非线性效应对混沌信号传输以及发射和接收激光器的混沌同步特性的影响,目的是为远程光纤混沌保密通信提供理论指导。数值模拟结果表明:光纤非线性效应只影响信号的位相,不会影响混沌信号的强度;光纤色散将使混沌信号发生严重变形,影响混沌系统的同步性能:通过在接收器的前端放置放大器以补偿光纤的损耗,信号经过200km的色散位移光纤传输后,发射和接收激光器输出混沌信号的关联系数仍可达到0.99,即系统可达到很好的同步性能。     

色散平坦光纤中的高速率PM-16QAM信号传输研究

提出了一种高速率、偏振复用、正交幅度调制信号的色散平坦光纤传输系统,传输速率分别为160 Gbps和256 Gbps,调制格式为PM-16QAM。实验研究了色散平坦光纤链路系统的传输特性,并分别与非零色散位移光纤和标准单模光纤链路传输特性做了比较。实验结果表明,较低输入光功率情况下,PM-16QAM信号在160 Gbps传输50 km时,经色散平坦光纤传输后的误差矢量幅度EVM优于经非零色散位移光纤传输情况0.5%,比特误码率BER优于非零色散位移光纤传输情况两个数量级;色散平坦光纤链路能更好地衰减旁瓣噪声;256 Gbps传输50 km和75 km时,仅在色散平坦光纤链路传输后可以较好地解调出信号;传输距离越长,保持较好特性时输入光功率范围越小。对比160 Gbps和256 Gbps情况,高速率PM-16QAM信号在色散平坦光纤链路的传输特性优于非零色散位移光纤和标准单模光纤链路的传输特性,传输速率越高、传输距离越长效果越明显。     

适合光纤通信的一种准循环LDPC编码器的实现

针对光纤通信系统中对传输速率和误码率要求的不断提高,研究了一种具有特殊结构的、适合光纤通信中高速率实现的低密度奇偶校验码(LDPC)。仿真结果表明,该LDPC码与RS(255,239)编码方式相比,可以获得约2dB的编码增益。同时,针对该LDPC码的准循环结构,该编码器结构可以有效地降低编码复杂度,并在编码实现方面采用流水线并行结构保证编码的实时性。该编码器结构已在现场可编程门阵列(FPGA)上得到了验证。实验结果表明,采用Stratix GX片内集成的高速发送端口,在单片FPGA上完成了整个编码系统的设计,该编码系统可以2.4Gbps的编码速率稳定工作。     

Theoretical model of optical fiber secure communication system with chaotic multiple-quantum-well lasers

Chaotic synchronization of injected multiple-quantum-well lasers of optical fiber system and a theoretical model of optical fiber chaotic secure communication system are presented by coupling a chaotic multiple-quantum-well laser synchroniza- tion system and a fiber channel. A new chaotic encoding method of chaos phase shift keying On/Off is proposed for optical fiber secure communications. Chaotic synchronization is achieved numerically in long-haul fiber system at wavelength 1.55 μm. The effect of the nonlinear-phase of fiber is analyzed on chaotic signal and synchronization. A sinusoidal signal of 0.2 GHz frequency is simulated numerically with chaos masking in long-haul fiber analog communication at wavelength 1.55 μm while a digital signal of 0.5 Gbit/s bit rate is simulated numerically with c1haos masking and a rate of 0.05 Gbit/s are also simulated numerically with chaos shift keying and chaos phase shift keying On/Off in long-haul fiber digital communica- tions at wavelength 1.55 μm     

4 × 10 Gbps WDM repeaterless transmission system using asymmetrical dispersion compensation for rural area applications

We demonstrate experimentally 4?×?10 Gbps wavelength division multiplexing repeaterless transmission system using non-return-to-zero differential phase-shift keying modulation format over 300-km standard single-mode fiber. The channels used were 1546.9, 1547.7, 1548.51 and 1549.2 nm with 100 GHz spacing. In this system design, a dispersion compensation module is used; multi-channel-chirped fiber Bragg grating was deployed with asymmetrical configuration with different compositions of dispersion values at the transmitting and the receiving sides. The transmission system was pumped bidirectionally with 1445 and 1455 nm wavelength in a forward direction, and three pump wavelengths of 1430, 1440 and 1450 nm are deployed for the backward direction. The total on–off Raman gain is 47 dB from total pump power of 1.862 W. The result for dispersion pre-compensation of ??2006.0 and ??2338.3 ps/nm has minimal effect on nonlinearity showing the best performance for 300-km repeaterless transmission system.     

