利用光锁相环路实现40 Gb/s时钟恢复

提出并建立了一种新型的基于光纤四波混频效应和压控光脉冲源的光锁相环路(OPLL),用于光时分复用系统(OTDM)中的时钟恢复过程。从理论上分析了其工作原理,及各模块结构和功能。利用高非线性光纤中的四波混频效应实现全光鉴相器,有效缩短了光纤长度,减小了光纤色散引起的脉冲走离,鉴相器消光比超过30 dB。采用再生锁模光纤激光器实现压控光脉冲源,在保证脉冲质量的前提下,重复频率调节范围达到380 kHz。在40 Gb/s时钟恢复实验中,获得脉宽为7.2 ps、接近变换极限的时钟脉冲,时间抖动(RMS)为152 fs,超模抑制比大于60 dB。实验证明,输入信号幅度波动和码型效应对环路影响很小。     

Signal design using nonlinear oscillators and evolutionary algorithms: application to phase-locked loop disruption

This work describes an approach for efficiently shaping the response characteristics of a fixed dynamical system by forcing with a designed input. We obtain improved inputs by using an evolutionary algorithm to search a space of possible waveforms generated by a set of nonlinear, ordinary differential equations (ODEs). Good solutions are those that result in a desired system response subject to some input efficiency constraint, such as signal power. In particular, we seek to find inputs that best disrupt a phase-locked loop (PLL). Three sets of nonlinear ODEs are investigated and found to have different disruption capabilities against a model PLL. These differences are explored and implications for their use as input signal models are discussed. The PLL was chosen here as an archetypal example but the approach has broad applicability to any input∕output system for which a desired input cannot be obtained analytically.     

Optimization analysis on the bandwidth algorithm for the phase-locked loop (PLL) in OTU

The bandwidth of phase-locked loop (PLL) in optical transponder unit (OTU) is affected by both the external input jitter and the internal phase noise jitter, so the selection for the bandwidth of the PLL has a contradiction and it is necessary that the bandwidth is optimally designed. Under the consideration of both the external input jitter and the internal phase noise, the bandwidth algorithm of the PLL is comprehensively analyzed, and the optimization algorithm of the bandwidth for the PLL of the OTU can be deduced and obtained through improving the former calculation and analytical methods. The optimal bandwidth of the PLL has been analyzed and obtained so as to ensure that the clock output of the OTU has a lower jitter noise. And then the optimization algorithm is applied in 2.5 Gbit/s and 10 Gbit/s OTU, the optimal parameters of the PLL and the output jitter value of the OTU have been acquired by taking the quantitative and qualitative analysis of the PLL parameters. The study shows the optimization algorithm is superior and feasible as well as it is better used in the OTU and plays an important part in the practical application.     

非PLL相位平均型参考线原型验证

射频相位参考线是粒子加速器的重要组成部分之一,为射频低电平控制系统(LLRF)、束流诊断系统、定时系统等提供稳定的相位锁定参考信号。为减少远距离传输过程中由环境温度变化导致的射频传输线中的射频相位漂移,多个加速器装置中已经采用射频相位参考线提供射频相位参考,这些相位参考的实现方案主要是基于恒温控制和基于光纤锁相。与这些方案相比,采用相位平均方法不仅可以保持长距离节点之间的相位稳定,而且更易于现场安装与维护。现有的带有锁相环(PLL)的终端短路方式实现相位平均参考线的方案仍有一些节点数量限制等方面的不足,本文对相位平均参考线结构进行了去除PLL的简化设计并进行了验证,以期增加更多的相位分配节点以及降低对射频器件参数的要求。对非PLL的单端输入终端短路相位平均方案与两端输入各节点间互为参考的相位平均方案分别进行了实验测试,结果表明两者的相位RMS精度可以达到0.1°~0.3°。并对不同的相位平均实现方案中相位不稳定的产生原因进行了分析,结果表明,除环境温度外,同轴线缆材质、合成相位与幅度的不平衡合成等也是重要影响因素。     

Energy-based analysis of frequency entrainment described by van der Pol and phase-locked loop equations

This paper analyzes frequency entrainment described by van der Pol and phase-locked loop (PLL) equations. The PLL equation represents the dynamics of a PLL circuit that appear in typical phase-locking phenomena. These two equations describe frequency entrainment by a periodic force. The entrainment originates from two different types of limit cycles: libration for the van der Pol equation and rotation for the PLL one. To explore the relationship between the geometry of limit cycles and the mechanism of entrainment, we investigate the entrainment using an energy balance relation. This relation is equivalent to the energy conservation law of dynamical systems with dissipation and input terms. We show response curves for the dc component, harmonic amplitude, phase difference, and energy supplied by a periodic force. The obtained curves indicate that the entrainments for the two equations have different features of supplied energy, and that the entrainment for the PLL equation possibly has the same mechanism as does the regulation of the phase difference for the van der Pol equation.     

