一种基于FPGA和Matlab的时延测量方法

针对航天测控等领域对精密测量时延的需要,提出了一种基于FPGA和Matlab的时延测量方法,阐述了其测量原理,并对1 km光纤链路的时延进行测量。实验结果表明,该方法的单频点时延测量精度可以达到ps量级,在没有考虑色散的情况下,传输链路的时延测量值在800～900 MHz频率范围内标准差为2.0 ps。     

光纤偏振模色散的测量

介绍了时域法与频域法的几种偏振模色散(PMD)的测量方法，其中包括了一种新的测量方法——调制相移法。分别介绍了它们测量原理，并对各种方法进行了比较，概括了各种方法的优缺点。     

一种适用于外场站接收机设备时延的标定方法

本文主要研究了卫星导航系统参考站监测接收机时延基线测量方法,并采用此方法对监测接收机通道时延进行了测量。通过与传统的直接测量法测出的结果相比,零基线测量方法简单,精度满足系统要求,是适合外场参考站接收机时延测量和校正的便捷方法。     

变频器的时延测量方法

在无线电高精度测距系统中,对变频器进行准确的时延测量具有很重要的意义。对频率变换器件时延特性的把握无疑决定了测距的精度。阐述了时延的概念以及时延的测量方法,重点分析了基于矢量网络分析仪的2种测量方法。提出分析了一种基于时延测量设备,利用高速示波器进行准确的变频器时延测量方法,分析了该测量方法的性能。实践证明该方法切实可行,可以提高变频器时延测量的准确度。     

光学镜面间距测量技术研究进展

透镜作为光学系统中最基本的光学元件,其中心厚度的加工误差和装配精度将直接关系到整个光学系统的成像质量。对镜面间距非接触测量技术进行了研究,重点介绍了图像法、轴向色散法、差动共焦法、低相干光干涉法等方法的测量原理和研究进展,指出了这些方法的优缺点和适用范围。这些方法都能满足一般光学系统的精度要求,其中低相干光干涉法测量精度最高,轴向色散法、差动共焦法次之,图像法测量精度最低。对光学镜面间距测量技术的发展趋势进行了论述。     

导航设备时延测量技术分析

为了提高无线电卫星导航定位系统(RNSS)的精度,需要对导航设备时延进行精确测量。给出了导航设备的时延测量方法,研究了使用专用时延传递设备进行时延测试的实现方案,介绍了专用时延传递设备对接收链路和发射链路进行时延测量的方法,指出了该方法的创新性和实际测试过程中的应该注意的问题,给出了测试结果及误差分析。     

天线时延标定在卫星导航技术中的应用

卫星导航系统通过信号传播时延的测量来实现定位、导航和授时,信号传播时延测量计算需要已知天线时延,天线时延标定准确度是影响系统服务精度的关键因素。叙述了卫星导航系统中天线时延的定义及通常测量方法,提出了2种利用卫星导航系统自身测距能力的天线时延标定方法,介绍了天线相位中心测量方法,并给出了卫星导航系统应用中的天线相位中心点坐标的归算方法。     

光纤时频传输及其在航天探测中的应用

面向航天探测等应用中对时频同步的需求,针对传统时频传输方法精度不足的问题,提出了一种基于光纤色散时延调控的时频传递系统。分析了利用不同光载波波长产生不同色散时延的方法,来补偿光纤信道由于环境因素的变化产生的时延随机抖动的原理。设计了多个频率传输实验,实验结果表明,该系统可以获得6.5×10-14@1 s和2.1×10-17@104s的频率稳定度。该时频传递技术已成功应用于"嫦娥三号"精密测定轨试验和北斗导航卫星连线干涉测量系统。     

使用干涉法对电力系统OPGW光缆PMD的测量

文章对偏振模色散对光通信系统的影响作了简要说明,详细介绍了干涉法测量偏振模色散的原理并分别说明了干涉法测量偏振模色散的两种方式.结合实际OPGW光缆线路,给出了测试结果,测试结果表明,该光缆线路偏振模色散性能良好.     