光注入多模半导体激光器的混沌及其同步

为了在光纤通信中实现多模同步传输以提高通信容量,构建了一个光注入多模半导体激光器开环混沌通信系统,并利用MATLAB数值仿真了系统的同步性能。结果表明,选取合适的系统参量,多模半导体激光器混沌通信系统能够实现完全同步;发射激光器和接收激光器对应模式可以实现完全同步,而且系统对内部参量失配具有较好的容忍性。     

Performance of open-loop all-optical chaotic communication systems under strong injection condition

A numerical investigation of the performance of an open-loop optical chaotic communication system for the isochronous synchronization solution has been carried out, under strong optical injection conditions achieved using antireflective coating at the input facet of the receiver laser in combination with an optical erbium-doped fiber amplifier (EDFA). Different message encoding techniques have been considered and tested at multigigabit rates and for different levels of optical injection to the receiver. The effects induced by the amplified spontaneous emission (ASE) noise of the EDFA to the performance of the chaotic communication system have also been studied. The performance of all the examined encryption methods for the 1 Gb/s bit-rate messages was quite satisfactory and was characterized by Q-factor values that exceeded 10, after synchronizing in the strong injection regime. For higher message bit rates, the Q-factor values for all methods decrease considerably due to the residual frequency components of the chaotic carrier that are now more significant in the message spectral region. The effect of the amplifier's ASE noise to the system's performance was deteriorated as long as the EDFA chaotic input was kept in relatively high power levels.     

Performance of Bipolar Optical Spectral Encoding CDMA with Modified PN Codes

Experimental demonstration of bipolar spectral encoding code‐division multiple‐access with modified pseudorandom noise codes is presented. Bipolar spectral encoding is achieved with an erbium‐doped fiber amplifier amplified spontaneous emission source and arrayed waveguide gratings. The bit‐error rate performance of 1.25 Gbps signal transmission over 80 km single mode fiber is measured in a multiple‐user environment.     

混沌信号在色散光纤传输过程中的演化

研究了色散光纤混沌传输理论及混沌信号与色散光纤相互作用的物理机制;通过耦合激光混沌系统和色散光纤传输信道,提出了色散光纤混沌信号传输演化物理模型;提出混沌信号在色散光纤传输中的非线性演化频率啁啾和公式;着重分析光纤色散对激光混沌信号传输与演化的作用,色散能够展宽混沌信号脉冲,但不影响混沌信号的形状;色散能够改变混沌信号每个频谱分量相位,但不影响混沌信号频谱形状;色散能够改变混沌信号光场慢变场分量的变化,但不改变混沌信号包络时变特性,也不影响混沌信号脉冲的功率分布和场强分布;色散能够改变混沌吸引子在相空间整体旋转角度并使其旋转角度随光纤传输长度而发生改变,但不改变混沌吸引子在相空间中的内部结构.最后数值模拟了混沌信号在光纤传输过程中的相位、场慢变部分分量以及混沌吸引子等演化形式等.     

