Phase calculation with a swept source in optical coherence tomography: Jitter influence

An analysis of phase modifications introduced by laser jitter in frequency-domain optical coherence tomography (OCT) is described. It is shown that a 1D spurious phase function is introduced as a consequence of this phenomenon. This phase function is added to any other introduced by the object under analysis causing a superposition of both. The result may impose some limitations for unambiguous determination of phase changes of objects. Experimental and theoretical results are presented.     

LIA组元的脉冲功率调制系统研制

本文介绍一种以加速组元为终端负载的纳秒脉冲功率系统。获得的加速间隙电压为350kV，90ns(半高宽)，波形上升时间为30ns；Blumlein主开关工作电压大于280kV，抖动小予1.5ns(均方根值)。对同轴场畸变开关性能的进一步改善作了必要的讨论，提出了用等场强原则偏置触发极，比通常采用自然中位面方法，可使开关工作电压提高8．7％。     

针板型触发电晕稳定开关的特性

 为了验证在空气状态下电晕稳定开关的重复频率特性,对自行研制的盘式触发三电极电晕稳定开关的工作特性进行了实验研究,并分析了实验结果。结果表明,在空气状态下,开关具有良好的触发特性,开关抖动和导通时延最小可以分别控制在4, 36 ns;同时,还可以通过减小触发间隙,进一步减小开关的导通时延和增加开关的稳定性。     

Decomposition of Vocal Cycle Length Perturbations into Vocal Jitter and Vocal Microtremor, and Comparison of Their Size in Normophonic Speakers

A statistical method that enables raw vocal cycle length perturbations to be decomposed into perturbations ascribed to vocal jitter and vocal tremor is presented, together with a comparison of the size of jitter and tremor. The method is based on a time series model that splits the vocal cycle length perturbations into uncorrelated cycle-to-cycle perturbations ascribed to vocal jitter and supra-cycle perturbations ascribed to vocal tremor. The corpus was composed of 114 vocal cycle length time series for sustained vowels [a], [i], and [u] produced by 22 male and 16 female normophonic speakers. The results were the following. First, 100 out of 114 time series were decomposed successfully by means of the time series model. Second, vocal perturbations ascribed to tremor were significantly larger than perturbations ascribed to jitter. Third, the correlation between vocal jitter and vocal tremor was moderate, but statistically significant. Fourth, small but statistically significant differences were observed among the three vowel timbres in the relative jitter and the arithmetic difference of jitter and tremor. Fifth, the differences between male and female speakers were not statistically significant in the relative raw perturbations, the relative jitter, or the modulation level owing to tremor.     

1.5MeV LIA脉冲功率系统

本文简要介绍了1.5MeV LIA脉冲功率系统的结构、组成和设计思想;给出了开关运行参数和确定开关时间抖动指标的方法、闭环系统的总抖动对加速电压相对变化的影响、脉冲功率系统各段输出波形和电压幅度的调制关系;测量结果表明,1.5MeV LIA的运行功率和时间同步满足总体设计要求。     

一种同轴低电感低抖动多级多通道气体开关

 研制了一种触发电极位于放电通道之外、间隙电极为环状不锈钢弹簧的同轴多级多通道气体开关。该开关通过分布电容耦合实现触发，利用多间隙串联减小抖动，利用弹簧不同匝之间电感隔离形成多通道放电。实验表明：该开关触发可靠、电感低（～20nH）、抖动小（～3ns）、触发特性稳定。     

Analysis of bit error rate in an optical soliton communication system

An analytical model to describe the Gordon-Haus jitter has been introduced. We have analysed the effects of accumulated amplified spontaneous emission and Gordon-Haus jitter on the bit error rate (BER) performance for various digital modulation formats (that is, ASK, FSK and DPSK).     

On timing Jitter in wavelength-division multiplexed soliton systems

Collision-induced timing shifts in a wavelength-division multiplexed soliton system are computed when damping, amplification, filtering and positive dispersion management following the loss profile are included. A statistical analysis is presented which takes into account the resulting effect of the large number of collisions occurring in the fiber. Analytic expressions are derived for the root mean square timing jitter and the maximum length of error-free transmission with an arbitrary number of channels. An extensive analysis of system performance corresponding to situations with and without filters and/or dispersion management is carried out.     

用光脉冲注入从锁模激光二极管再生低抖动高Q值光时钟

采用１０ＧＨＺ基准时钟光和１０Ｇｂｉｔ／ｓ的数据脉冲信号光注入到锁模激光二极管，降低了周期抖动，当注入功率为－５ｄＢｍ，在基准时钟光波长等于锁模激光二极管的光波长时，获得的最小抖动为０．２５ｐｓ，采用给锁模激光二极管，在注入功率为＋２７ｄＢｍ时，其Ｑ值达３０００。     

Attosecond‐precision ultrafast photonics

We review our recent progress toward attosecond‐precision ultrafast photonics based on ultra‐low timing jitter optical pulse trains from mode‐locked lasers. In femtosecond mode‐locked lasers, the concentration of a large number of photons in an extremely short pulse duration enables the scaling of timing jitter into the attosecond regime. To characterize such jitter levels, we developed new attosecond‐resolution measurement techniques and show that standard fiber lasers can achieve sub‐fs high‐frequency jitter. By leveraging the ultra‐low jitter of free‐running mode‐locked lasers, we pursued high‐precision optical‐optical and optical‐microwave synchronization techniques. Optical signals spanning 1.5 octaves were synthesized by attosecond‐precision timing and phase synchronization of two independent mode‐locked lasers. High‐stability microwave signals were also synthesized from mode‐locked lasers with drift‐free sub‐10‐fs precision. We further demonstrated the attosecond‐precision distribution of optical pulse trains to remote locations via timing‐stabilized fiber links. Finally, the application of optical pulse trains for high‐resolution sampling and analog‐to‐digital conversion is discussed.