Modeling of cascaded high isolation bidirectional amplification in long-distance fiber-optic time and frequency synchronization system

We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs),no spontaneous lasing even with high gain,in longdistance fiber-optic time and frequency(T/F)synchronization system.It is found that the Rayleigh scattering noise can be suppressed due to the high isolation design,but the amplified spontaneous emission(ASE)noise generated by the high isolation Bi-EDFA and the bidirectional asymmetry of the transmission link caused by the high isolation Bi-EDFA will deteriorate the stability of the system.The calculated results show that under the influence of ASE noise,the frequency instability of a 1200 km system composed of 15 high isolation Bi-EDFAs is 1.773×10^(-13)/1 s.And the instability caused by asymmetry is 2.6064×10^(-16)/30000–35000 s if the total asymmetric length of the bidirectional link length is 30 m.The intensity noises originating from the laser and detector,the transfer delay fluctuations caused by the variation in ambient temperature and the jitter in laser output wavelength are also studied.The experiment composed of three high isolation Bi-EDFAs is done to confirm the theoretical analysis.In summary,the paper shows that the short-term instability of the T/F synchronization system composed of high isolation Bi-EDFAs is limited by the accumulation of ASE noise of amplifiers and the laser frequency drift,while the long-term instability is limited by the periodic variation in ambient temperature and the asymmetry of the amplifiers.The research results are useful for pointing out the direction to improve the stability of the fiber-optic T/F synchronization system.

Fiber-based multiple-access frequency synchronization via 1f–2f dissemination

Considering the reference frequency dissemination requirements of the Square Kilometre Array telescope（SKA）project,on the basis of the 1f–2f precision frequency synchronization scheme,we propose and demonstrate a fiber-based multiple-access frequency synchronization scheme.The dissemination reference frequency can be recovered at arbitrary nodes along the entire fiber link.It can be applied to antennas close proximity to the SKA central station,and will lead to a better SKA frequency synchronization network.As a performance test,we recover the disseminated 100-MHz reference frequency at an arbitrary node chosen as being 5 km away from the transmitting site.Relative frequency stabilities of2.0×10^（-14）/s and 1.6×10^（-16）/10~4 s are obtained.We also experimentally verify the feasibility of a frequency dissemination link with three access points.

Network-Wide Time Synchronization in Multi-Channel Wireless Sensor Networks

Recent advances in wireless sensor technology have enabled simultaneous exploitation of multiple channels in wireless sensor systems. In this paper, a novel time synchronization algorithm is proposed for multi- channel Wireless Sensor Networks (WSNs) called Multi-Channel Time Synchronization (MCTS) protocol. Time synchronization is critical for many WSN applications and enables efficient communications between sensor nodes along with intelligent spectrum access. Contrary to many existing protocols that do not exploit multi-channel communications, the protocol takes advantage of potential multiple channels and distributes the synchronization of different nodes to distinct channels and thus, reduces the convergence time of synchronization processes significantly.

Synchronously Pumped Mode-Locked 1.89 μm Tm-Doped Fiber Laser with High Detuning Toleration

We propose and demonstrate a synchronously pumped mode-locked Tm-doped fiber（TDF） laser without any extra mode-locking elements. Pumped by a 1.56 μm pulse fiber laser, the TDF laser generates 1.17 ps pulses with a spectral width of 9.7 nm and a repetition rate of 9.33 MHz. The emission wavelength is tunable along with the cavity length detuning in a wide range of 3 mm. The high detuning toleration is beneficial to achieve high temperature and vibration stability in all-fiber configuration lasers.

Experimental Investigation on Dual Wavelength High-Frequency Chaos Generation and Synchronization

双波长高周波的混乱在做耳的纤维戒指激光基于非线性的效果被产生，在悦耳的过滤器(TF ) 被用来选择收到纤维的 wavelength.A 的地方，有开环的结构的激光作为播送纤维激光与相同参数被构造。由在收到的纤维激光调节 TF 和纤维延期线，混乱同步在任何人被观察了在混乱以后的二波长在 1 km 上被播送。具有远方到达重要性构造高能力混乱通讯系统。

