A NEW DECODER OF SYNCHRONOUS OPTICAL CODE DIVISION MULTIPLE ACCESS SYSTEMS USING SEGMENTED CORRELATION

A new segmented correlating decoder of synchronous optical CDMA using modified prime sequence codes is proposed. The performance of the proposed system is analyzed under the assumption of Poisson shot noise model for the receiver photodetector. The decoder technique is shown to be more effective to improve the bit error probability performance than the method using an optical hard-limiter.

A 45-μJ,10-kHz,burst-mode picosecond optical parametric oscillator synchronously pumped at a second harmonic cavity

A novel high-energy picosecond optical parametric oscillator(OPO)was realized by placing an OPO in a secondharmonic(SH)cavity.In a proof-of-principle experiment,we demonstrated excellent burst energy of 45μJ for the OPO signal at 900 nm that operates at a pulse repetition rate of 10 k Hz and a pulse width of 46.8 ps.The beam quality was measured as M_(x)^(2)=1.44 and M_(y)^(2)=1.40 in the orthogonal directions,corresponding to an average beam factor M^(2)=1.42.So far,this study is the first to investigate high-energy ps OPO synchronously pumped in a second-harmonic cavity.

Chaos synchronization in injection-locked semiconductor lasers with optical feedback

Based on the rate equations, we have investigated three types of chaos synchronizations in injection-locked semiconductor lasers with optical feedback. Numerical simulation shows that the synchronization can be realized by the symmetric or asymmetric laser systems. Also, the influence of parameter mismatches on chaos synchronization is investigated, and the results imply that these two lasers can achieve good synchronization, with smaller tolerance of parameter mismatch existing.

High power,widely tunable femtosecond MgO:PPLN optical parametric oscillator

We demonstrate a high power,widely tunable femtosecond MgO-doped periodically poled lithium niobate(MgO:PPLN)optical parametric oscillator(OPO)at 151 MHz,pumped by a Kerr-lens mode-locked Yb:KGW laser.With a maximum pump power of 7 W,the OPO is capable of delivering as high as 2.2 W of the signal centered around 1500 nm with tunable signal spectrum ranges of 1377 nm-1730 nm at an extraction efficiency of 31.4%,which exhibits a long-term passive power stability better than 0.71%rms over 4 h.The maximum idler bandwidths of 185 nm at 3613 nm are obtained across the idler tuning ranges of 2539 nm-4191 nm.By compensating intracavity dispersion,the signal has the shortest pulse duration of 170 fs at 1428 nm.

Controlling and synchronizing spatiotemporal chaos of the coupled Bragg acousto-optical bistable map system using nonlinear feedback

In this paper we present the control and synchronization of a coupled Bragg acousto-optic bistable map system using nonlinear feedback technology. This nonlinear feedback technology is useful to control a temporally chaotic system as well as a spatiotemporally chaotic system. It can be extended to synchronize the spatiotemporal chaos. It can work in a wide range of the controlled and synchronized signals, so it can decrease the sensitivity down to a noise level. The synchronization can be obtained by the analysis of the largest conditional Lyapunov exponent spectrum, and easily implemented in practical systems just by adjusting the coupled strength without any pre-knowledge of the dynamic system required.

Timing Synchronization Method for Asymmetrically Clipped DC Biased Optical OFDM System

In a typical intensity-modulated direct-detection optical system, the information is carried on the intensity of the optical signal, and therefore can only be positive. Existing synchronization methods for RF-based OFDM system cannot be used directly in asymmetrically clipped DC biased optical of DM (ADO-OFDM) system. In order to solve the above problem, according to the characteristics of ADO-OFDM signal, the modified training symbol is presented. The simulation results show that the modified synchronization method gives good performance.

Design and Realization of Phased Array Radar Optical Fiber Transmission System

One optical fiber transmission system is designed. The modularization optical fiber transmission adapters were utilized in the system, so the system structure could be flexibly sealable. The sub-array adapter and signal processor adapter were designed and realized utilizing the new field programmable gate array （FP- GA） which could drive the optical transceiver. The transmission agreement was designed based on the data stream. In order to solve the signal synchronization problem of the optical fiber transmitted phased array radar, a method named synchronous clock was designed. The fiber transmission error code rate of the system was zero with an experimental transmission velocity of 800 Mbit/s. The phased array radar system has detected the airplane target, thus validated the feasibility of the design method.

Synchronous implementation of optoelectronic NOR and XNOR logic gates using parallel synchronization of three chaotic lasers

The parallel synchronization of three chaotic lasers is used to emulate optoelectronic logic NOR and XNOR gates via modulating the light and the current. We deduce a logical computational equation that governs the chaotic synchronization, logical input, and logical output. We construct fundamental gates based on the three chaotic lasers and define the computational principle depending on the parallel synchronization. The logic gate can be implemented by appropriately synchronizing two chaotic lasers. The system shows practicability and flexibility because it can emulate synchronously an XNOR gate, two NOR gates, and so on. The synchronization can still be deteceted when mismatches exist with a certain range.