Dispersion compensation optical fiber modules for 40 Gbps WDM communication systems

Dispersion compensation was originally proposed to equalize pulse distortion.With the development of wavelength division multiplexing (WDM) techniques for large capacity optical communication systems,dispersion compensation technologies have been applied into the field.Fiber-based dispersion compensation is an attractive technology for upgrading WDM communication systems because of its dispersion characteristics and good compatibility with transmission optical fibers.Dispersion compensation fibers and the modules are promising technologies,so they have been receiving more and more attention in recent years.In this work,high performance dispersion compensation fiber modules (DCFMs) were developed and applied for the 40 Giga bit-rate systems.First,the design optimization of the dispersion optical fibers was carried out.In theory,the better the refractive index profile is,the larger the negative dispersion we could obtain and the higher the figure of merit (FOM) for the dispersion optical fiber is.Then we manufactured the fiber by using the plasma chemical vapor deposition (PCVD) process of independent intellectual property rights,and a high performance dispersion optical fiber was fabricated.Dispersion compensation fiber modules are made with the dispersion compensating fibers (DCFs) and pigtail fibers at both ends of the DCFs to connect with the transmission fibers.The DCFMs present the following superior characteristics:low insertion loss (IL),low polarization mode dispersion,good matched dispersion for transmission fibers,low nonlinearity,and good stability for environmental variation.The DCFMs have the functions of dispersion compensation and slope compensation in the wavelength range of 1525 to 1625nm.The experiments showed that the dispersion compensation modules (DCMs) met the requirements of the GR-1221-CORE,GR-2854-CORE,and GR-63-CORE standards.The residual dispersions of the G.652 transmission lines compensated for by the DCM in the C-band are less than 3.0ps/nm,and the dispersion slopes are also compensated for by 100%.With the DCFMs,the 8×80km unidirectional transmission experiments in the 48-channel 40Gbps WDM communication system was successfully made,and the results showed that the channel cost was smaller than 1.20dB,without any bit error.     

A hybrid chaotic map for communication security applications

Recently, the synchronization between two matching chaotic systems to provide confident communication has gained a lot of interest. Continuously, there is a necessity to produce a novel dynamical system to be used in synchronization to implement a strong security system. In this paper, a hybrid chaotic system is suggested and verified for the potential use of secure communication through chaos synchronization. The Lyapunov exponent (LE) and zero‐one (0‐1) tests have been used to verify the performance of the suggested hybrid chaotic system, while National Institute of Standard and Technology (NIST) tests have been applied to verify the randomness properties. And the synchronization has been achieved between master and slave systems by using nonlinear control laws. The simulation outcomes demonstration that the hybrid system has chaotic performance and outstanding randomness characteristic. The statistical results gained for LE test was 0.8822, and for frequency test (FT) was 0.2028, while for the run test (RT) was 0.1924. Accordingly, the suggested hybrid system can be used to evolve functional synchronization algorithms and encryption for image, video, and voice secure communication applications.     

The effect of chirping-induced pulse shaping on the performance of11 Gbit/s lightwave systems

The influence of laser chirping, fiber chromatic dispersion, and receiver filtering on the shape of the pulses in 11 Gb/s lightwave transmission systems is discussed. Both the NRZ and RZ encoding formats are considered as well as positive and negative dispersion. The results quantify the sensitivity of the system performance to the receiver decision time, the maximum permissible deviation of the laser wavelength from the fiber zero dispersion wavelength, and the improvement in transmission performance offered by pulse compression arising from negative dispersion     

光纤产品市场的新发展

电信网的变革促成光纤产品市场新一轮的大发展。非零色散位移单模光纤大量使用;全球光连接器和光缆组件市场到２００３年将增加到３８亿美元,双向／多纤连接器成为最快的增长点;而光纤拉曼放大器已成为开发热点,以用于１０Ｇｂｉｔ／ｓ、４０Ｇｂｉｔ／ｓ的高速光纤网。本文最后介绍了北美、中国和俄罗斯光产品需求和生产市场的特点。     