光纤偏振模色散的测量方法

根据ITU-T G.650(2000)和IEC61941(1999)的建议，偏振模色散(PMD)的测量方法有斯托克斯参数测定法、波长扫描法和干涉法。斯托克斯参数测定法为测量单模光纤PMD的基准试验方法，后两种方法为替代试验方法。由于干涉法具有测量速度快、测量设备体积小、适合测量处于动态中的光缆、特别适合现场使用等优点，已被许多仪表厂商所采用，如EXFO公司的FTB-5500、NETTEST公司的UBI-PMD等均采用干涉法测量PMD。因此，下面仅介绍干涉法。干涉法的测量原理干涉法是一种测量单模光纤和光缆的平均偏振模色散的方法，它直接测量PMD，属于…     

All-fiber interferometer for chromatic dispersion measurements

An all-fiber interferometric method for chromatic dispersion measurements in meter-length single-mode fibers is presented. In a Michelson setup the physical length of a reference fiber was varied so as to obtain adjustable optical delay. Time resolution, ease of manipulation, and mechanical isolation are considerably improved with respect to conventional interferometers. Resolution of group delay measurement and chromatic dispersion over the full 1100-1700-nm spectral range are better than 5 fs and 0.1 ps/nm-km, respectively     

The measurement of chromatic dispersion in single-mode fibers byinterferometric loop

A method for chromatic dispersion measurement in long-length fibers (1-10 km) based on the application of an interferometric loop (IL) with phase modulation and lamp/monochromator light source is described. The wavelength region of the measurement is 1.1-1.6 μm and the dynamic range is >15 dB. The reproducibility error of the measured group delay and chromatic dispersion is 40 ps/km and 0.1 ps/km-nm respectively. The results obtained by the IL method and Nd-YAG/Raman laser technique are compared. The measured dispersion agrees with the theoretical results calculated from the refractive index profile of the preform. The influence of the type of phase modulation and the length source spectral width on the accuracy of chromatic dispersion measurements by IL technique is analyzed theoretically     

Simple chromatic dispersion measurement by use of wavelength-tunable Raman soliton pulse and two-photon absorption

A simple and high-speed chromatic dispersion measurement of an optical device is presented. The dispersion parameter is measured at the longer-wavelength region of 1.6-1.9 /spl mu/m by utilising the two-photon absorption of the optical pulse in an Si avalanche photodiode. The results obtained are in good agreement with those from the interferometric method.     

Highly accurate long-span chromatic dispersion measurement system by a new phase-shift technique

A highly accurate long span chromatic dispersion measurement system, which is based on a wavelength-division-multiplexing phase-shift technique and utilizes six laser diodes in1.2 sim 1.6 mum spectral region, has been developed. It is intrinsically free from error due to the fiber length variation caused by temperature changes under the measurement. The measurement accuracies of dispersion and Zero-dispersion wavelength are extremely good and within ±0.02 ps/km . nm and ±0.1 nm in 1250 ∼ 1450 nm spectral region in the case of a 10.5-km single-mode fiber measurement. The dynamic range is over 50 dB excluding system theS/Nmargin of 5 dB. Using this system, chromatic dispersion measurements of a 101.9-km pure-silica-core single-mode fiber and a 100.7 km concatenated dispersion-shifted single-mode fiber have been successfully carried out. The measured result has coincided with the arithmetical mean of those of constituent fibers.     