Chaos-based Applications in Secure Optical Communications

A comprehensive study of an all-optical chaotic communication system,including experimental realization,real-world testing and performance characterization through bit-error-rate analysis,is presented.Pseudorandom bit sequences that are effectively encrypted in a broadband carrier produced by a chaotic emitter and sent for transmission are recovered at the receiver side.Bit-error-rate(BER) values as low as 10-7 for 1 Gb/s data rate have been achieved.Different data code lengths and bit-rates at the Gb/s region have been tested.The application of optical transmission using 100km fiber spools in an in-situ experiment and 120km in an installed optical network showed that transmission effects do not act as a considerably deteriorating factor in the final performance of chaos-based optical communication systems.

Multi-target ranging using an optical reservoir computing approach in the laterally coupled semiconductor lasers with self-feedback

We utilize three parallel reservoir computers using semiconductor lasers with optical feedback and light injection to model radar probe signals with delays.Three radar probe signals are generated by driving lasers constructed by a threeelement laser array with self-feedback.The response lasers are implemented also by a three-element lase array with both delay-time feedback and optical injection,which are utilized as nonlinear nodes to realize the reservoirs.We show that each delayed radar probe signal can be predicted well and to synchronize with its corresponding trained reservoir,even when parameter mismatches exist between the response laser array and the driving laser array.Based on this,the three synchronous probe signals are utilized for ranging to three targets,respectively,using Hilbert transform.It is demonstrated that the relative errors for ranging can be very small and less than 0.6%.Our findings show that optical reservoir computing provides an effective way for applications of target ranging.

Real-Time Upstream Services Demonstration in Orthogonal Frequency Division Multiplexing- Passive Optical Network System

In recent years,dual-homed topologies have appeared in data centers in order to offer higher aggregate bandwidth by using multiple paths simultaneously.Multipath TCP(MPTCP) has been proposed as a replacement for TCP in those topologies as it can efficiently offer improved throughput and better fairness.However,we have found that MPTCP has a problem in terms of incast collapse where the receiver suffers a drastic goodput drop when it simultaneously requests data over multiple servers.In this paper,we investigate why the goodput collapses even if MPTCP is able to actively relieve hot spots.In order to address the problem,we propose an equally-weighted congestion control algorithm for MPTCP,namely EW-MPTCP,without need for centralized control,additional infrastructure and a hardware upgrade.In our scheme,in addition to the coupled congestion control performed on each subflow of an MPTCP connection,we allow each subflow to perform an additional congestion control operation by weighting the congestion window in reverse proportion to the number of servers.The goal is to mitigate incast collapse by allowing multiple MPTCP subflows to compete fairly with a single-TCP flow at the shared bottleneck.The simulation results show that our solution mitigates the incast problem and noticeably improves goodput in data centers.

IPRAN网络下5G时间同步优化方案研究

针对5G基站采用GPS同步方式时成本高、安全性低等问题,提出一系列的解决方案。首先,用双模模块解决卫星授时的安全性问题。其次,采用有源功率分配和无源功率分配方案解决卫星天线安装受限问题,并降低建设成本。在无法安装卫星天线的情况下,采用1588v2技术在IPRAN接入环内部署主从时钟源。该方案可以满足100 ns的同步精度需求,并且可以大幅度降低5G时间同步的部署成本,对5G时间同步技术的优化和部署有一定的借鉴作用。

长距离光纤频率级联传递技术发展现状及其在电力系统中的应用

我国电力系统自动化技术与智能电网的建设与发展对长距离时频传递精度与可靠性提出更高需求。地基光纤授时由于其传输媒介具有抗干扰能力强和抗毁性高等优点,结合级联传递技术,可为长距离、高稳定、高可靠的频率传递提供坚实保障。文章详细总结分析了近些年国内外光纤频率级联传递系统架构和发展现状,并对未来长距离光纤频率传递技术的发展趋势及其在电力系统中的应用前景进行展望,为天地互备的时频同步网建设提供支撑。

超宽调谐(2.6~5μm)中红外皮秒脉冲激光的研究

在超快脉冲激光中,超宽调谐通常应用于超连续谱产生、光谱分析和调制等多个领域。文章利用皮秒脉冲同步泵浦技术,搭建了一种基于MgO:PPLN晶体的“Z”形光参量振荡器,通过具有扇形周期极化的晶体在中红外波段产生了高功率、波长超宽调谐(2.6~5μm)的皮秒脉冲激光源输出。该振荡器由五镜一晶体组成,这五镜片的选择和精确调整是提高光参量振荡器输出性能的关键因素,采用波长为1.064μm的Nd:YVO_(4)皮秒脉冲激光源,选择周期在26~32μm可调谐的MgO:PPLN晶体,最大泵浦功率为15W时,2.66μm、3.44μm和4.99μm处获得了最大输出功率分别为3.41W、2.78W和0.52W的闲频光,相应的光-光转换效率分别为58%、55%、15%,测量到中红外光谱谱宽为2.37nm(2615nm)、Δλ=1.87nm(3687nm)、Δλ=1.30nm(4992nm),观察到在没有任何窄化光学元件条件下长脉冲随波长光谱谱宽具有线性变窄的过程。在2.6~4.5μm波段的激光输出功率均大于1W,实现了高功率,波长超宽调谐的中红外皮秒激光的连续输出。窄谱宽超宽调谐中红外皮秒脉冲激光为超快过程研究和应用领域提供了一种强大的工具。通过优化波长调谐范围和脉冲宽度能够满足不同领域对中红外激光的高要求,对推动相关领域的研究和发展至关重要。