光纤时间频率同步技术及应用

时间是人类目前测量和复现不确定度指标最高的物理量,代表了人类科技发展的最高水平。光纤时频同步技术经过几十年的发展,目前已广泛应用于量子计量、射电干涉测量、定位导航、现代通信、电力电网、高能物理、大地测量等诸多领域,成为人类社会高效运行的重要支撑。得益于光纤时频同步技术的高可靠性和高稳定度,综合原子时“分布式”和“实时性”这一长期存在的矛盾得到了解决。文章介绍了光纤时频同步技术的发展历史、各技术路径的研究现状,以及基于北京地区光纤时频同步网生成的分布式实时综合原子时。在此基础上,指出光纤时频同步的发展重点正从技术研究转为大规模网络化应用,开展基于光网络的多功能、多应用融合研究,实现一体化通信、感知、计算、测量、控制,将是未来的重要发展趋势。

超微粉碎/NaOH同步处理麦秸纤维素分离特性研究

为了探究超微粉碎/NaOH同步处理对小麦秸秆纤维素分离及其微观形貌结构和热稳定性的影响,将小麦秸秆与质量分数6%的NaOH溶液按照料液比0.1 g/mL混合,进行了不同时长的超微粉碎/NaOH同步处理,并使用1.4%酸性亚氯酸钠溶液漂白和水浴式超声处理,分离得到纤维素纤维。系统表征了不同处理时长对小麦秸秆木质纤维素分离以及小麦秸秆纤维素微观形貌、晶体结构和热稳定性影响。结果表明:在同步处理0~60 min范围内,机械力显著降低了麦秸样品的粒度,有效促进了秸秆木质纤维组分分离;经不同时长超微粉碎/NaOH同步处理后分离获得的小麦秸秆纤维素中,大量微米和纳米纤维素呈相互缠绕的网状分布;随处理时间延长,纤维素结晶度先降低后趋于稳定,处理30~60 min是纤维素结晶度降低的转折点;Person相关性分析结果表明,小麦秸秆纤维素热稳定性与其结晶度以及处理时长呈现显著相关性(P<0.05)。

Chaos synchronization of semiconductor lasers over 1040-km fiber relay transmission with hybrid amplification

Optical chaos communication and key distribution have been extensively demonstrated with high-speed advantage but only within the metropolitan-area network range of which the transmission distance is restricted to around 300 km.For secure-transmission requirement of the backbone fiber link,the critical threshold is to realize long-reach chaos synchronization.Here,we propose and demonstrate a scheme of long-reach chaos synchronization using fiber relay transmission with hybrid amplification of an erbium-doped fiber amplifier(EDFA)and a distributed fiber Raman amplifier(DFRA).Experiments and simulations show that the hybrid amplification extends the chaos-fidelity transmission distance thanks to that the low-noise DFRA suppresses the amplified spontaneous emission noise and self-phase modulation.Optimizations of the hybrid-relay conditions are studied,including launching power,gain ratio of DFRA to EDFA,single-span fiber length,and number of fiber span.A 1040-km chaos synchronization with a synchronization coefficient beyond 0.90 is experimentally achieved,which underlies the backbone network-oriented optical chaos communication and key distribution.

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。

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。

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.

Fiber-Optically Triggered Four Parallel GaAs Photoconductive Semiconductor Switches

Four parallel GaAs photoconductive semiconductor switches （PCSSs） were triggered simultaneously by four 1064 nm laser beams. The transient characteristics of four linear electrical pulses were investigated. When the energy of four laser beams were 16.4 m J, 15.6 m J, 15.3 m J, and 13.7 m J, respectively, four stable electrical pulses of about 25 ns width and 10 ns rise time were obtained at the same bias voltage of 8 kV. The maximum switching voltage amplitude was 3.8 kV. With the triggering pulse energy and bias voltage kept constant, the three GaAs PCSSs were triggered at 10 Hz laser pulse. The method of synchronization calculation was given, and the synchronization of four parallel GaAs PCSSs was calculated to be 79 ps. The influence of bias voltage and laser energy on the voltage amplitude of electrical pulse was analyzed. Furthermore, relationship between the synchronization and the jitter time was also discussed.

Wireless Infrared Pyrometer with Fiber Optic: Construction and Processing Algorithms

In this paper, developed wireless portable infrared pyrometer with dual channel fiber optic is described. The pyrometer measures surface temperature in wide infrared spectral range of 2 - 25 um. A data processing algorithm based on the methods of synchronous detection providing

Fiber Optic 3-D Space Piezoelectric Accelerometer and its Antinoise Technology

The mechanical structure of piezoelectric accelerometer is designed, and the operation equations on X , Y , and Z axes are deduced. The test results of 3 D frequency response are given. Noise disturbances are effectively eliminated by using fiber optic transmission and synchronous detection.