脉冲发电机电源宽频变化情况下锁相技术仿真

针对在基波频率变化情况下传统锁相环无法进行正确锁相的问题,提出了基于同步参考坐标系的追踪型三相软件锁相环。三相电压信号(V_a、V_b、V_c)经同步坐标变换后,得到两相静止坐标(V_α、V_β)信号,再经过旋转坐标变化后获得(V_d、V_q)信号;V_q信号经过低通滤波后,进行动态信号延迟,其延迟的时间由输出的频率信号获得;把延迟前后的信号做差,经过PID调节后输出为角频率,对角频率积分后获得稳定基波正序相位。为了验证该算法,基于matlab建立了仿真模型。仿真结果表明,该锁相环在电源基波频率线性变化情况下其相移时间小于0.2ms,在脉冲发电机电压基波频率非线性变化情况下需要经过一个周波也能获得精准地锁相,其运用于有源电力滤波器有效地抑制了脉冲发电机的输出谐波。     

Phase Noise in Millimeter Wave Phase-Locked Loop with Mixer

In order to estimate the phase noise of millimetre wave (MMW) phase-locked oscillator (PLO), the phase noise relation of signals in MMW phase-locked loop (PLL) with frequency conversion is analyzed. The signals include output of MMW PLO, intermediate frequency (IF) output of harmonic mixer and output of microwave oscillator serving as local oscillator (LO). A method to estimate the phase noise of MMW PLO is presented, which is based on the phase noise of LO and IF. At the same time, a W-band PLO is achieved, and the phase noise values of the three signals are measured. It is shown that the experimental result is well coincident with the analysis of phase noise relation.     

W-band Communication System with Direct Frequency Shift Keying Modulation to Phase-locked Oscillator

Based on the theory of phase-locked loop, the analysis and simulation of direct frequency shift keying to phase-locked oscillator is presented. Then, a W-band digital communication system is developed, in which the millimeter wave phase-locked oscillator of the transmitter is modulated directly by 15grades 2048 kbit/s signal. The results of the experiment in the field show that the phase-locked loop has little influence on the modulating signal. It is a good way to simplify the transmitter configuration and suitable for high bit rate communication.     

Phase Noise Analysis and Estimate of Millimeter Wave PLL Frequency Synthesizer

Phase noise is an important index in evaluating the performance of millimeter wave (MMW) frequency source. Because of the high frequency, it is difficult to measure its phase noise directly. So it is very necessary to find new methods for estimating it effectively and easily. In this paper, the main factors affecting phase noise of MMW PLL frequency source are analyzed, and then a new method to estimate the phase noise is presented, which is based on the comparison of the phase noise of microwave phase-locked frequency source with phase-locked intermediate frequency in MMW phase-locked loop. In order to demonstrate the validity of this method of phase noise estimate, it is applied to estimate the phase noise of 95GHz double PLL frequency synthesizer. The result shows that the theoretical estimate value is well coincident with the experimental value.     

Phaselock system for millimeter-wave Gunn oscillators used in radio astronomy and laboratory spectroscopy

A frequency-agile heterodyne phaselock loop (PLL) system for millimeter-wave Gunn-effect oscillators between 40 and 110 GHz is described. The Gunn oscillators are phase-locked via the bias in an active second-order servo loop. A facility for fast frequency switching with a maximum rate of 10 kHz and a frequency separation up to 80 MHz is provided. Measurements on the spectral characteristics of a phase-locked Gunn oscillator are presented. The described PLL system is used in radio astronomy and laboratory molecular spectroscopy.     

Demultiplexing of OTDM-DPSK signals based on a single semiconductor optical amplifier and optical filtering

We propose and demonstrate the use of a single semiconductor optical amplifier (SOA) and optical filtering to time demultiplex tributaries from an optical time division multiplexing-differential phase shift keying (OTDM-DPSK) signal. The scheme takes advantage of the fact that phase variations added to the target channel by cross-phase modulation from the control signal are effectively subtracted in the differential demodulation scheme employed for DPSK signals. Demultiplexing from 80 to 40 Gbit/s is demonstrated with moderate power penalty using an SOA with recovery time twice as long as the bit period at 80 Gbit/s. Large dynamic ranges for the input power and SOA current are experimentally demonstrated. The scheme is expected to be scalable toward higher bit rates.     