Cross-correlation measurement without mechanical delay scanningusing electronically controlled wavelength-tunable femtosecond solitonpulse

A novel cross-correlation measurement system without mechanical action has been demonstrated in which the delay time between the reference and signal pulse can be electronically scanned by utilising the soliton self-frequency shift and the chromatic dispersion in the optical fibre. In this system, the reference pulse is the ideal femtosecond soliton pulse. The scanning range, the resolution and the scanning speed of the delay time can be arbitrarily changed only by the electronic control     

Impact of chromatic and polarization-mode dispersions on DPSK systems using interferometric demodulation and direct detection

We study the impact of chromatic dispersion (CD) and first-order polarization-mode dispersion (PMD) on systems using binary differential phase-shift keying (2-DPSK) or quaternary DPSK (4-DPSK) with nonreturn-to-zero (NRZ) or return-to-zero (RZ) formats. These signals are received using optical preamplification, interferometric demodulation, and direct detection. We consider the linear propagation regime and compute optical power penalties at fixed bit-error ratio (BER). In order to evaluate the BER precisely taking account amplifier noise, arbitrary pulse shapes, arbitrary optical and electrical filtering, CD, and PMD, we introduce a novel model for DPSK systems and compute the BER using a method recently proposed by Forestieri for on-off keying (OOK) systems. We show that when properly applied, the method yields highly accurate results for DPSK systems. We have found that when either the NRZ or RZ format is used, 2-DPSK exhibits lower power penalties than OOK in the presence of CD and first-order PMD. RZ-2-DPSK, as compared with NRZ-2-DPSK, incurs smaller penalties due to PMD, but offers no advantage in terms of CD. 4-DPSK, as it has twice the symbol duration of OOK or 2-DPSK for a given bit rate, incurs much lower CD and PMD power penalties than either of these techniques. RZ-4-DPSK is especially promising, as it offers CD and PMD penalties significantly smaller than all other techniques, including NRZ-4-DPSK.     

Soliton robustness to the polarization-mode dispersion in opticalfibers

The influences of chromatic dispersion, coupling length, and soliton energy on the soliton robustness to polarization-mode dispersion (PMD) are investigated numerically. We find that both chromatic dispersion and soliton energy have significant effects on the soliton robustness to PMD, and by optimizing chromatic dispersion and soliton energy, soliton pulse broadening can be depressed to within 10% even when the differential group delay is about twice the input pulse width. In addition, a recent experimental result on soliton robustness is numerically verified     

Measurement Scheme for One‐Way Delay Variation with Detection and Removal of Clock Skew

One‐way delay variation (OWDV) has become increasingly of interest to researchers as a way to evaluate network state and service quality, especially for real‐time and streaming services such as voice‐over‐Internet‐protocol (VoIP) and video. Many schemes for OWDV measurement require clock synchronization through the global‐positioning system (GPS) or network time protocol. In clock‐synchronized approaches, the accuracy of OWDV measurement depends on the accuracy of the clock synchronization. GPS provides highly accurate clock synchronization. However, the deployment of GPS on legacy network equipment might be slow and costly. This paper proposes a method for measuring OWDV that dispenses with clock synchronization. The clock synchronization problem is mainly caused by clock skew. The proposed approach is based on the measurement of inter‐packet delay and accumulated OWDV. This paper shows the performance of the proposed scheme via simulations and through experiments in a VoIP network. The presented simulation and measurement results indicate that clock skew can be efficiently measured and removed and that OWDV can be measured without requiring clock synchronization.     

Phase-shift technique for the measurement of chromatic dispersion in single-mode optical fibres using LEDs

The phase-shift technique has been successfully extended to chromatic dispersion measurements in single-mode optical fibres. Using only two sinusoidally modulated LEDs operating at 1.33 and 1.47 ?m, accurate results have been achieved in the spectral region of interest, in good agreement with those obtained with the Nd-Yag laser and Raman fibre technique.     

光纤传感器用于单模光纤色散测试的研究

光纤传感器可以探测诸种外界因素的变化，如速度，电流，温度等。文中介绍了将相位调制．干涉型光纤传感器用于测量单模光纤的色散，给出了详细的分析，并通过实验进行了有益的探索，最后的结果是令人满意的。