光纤网时间同步性能计量校准装置研制

为解决光纤时间传递系统中存在的远距离传递准确度低的问题,分析了环回法、双纤双向时间同步、双向波分复用、双向时分复用四种主流的高精度光纤时间传递方法的基本原理和技术特点,在此基础上研制了单信道时频传递装置。该装置采用电学相位补偿法实现频率传递同步,采用环回法与时分复用相结合的方法实现时间传递同步;使用1秒脉冲(Pulse Per Second,PPS)和100 MHz共同标记时刻信号,其中1 PPS作为时刻粗标记,100 MHz作为时刻细标记,实现高精度时间同步。经实验证明,单信道时频传递装置的不确定度约为13 ps,能够满足现有光纤时频同步网计量校准的要求。该装置在多级时间传递同步、光纤时频同步网计量校准等领域中具有广阔的应用前景,为建设高稳定性、高可靠性和高精度的授时体系提供了重要技术支撑。

冲击波超压测试系统的时基高精度同步

针对存储式冲击波超压测试系统时基不能高精度同步的问题,提出一种光纤触发与高精度算法结合的处理方法。利用光纤对不同装置同时发出触发信号,实现多个装置的同步触发;计数频率远大于测试装置的采样频率,对触发时刻和触发后第一个采样时刻之间的时间间隔进行计数;对相邻两个采样点之间进行插值处理,根据计数值N确定测试数据在时间轴上的位置,实现时基的高精度同步。该方法可使得测试系统在12 m布场距离处触发响应时间小于150 ns,测试系统的时间误差为30 ns,测试装置之间的同步误差为20 ns。该方法提高了测试系统的测量精度,可为冲击波传播规律的研究提供依据。

基于光纤与可见光结合的短距分布式时间同步方案

针对局域分布式时间同步的需求,提出了一种基于光纤和可见光结合的短距分布式时间同步方案。融合了光纤时间同步高精度与可见光时间同步高灵活性的优势,设计了相应的时间同步端机,并进行了分布式实验。实验结果表明:当光纤链路长度为3 km时,光纤时间同步从端与光纤时间同步主端的3σ钟差优于448 ps,时间同步秒稳优于150 ps,万秒稳优于4 ps;当光纤链路长度为1 km、可见光链路长度为5 m时,可见光时间同步从端与光纤时间同步主端的3σ钟差优于1.8 ns,时间同步秒稳优于400 ps,万秒稳优于15 ps。

Chaotic laser synchronization and its application in optical fiber secure communication

In this paper, optical fiber chaotic secure communication is proposed bycoupling chaotic laser synchronous system with optical fiber propagation channel.Feedback synchronous system of chaotic semiconductor lasers is presented andsynchronous error and decoding formulae are demonstrated. Synchronization betweentwo chaotic laser systems with distributed feedback semiconductor lasers at wavelengthof 1.31 μm is simulatively achieved with almost zero synchronous error. Parametermismatch, synchronous transient response and noise effect on the system are studied.Robustness of synchronization and anti-perturbation can increase by increasing thefeedback coefficient of the system. Influence of group-velocity-dispersion and self-phasemodulation of optical fiber on chaotic laser signal and synchronization are analyzed, and itis found that group-velocity-dispersion affects pulse shape, synchronization and decoding,and limits optical fiber propagation distances, and self-phase modulation does not affectpulse shape, while its product of nonlinear phase shift can affect synchronization anddecoding, and restrict propagation distances of optical fiber chaotic communicationsystem and hence the maximum optical power formula is educed. Injecting parametermodulation and amplitude modulation are numerically simulated in long-haul optical fibersecure communication systems.

Simultaneous frequency transfer and time synchronization over a 430 km fiber backbone network using a cascaded system

Based on dense wavelength-division multiplexing technology, frequency transfer and time synchronization are simultaneously realized over a compensated cascaded fiber link of 430 km, which is a part of the Beijing- Shanghai optical fiber backbone network. The entire cascaded system consists of two stages with fiber links of 280 and 150 km, respectively. To keep high symmetry and low noise, specific bi-directional erbium-doped fiber amplifiers are used to compensate the large optical attenuation of each fiber link. When the compensation servo is active in every stage, the cascaded system achieves the stability of 1.94 × 10-13 at I s and 1.34 × 10-16 at 104 s, for frequency transfer. It is also verified that the actual results of the cascaded system are in good agreement with the theoretical ones calculated from error theory. Simultaneously, after calibration of each stage, time synchronization is also realized. The final accuracy of the whole system is within 94 ps.