光电振荡器中锁相环和注入锁定技术的比较和优化

分析比较了基于锁相环技术和基于注入锁定技术的两种光电振荡器的特性,推导了两种光电振荡器的噪声传递函数,并进行了实验验证,得出了这两种技术应用于光电振荡器的相似性和各自的优缺点.由于光纤对温度的高敏感性,采用这两种技术的光电振荡器都存在着易失锁的问题.为解决这一问题,分别分析了两种光电振荡器输出信号与参考信号间的相位关系,基于此关系设计了锁定状态监测和反馈系统,并实验验证了系统的有效性.     

Chaotic transition in a three-coupled phase-locked loop system

The chaotic transition is observed in a three-coupled phase-locked loop (PLL) system in both experiments and numerical simulations. In this system, three PLL oscillators are connected with the periodic boundary condition. Intermittency is found in partially synchronized phase, in which two of three oscillators synchronize with each other and form a pair, and the chaotic transition occurs due to the recombination of synchronized pairs so that different pair is re-formed. In this phase, on-off intermittency is also observed and statistical analyses are carried out for on-off intermittent time series. This intermittency is considered as a hybrid type of intermittency with both on-off intermittency and intermittency due to the recombination of synchronized pairs present in the same time series. We also show the chaotic transition phenomena in a three-coupled logistic map system. (c) 2001 American Institute of Physics.     

Optical phase locking in the microradian domain: potential applications to NASA spaceborne optical measurements

We have constructed and demonstrated a high-performance optical phase-locked loop between two cw Nd:YAG lasers. The feedback system is relatively simple, employing only the laser's internal piezoelectric transducer and an external acousto-optic modulator. A residual phase noise of the order of 1microrad between two optical fields is achieved in the locked condition, as is verified by time- and frequency-domain analyses by the two-oscillator approach that is conventionally used in rf measurement. Potential applications to NASA space-based optical measurements are discussed.     

汤姆逊硬X射线源中锁模脉冲激光稳频方法

 汤姆逊硬X射线源中，光阴极微波电子枪要求触发激光脉冲与腔中微波场相位的精确时间同步。理论分析了锁模脉冲激光器相位噪声，探讨了对激光脉冲相位探测和控制的方法，并通过实验构建了激光相位抖动测量系统和锁相环稳频回路，用基频鉴相信号驱动压电陶瓷晶体改变谐振腔长，实现了从开环3.42 ps到闭环1.46 ps的均方根相位抖动的测量和控制。     

Regeneratively mode-locked fiber laser with a repetition rate stability of 4.9x10-15 using a hydrogen maser phase-locked loop

We demonstrate an ultrastable regeneratively mode-locked fiber laser that employs a phase-locked loop (PLL) circuit with a hydrogen maser. The stability for an integration time of 1s was 6.2x10(-13), which is 16 times better than that of a conventional PLL laser. For an integration time of 1000s, the stability reached as high as 4.9x10(-15). The repetition-rate stability was limited by the synthesizer used for the PLL operation, and there was no additional fluctuation induced by the laser operation.     

Demonstration of a directed optical encoder using microring-resonator-based optical switches

We propose and demonstrate a directed optical logic circuit that performs the encoding function from a 4 bit electrical signal to a 2 bit optical signal based on cascaded microring switches. The four logic input signals control the states of the switches, while the two logic outputs are given by the optical power at the output waveguides. For proof of concept, a thermo-optic switching effect is used with an operation speed of 10 kbps.     

Spread spectrum communication system with chaotic frequency modulation

A new spread spectrum communication system utilizing chaotic frequency modulation of sinusoidal signals is discussed. A single phase lock loop (PLL) system in the receiver is used both to synchronize the local chaotic oscillator and to recover the information signal. We study the dynamics of the synchronization process, stability of the PLL system, and evaluate the bit-error-rate performance of this chaos-based communication system.     

利用锁相环和TV-Rb钟控制飞秒激光脉冲的载波包络相移

为了实现对锁模飞秒钛宝石激光器的相位控制，采用改进的相移测量装置，使载波包络频移信号的信噪比提高到了40 dB以上.在此优化测量结果的基础上，利用电子锁相环技术，通过PZT改变激光器腔内端镜的倾斜将飞秒激光脉冲的载波包络相位锁定到了微波参考源TV-Rb钟10 MHz标准信号上，同时激光脉冲重复频率也采用另一个PZT控制激光腔长锁定到了同一个TV-Rb钟10 MHz信号上.锁定后的结果显示重复频率的锁定达到了TV-Rb钟本身的稳定度，而载波包络相位锁定后比锁定前稳定度提高了三个数量级.     

锁相环的相位模型与实验电路

讨论了锁相环的相位数学模型,给出了一种适合于数学的锁相环实验电路．