Bi-end dispersion compensation for ultralong optical communicationsystem

Bi-end dispersion compensation (DC) for ultralong nonreturn-to-zero (NRZ) optical transmission system is studied. Both the loss and dispersion of the transmission fiber are periodically compensated. Two dispersive elements are placed at the input and output ends of a compensation period, respectively, to compensate for fiber dispersion. The pulse compression owing to self-phase modulation (SPM) can be adjusted by the compensation ratios of the dispersive elements at the two ends of a compensation period. Therefore, the pulse compression can be optimized and the system performance can be improved to compare with the system with either pre- or postdispersion compensation. The rules to design the system are considered. The transmission system of 10-Gb/s bit rate, 9000-km transmission distance, and 100-km compensation period is taken as an example. The second-order fiber dispersion is assumed to be completely compensated. Wave equation is numerically solved to study the system performance which is represented by Q factor. The relations of several system parameters and Q factor are studied. The system parameters include the compensation ratios of the dispersive elements at the two ends of a compensation period, dispersion of transmission fiber, signal power, and the compensation ratios of third-order fiber dispersion. If the third-order fiber dispersion cannot be completely compensated, it is found that one can use a higher signal power to improve the system performance     

多变量耦合实现双环掺铒光纤激光器混沌同步

根据双环掺铒光纤激光器的理论模型,提出多变量单向耦合法实现混沌同步,对主从系统模型进行数学推导,研究不同参数条件下双环掺铒光纤激光器的混沌同步,得到实现混沌同步的条件,并在Simulink平台下动态仿真。结果表明,衰减系数不同的两个双环掺铒光纤激光器,主激光器通过定向耦合器驱动从激光器,主从系统可以实现精确混沌同步,且随着反馈强度的增大,实现系统混沌同步的时间越短,反馈强度的取值范围由衰减系数和耦合系数确定;选取不同的系统初值,主从系统可实现混沌同步,系统初值对达到混沌同步时间的影响可忽略不计;在主从系统中引入随机高斯噪声,主从系统仍可实现较好的混沌同步。     

Performance verification of tera-bit transmissions using 30 ch×40 Gb/s WDM signals over NZDSFs

We investigate the performance of Tbps transmissions using wavelength-division multiplexing (WDM) technologies based on the 40 Gbps line rate. To find the optimum conditions, the transmission performance is theoretically evaluated for various fiber types. To confirm modeling, the transmission performance is experimentally measured for TWF transmissions over 85 and 342 km. Bit error rates (BERs) and eye-diagrams have been calculated and measured to investigate the system performance. All the channels have characteristics of error free transmission. The calculated BERs and eye-diagrams have a good agreement with the experimental results.     

40Gbps甚短距离并行光传输技术与实验系统

介绍了40Gbps甚短距离(vsR)并行光传输系统的实现和测试.用两片Altera Stratix II GX FPGA分别实现发送/接收转换芯片,通过对FPGA内嵌的吉比特收发器的合理配置,以及在去斜移电路中采用滑动窗口生成器和共用窗口比较器的方法节省了硬件资源;基于异或定位原理,采用二分查找法大大提高了帧同步电路的...     

A study on the relationship between DWDM transmission performance and chromatic dispersion

In this letter, we numerically study the relationship between 40-Gb/s-based dense wavelength-division-multiplexing (DWDM) transmission performance and chromatic dispersion in two different transmission lines. We show that the optimum chromatic dispersion region for improving the DWDM transmission performance varies with the type of transmission line. We also show that a hybrid transmission line has a greater potential to resist any change in the dispersion slope compensation characteristics than a single fiber transmission line with a dispersion compensation fiber module. Finally, we show that chromatic dispersion of more than 12 ps/nm/km in a hybrid transmission line is optimum for a 40-Gb/s-based DWDM transmission system by taking the design of a dispersion compensating fiber into account.     

GHz Bandwidth Message Transmission Using Chaotic Vertical-Cavity Surface-Emitting Lasers

Chaotic message encoding and decoding in unidirectionally coupled vertical-cavity surface-emitting lasers (VCSELs) with polarization-preserved and polarization-selected optical injection has been studied experimentally. A GHz message has been successfully encoded in the chaotic transmitter and decoded from the receiver with polarization-preserved optical injection. In contrast decoding using polarization-selected optical injection was achieved at only 330 MHz. It has also been demonstrated that GHz message extraction can be achieved using both normal and inverse chaos synchronization thus providing an opportunity for exploiting polarization properties of VCSELs for duplexed chaotic message transmission.