光波导输入的双通道同步定标虚拟成像相位阵列光谱仪

激光频率梳定标的虚拟成像相位阵列光谱仪有潜力同时实现超高光谱分辨率与波长定标精度,对于天文光谱探测有重要意义。然而,现有的研究工作中,虚拟成像相位阵列光谱仪采用常规的双通道光纤输入模式,在受环境干扰时,两个通道的同步性较差,相对漂移严重,从而降低了光谱仪的重复性定标精度。为解决该问题,提出一种以光波导作为输入器件的双通道虚拟成像相位阵列光谱仪,利用波导通道之间相对稳定的特性,实现更高水平的同步定标精度。通过对不同环境下光谱仪的稳定性进行研究得出,在相似的测试条件下,波导输入的虚拟成像相位阵列光谱仪的重复性定标精度明显优于光纤输入时的定标表现。

基于OTN技术的电力光通信网络延时误码修正技术

为了保证电力大数据的完整和安全传输,并保证该数据的传输时效性,研究基于OTN技术的电力光通信网络延时误码修正技术。分析电力光通信网络中的延时和误码特性,结合分析结果和电力企业对光通信网络的传输需求,采用OTN技术优化电力光通信网络,保证电力大数据的传输可靠性。测试结果显示:混频效应指标结果均高于0.922,误码率指标均低于0.0085%;主、从时钟的最大偏差和平均偏差结果最大值分别为0.0031 ms和0.0007 ms;接收端风险均衡度和接收业务风险度的最高值分别为3.4%和1.05%,保证电力大数据传输时效性和完整性。

煤矿变电站纵差防越级跳闸保护装置的设计及实验测试

为解决供电系统中下级变电所线路故障使上级变电所跳闸的越级跳闸故障,在分析供电系统的基础上,提出在供电网络中应用基于光纤通信的纵联差动防越级跳闸保护技术。重点研究光纤电流纵差防越级跳闸保护技术的原理,设计防越级跳闸保护装置,并基于实验平台测试该装置的性能,发现其能处理越级跳闸故障。

电力通信SDH光纤传输网建设及应用

同步数字体系(Synchronous Digital Hierarchy,SDH)光纤传输网在电力通信中扮演着至关重要的角色。光纤传输网凭借其高带宽、大容量以及高可靠性的特性,已成为电力通信的骨干网络技术。该技术支持电力系统的远程控制、实时监测以及灾难恢复等关键功能,显著提高了电力系统的运行效率和服务质量。通过分析SDH技术的基本概念、建设流程及其在电力通信中的应用,揭示SDH光纤传输网对于电力系统稳定运行的重要贡献,并对其未来发展趋势进行展望。

Synchronously pumped femtosecond optical parametric oscillator at 1053 nm

A femtosecond optical parametric oscillator synchronously pumped by a Ti:Sapphire oscillator is reported.By the cavity length tuning,the signal wavelength is continuously tuned from 1000 to 1200 nm.The average output power of 32 mW is obtained at 1053 nm.The pulse width is measured to be 342 fs by intensity autocorrelation method.In addition,we observed bichromatic emission during the cavity length tuning process.

Joint transfer of time and frequency signals and multi-point synchronization via fiber network

A system of jointly transferring time signals with a rate of 1 pulse per second （PPS） and frequency signals of 10 MHz via a dense wavelength division multiplex-based （DWDM） fiber is demonstrated in this paper. The noises of the fiber links are suppressed and compensated for by a controlled fiber delay line. A method of calibrating and characterizing time is described. The 1PPS is synchronized by feed-forward calibrating the fiber delays precisely. The system is experimen- tally examined via a 110 km spooled fiber in laboratory. The frequency stabilities of the user end with compensation are 1.8x 10-14 at 1 s and 2.0x 10-17 at 104 s average time. The calculated uncertainty of time synchronization is 13.1 ps, whereas the direct measurement of the uncertainty is 12 ps. Next, the frequency and 1PPS are transferred via a metropoli- tan area optical fiber network from one central site to two remote sites with distances of 14 km and 110 km. The frequency stabilities of 14 km link reach 3.0x 10-14 averaged in 1 s and 1.4x 10-17 in 104 s respectively; and the stabilities of 110 km link are 8.3 x 10-14 and 1.7 x 10-17, respectively. The accuracies of synchronization are estimated to be 12.3 ps for the 14 km link and 13.1 ps for the 110 km link, respectively.